Dissertations / Theses: 'Alginate'

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Márquez, Maqueda Augusto. "Alginate and silk fibroin based technologies for biosensing." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670117.

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A causa de el fort impacte de la diabetis com a malaltia d’extensió mundial ia les perspectives d’increment en el nombre de persones afectades durant els propers anys, especialment en països subdesenvolupats, hi ha una gran necessitat de producció de sistemes de detecció i quantificació de glucosa, que puguin ser implementats en dispositius portables robustos, miniaturitzats, de baix cost i llarga durada, tipus Point of Care (POC). En aquest sentit, en aquesta tesi es proposa l’ús de biomaterials d’origen natural, com l’alginat i la fibroïna de seda, procedents de l’alga bruna (classe Phaeophyceae) i de l’cuc de seda (Bombyx mori) respectivament, i la seva combinació amb tecnologies de microfabricació per a la producció d’una nova generació de dispositius POC.
Debido al fuerte impacto de la diabetes como enfermedad de extensión mundial y a las perspectivas de incremento en el número de personas afectadas durante los próximos años, especialmente en países subdesarrollados, existe una gran necesidad de producción de sistemas de detección y cuantificación de glucosa, que puedan ser implementados en dispositivos portables robustos, miniaturizados, de bajo coste y larga duración, tipo Point of Care (POC). En ese sentido, en esta tesis se propone el uso de biomateriales de origen natural, como el alginato y la fibroína de seda, procedentes del alga parda (clase Phaeophyceae) y del gusano de seda (Bombyx mori) respectivamente, y su combinación con tecnologías de microfabricación para la producción de una nueva generación de dispositivos POC.
Due to the impact of diabetes as a worldwide disease and the expected increment in the number of people affected in the following years, especially in underdeveloped countries, there is a need for the production of precise and long-life glucose biosensors to be implemented in simple, low-cost, robust, miniaturized and portable point of care systems. In that sense, this thesis proposes the use of biomaterials of natural origin, such as alginate and silk fibroin, from brown algae (Phaeophyceae class) and silkworm (Bombyx mori) respectively, and their combination with microfabrication technologies for the production of the new generation of electrochemial and optical point of care devices.

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Aarstad, Olav Andreas. "Alginate sequencing : Block distribution in alginates and its impact on macroscopic properties." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20246.

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Hadjialirezaei, Soosan. "Coating of alginate capsules." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22908.

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Alginate is a popular candidate for encapsulation of cells due to the formation of gels with divalent ions under physiological conditions. Stable alginate gels can be formed by the selection of alginates with a high content of guluronic acid (G) and gelling in a mixture of calcium and barium. These alginate gels have been proposed as immune protective barriers for the transplantation of human pancreatic islets (insulin producing cells) for the treatment of type 1 diabetes where the alginate gel protects the transplant from the host immune system. Microencapsulation can thus provide a way to overcome the need for immunosuppressive drugs. Although showing promising results in animal models, there are potential limitations of the Ca2+/Ba2+-beads concerning growth of host cells on the surface of capsules in primate models. Development of coating strategies for alginate based capsules could thus be beneficial for reducing the attachment of host cells. Alginate microbeads/capsules were formed by electrostatic bead generator producing beads of 400µm. Afterward, the alginate beads were coated by fluoresceinamine labeled alginate that was visualized by confocal laser scanning microscopy (CLSM) and quantified by fluorescent spectroscopy. The binding of coating alginate to alginate-poly-L-lysine (PLL) capsules was also studied.In this project, in the optimalisation of coating of alginate beads some parameters were studies such as concentration of coating alginate, different gelling ions both for core and coating alginate, exposure time for gelling solution for fixation of coating layer and different washing solution.The long-term stability of coating layer of coated alginate beads was determined by measuring the fluorescent intensity of fluorescently labeled of coating alginate during a period of forty nine days. A stability study of alginate-alginate capsules revealed that Ca2+/Ba2+ alginate coated with high-G alginate and washed with saline and used Ca2+ and Ba2+ with ratio 50:1 for fixation of coating layer were more stable coating than other capsules. The alginate beads coated with high-M or epimerized alginate were produced. It shows higher intensity of coating layer in both capsules coated with high-M or epimerized alginate than alginate beads coated with high-G alginate. In continue of the study, the alginate-PLL capsules were coated with high-G, high-M, and epimerized and sulfated alginate. Alginate-PLL capsules coated with high-G, high-M and epimerized alginate shows no detective signal by confocal images and sulfated alginate coating shows some signal of coating. The stability of coating for alginate-PLL-alginate capsules and alginate beads coated with epimerized or high-M alginate revealed that both kind of coating have high-stability over one week screening.Three dimensional images of capsules, in confocal microscope, both epimerized and high-M coating alginates cover whole of capsules. However, in 3D images we have seen some fragment of coating gelling in the surround solution and attached to the capsules which can make disturbance in spectroscopy measurement. 3D images of alginate-PLL capsules coated with sulfated alginate show evenly distribution of coating.

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Brivonese, Anne Caterina. "Alginate biosynthesis in Azotobacter vinelandii." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/16946.

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Lima, Caroline Santos Alves de. "Estudo do desenvolvimento de microcápsulas de polímeros naturais para aplicação em têxteis médicos." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/100/100133/tde-01112017-144224/.

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A indústria têxtil busca recuperar a diminuição do ritmo dos negócios, notado principalmente em países desenvolvidos devido ao cenário da economia mundial, por meio da elaboração de têxteis com maior valor agregado. A microencapsulação é uma técnica versátil e flexível que apresenta diversas vantagens, como evitar que o princípio ativo reaja com outros compostos presentes no sistema e possibilitar a liberação controlada, que aumenta potencialmente a eficiência do produto. O principal objetivo deste trabalho foi desenvolver microcápsulas de quitosana e alginato com incorporação de Triclosan, que possui propriedades bactericida e fungicida, para aplicação em substratos têxteis para utilizações médicas. As microcápsulas foram produzidas a partir do método de emulsificação e reticulação, e caracterizadas por Termogravimetria (TG), Calorimetria Exploratória Diferencial (DSC), Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), capacidade de absorção de água e perda de massa, Microscopia Eletrônica de Varredura (MEV), ensaio de atividade bactericida e liberação in vitro. Após caracterizadas, as microcápsulas foram impregnadas em tecidos 100% algodão com ligamentos tela e sarja. Estes foram submetidos a testes físicos e análise de resistência à lavagem. As microcápsulas produzidas apresentaram forma esférica e tiveram 80,78% de eficiência de encapsulação do fármaco. Os ensaios de liberação mostraram que o fármaco não foi liberado em 24h, entretanto, o material apresentou atividade bactericida contra a bactéria gram-positiva S. aureus, com halo de inibição de até 60 mm e também contra a bactéria gram-negativa E. coli, com halo de até 25 mm. Os resultados de resistência à lavagem avaliados por MEV mostraram que as microcápsulas não permenceram no substrato. Entretanto, o material apresentou atividade antibacteriana podendo ser interessante para aplicação em materiais têxteis descartáveis, como bandagens utilizadas na área médica
The textile industry seeks to recover the decrease of the pace of business, noted mainly in developed countries due to the scenario of the world economy, through the development of textiles with higher added value. The microencapsulation is a versatile and flexible technique that presents several advantages such as to avoid that the active ingredient react with other compounds present in the system, and allow controlled release that potentially increases the efficiency of the product. The main objective of this work was to develop microcapsules of chitosan and alginate with incorporation of triclosan, which has bactericidal and fungicide properties, for use in textile substrates for medical uses. The microcapsules were produced from the method of emulsification and crosslinking, and characterized by Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Infrared Spectroscopy Fourier Transform (FTIR), water absorption capacity and mass loss, Scanning Electron Microscopy (SEM), bactericidal activity assay and in vitro release. After characterized, the microcapsules were impregnated in 100% cotton twill and taffeta woven. Physical tests and analysis of resistance to washing were carried out. The microcapsules produced presented spherical shape and had 80.78% of drug encapsulation efficiency. Release tests showed that the drug was not released in 24 hours, however, the material presented bactericidal activity against the gram-positive bacterium S. aureus, with inhibition halo up to 60 mm and also against the gram-negative bacterium E. coli, with halo of up to 25 mm. The results of washing resistance evaluated by SEM showed that the microcapsules did not remain in the substrate. However, the material showed antibacterial activity and may be interesting for application in disposable textiles, such as bandages used in the medical field

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Reehorst, Camilla M. "The Mucin-Alginate Interplay : Investigating the Rheological Impact of Alginates and Their Influence on Particle Mobility." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24921.

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Mucus is a hydrogel that covers epithelial cells and acts as an intermediary between the exterior and interior surfaces of the human body. It is complex and diverse, comprised of various compounds and serves as a selective barrier to pathogens, nutrients and administered substances. It is therefore important to circumvent or penetrate this barrier to increase drug bioavailability. The most important constituent of mucus is mucin glycoprotein that enables gel formation. Due to the molecular nature of mucin, it interacts with most substances including polyanionic biopolymers like alginates. Alginate molecules have been extensively used in pharmaceutical and medical industries as mediators because they possess suitable characteristics for a variety of biomedical applications. They have also been shown to influence mucus rheology, and could hold potential to alter other properties of mucus as well, such as particle mobility. In this thesis, the effect of different molecular weight alginates were investigated on the rheology of porcine gastric (PG) mucin, porcine small intestinal mucus (PSIM), porcine tracheobronchial mucus (PTBM) and bio-similar mucus. In addition, the effect of alginate on particle mobility in PG mucin samples were investigated using multiple particle tracking (MPT). The rheological effect of alginate G-block DPn 12, DPn 24, DPn 33 and alginate LFR 5/60 on PG mucin was inconclusive as the sample suffered from pH and mechanical instabilities. Particle mobility was greatest for G-block DPn 12 and G-block DPn 33 treated PG mucin at long time scales. In addition, their mean-square displacement (MSD) trajectories were more narrowly distributed than the other samples, which correlates to a higher degree of uniform pore sizes. The rheological behaviour of bio-similar mucus and PSIM after treatment of G-block DPn 12, G-block DPn 33 and LFR 5/60 did not coincide, despite bio-similar mucus being a model system for porcine intestinal mucus (PIM). This was ascribed interactions between alginate and polyacrylate in the bio-similar mucus causing phase separation. Alginate G-block DPn 12 weakened the PSIM and PTBM gel, while G-block DPn 33 and LFR 5/60 had minor strengthening effects on PSIM.

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Silva, Adriana Navarro da [UNESP]. "Substratos alternativos para a produção de poli-hidroxibutirato e alginato por Azotobacter vinelandii." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/100889.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Atualmente a destinação do lixo é uma das grandes preocupações da organização urbana e os problemas ambientais causados pela produção e acúmulo de materiais plásticos de origem petroquímica têm incentivado muitos países a realizarem estudos de gerenciamento do volume de lixo sólido, incluindo a diminuição de resíduos plásticos por meio do desenvolvimento de bioplásticos. Os bioplásticos possuem propriedades semelhantes às dos plásticos convencionais e apresentam a vantagem de serem facilmente degradados pela ação de microrganismos no ambiente, podendo citar como exemplo os poli-hidroxialcanoatos (PHA), dentre eles o poli-hidroxibutirato (PHB). Estes polímeros podem representar até 80% da massa seca total da célula, tendo como característica principal a biodegradabilidade em solos e a biocompatibilidade com o tecido animal. Entre os microrganismos produtores de PHAs, a bactéria Azotobacter vinelandii pode acumular grandes quantidades de PHB intracelular com a vantagem de utilizar durante seu crescimento uma ampla variedade de açúcares como os encontrados em melaço de cana-de-açúcar, beterraba e xarope de milho, além de resíduos da suinocultura, agroindustriais, etc. Além do PHB, a bactéria A. vinelandii é capaz de produzir alginato, composto muito empregado na área de análogos de frutas ou produtos tipo imitação como: fatias de pimentão para recheios de azeitonas, imitação de anéis de cebola, imitações de caviar, carne, pescados, produtos marinhos, etc. Tendo em vista que os principais fatores limitantes para a produção de biopolímeros estão associados, principalmente, com os custos dos substratos e ao fato de que muitos microrganismos são patogênicos dificultando a sua aceitação pela comunidade em geral, este trabalho teve como objetivo utilizar...
Currently, the waste disposal is a major concern of urban organization and the environmental problems caused by production and accumulation of petrochemical plastics have encouraged many countries to management studies of the solid waste volume, including the waste plastics reduction through the bioplastics development. Bioplastics have similar properties to conventional plastics and the advantage of being easily degraded by the microorganisms action in the environment, for example, poly-hydroxyalcanoatos (PHA), including poly-hydroxybutyrate (PHB). These polymers can represent up to 80% of total dry mass of the cell, having as main feature the biodegradability in soil and the biocompatibility with animal tissue. Among the microorganisms producing PHAs, the bacterium Azotobacter vinelandii can accumulate large amounts of intracellular PHB with the advantage that they grow a wide sugars variety like those found in molasses cane sugar, beet sugar and corn syrup, and swine waste, agribusiness, etc.. Besides the PHB, the bacterium A. vinelandii is able to produce alginate, a very useful compound in the similar area of type of fruit and imitation as sliced peppers for stuffing olives, onion rings imitation, caviar, meat, fish and marine products imitation, etc.. Given that the main limiting factors for the biopolymers production are mainly associated with the substrates costs and the fact that many microorganisms are pathogenic hindering its acceptance by the community in general, this study aimed to use the pollutant by-products environment (residual oil frying, glycerin, cassava wastewater – “manipueira”, vinasse and wastewater industry carbonated beverages or soft drinks) as a substrate for the poly-hydroxybutyrate and alginate production by non-pathogenic bacterium Azotobacter vinelandii. Fermentations... (Complete abstract click electronic access below)

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Dumont, Mélanie. "Élaboration et caractérisation de fibres mixtes Alginate / Chitosane." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1303/document.

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Dans ces travaux de recherche, la préparation de fibres d'alginate de calcium revêtues de chitosane par un procédé de filage par mouillage et la caractérisation de ces fibres dont leur activité antibactérienne sont présentées. Un métier à filer à l'échelle pilote a été conçu et développé au cours de ces travaux de thèse pour l'élaboration de fibres d'alginate de calcium. Ces dernières, préalablement fabriquées, sont immergées dans une solution d'acétate de chitosane. Trois méthodes de coagulation de l'enduit de chitosane ont été explorés dont deux consistent en l'immersion des fibres dans un bain neutralisant : une solution de dihydroxyde de calcium ou une solution d'hydroxyde de potassium. La dernière méthode consistait à neutraliser le chitosane par séchage sous air chaud soufflé. Une caractérisation structurelle, mécanique et d'absorption des fibres, ainsi qu'un dosage du chitosane revêtu ont été réalisés. De plus, une évaluation antibactérienne a été accomplie par une méthode de comptage des UFC (Unité Formant Colonie) après 6 h d'incubation à 37 °C. L'incorporation de chitosane aux fibres d'alginate de calcium apporte une activité antibactérienne contre Staphylococcus epidermidis, Escherichia coli et divers Staphylococcus aureus tels que MSSA (Methicillin Sensitive Staphylococcus aureus), CA-MRSA (Community Associated Methicillin Resistant Staphylococcus aureus) et HA-MRSA (Healthcare Associated Methicillin Resistant Staphylococcus aureus). Ces fibres revêtues sont alors des candidats de choix pour l'élaboration de tissus destinés à la cicatrisation des plaies. Développer des compresses avec les propriétés hémostatiques et cicatrisantes de l'alginate de calcium combinées aux propriétés antibactériennes du chitosane peut être envisagé pour lutter contre les infections et plus particulièrement les maladies nosocomiales
In this work, the preparation of chitosan-coated alginate fibers by a wet spin process and the characterization of these fibers, particularly their antibacterial activities are presented. A pilot scale spinning machine was developed during this thesis for the elaboration of calcium alginate fibers. These last, preformed produced were immersed in chitosan acetate solutions. Three coagulation methods of the chitosan coating were explored two of which consist to the immersion of the fibers in a neutralizing bath: a calcium hydroxide solution or a potassium hydroxide solution. The last method is to neutralize chitosan by drying under hot air blown. Structural, mechanical and absorption characterization of fibers and a dose of the coated chitosan have been made. Furthermore, the antibacterial evaluation was achieved by a CFU (Colony-Forming Units) counting method after 6 h of incubation at 37 °C. The incorporation of chitosan on calcium alginate fibers brings antibacterial activities against Staphylococcus epidermidis, Escherichia coli and various Staphylococcus aureus strains namely MSSA (Methicillin Sensitive Staphylococcus aureus), CA-MRSA (Community Associated Methicillin Resistant Staphylococcus aureus) and HA-MRSA (Healthcare Associated Methicillin Resistant Staphylococcus aureus) which make these chitosan-coated fibers potential candidates for wound dressing materials. Developing a wound dressing with the haemostatic and healing properties of alginate combined with antibacterial properties of chitosan can be envisioned for fighting against the infections and more particularly nosocomial infections

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Monteiro, Centeno da Costa Filipe. "Procédé d’immobilisation de levures pour applications oenologiques. Etudes des paramètres du procédé. Validations experimentales." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0061.

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L'étude et le développement des procédés de fabrication de levures immobilisées en vue de la réalisation de fermentations de vins a débuté au milieu des années 80. Malgré les bénéfices potentiels que cette technologie pouvait apporter pour le secteur œnologique, peu de procédés d'immobilisation ont réussi à dépasser l'échelle laboratoire ou pilote et ceux qui sont arrivés à l'échelle industrielle n'ont pas eu le succès désiré pour des questions d'ordre technique ou économique. Le premier objectif de ce travail concerne la mise au point du procédé industriel en insistant sur les aspects les plus sensibles, et qui comme tels ont exigé des études complémentaires. Le deuxième objectif de ce travail vise à caractériser du point de vue cinétique et lorsque possible sensoriel, les fermentations avec les levures immobilisées pour la production de vins effervescents et pour la désacidification biologique de moûts. Le troisième et dernier objectif de ce travail consiste à évaluer l'utilisation de levures immobilisées pour la réalisation de la fermentation alcoolique en continu de moût. Pour cela on a fait appel à des fermenteurs continus à lit fixe et à lit fluidisé
The study and development of yeast immobilization processes for wine fermentations started in the mid 80’s. Even though this technology could be of great benefit for the oenological sector very few process left the laboratory or pilot scale and those which arrived to industrial scale didn’t have the ambitioned success due to technical or economical constraints. The first goal of this work was to develop an industrial process for yeast immobilisation with emphasis on the most sensitive aspects which required further studies. The second objective of this work was to characterise the fermentation kinetics of immobilised yeasts cells during the production sparkling wines and during the deacidification of grape must. Whenever possible the wines produced were also characterised from a sensorial point of view. The third and last goal was to evaluate the use of immobilised yeast cells for continuous fermentation of grape must. For that we have used continuous fixed bed and fluidized bed fermenters

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Govan, John R. W. "Pseudomonas, alginate biosynthesis and cystic fibrosis." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/28137.

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Parsian, Ava. "Simvastatin Encapsulation in Alginate-Based Microspheres." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34439.

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Despite the great success of hip implant surgeries, wear particle-induced implant aseptic loosening still limits the implant longevity. Simvastatin, an FDA-approved cholesterol lowering statin, is a promising drug candidate for the treatment of implant aseptic loosening due to its anti-inflammatory properties as well as its ability to stimulate bone growth and inhibit bone resorption. In addition, alginate microspheres have been used extensively in drug delivery applications because of alginate properties, including biocompatibility and gelation in mild conditions. However, the hydrophobicity of simvastatin, as well as the large alginate microsphere pore size leading to the leakage of low molecular weight drugs are limiting factors for their use as a delivery system for simvastatin. Therefore, the objectives of this thesis were twofold: 1. To complex simvastatin with 2-hydroxypropyl-β-cyclodextrin (HP-βCD) in order to increase its solubility; and 2. To increase simvastatin encapsulation efficiency in alginate microspheres by coating the microspheres with chitosan, adding dextran sulfate in the alginate solution, and optimizing the gelation conditions used for the synthesis of the microspheres (e.g., volume of gelation medium, curing time, and addition of simvastatin in the gelation medium). Results showed that simvastatin complexation with HP-βCD increased with HP-βCD to simvastatin molar ratio, to a maximum of 97.6% at the molar ratio of 10. Results also showed that chitosan coating of the alginate microspheres increased simvastatin encapsulation efficiency (up to 10.6%), which was further improved (up to 14.0%) when adding 2.0% (w/v) dextran sulfate to the alginate solution. This increase was likely due to electrostatic interactions between dextran sulfate and chitosan in addition to alginate, resulting in a denser coating. Finally, the addition of simvastatin in the gelation medium was shown to also increase simvastatin encapsulation (up to 22.4%), likely because of a decrease in the diffusion of simvastatin out of the microspheres. Overall, this work completed the initial steps for the development of an alginate-based drug delivery system for simvastatin with the long-term goal of providing a local delivery of simvastatin to modulate implant aseptic loosening.

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Zou, Jennifer. "Membrane coating of alginate-DNA microspheres." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29639.pdf.

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Oates, Christopher G. "Soya/alginate interactions in extrusion cooking." Thesis, University of Nottingham, 1988. http://eprints.nottingham.ac.uk/11161/.

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Previous work has shown that following the inclusion of alginate high in mannuronic acid there is a reduction in the viscosity of soya melt during extrusion, this work attempts to identify the mechanism for this effect. The effect of water content and hydrocolloid inclusion on the denaturation behaviour and water binding properties of soya protein has been investigated, mainly by the use of differential scanning calorimetry. Of a range of parameters investigated, transition onset temperature and enthalpy, change in specific heat function and coopertivity of the transition all show a dependence on initial moisture content. These parameters are all changed if soya is heated in the presence of a high mannuronic acid alginate. With the exception of changes in enthalpy these effects are not seen to the same extent with other added hydrocolloids. These changes have been attributed to the production of water during heating. Measurements of freezable water and sorption isotherms suggest that alginate addition increases the water binding ability of soya isolate after denaturation. When heated at high temperatures only soya and gluten (out of 7 proteins tested) produced measurable quantities of additional water. In the presence of 2% Manucol DM the formation of water was markedly increased in the soya and gluten samples but not in the other proteins. Production of increased amounts of water after alginate addition was demonstrated to be dependent on the quantity of mannuronic acid in the alginate. The dependence of this effect on water activity suggests that it is the result of browning or condensation reactions. Glutamic acid was implicated with the specific reaction between soya and alginate, though in heated soya both loss of lysine and serine were found. Differential rates of degradation were found between a high mannuronic acid alginate and a high guluronic acid alginate after heat treatment. The alginate high in mannuronic acid was shown to depolymerise to a far greater extent. Various estimates for the molecular weight of the heat treated samples were obtained and no correlation could be found between increased reducing capability of the sample and extent of depolymerisation. Furthermore the production of volatiles that may be expected from sugar ring degradation were not found. Increased brown colour formation and water production and concomittant decreased glutamic acid content were found in soya samples extruded in the presence of 1% Manucol DM. It was concluded that the chemical reactivity of glutamic acid with alginates rich in mannuronic acid explains the well established effect of this type of polysaccharide in extrusion processing.

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Jitraruch, Suttiruk. "Alginate-encapsulated human hepatocytes for transplantation." Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/alginateencapsulated-human-hepatocytes-for-transplantation(d2b15a91-c475-4c15-9a44-84f7fdf87156).html.

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Intraperitoneal transplantation of alginate-microencapsulated human hepatocytes is an attractive option for the management of acute liver failure by providing short-term support to bridge patients to liver transplantation or allow native liver regeneration. Its success depends on mechanical stability, optimal permeability, and biocompatibility of the encapsulated cells to provide good viability and function. The main aims of this study were to optimise protocols for production and cryopreservation of human hepatocyte microbeads (HMBs) for future clinical use. HMBs were prepared using sterile ultrapure materials. Physical integrity of HMBs was evaluated using an osmotic stress test. A polymerisation of 15min provided mechanical stability with well-maintained cell viability and function. Cell content in HMBs was optimised and a density of 3.5x106cells/ml alginate provided the highest cell viability with hepatocytes evenly distributed within microbeads. Permeability of optimised HMBs was measured and the largest protein which could diffuse out of microbeads had a molecular weight of 164kDa. Immune activation of human peripheral blood mononuclear cells was assessed by flow cytometry after co-culture with empty microbeads and HMBs. No evidence of cellular immune activation was observed. Optimisation of hepatocyte microbead cryopreservation was performed using rat and human hepatocytes. Improved outcome of cryopreservation was found when hepatocyte microbeads were cryopreserved in UW solution containing 10% DMSO, 5% glucose and 60μM benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (ZVAD). Safety, therapeutic effects, and immunogenicity of hepatocyte microbeads produced were confirmed in immunocompetent rats with and without acute liver failure. HMBs showed functionality with no inflammatory response in rats over 7 days. Transplantation of rat hepatocyte microbeads was safe and able to support the failing liver. Cryopreserved microbeads showed an encouraging outcome, but may require greater cell numbers compared to fresh microbead. In conclusion, optimised protocols for production and cryopreservation of GMP grade alginate-encapsulated hepatocytes were established. These high quality microbeads are suitable for clinical transplantation.

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Silva, Adriana Navarro da. "Substratos alternativos para a produção de poli-hidroxibutirato e alginato por Azotobacter vinelandii /." São José do Rio Preto : [s.n.], 2012. http://hdl.handle.net/11449/100889.

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Orientador: Crispin Humberto Garcia-Cruz
Banca: Eleni Gomes
Banca: José Roberto Ernandes
Banca: Mário Antônio Alves da Cunha
Banca: Vanildo Luiz Del Bianchi
Resumo: Atualmente a destinação do lixo é uma das grandes preocupações da organização urbana e os problemas ambientais causados pela produção e acúmulo de materiais plásticos de origem petroquímica têm incentivado muitos países a realizarem estudos de gerenciamento do volume de lixo sólido, incluindo a diminuição de resíduos plásticos por meio do desenvolvimento de bioplásticos. Os bioplásticos possuem propriedades semelhantes às dos plásticos convencionais e apresentam a vantagem de serem facilmente degradados pela ação de microrganismos no ambiente, podendo citar como exemplo os poli-hidroxialcanoatos (PHA), dentre eles o poli-hidroxibutirato (PHB). Estes polímeros podem representar até 80% da massa seca total da célula, tendo como característica principal a biodegradabilidade em solos e a biocompatibilidade com o tecido animal. Entre os microrganismos produtores de PHAs, a bactéria Azotobacter vinelandii pode acumular grandes quantidades de PHB intracelular com a vantagem de utilizar durante seu crescimento uma ampla variedade de açúcares como os encontrados em melaço de cana-de-açúcar, beterraba e xarope de milho, além de resíduos da suinocultura, agroindustriais, etc. Além do PHB, a bactéria A. vinelandii é capaz de produzir alginato, composto muito empregado na área de análogos de frutas ou produtos tipo imitação como: fatias de pimentão para recheios de azeitonas, imitação de anéis de cebola, imitações de caviar, carne, pescados, produtos marinhos, etc. Tendo em vista que os principais fatores limitantes para a produção de biopolímeros estão associados, principalmente, com os custos dos substratos e ao fato de que muitos microrganismos são patogênicos dificultando a sua aceitação pela comunidade em geral, este trabalho teve como objetivo utilizar... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Currently, the waste disposal is a major concern of urban organization and the environmental problems caused by production and accumulation of petrochemical plastics have encouraged many countries to management studies of the solid waste volume, including the waste plastics reduction through the bioplastics development. Bioplastics have similar properties to conventional plastics and the advantage of being easily degraded by the microorganisms action in the environment, for example, poly-hydroxyalcanoatos (PHA), including poly-hydroxybutyrate (PHB). These polymers can represent up to 80% of total dry mass of the cell, having as main feature the biodegradability in soil and the biocompatibility with animal tissue. Among the microorganisms producing PHAs, the bacterium Azotobacter vinelandii can accumulate large amounts of intracellular PHB with the advantage that they grow a wide sugars variety like those found in molasses cane sugar, beet sugar and corn syrup, and swine waste, agribusiness, etc.. Besides the PHB, the bacterium A. vinelandii is able to produce alginate, a very useful compound in the similar area of type of fruit and imitation as sliced peppers for stuffing olives, onion rings imitation, caviar, meat, fish and marine products imitation, etc.. Given that the main limiting factors for the biopolymers production are mainly associated with the substrates costs and the fact that many microorganisms are pathogenic hindering its acceptance by the community in general, this study aimed to use the pollutant by-products environment (residual oil frying, glycerin, cassava wastewater - "manipueira", vinasse and wastewater industry carbonated beverages or soft drinks) as a substrate for the poly-hydroxybutyrate and alginate production by non-pathogenic bacterium Azotobacter vinelandii. Fermentations... (Complete abstract click electronic access below)
Doutor

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Chavagnat, Frédéric. "Production d'anticorps monoclonaux anti-alginate : surproduction, structure et activité des alginate lyases bactériennes AlxM et Algi en vue de la préparation d'un complexe anti-alginate contre Pseudomonas aeruginosa." Lyon 1, 1996. http://www.theses.fr/1996LYO10040.

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L'alginate, polymere d'acides mannronique et guluronique, est un facteur de virulence de pseudomonas aeruginosa. Il protege la bacterie de la phagocytose et de l'action des antibiotiques. Le but de mon travail etait d'obtenir des anticorps anti-alginate et de produire en grande quantite des alginate lyases actives sur l'alginate de p. Aeruginosa. Des anticorps monoclonaux igm anti-alginate ont ete obtenus par immunisation de souris avec un conjugue bsa/alginate de p. Aeruginosa. Ils ont ete purifies puis reduits en monomeres pour un couplage avec la peroxydase. Le conjugue fonctionnel obtenu a permis de valider la methode pour la synthese du conjugue alginate lyase/anticorps anti-alginate. L'alginate lyase alxm de la bacterie marine atcc 433367 a ete surproduite chez e. Coli et purifiee en une seule etape: sa masse est de 30 kda, le rendement de purification est de 90% (32 mg/l de culture). Les conditions optimales d'activite de alxm ont ete determinees, puis utilisees pour l'etude de sa specificite. Alxm est une mannuronate lyase, elle produit, par un mecanisme de -elimination avec retention de configuration, un oligomere de dp3 quel que soit le substrat. Ses parametres cinetiques ont ete determines pour des substrats oligomeriques de structure definie. Le gene algi codant pour l'alginate lyase produite par pseudomonas alginovora a ete amplifie par pcr directe et inverse, sequence puis clone dans le vecteur de surexpression pet-22b. L'enzyme surproduite a 18c dans e. Coli, algisur, a ete purifiee en une seule etape par chromatographie d'affinite avec un rendement de 67% (5 mg/l de culture). Conformement a la strategie de surexpression, sa masse de 24635 da correspond a celle de algi additionnee de la sequence poly(his). Algi et algisur ont le meme profil d'activite avec une specificite de type mannuronate lyase. Une etude par hca sur alxm, algi et quatre autres alginate lyases de structures primaires connues a permis de classer ces enzymes deux par deux en trois familles

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Pettignano, Asja. "Alginate : a versatile biopolymer for functional advanced materials." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2016. http://www.theses.fr/2016ENCM0004.

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Les alginates, des polysaccharides produits par les algues brunes, sont des copolymères à blocs linéaires, formés d’unités mannuronate (M) et guluronate (G). En raison de leur abondance naturelle, prix et propriétés physicochimiques avantageuses, les alginates représentent une classe de biopolymères très intéressante et relativement inexplorée pour des applications dans le domaine des matériaux avancés. Dans ce contexte, le présent travail vise à enrichir la gamme des applications des matériaux dérivés d’alginates, en exploitant les propriétés de cette classe de polysaccharides naturels. En particulier, la préparation de matériaux à base d'alginate pour la catalyse, l'adsorption et le domaine biomédical a été étudiée, avec des résultats encourageants dans toutes les applications testées. L'utilisation bénéfique de l'acide alginique en catalyse hétérogène a été démontrée, en tant que promoteur de réaction et support pour l’hétérogénéisation d'un organocatalyseur. L'activité du catalyseur a été trouvée très dépendante de l'accessibilité des groupes fonctionnels, mettant en évidence l’avantage de l’emploi de formulations plus accessibles. La texturation des alginates a été aussi avantageuse dans la préparation de matériaux pour applications en flux. Des mousses d'acide alginique, avec une structure hiérarchique macro-mésoporeuse, ont été développées à cet effet. Une caractérisation précise des matériaux a été réalisée, afin d'optimiser la procédure de préparation et de corréler les propriétés texturales obtenues avec les paramètres utilisés. L'intérêt dans l’utilisation de mousses à base d'acide alginique a été démontré dans une application modèle, l'adsorption de bleu de méthylène à partir de solutions aqueuses, à la fois en batch et en flux. La possibilité de modifier facilement les groupes fonctionnels de l’alginate, couplée avec la nature biocompatible et biodégradable de ces biopolymères, a finalement été exploitée pour le développement de gels auto-réparants, obtenus grâce à la formation de deux types d'interactions covalentes dynamiques : base de Schiff et ester de boronate. Les deux systèmes examinés ont présenté une remarquable habilité à se reconstruire après un dégât, même si l'ampleur de la reconstruction et la stabilité des gels étaient fortement dépendantes des paramètres de préparation des gels et des conditions environnementales utilisées. Les résultats obtenus dans le cadre de cette étude démontrent clairement comment la compréhension et un emploi conscient des propriétés physico-chimiques des alginates peuvent maximiser le potentiel que cette ressource durable dans le domaine de la chimie des matériaux
Alginates, polysaccharides produced by brown algae, are linear block-copolymers formed by mannuronate (M) and guluronate (G) units. Because of their huge natural abundance, cheapness and physicochemical properties, alginates represent a highly attractive and still relatively unexplored class of biopolymers for applications in the field of advanced materials. In this context, the present work aimed to enrich the range of possible applications of alginate-derived materials, making the most of the peculiar features of this class of natural polysaccharides. In particular, the preparation of alginate-based active materials to be employed in the catalysis, adsorption and biomedical field was studied, achieving encouraging results in all the tested applications. The beneficial use of alginic acid in heterogeneous catalysis, both as reaction promoter and as support for the heterogeneization of an organocatalyst, was demonstrated. The activity of the material was found highly dependent on the accessibility of the active functions, highlighting the advantage of employing more accessible alginate formulations. The texturation of alginates was further advantageous for the preparation of materials with improved flowability. Alginic acid foams, bearing a hierarchical macro-mesoporous structure were developed by means of a simple procedure. Accurate characterization was performed to optimize the preparation procedure and to correlate the textural properties of the obtained materials with the parameters used. The interest of the prepared alginic acid foams was demonstrated in a model application, the adsorption of methylene blue from aqueous solutions, both in batch and in flow conditions. The possibility to easily modify alginate functional groups, coupled with the biocompatible and biodegradable nature of alginates, was finally employed for the development of self-healing gels, thanks to the formation of two types of dynamic covalent interactions: Schiff base and boronate ester bonds. Both the examined systems presented a marked ability to recover after damage, even if the extent of the recovery and the stability of the gels was highly dependent on the preparation parameters and environmental conditions used. The results obtained in the course of this study clearly demonstrate how a full comprehension and conscious employment of alginate physicochemical properties can maximize the potential of this sustainable resource in the field of material chemistry

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Barbier, Lucile. "Hydrogels injectables thermostimulables : relations structure/propriétés." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS394.

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Ce travail de thèse porte sur le développement d’hydrogels injectables thermostimulables. Dans le cadre de la délivrance de principes actifs, l’objectif est de partir d’une solution de polymère suffisamment fluide à température ambiante pour pouvoir être injectée à un endroit ciblé du corps et d’obtenir une gélification rapide de la formulation une fois introduite en milieu physiologique. Pour aborder cette étude, une large plateforme de copolymères greffés a été développée à partir de squelettes hydrophiles et de greffons thermosensibles caractérisées par leur LCST en milieu aqueux. Dans un premier temps, un système entièrement synthétique à base de poly(acide acrylique)-g-poly(N-isopropyl acrylamide) a été utilisé comme système modèle. Les relations structure/propriétés ont alors été établies en étudiant l’impact de la taille du squelette, de la taille des greffons et du taux de greffage sur la transition de phase et sur les propriétés rhéologiques dans le domaine linéaire (modules dynamiques) ainsi qu’aux grandes déformations (test d’adhésion). En régime enchevêtré, il a été montré que les propriétés élastiques générées à haute température pouvaient être décrites à partir d’un paramètre réduit prenant en compte la concentration en copolymère, la concentration d’enchevêtrement des chaînes ainsi que la fraction massique de greffons à LCST. Dans une seconde étape, cette étude a été élargie en utilisant des greffons de poly[oligo(éthylène glycol) méthyl éther méthacrylate]. Dans cette étude comparative, nous montrons que si la température de transition de phase des greffons est importante pour le déclenchement du processus associatif, les propriétés thermodynamiques des greffons gouvernent les propriétés élastiques à haute température. Dans une dernière partie, cette étude a été transposée à des squelettes polysaccharides de type alginate et acide hyaluronique afin d’améliorer la biocompatiblité. Avec ces copolymères de nature chimique pourtant très différente, la corrélation précédente entre module élastique et concentration réduite est de nouveau observée. Enfin, dans le cadre d’études plus appliquées, le caractère injectable des solutions a été vérifié pour les copolymères à base d’alginate, de même que leur cinétique de gélification extrêmement rapide en milieu physiologique qui permet de conserver l’intégrité des gels sur des temps longs tout en favorisant un relargage ralenti des molécules d’intérêt dans le milieu extérieur
This thesis work focuses on the development of thermoresponsive injectable hydrogels. In the context of drug delivery, the objective is to start from a polymer solution that is sufficiently fluid at room temperature to be injected into a targeted area of the body and to obtain a rapid gelation of the formulation once introduced in a physiological environment. To address this problem, a large platform of graft copolymers has been developed using hydrophilic backbones and thermoresponsive side-chains characterized by their LCST in aqueous medium. In a first step, a fully synthetic macromolecular architecture based on poly(acrylic acid)-g-poly(N-isopropyl acrylamide) was used as a model system. The structure/properties relationships were then established by studying the impact of the size of the backbone, the size of the grafts and the rate of grafting on the phase transition and on the rheological properties determined in the linear domain (dynamic moduli) as well as at large deformations (adhesion test). In the entangled regime, it was shown that the elastic properties triggered at high temperature could be described from a reduced parameter taking into account the copolymer concentration, the entanglement concentration of chains as well as the weight fraction of LCST grafts. In a second step, this study was extended to the same copolymers using poly[oligo(ethylene glycol) methyl ether methacrylate] as responsive grafts. In this comparative study, we show that while the association temperature of the grafts is important for triggering the associative process, their thermodynamic properties control the elastic properties at high temperature. In a last part, this study was transposed to polysaccharide backbones, alginate and hyaluronic acid, to improve their biocompatibility. With these copolymers of very different chemical nature, the previous correlation between elastic modulus and reduced concentration is still observed. Finally, in a more applicative context, the injectability of alginate-based copolymers solutions was verified, as well as their extremely rapid kinetics of gelation in a physiological environment, which leads to the conservation of the integrity of gels over long periods of time while favouring a slower release of the molecules of interest into the external environment

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Sabra, Wael. "Microaerophilic production of alginate by Azotobacter vinelandii Mikroaerophile Alginatproduktion mit Azotobacter vinelandii /." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=956360513.

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Rokstad, Anne Mari Aukan. "Alginate capsules as bioreactors for cell therapy." Doctoral thesis, Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1535.

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McDonagh, Birgitte Hjelmeland. "Optimalised Carbodiimide Chemistry for RGD-coupled Alginate." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16807.

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Alginate is a naturally ocurring polyanion of (1→4)linked β-d-mannuronic acid (M)and its C-5 epimer α-l guluronic acid (G). The polyanion, and particularly longstretches of guluronic acids, chelates and form hydrogels in the presence of divalentcations such as Ca2+ . Chelation occur at physiological conditions and the formed hy-drogels are biocompatible and stable. These properties nominates alginate hydrogelsas promising biomaterials in tissue engineering applications. Encapsulation of cells inalginate beads is easily prepared by mixing cells with high molecular weight alginate,and dripping the solution into a CaCl2 solution. When alginate comes into contactwith Ca2+ ions, alginate beads are immediately formed and the cells are captured ina three dimensional alginate matrix. Once inside the alginate capsule, the cells canbe transplanted into a host deﬁcient in the particular cells. The alginate protectsthe cells against the immune system of the host, opening for allograf transplantationwithout immunosuppressiva. The pores in the alginate network are big enough toenable diﬀusion of waste and nutrition through the membrane, which is importantfor cell survival.Alginate is in itself not cell adhesive. However, alginate can be tailored into a celladhesive biomaterial by attachement of cell adhesive peptides, such as the RGDmotif found in extracellular matrix molecules such as ﬁbronectin. Coupling of celladhesive peptides increase cell survival in three dimensional alginate matrices. Inthis study, RGD-alginate is tailored with a chemoenzymatic approach that ensuresRGD-coupling to non-gelling residues. This procedure starts with non-gelling man-nuronan that is chemically modiﬁed by attachement of the cell adhesive peptideGRGDYP by carbodiimide chemistry. Gelling residues are introduced to peptidecoupled mannuronan by a two step epimerisation catalyzed by the epimerases AlgE4and AlgE6.In this study, the carbodiimide chemsitry used for coupling GRGDYP to mannuro-nan is optimalised to create alginate with more than 0.2% bound peptide. Themodel molecules ﬂuoresceinamine, 4-aminophenol and L-tyrosine-methyl ester areused for optimalisation, and the latter model molecule was found to give the bestrepresentation of peptide coupling to mannuronan. The carbodiimide mediated cou-pling to mannuronan is investigated by varying the pH, temperature and reactantconcentrations. The degrees of coupling for each intervention is assessed by 1 H NMRand UV/vis spectroscopy. The presence of covalently bound by-products, namedN-acylurea adducts, to mannuronan is assessed by 1 H NMR spectroscopy and acontrolled reduction of these unwanted compounds is attempted. The results from the optimalisation indicates that coupling of Me-O-Tyr and GRGDYP to mannuro-nan is concentration-dependent, as an increase in coupling was observed when theGRGDYP and Me-O-Tyr concentrations was increased. The highest peptide incor-poration described in this study was 3.4% GRGDYP coupled to mannuronan, whichis higher compared to similar studies.The optimalised carbodiimide chemistry is applied to a large scale batch of RGD-coupled alginate that is to be used for cell encapsulation of olfactory ensheating cellsfrom neonatal rat brain.High molecular weight alginate was coupled with 0.45% GRGDYP and ﬁltratedwith active coal before cell encapsulation. The coal ﬁltration removed a substantialamount of the unwanted N-acylurea adducts but also removed peptides, resultingin a GRGDYP coupling of 0.1% calculated from UV/vis spectroscopy, and 0.4%calculated from 1 H NMR spectroscopy. This indicates that peptides are associatedwith N-acylurea adducts and that active coal ﬁltration is necessary to remove them.Encapsulation of olfactory ensheating cells to RGD-coupled alginate gave no mor-phology changes or enhanced cell viability compared to non-peptide coupled alginate.It is believed that the low enzymatic action of the AlgE6 epimerase, a low concen-tration of peptides or a combination of both, have inﬂuenced the cell viability andlack of morphology changes. Enhanced peptide incorporation can be achieved byincreasing the reactant concentrations of the peptides, but this would lead to a moreexpensive procedure. Increased eﬃcacy, meaning a higher peptide coupling withlower adduct formation, at lower peptide concentrations was not achieved. However,the use of sodium borohydride in combination with periodate oxidised alginates forpeptide coupling should be assessed as a novel approach for increased peptide yieldsat lower peptide concentrations.

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Quong, Douglas. "DNA encapsulation within membrane-coated alginate beads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0017/NQ44561.pdf.

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Hayes, Thomas. "Electrospinning of alginate nanofibres for medical applications." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503858.

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Effective wound management and tissue repair is of significant importance for our increasingly ageing population. The aims of this research were to develop natural polymeric nanofibrous materials and investigate their potential for use in wound dressings and tissue engineering scaffolds; the enhanced performance of which, will improve patient comfort and recovery. This work has focused on the fabrication of alginate nanofibrous materials by electrospinning.

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Richardson, J. Craig. "Bioadhesive sodium alginate suspensions as oesophageal protectants." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410337.

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Anozie, Uchechukwu Chamberlin. "Microencapsulation of Soluble Sulfur by Calcium Alginate." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353388178.

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ANDRIEU, LAURENCE. "Caracterisation d'une alginate lyase de pseudomonas aeruginosa." Paris 11, 1995. http://www.theses.fr/1995PA112264.

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Pseudomonas aeruginosa est une bacterie pathogene opportuniste pouvant entrainer des infections graves, surtout au niveau des poumons des malades atteints de mucoviscidose. Sous l'effet de facteurs environnementaux, les bacteries vont produire des exopolysaccharides, les alginates, facteur important de la virulence de la bacterie. Les alginates sont des polymeres d'acides d-mannuronique et l-guluronique en liaison 1-4. Ils sont hydrolyses par un enzyme specifique, l'alginate lyase, qui catalyse une reaction de -elimination entre deux residus d-mannurosyl ou l-gulurosyl. Une activite alginolytique a ete mise en evidence chez deux souches mucoides de p. Aeruginosa. Cette activite est portee par une proteine homodimerique de 130 kda, intracellulaire en association avec la face interne de la membrane cytoplasmique. Le gene de structure de l'alginate lyase a ete clone a partir d'une banque d'adn genomique construite dans l'adn du phage lambda gt 11. Le gene algl, porte par un fragment de 4,4 kpb, est exprime chez e. Coli y 1090 en une proteine de 130 kda. Le sous-clonage de fragment de 4,4 kpb dans le gene cat du plasmide pbr 329 nous a permis de construire la carte de restriction du fragment, et de montrer que ce gene introduit chez e. Coli mc 1061, etait exprime, ce qui suggere que le gene a ete clone avec son propre promoteur. Les sous-clonages du fragment entier et de fragments de restriction, puis le clonage de fragments issus de l'hydrolyse controlee de l'insert de 4,4 kpb par la dnase i nous ont permis de determiner la totalite de la sequence nucleotidique. L'analyse de la sequence a revele la presence d'une phase ouverte de lecture de 2052 nucleotides, codant pour une proteine de poids moleculaire predit de 74 kda qui est en accord avec celui du monomere de l'alginate lyase determine par electrophorese sur gel sds, et qui doit correspondre au gene algl. De plus, la presence de sequences de fixation des ribosomes et de l'arn polymerase confirment que le gene algl possede son propre promoteur. Ces resultats montrent que l'alginate lyase mise en evidence est differente de celles caracterises chez d'autres souches de p. Aeruginosa

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Damron, Frederick H. "Regulation of alginate production of Pseudomonas aeruginosa." [Huntington, WV : Marshall University Libraries], 2009. http://www.marshall.edu/etd/descript.asp?ref=999.

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Segato, Milena Pinotti. "\"Estudos termoanalíticos do ácido algínico e dos alginatos de metais alcalinos, alcalino-terrosos, amônio, mono-, di- e trietanolamônio\"." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-14052007-103912/.

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Os alginatos de metais alcalinos (Li+, Na+ e K+), alcalino-terrosos (Mg2+, Ca2+, Sr2+ e Ba2+), de amônio, mono-, di- e trietanolamônio foram sintetizados por neutralização do ácido algínico com os respectivos hidróxidos, ou carbonatos, e com as aminas. Os sais foram caracterizados por análise elementar e espectroscopia na região do infravermelho, confirmando as sínteses. Após caracterização, os compostos foram submetidos à análise térmica (TG/DTG, DTA e DSC) para avaliar seu comportamento térmico e seus resíduos de decomposição, que foram caracterizados por IR e XRD. Os alginatos de amônio e etanolamônio se decompuseram com liberação de amônia ao final do experimento. Os alginatos de metais alcalinos foram convertidos nos seus respectivos carbonatos, enquanto os alginatos de metais alcalino-terrosos se decompuseram formando carbonatos, em seguida óxidos. Foi feita uma avaliação de procedimentos de secagem por estufa a vácuo a 40 ºC e liofilização; e o último método mostrou-se mais eficaz. A água residual, não-congelável, sai associada à decomposição do material e não foi possível definir exatamente seu teor. Um método de medir o grau de substituição nos sais das aminas foi desenvolvido com base em 13C ? NMR em fase sólida.
The alkaline (Li+, Na+ and K+), earth-alkaline (Mg2+, Ca2+, Sr2+ and Ba2+), ammonium, mono-, di- and triethanolammonium alginic acid salts were obtained from the neutralization reaction between alginic acid and the respective hydroxides or carbonates, and the amines, The salts were characterized by elemental analysis and infrared spectroscopy, confirming the synthesis. After the characterization, the compounds were submitted to thermal analysis (TG/DTG, DTA and DSC), in order to evaluate their thermal behavior. The thermal decomposition residues were characterized by IR and/or XRD. The NH4+ and ethanolammonium alginates decomposed via NH3 release without residue in the crucible at the end of the experiment. The alkaline alginates were converted to the respective carbonates, and the earth-alkaline decomposed with production of the carbonates followed by convertion to the oxides. An evaluation of drying procedures involving heating under vaccum up to 40°C and lyophilization were performed, pointing better results in the last case. The residual water, of the non-freezing type, was completely released only during the decomposition of the biopolymer, and it was not possible to define its exact content in the samples. An attempt to estimate the substitution degree in the ethanolammonium salts using 13C ? NMR data, in solid state, was also described.

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Jesus, Geise Cristina de. "Desenvolvimento de matrizes poliméricas de alginato e pectina para o cultivo de células imobilizadas de Desmodesmus subspicatus em vinhaça de cana-de-açúcar." Universidade Federal de São Carlos, 2018. https://repositorio.ufscar.br/handle/ufscar/10472.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Among the main industrial wastewaters, sugarcane vinasse figures as an actual environmental concern, due to its polluting potential and large volumes available, about 10 liters per liter of ethanol. Considering the alternatives to vinasse disposal, fertirrigation is the most commonly used. However, it is currently being questioned due to its effects on the soil and on groundwaters, caused by nutrient lixiviation such as potassium. The application of immobilized microalgae for wastewater treatment with emphasis on the removal of nutrients has increased over the last years. The aim of this study was to develop uniform alginate and pectin beads for immobilization of Desmodesmus subspicatus and evaluate its growth and ability to carbon, nitrogen and potassium removal in vinasse. The process parameters of bead production, type and concentration of biopolymer (alginate 1, 2, and 3% w/v and pectin 5, 7 and 10% w/v) and crosslinking agent concentration (calcium chloride 2, 5 and 10% w/v), were varied in order to evaluate their influence on bead characteristics. Results indicated that stable alginate and pectin beads were produced and according to the preliminary particle characterization, concentrations of 2% alginate and 7% pectin were chosen for immobilization of D. subspicatus and growth in vinasse. Immobilized D. subspicatus showed cellular growth in vinasse, with maximum specific rates of 0.009 h-1 and 0.002 h-1 in alginate and pectin beads, respectively. In the tests performed with 2% alginate, the immobilized microalgae reached 42, 49 and 48% carbon; 34, 35 and 34% nitrogen and 22, 23 and 32% potassium removal; and for pectin 7%, the removals were 32, 39 and 41% for carbon; 11, 24 and 34% for nitrogen and 39, 36 and 35% for potassium, for 2, 5 and 10% of calcium chloride, respectively. The microalgae were able to grow and remove appreciable amounts of nutrients from the vinasse. Compared with the free microalgae cultivation, immobilized microalgae indicate good prospects for the use of nutrient removal from vinasse.
A vinhaça é considerada a principal água residuária do setor sucroalcooleiro, sendo obtida pela destilação alcoólica do vinho para a obtenção do etanol. Considerando as alternativas para sua disposição, a fertirrigação na cultura da cana-de-açúcar é a mais utilizada. No entanto, o seu uso deve ser cauteloso, uma vez que em excesso pode culminar na contaminação dos lençóis freáticos, acarretando problemas ambientais. A aplicação de microalgas imobilizadas no tratamento de águas residuárias com ênfase principalmente na remoção de nutrientes tem aumentado nos últimos anos. Quanto aos métodos de imobilização celular, o sistema de encapsulamento em matrizes de macromoléculas como alginato e pectina vem despertando interesse devido às suas características de biodegradabilidade, biocompatibilidade e não toxicidade. Neste contexto, o objetivo do trabalho foi o desenvolvimento de esferas de alginato e de pectina para a imobilização da microalga Desmodesmus subspicatus, assim como a avaliação do seu crescimento e habilidade na remoção de carbono, nitrogênio e potássio da vinhaça. Os parâmetros do processo de produção das esferas, tais como tipo e concentração de biopolímero (alginato 1, 2, e 3% m/v e pectina 5, 7 e 10% m/v) e concentração de reticulante (cloreto de cálcio 2, 5 e 10% m/v) foram estudados quanto a sua influência nas características das esferas. Os resultados indicaram a obtenção de esferas estáveis de alginato e de pectina e, de acordo com os testes, optou-se por utilizar alginato 2% e pectina 7% para imobilização da D. subspicatus e seu cultivo na vinhaça. A microalga D. subspicatus imobilizada apresentou crescimento celular em vinhaça, com velocidades específicas máximas de 0,009 h-1, e 0,002 h-1 em esferas de alginato e de pectina, respectivamente. Nos ensaios realizados com alginato 2%, a microalga imobilizada atingiu remoções de 42, 49 e 48% de carbono; 34, 35 e 34% de nitrogênio e 22, 23,2 e 31,6% de potássio; e para a pectina 7%, as remoções foram de 32, 39 e 41% para carbono; 11, 24 e 34% para nitrogênio e 39,2, 35,8 e 35,2% para potássio para 2, 5 e 10% de cloreto de cálcio, respectivamente. Os resultados demonstraram a viabilidade do cultivo desta microalga, assim como a capacidade de remoção de compostos da vinhaça.

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Alves, Fernanda Germano. "Produção de β-galactosidade de Kluyveromyces marxianus CCT 7082 em fermentador e caracterização parcial da enzima livre e imobilizada." reponame:Repositório Institucional da FURG, 2008. http://repositorio.furg.br/handle/1/2566.

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Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia e Ciência de Alimentos, Escola de Química e Alimentos, 2008.
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A β-galactosidase é amplamente distribuída na natureza, podendo ser encontrada em plantas, órgãos de animais e microrganismos. A hidrólise da lactose via enzimática vem sendo uma alternativa para as indústrias alimentícias, visto que os açúcares resultantes deste processo, glicose e galactose, são mais solúveis e doces, o que proporciona melhorias nas características sensoriais de produtos lácteos e, desenvolvimento de alimentos com baixo teor desse carboidrato, tornando-os ideais a consumidores intolerantes a este açúcar. O aumento da demanda industrial da β-galactosidase resulta na necessidade do estudo da agitação e da aeração, visando obter um produto de elevada atividade. A utilização de enzimas na indústria alimentícia é muitas vezes limitada devido a sua baixa estabilidade. Uma das alternativas é o emprego de enzimas imobilizadas para reduzir os problemas causados pela utilização de enzimas solúveis em aplicações industriais. A presente dissertação teve por objetivo geral o estudo das condições de produção da β-galactosidase de Kluyveromyces marxianus CCT 7082 e caracterização parcial da enzima livre e imobilizada. No primeiro estudo foi avaliada a influência da agitação e da aeração na produção da enzima por fermentação submersa em fermentador Biostat B de 2 L, utilizando a técnica de planejamento experimental, através de um planejamento experimental 22 (4 ensaios e 3 pontos centrais), onde as condições estudadas foram: 200; 350; 500 rpm e 0,5; 1,0; 1,5 vvm para a agitação e a aeração, respectivamente. Neste estudo verificou-se que a agitação e a aeração, exerceram influência na produção da enzima, sendo a condição mais favorável 500 rpm e 1,5 vvm, respectivamente, atingindo uma produtividade de 1,2 U.mL-1.h-1, uma atividade enzimática de 17 U.mL-1 e uma concentração celular de 11 mg.mL-1. Em um segundo estudo foi realizada a imobilização da β-galactosidase empregando a técnica de inclusão em gel de alginato de cálcio, seguida da caracterização das enzimas livre e imobilizada, quanto ao pH e temperatura ótimos, parâmetros cinéticos e estabilidade térmica. Para o estudo da influência do pH na atividade enzimática foram testados valores de pH entre 4,6 e 8,6. A influência da temperatura na reação enzimática foi determinada pela atividade de β-galactosidase nas temperaturas de 25 a 60ºC. Os parâmetros cinéticos foram determinados utilizando como substrato o-nitrofenil-b-D-galactopiranosídeo (ONPG) e lactose. A estabilidade térmica foi estudada determinando-se a constante cinética de desnaturação térmica, o tempo de meia vida e a energia de ativação da reação de desnaturação, incubando-se a enzima nas temperaturas de 30 a 45ºC. Os valores ótimo de pH e temperatura não foram alterados quando a enzima foi imobilizada, obtendo como resultados pH 6,6 e 37ºC, respectivamente, para ambas as formas enzimáticas. Os resultados dos parâmetros cinéticos, Km e Vmax, para a enzima livre foram 15,1 mM e 18,9 U.mL-1; 93,71 mM e 43,9 U.mL-1 para os substratos ONPG e lactose, respectivamente. Para a enzima na forma imobilizada os resultados para Km e Vmax foram 18,5 mM e 3,9 U.mL-1; 115,7 mM e 3,7 U.mL-1, respectivamente, utilizando ONPG e lactose. Com relação à estabilidade térmica enzimática, a equação de Arrhenius pôde ser aplicada para estabelecer uma relação entre a constante cinética de desnaturação térmica e a temperatura. Pela equação de Arrhenius determinou-se as energias da reação de ativação (9,4 e 2,1 Kcal.mol-1) e de ativação da reação de desnaturação (100 e 106 Kcal.mol-1), respectivamente, para b-galactosidase livre e imobilizada.
Production of b-galactosidase from Kluyveromyces marxianus CCT 7082 in fermenter and partial characterization of the soluble and immobilized enzyme β-galactosidase is widely distributed in nature and it can be found in plants, organs of animals and microorganisms. The enzymatic hydrolysis of lactose has been an alternative to the food industries, because the result sugars of this process, glucose and galactose, are more soluble and sweet, providing improvements in sensory characteristics of dairy products, and development of products without lactose, ideal to consumers intolerant to this sugar. The increased of the industrial demand of β-galactosidase results in the necessity to study the agitation and aeration, to obtain a product of high activity. The use of enzymes in the food industries is sometimes limited due to the low stability. One of the alternatives is the use of immobilized enzymes to reduce the problems caused by the use of soluble enzymes in industrial applications. The present dissertation had as main goal the study of the conditions of β-galactosidase production from Kluyveromyces marxianus CCT 7082 and the partial characterization of the free and immobilized enzyme. In the first study, the influence of the agitation and the aeration was evaluated in the enzyme production by submerged fermentation in Biostat B fermenter of 2 L, using experimental design 22 (4 assays with three replicates at the center point); the study conditions were: 200, 350, 500 rpm and 0.5, 1.0, 1.5 vvm for agitation and aeration, respectively. In this study the agitation and aeration, influenced in the β-galactosidase production, and the favorable condition was 500 rpm and 1.5 vvm, respectively, obtaining 1.2 U.mL-1.h-1 for productivity, 17 U.mL-1 for the enzymatic activity and a cellular concentration of 11 mg.mL-1. In a second study of β-galactosidase was immobilized employing the technique of calcium alginate gel inclusion, followed by the characterization of this enzyme, and comparison between free and immobilized enzymes, as for optimum pH and temperature, kinetic parameters and thermal stability. For the study of the influence of pH on the enzymatic activity, values of pH between 4.6 and 8.6 were tested. The influence of temperature on the enzyme reaction was determined at 25 to 60°C. The kinetic parameters were determined employing o-nitrophenyl-b-D-galactopyranoside (ONPG) and lactose. The thermal stability was studied in order to determinate the deactivation rate constant, the half-life and the deactivation energy, incubating the suspension enzyme at 30 to 45°C. The optimum values for pH and temperature weren’t changed by the immobilization process, obtaining as results pH 6.6 and 37°C, respectively. The results for the Km and Vmax for soluble enzyme were 15.1 mM and 18.9 U.mL-1; 93.7 mM and 43.9 U.mL-1 for ONPG and lactose, respectively; and for immobilized enzyme the results for Km and Vmax were 18.5 mM and 3.9 U.mL-1; 115.7 mM and 3.7 U.mL-1, respectively, for ONPG and lactose. In relation to the enzymatic thermal stability, the Arrhenius equation could be applied to establish a relation between deactivation rate constant and temperature. By the Arrhenius equation were determinated the activation energy (9.4 e 2.1 Kcal.mol-1) e deactivation energy (100 e 106 Kcal.mol-1), respectively, for the soluble and immobilized enzyme.

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Mo, Yayuan. "Elaboration et mise en oeuvre de membranes alginate, polyethylenimine à haut pouvoir de percolation : application en tant que matériaux adsorbants ou catalyseurs supportés." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG014.

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L'alginate est un polymère hydrophile et biocompatible portant de nombreuses fonctions carboxyliques et de nombreux groupes hydroxyles. Ce travail a développé et optimisé le procédé de fabrication de membranes à haute pouvoir de percolation à base d'alginate. Ce procédé simple permet, par mélange de deux solutions d’alginate et de polyethyleneimine (PEI), d’obtenir un hydrogel structuré dont la stabilité est améliorée par réticulation (des fonctions aminées de la PEI par le glutaraldéhyde (GA)). Cette double interaction (PEI/alginate, PEI/GA) permet d’obtenir après séchage à l’air libre (donc peu énergivore et sans moyen sophistiqué contrairement aux procédés conventionnels) de produire des membranes macroporeuses autorisant la percolation par drainage simple de solutions. Ce matériau a été développé et utilisé pour deux types d’applications : (a) l’adsorption d’ions métalliques (cationiques et anioniques), et (b) l’hydrogénation de composés nitrophénoliques par catalyse hétérogène. Les membranes et leur interaction avec les ions métalliques ont été analysées par spectroscopie infrarouge et par FTIR, MEB, et XPS. L'adsorbant est caractérisé par la présence de groupements carboxyliques et de fonctions aminées qui offre de nombreuses possibilités d’interaction avec les ions métalliques en jouant tant sur des propriétés de chélation (carboxylates, amines libres) que sur des propriétés d’échange ionique/attraction électrostatique (amines protonés) en fonction de la typologie du métal, de sa spéciation et du pH de la solution. Ces différentes possibilités ont été illustrées par une série d’expérimentations portant sur des ions métalliques tels que : Hg(II), Cu(II), Se(VI), Cr(VI), As(V). Ces différentes études ont permis d’illustrer : l’affinité particulière des membranes pour les anions métalliques (préférentiellement aux cations) en raison notamment de la plus grande disponibilité des fonctions aminées protonées. Par ailleurs, une étude complémentaire a été menée sur de la PEI réticulée par le GA (conditionnée sous forme de poudre) pour explorer l’effet de réticulation de la PEI sur la fixation des ions métalliques. L’étude a permis de démontrer que le taux de réticulation a un effet modéré sur l’adsorption des ions Se(VI). Enfin, après avoir brièvement étudié l’adsorption du Pd(II) sur les membranes, il a été procédé à une réduction du Pd(II) fixé sur le support (partiellement converti en Pd(0)) afin de synthétiser des membranes Pd/PEI/Alginate pour étudier une réaction simple d’hydrogénation du 3-NP en 3-AP. Ceci démontre la faisabilité d’application de ces supports pour une application en catalyse hétérogène
Alginate is a hydrophilic and biocompatible polymer with abundant free carboxyl and hydroxyl groups. This work developed and optimized the process for the fabrication of highly-percolating membranes based on alginate. The simple process has been designed by mixing alginate and polyethyleneimine (PEI) to obtain a structured hydrogel and subsequently improved stability by crosslinking between glutaraldehyde (GA) and amine groups of PEI. This double interaction (PEI/alginate, PEI/GA) makes it possible to produce macroporous membranes, after air-drying (without energy-consuming and sophisticated drying procedure), allowing natural drainage. The prepared membranes have been used for two applications: (a) sorption of metal ions (cationic and anionic), and (b) hydrogenation of nitrophenolic compounds by heterogeneous catalysis. The membranes and their interactions with metal ions were analyzed by FTIR, SEM, and XPS. The adsorbent was characterized by the presence of carboxylic groups and amino functions, which offers numerous possibilities for interacting with metal ions by complexation (i.e., carboxylates, free amines) and ion exchange/electrostatic attraction (i.e., protonated amine groups) depending on the pH of solution and metal speciation. These different possibilities have been illustrated by a series of experiments on metal ions such as Hg(II), Cu(II), Se(VI), Cr(VI), As(V). These various studies illustrate the particular affinity of membranes for metal anions (preferentially to cations) due in particular to the greater availability of protonated amino functions. Furthermore, an additional study was conducted on PEI crosslinked with GA (as a powder) for exploring the effect of the crosslinking of PEI on the binding of metal ions. The study demonstrated that the crosslinking rate has a moderate effect on the sorption of Se(VI) ions. At last, after briefly studying the sorption of Pd(II) on the membranes, a reduction was made of Pd(II) loaded on the support (partially converted to Pd(0)) in order to synthesize catalysis for the hydrogenation of 3-NP to 3-AP. This demonstrates the feasibility of applying these supports for heterogeneous catalysis

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Ben, Amara Chedia. "Étude des interactions polysaccharides – biomolécules antimicrobiennes de nature protéique : application à l’élaboration de microcapsules et de films actifs pour la conservation des aliments." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1247/document.

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Ce travail porte sur le développement de systèmes d’encapsulation à base de polysaccharides et de molécules antimicrobiennes de nature protéique comme le lysozyme du blanc d’œuf et la nisine produite par la bactérie Lactococcus lactis. La coacervation complexe de l’alginate ou la pectine (deux polysaccharides anioniques) avec le lysozyme ou la nisine, chargés positivement sur une large gamme de pH, serait une solution pour protéger ces molécules et assurer une libération contrôlée lors de la conservation d’un aliment. Les polysaccharides utilisés ont été choisis en fonction de leur sensibilité aux enzymes produites par les bactéries cibles. L’ensemble des travaux menés à différentes échelles a mis en évidence (i) le rôle de certains facteurs physico-chimiques (ratio, pH, force ionique,…) sur les interactions mises en jeu entre le lysozyme ou la nisine et l’alginate ou la pectine, (ii) l’influence de ces facteurs sur les propriétés des complexes formés et (iii) le rôle des polysaccharides sélectionnés dans la stabilisation de la structure du lysozyme ou de la nisine lors du séchage par atomisation. Enfin, la structure et l’activité antimicrobienne des films obtenus par voie solvant (casting) et des microcapsules obtenues par atomisation sont étudiées en relation avec les propriétés des complexes formés. Ce travail a permis une meilleure compréhension des mécanismes impliqués dans la formation des complexes peptides/polysaccharides ou protéines/polysaccharides, leur résistance au séchage par atomisation ainsi que leur capacité à protéger et à libérer des molécules actives
This work deals with the development of encapsulation systems based on polysaccharides and antimicrobial molecules of protein nature such as hen egg-white lysozyme and nisin produced by Lactococcus lactis. Complex coacervation of alginate or pectin (two anionic polysaccharides) with lysozyme or nisin, positively charged over a wide range of pH, would be a solution to protect these molecules and ensure their controlled release during food preservation. The used polysaccharides were chosen according to their sensitivity to the enzymes produced by the targeted bacteria. The whole of this work performed at various levels showed (i) the impact of some physicochemical factors (ratio, pH, ionic strength,…) on the interactions between lysozyme or nisin and alginate or pectin, (ii) the influence of these factors on the properties of the formed complexes, and (iii) the role of the selected polysaccharides in stabilizing the structure of lysozyme or nisin during spray-drying. Finally, the structure and the antimicrobial activity of films produced by casting and microcapsules obtained by spray-drying were studied in relation to the properties of the formed complexes. This work makes it possible to contribute to a better understanding of the various mechanisms implied in the formation of peptide/polysaccharide or protein/polysaccharide complexes, their resistance to spray-drying and their ability to protect and release active molecules

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Lima, Daniel Oliveira de. "Influencia de alginato e quitosana na precipitação de fosfatos de calcio." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266944.

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Orientador: Marisa Masumi Beppu
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Abstract: Natural systems are able to create organic-inorganic composites of remarkable properties. Bone, for instance, presents properties that are found both in ceramics and polymers. This effect is related to the organic matrix, which controls nucleation and growth of calcium phosphate crystals, besides composite's organization and architecture in nanometric levels, in order to achieve a better understanding of this process, precipitation of calcium phosphate was carried out in a medium which contained small amounts of alginate and chitosan, seeking to emulate the matrix effect. Calcium phosphates precipitates were obtained using two different concentrations of the biopolymer and one control sample. The experiments were divided in two groups, depending on the system's initial pH. In the first group, the starting pH was acid. However, part of the reaction medium was separated and had its pH adjusted to an alkaline range. In the second group, the initial pH was calculated in order to be in the range of hydroxyapatite stability. Characterization was accomplished by scanning electron microscopy, X-Ray diffraction and Fourier-transform infrared spectroscopy. The powders obtained in the first group were compose mainly by brushite (CaHPO4.2H2O) and its anhydrous phase, monetite, CaHP04. In the first group of experiments with alginate, monetite concentration was related mainly to the reaction medium pH, suggesting that alginate-calcium interaction was strongly dependent on the formation of complexes among carboxyl radicals and calcium, which avoided water bonding. Chitosan-doped samples, on the other hand, seemed to be affected mainly by the biopolymer concentration. Chitosan and monetite concentration seemed to be inversely proportional. This is attributed to the ionotropic effect, which reduced auto-diffusion and consequently, calcium phosphate-chitosan interaction. These samples also possessed an apparent degree of orientation, supposedly due to a coherent growth of calcium phosphate crystals over heterogeneous nuclei. Alginate-doped samples obtained in the second group of experiments presented reduced cristal Unity, which was related to reprecipitation of the crystals over biopolymers nuclei. Chitosan-doped samples, however, presented an increase in crista!Iinity. This may be attributed to a process of nucleation inside the gel, implying in crystalline growth controlled by sterical effects
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

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Paiva, Rafael Gonçalves de. "Obtenção e caracterização de membranas multicamadas de quitosana e alginato contendo cobre." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267188.

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Orientador: Marisa Masumi Beppu
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Estudos envolvendo membranas têm atraído muito interesse nos últimos anos, uma vez que, além da aplicação clássica em processos de separação, estas têm sido usadas também em áreas como medicina, microeletrônica, tratamento de água, etc. À medida que o número de aplicações cresce, a necessidade de criação de estruturas elaboradas também aumenta. Neste contexto, este trabalho realizou a adaptação da técnica "layer-by-layer" de produção de membranas multicamadas, porém visando a produção de membranas com espessuras de ordem micrométricas. Foi realizada, também, a subseqüente incorporação de íons cobre a estas membranas. Caracterizações morfológicas, químicas e cristalinas, além de testes de difusão de íons e avaliação de capacidade bacteriostática das membranas foram realizados. As análises químicas mostraram a interação entre as cadeias de quitosana e alginato, garantindo a estabilidade dimensional da membrana. Foi possível observar também mudanças na cristalinidade das membranas, que se tornaram mais amorfas após a incorporação de íons cobre em sua estrutura. Análises de EXAFS mostraram que estes átomos se ligam preferencialmente aos átomos de oxigênio e nitrogênio constituintes dos grupos funcionais de alginato e quitosana, respectivamente. Além disso, a incorporação de cobre às membranas causou mudanças notáveis na difusividade destas, tornando a difusão de cloreto de sódio mais lenta do que nas membranas sem cobre. A capacidade bacteriostática foi sensivelmente influenciada pela presença do metal nas membranas: as amostras com cobre, independente de sua composição, proporcionaram inibição do crescimento bacteriano, tanto para E. coli quanto para S. aureus, ao passo que as amostras sem cobre não apresentaram capacidade bacteriostática. Esses resultados mostram potencial aplicabilidade destas membranas em situações onde este tipo de capacidade é requerida.
Abstract: Study of membranes has attracted much interest in recent years due to their applicability in areas such as medicine, microelectronics, water treatment, etc. rather than in traditional separation processes. As the application range arises, the need for establishing more elaborated structures also increases. In this context, the present study adapts the layer-by-layer technique for production of micro-scale multilayer membranes. Subsequent incorporation of copper ions is performed n these membranes. Morphological, chemical and crystalline characterizations, besides ion diffusion tests and evaluation of bacteriostatic ability were performed. The chemical analysis showed the interaction between the chains of chitosan and alginate, ensuring the dimensional stability of the membrane. Changes in crystallinity of membranes were also observed, as they became amorphous after the incorporation of copper ions in its structure. EXAFS analysis indicated that these atoms are linked preferentially to oxygen and nitrogen atoms, constituents of alginate and chitosan functional groups, respectively. Moreover, the amount of copper to the membrane caused remarkable changes in its diffusivity, reducing its value in comparison to membranes without copper. The bacteriostatic capacity was significantly influenced by the presence of metal in membranes: the samples with copper, regardless of its composition, provided inhibition of bacterial growth, both for E. coli and for S. aureus, while the untreated control samples showed no bacteriostatic capacity. These results show the potential of using these membranes in applications where this kind of capacity is required.
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

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Mørch, Yrr A. "Novel Alginate Microcapsules for Cell Therapy – A study of the structure-function relationships in native and structurally engineered alginates." Doctoral thesis, Norwegian University of Science and Technology, Norwegian University of Science and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2003.

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Alginate microcapsules have the potential as immune barriers for cell transplantation where the alginate gel protects the transplant from the host immune system. Microencapsulation can thus provide a way to overcome the need for immunosuppressive drugs. The successful use of alginates as immobilization material has, however, been hampered by their mechanical instability and high porosity. To overcome this problem, a polycation layer has traditionally been added to the alginate gels. However, polycations are toxic to cells and provoke inflammatory reactions. Hence, the main goal of the present work was to improve the functionality of alginate gels in order to omit the use of polycations. Alginate gel properties were found to depend strongly on many factors such as the choice of alginate material, choice of gelling ion and method of preparation, all which can be manipulated to form alginate gel beads with enhanced functionality.

In particular, specific enzymes (C-5 epimerases) that modify the alginate chain were used to form novel alginate materials, some with extreme composition not found in nature. Gels of enzymatically engineered alginate were found to be more elastic and compact, less permeable, and extremely stable under physiological conditions, offering significant advantages over native alginates. Hence, by controlling alginate nanostructure in a highly specific way, we were able to manipulate the macroscopic properties.

One of the most striking features of epimerization was the effect seen upon increasing the amount of alternating sequences in the alginate chains using the specific epimerase AlgE4. On the basis of a detailed study on the resulting products of AlgE4 epimerized alginate we hypothesized the direct involvement of the alternating sequences in junction formation. The choice of gelling ions for alginate gel formation was also found to have significant effects on the final gel properties. Interestingly, the effect was highly dependent on the alginate material used. Application of alginates with extreme composition revealed that different block structures in the alginate bound the ions to different extent. Alginate beads with enhanced functionality could hence be formed using a proper combination of ions and alginate material. Finally, confocal laser scanning microscopy (CLSM) was established as a versatile and easy method to visualize the macroscopic character of alginate microcapsules such as the polymer distribution in capsules. Further, effect of different encapsulation procedures on the final capsule characteristics was revealed.

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Behar, Siham. "Synthèse d’oxydes métalliques par voie alginate et leur application dans l’oxydation catalytique des COV." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2013. http://www.theses.fr/2013ENCM0003/document.

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Les composés organiques volatils (COV) contribuent fortement à la pollution atmosphérique. Plusieurs techniques sont possibles pour leur élimination parmi lesquelles, l'oxydation catalytique est une alternative intéressante. Ces dernières années de nombreux efforts ont été entrepris pour la conception de catalyseurs à base d'oxyde de métaux de transition afin de remplacer les métaux nobles, généralement plus actifs pour cette réaction, mais chers. Le principal objectif de cette thèse est le développement de nouveaux catalyseurs à base d'oxyde métallique pour l'élimination du toluène, choisi comme modèle de COV, utilisant l'air comme oxydant. Les catalyseurs ont été préparés à partir de gels ionotropiques d'alginate. Ce biopolymère, un polysaccharide extrait des macro-algues brunes, est un copolymère à blocs fonctionnalisés sur chaque sucre par une fonction carboxylate. La coordination des cations conduit à la formation des gels. Après séchage, la matrice est sacrifiée par traitement thermique et cette voie de synthèse permet d'aboutir à des oxydes métalliques non supportés mais bien dispersés, ainsi qu'un contrôle de la structure, de la composition et de la taille des particules. Tous les matériaux obtenus à base de Fe, Co, Mn, Cu, sont caractérisés par DRX, TPR, MEB, MET, ATG, XPS, EDS, AE, adsorption-désorption d'azote. Parmi les oxydes (oxydes simples et mixtes) évalués comme catalyseurs dans la réaction d'oxydation totale du toluène en phase gaz, l'oxyde mixte cuivre-manganèse a été le plus prometteur. Sa performance est attribuée à la présence de la phase mixte de type spinelle Cu1.5Mn1.5O4 obtenus indépendamment de la structure de l'alginate. Ce catalyseur n'a pas montré de désactivation en fonction du temps (75 h) ni au cours de cycles successifs d'utilisation. Ses propriétés texturales et structurales sont conservées. Enfin, plusieurs modèles cinétiques (loi de puissance, modèle de Langmuir – Hinshelwood et le modèle de Mars-van Krevelen) ont été ajustés aux données expérimentales. L'analyse complète des données cinétiques a permis de conclure que la vitesse de réaction d'oxydation totale du toluène en phase gaz sur l'oxyde mixte cuivre manganèse, est mieux décrite par un modèle de type Mars-van Krevelen
Volatile organic compounds (VOCs) contribute significantly to air pollution. Several techniques are available for their elimination including the interesting catalytic oxidation. In recent years many efforts have been made to design catalysts based on transition metal oxide to replace noble metals, usually more active for this reaction, but more expensive. The main objective of this thesis is the development of a new synthesis way to produce catalysts based on metal oxide for the removal of toluene, chosen as a model VOC, using air as oxidant. The catalysts were prepared using ionotropic alginate gels as precursors. This biopolymer, a polysaccharide extracted from brown macroalgae is a block copolymer functionalized on each sugar unit by a carboxylate function. The carboxylate- cations coordination leads to the formation of gels. After drying, the matrix is eliminated by thermal treatment and this synthesis route can lead to unsupported but well dispersed metal oxides with a good control of the structure, composition and particle size. All materials obtained based on Fe, Co, Mn, Cu, were characterized by XRD, TPR, SEM, TEM, TGA, XPS, EDS, EA, and adsorption-desorption of nitrogen. Among the oxides (single and mixed oxides) evaluated as catalysts in the reaction of toluene oxidation in gas phase, the copper manganese oxide was the most promising catalyst. Its performance is attributed to the presence of the spinel mixed phase Cu1.5Mn1.5O4, obtained independently of the alginate structure. This catalyst showed no deactivation over time (75 h) or after successive uses. Its textural and structural properties were preserved. Finally, several kinetic models (power law model, Langmuir - Hinshelwood model and Mars-van Krevelen model) were fitted on experimental data. The complete analysis of the kinetic data allowed to conclude that the rate of toluene total oxidation reaction in gas phase on copper manganese mixed oxide, is best described by a Mars-van Krevelen model

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Lins, KÃzia Oliveira Abrantes de Lacerda. "Estudo das atividades antitumoral e inflamatÃria do alginato isolado da alga Sargassum Vulgare C. Agardh." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7855.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
O cÃncer Ã uma doenÃa que afeta cada vez mais um nÃmero maior de pessoas em todo o mundo. As terapias atuais utilizadas para o tratamento do cÃncer sÃo ainda insatisfatÃrias. Produtos naturais tÃm sido avaliados para seleÃÃo de compostos ativos, capazes de reduzir os tumores malignos de uma forma mais eficiente e com menos efeitos indesejÃveis. O alginato extraÃdo da alga Sargassum vulgare C. AGARDH (SVHV) foi testado para avaliaÃÃo do seu potencial antitumoral e imunoestimulante. AlÃm disso, foram feitos testes de toxicidade do fÃgado, rins e baÃo apÃs o tratamento com SVHV. Os resultados demonstraram que SVHV nÃo apresenta citotoxicidade in vitro, mas Ã capaz de reduzir o tumor Melanoma B-16 implantado em camundongos em 75,8% na dose de 25mg/kg/dia, quando administrado por via intraperitoneal (p < 0,05), enquanto nÃo houve inibiÃÃo por via oral. As anÃlises do fÃgado e rins revelaram que houve toxicidade no rim, com Ãreas de hemorragia glomerular e intersticial nos camundongos tratados com SVHV. Essas alteraÃÃes sÃo, entretanto, consideradas reversÃveis. As anÃlises bioquÃmicas, revelaram um aumento nos nÃveis sÃricos da alanina aminotransferase (ALT) nos grupos com tumor ou tratado com SVHV por via oral e os testes hematolÃgicos revelaram um aumento na porcentagem de neutrÃfilos nestes grupos, enquanto que a porcentagem de monÃcitos foi reduzida nos grupos com tumor e nos tratados com SVHV por via intraperitoneal. TambÃm foi demonstrado que SVHV age como agente imunoestimulante e imunomodulador, ativando macrÃfagos in vitro, assim como sendo capaz de causar inflamaÃÃo atravÃs do teste do edema de pata e induzir a migraÃÃo de neutrÃfilos para a cavidade peritoneal. Conclui-se entÃo que SVHV apresenta atividade antitumoral e que esta atividade estÃ relacionada com suas propriedades imunoestimulantes.
Cancer is a disease that occurs in a larger number of people each year. The therapies used to treat it are still not satisfatory. Natural products have been studied to select new compounds capable of reducing tumours and with fewer side effects. The alginate isolated from the seaweed S. vulgare (SVHV) was investigated for its antitumor and immunostimulating properties and also for the toxicological aspects related to SVHV treatment. The SVHV did not show any significant in vitro cytotoxic effect, but showed a strong in vivo antitumor effect. The inhibition rates of Melanoma B-16 tumor development was 75,8% at the dose of 25 mg/kg/day when treated by intraperitoneal route (p < 0,05). The histopathological analysis of liver and kidney showed that the kidneys were affected by SVHV-treatment, presenting some hemorragic areas. The enzymatic activity of alanine aminotransferase, was augmented in mice with tumor or treated with SVHV by oral route. In hematological analyses, these groups showed a higher percentage of neutrophils, while the group with tumor or treated with SVHV by intraperitoneal route showed a reduction in the percentage of monocytes. It was also demonstrated that SVHV acts as an immunomodulatory agent, stimulating macrophages in vitro, causing paw edema in rats and neutrophil migration to the intraperitoneal cavity. In conclusion, SVHV has some interesting antitumour activity that is associated with its immunostimulanting properties.

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Sachetto, João Paulo. "Efeito do tratamento térmico de STx-1b-Li+ na condutividade de filmes de STx-1b-Li+ /Alginato de sódio." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-06052016-084651/.

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Neste trabalho foram estudados os efeitos causados pelo tratamento térmico na argila STx-1b-Li+ na condutividade de filmes argila/alginato de sódio. O argilomineral STx-1b foi submetido à substituição isomórfica do cátion Na+ por Li+ e posteriormente ao tratamento térmico em diferentes temperaturas. As argilas STx-1b-Li+ não tratada e tratada termicamente foram caracterizada por difração de raios-X (DRX) e termogravimetria (TG). As curvas TG mostraram que o argilomineral STx-1b-Li+ apresentou três perdas de massa que podem ser atribuídas à água adsorvida na argila, a água de hidratação dos íons Li+ e a água estrutural da argila. Para as argilas STx-1b-Li+ tratadas termicamente não foi observado a perda de massa associada à água quimicamente ligada aos contra-íons Li+. Estes resultados estão em concordância com os obtidos por DRX, onde observou-se uma diminuição no espaçamento interlamelar nas argilas tratadas termicamente. Em adição, foram preparados filmes de alginato de sódio com as argilas STx-1b-Li+ não tratada e tratada termicamente e estes foram caracterizados por calorimetria exploratória diferencia (DSC) e espectroscopia de impedância eletroquímica (EIE). As curvas DSC mostraram um aumento na temperatura de transição vítrea (Tg) dos filmes com o aumento da temperatura utilizada no tratamento das argilas. Este aumento nos valores de Tg é um indicativo que a mobilidade das cadeias diminuiu nos filmes polímero/argila que contém argilas tratadas em temperaturas mais elevadas. A espectroscopia de impedância eletroquímica (EIE) foi usada para avaliar-se a condutividade iônica dos filmes. Os resultados indicaram que os filmes contendo argilas que foram tratadas com temperaturas mais altas apresentaram menor condutividade.
In this work the effects caused by the heat treatment in STx-1b-Li+ clay on the conductivity of sodium alginate/clay were studied. The clay mineral STx-1b was submitted to isomorphous substitution of the Na+ for Li+ cation and subsequently to heat treatment at different temperatures. The STx-1b-Li+ clays untreated and heats treated were characterized by X-ray diffraction (XRD) and Thermogravimetric Analysis (TG). The TG curve showed that the clay mineral STL-1b-Li+ had three mass losses which can be attributed to adsorbed water in the clay, the water of hydration of the Li+ ions and structural clay water. To STx-1b-Li+ clays heat treated there were no mass loss associated to the water chemically bound to Li+ counter ions. These results are in agreement with those obtained by XRD, which it was observed a decrease in interlayer spacing in the heat treated clay. In addition, they were prepared sodium alginate films with STx-1b-Li+ clays untreated and heat treated and these films were characterized by Differential Scanning Calorimetry (DSC) and Electrochemical Impedance Spectroscopy (EIS). DSC curves showed an increase in glass transition temperature (Tg) of the films with temperature increasing used in the treatment of clays. This increase in Tg value is an indicative that the mobility of the chains had decrease in the polymer/clay films which contains heat treated clays at higher temperatures. The electrochemical impedance spectroscopy (EIS) was used to evaluate the ionic conductivity of the films. The results indicate that films containing clays which have been treated at higher temperatures had lower conductivity.

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Meira, Daniela Martins. "Desinfecção de alginato." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/29453.

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A presente dissertação, composta de dois manuscritos, buscou preencher lacunas do conhecimento no que diz respeito à desinfecção de impressões de alginato. O primeiro trabalho foi realizado com o intuito de avaliar a eficácia antimicrobiana da solução de glutaraldeído 2% através do seu comportamento bactericida e bacteriostático quando utilizada para desinfecção de impressões de alginato dos pacientes de uma clínica de ensino odontológico de uma instituição federal, durante 28 dias. Logo após a ativação de 3L da solução desinfetante e sempre após a desinfecção de 10 impressões, foram coletadas amostras de 05 mL da solução para a análise microbiológica. No período avaliado, foram imersas 70 impressões de alginato na solução desinfetante. Nenhuma amostra apresentou bactérias viáveis, caracterizando o perfil bacteriostático da solução. Todas as amostras foram capazes de inibir o crescimento de Escherichia coli, Pseudomonas aeruginosa, e Staphylococcus aureus, confirmando o poder bactericida da solução, mostrando que um volume de 3L de glutaraldeído 2% é eficaz como desinfetante de até 70 impressões de alginato ao longo do período de 28 dias. O segundo estudo preocupou-se em avaliar a eficácia do glutaraldeído 2% e do ácido peracético 0,2% em eliminar o microrganismo Staphylococcus aureus, sabidamente presente nos corpos de prova de alginato. Os corpos de prova de alginato foram contaminados com caldo de cultura contendo S. aureus. Estes foram divididos em seis grupos: controle, lavado em água estéril, imersão em glutaraldeído 2% por 5 ou 10 min e imersão em em ácido peracético 0,2% por 5 ou 10 min. Após o tratamento, cada corpo de prova foi incubado em tubo de ensaio com 20 mL de caldo BHI estéril. Posteriormente, amostras do caldo de todos os grupos foram semeadas para determinar a presença de células viáveis. Os resultados mostraram que os grupos controle e o lavado em água estéril apresentaram crescimento bacteriano e que ambos desinfetantes foram eficazes em eliminar S. aureus do alginato tanto após 10 quanto 5 min, de imersão. Os achados desta dissertação permitem concluir que: 3L de solução de glutaraldeído são eficazes para desinfetar até 70 impressões de alginato e que o glutaraldeído 2% e o ácido peracético 0,2% são eficazes na desinfecção de alginato contaminado com S. aureus.
This research made an effort to amplify the knowledge about disinfection of alginate dental impression. The aim of the first study was to evaluate the efficacy of 2% glutaraldehyde solution after successive immersions of contaminated alginate impressions of dental patients from a Dental School by analyzing its bacteriostatic and bactericidal activity through 28 days. After the disinfection of every 10 alginate impressions a 10mL sample of the disinfectant solution (05mL) was collected to be microbiological analyzed. In this period, 70 alginate impressions were immersed in the solution. No viable bacterial grouth was observed at any of the microbiology analyses. All the samples tested were able to inhibit the bacterial growth of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The bacteriostatic and bactericidal activity of 2% glutaraldehyde solution was confirmed and 3L of the solution can be safetely used for the disinfection of at least 70 impression during 28 days. The aim of the second study was to evaluate the efficacy of 2% glutaraldehyde and 0.2% peracetic acid against Staphylococcus aureus. Alginate specimens were contaminated at S. aureus culture media. Specimens were divided into six groups: control, washed in sterile water, immersed in 2% glutaraldehyde for 5 or 10 minutes and immersed in 0,12% peracetic acid for 5 or 10 minutes. The results showed that control and sterile water showed bacterial growth and that both disinfectants (glutaraldehyde and peracetic acid) showed efficacy against S. aureus for both immersion period of time (5 and 10 minutes). The findings of these studies allowed the conclusion that 3L of glutaraldehyde solution showed efficacy to disinfect up to 70 alginate impressions and that, both 2% glutaraldehyde and 0.2% peracetic acid are efficient to disinfect S. aureus contamined alginate impressions.

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Laouadi, Ornella Laura Nathalie. "Enantioselective Friedel-Crafts reaction catalysed by alginate aerogels." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18622/.

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Alginates are polysaccharides derived from brown algae, available in nearly unlimited amounts at very low prices. In the presence of some divalent metals, these renewable biopolymers can readily form hydrogels, solvogels and aerogels, characterized by high surface areas, good mechanical properties, tolerance to different media, and easy manageability. For these reasons, alginates are nowadays being thoroughly studied in heterogeneous catalysis; several applications in supported metal catalysis and as heterogeneous Brønsted acids have emerged. However, none of these studies has given an answer to the following intriguing question: can we use the intrinsic chirality of alginates to induce enantioselectivity in a chemical reaction? In order to answer this question a representative reaction, the Friedel-Crafts alkylation of nitroalkenes with indoles, was tested in this master thesis. This study, which involved a large screening of a variety of alginate gels under different reaction conditions, showed that Cu2+ and Ba2+ are the best cross-linking metals to promote the Friedel-Crafts reaction. Indeed, good activity with moderate enantiomeric excesses were obtained under the optimized reaction conditions. Furthermore, these two metals allowed the access to both enantiomers of the products, an important aspect given that only one enantiomeric form of alginates is available. Finally, the heterogeneous nature of the catalysis by one of the two gels was proved, and a good recyclability was demonstrated, by showing that the same catalyst can be used at least five times with similar results.

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Ho, Jason G. S. "Retention of double-stranded DNA within alginate beads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0007/MQ45277.pdf.

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Partap, Sonia. "Controlled porosity alginate hydrogels from emulsion templating techniques." Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429360.

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Heywood, Hannah Kate. "Chondrocyte metabolism in alginate constructs for tissue engineering." Thesis, Queen Mary, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415428.

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Farrell, Robert. "Characterisation of alginate liquor extracts from brown seaweeds." Thesis, Glasgow Caledonian University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443163.

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Sartori, Celine. "The characterisation of alginate systems for biomedical applications." Thesis, Brunel University, 1997. http://bura.brunel.ac.uk/handle/2438/7399.

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This research project focused on a range of polysaccharides, including sodium alginates (with varying mannuronic (M)/guluronic (G) acid ratio), pectin and sodium carboxymethylcellulose (CMC), for wound dressing applications. The samples were prepared as mixed salts such as sodium/calcium salts as Ca2+ ions are known to promote faster healing. The aims of this research were: 1- to provide a greater insight into the nature of binding between various ions (NaT, Ca2+ as well as Zn2+ and Ag+) and the polysaccharide molecules. Interactions between alginate/pectin and alginate/CMC molecules were also studied. This was achieved using a range of analytical techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy and neutron spectroscopy, thermogravimetric analysis, microprobe analysis, X-ray diffraction and atomic absorption spectroscopy. It was found that sodium ions were bound to the carboxyl groups of the alginate molecules, whilst calcium ions attached themselves onto COO- as well as onto the alginate backbone, leading to crosslinked structures. Appearance of OH ... -OOC to the detriment of OH ... OH bonding was also observed. Addition of zinc ions involved greater constraint in the alginate network and the silver ions were believed to produce insoluble alginate salts, due to their larger ionic radius; furthermore hydroxyl-hydroxyl interactions in the silver alginate were rather between the polymer molecules than with the water. The addition of pectin to alginate led to partial binding between the two polysaccharides via hydrogen bonds. By contrast, carboxymethylcellulose molecules were found to act as independent entities in contact with alginate, and therefore suggested incompatibility. 2- to determine the performance of sodium/calcium alginate systems as well as Na/Ca alginate/pectin and Na/Ca alginate/CMC systems, in order to improve properties such as absorbency, gel strength and calcium release (to assess the haemocompatibility) in a simulated serum solution. A greater calcium and guluronic acid content was found to improve the gel strength of alginate samples, but decrease the swelling ability. Calcium release was favoured with a low G and a high calcium content. Addition of a second polysaccharide enhanced these gel properties. For example, the gel strength could be significantly increased with a 25 % pectin addition, while addition of CMC up to 50 % increased both the swelling and the calcium release. 3- to develop a new model of the ion release process for a polysaccharide system brought into contact with a simulated serum solution. It was based on a "hoppingtrapping" mechanism for the calcium ions, whereby different release rates are due to different affinities with the polysaccharide blocks.

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Laidler, Steven. "Gastric mucin glycoform structure and interaction with alginate." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427330.

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Johnson, Fiona Ann. "The physico-chemical characterisation of alginate raft systems." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297175.

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Tabriz, Atabak Ghanizadeh. "3D biofabrication of cell-laden alginate hydrogel structures." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3370.

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Biofabrication has been receiving a great deal of attention in tissue engineering and regenerative medicine either by manual or automated processes. Different automated biofabrication techniques have been used to produce cell-laden alginate hydrogel structures, especially bioprinting approaches. , These approaches have been limited to 2D or simple 3D structures, however. In this thesis, a new extrusion-based bioprinting technique and a new simple, manual 3D biofabrication method are presented to culture cells in 3D. These methods do not rely on any complex fabrication methods. The bioprinting technique was developed to produce more complex alginate hydrogel structures. This was achieved by dividing the alginate hydrogel cross-linking process into 3 stages: primary calcium ion cross-linking for printability of the gel, secondary calcium cross-linking for rigidity of the alginate hydrogel immediately after printing and tertiary barium ion cross-linking for the long-term stability of the alginate hydrogel in the culture medium. Simple 3D structures including tubes were first printed to ensure the feasibility of the bioprinting technique. Complex 3D structures, such as branched vascular structures, were subsequently printed successfully. The static stiffness of the alginate hydrogel after printing was 20.18 ± 1.62 kPa which was rigid enough to sustain the integrity of the complex 3D alginate hydrogel structure during the printing. The addition of 60 mM barium chloride was found to significantly extend the stability of the cross-linked alginate hydrogel from 3 days to beyond 11 days without compromising the cellular viability. The results based on cell bioprinting suggested that the viability of U87-MG cells was 92.94 ± 0.91 % immediately after bioprinting. Cell viability was maintained above 88 ± 4.3 % in the alginate hydrogel over a period of 11 days. On the other hand, the manual biofabrication approach developed in this thesis enabled the fabrication of scalable 3D cell-laden hydrogel structures easily, without complex machinery. The technique could be carried out using only apparatus available in a typical cell biology laboratory. The fabrication method would involve micro coating cell-laden hydrogels covering the surface of a metal bar by dipping into cross-linking reagent CaCl2 or BaCl2, to form hollow tubular structures. This method could be used to form single- or multi-layered tubular structures. This fabrication method has incorporated the use alginate hydrogel as the primary biomaterial and secondary biomaterial could be added depending on the desired application. The feasibility of this method has been demonstrated by showing the cell survival rate and normal responsiveness of cells within these tubular structures using mouse dermal embryonic fibroblast cells and human embryonic kidney 293 cells containing a tetracycline responsive red fluorescence protein (tHEK cells). By adjusting the fabrication protocol, complex hollow alginate hydrogel structures could be generated.

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Martins, Evandro. "Oil encapsulation in alginate membrane by inverse gelation." Nantes, 2015. http://www.theses.fr/2015NANT077F.

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L’encapsulation d’huile par gélification inverse consiste à ajouter, goutte-à-goutte, une émulsion de chlorure de calcium/huile dans un bain d’alginate. Lesions Ca2+ migrent ensuite à travers l’émulsion vers l’extérieur du bain et réticulent les macromoléculesd’alginate (gélification inverse). Des capsules millimétriques (3- 7 mm) avec une morphologie coeurcouronne sont ainsi formées. La production de capsules de taille inférieure à 1 mm par gélification inverse n’a cependant jamais été démontrée. L’intérêt des microcapsules repose sur un vaste champ d’applications pour lesquelles la capsule ne doit pas ou peu interférer avec la texture ou l’apparence du produit final. L’objectif de la thèse repose ainsi sur le développement de procédés de gélification inverse en visant une réduction de la taille des capsules. De plus, la compréhension du mécanisme de gélification inverse à partir des émulsions huile-dans-eau (H/E) et eau-dans-huile (E/H) a aussi été étudié. Une méthode de dispersion a ainsi été proposée afin de réduire la taille des capsules, qui consiste à former des gouttelettes par dispersion de l’émulsion dans un bain d’alginate sous agitation. Après réticulation de l’alginate pour former la membrane, des microcapsules de tailles comprises entre 370 et 600 μm ont été obtenues. La méthode de dispersion a ensuite été adaptée à un procédé millifluidique afin de contrôler la polydispersité en taille de microcapsules. Des capsules monodisperses en taille avec des diamètres de 140 μm jusqu’à 1. 4 mm ont ainsi été produites par millifluidique
Encapsulation of oil by inverse gelation consists of dropwise addition of a calcium chloride/oil emulsion into an alginate bath. Calcium ions inside the emulsion migrate towards the bath cross-linking the alginate molecules (inverse gelation). Millimetric capsules (3-7 mm) with a core-shell structure are formed. However, the production of capsules with sizes lower than 1 mm by inverse gelation was never demonstrated. The interest of microcapsules is based on a vast range of applications for which the capsule does not have to or little interfere with the texture or the appearance of the end product. The objective of this thesis is therefore to develop an inverse gelation process that yields capsules at reduced sizes. In this frame, the comprehension of the inverse gelation mechanisms from oil-in-water (O/W) and water-in-oil (W/O) emulsions was also studied. In order to reduce the capsules size, a dispersion method was proposed. A dispersion method was therefore proposed to reduce the size of capsules, which consists in the formation of droplets by dispersion of the emulsion in a bath of alginate under stirring. After cross-linking of alginate to form the membrane, microcapsules of sizes between 370 and 600 μm were obtained. To control the wide size distribution of the microcapsules, the dispersion method was adapted for the millifluidic method. Monodispersed capsules with desired mean particle size were produced. The mean size of the particles (within 140 μm to 1. 4 mm) was controlled by variation in the flow rates of the dispersed and continuous phases in the millifluidic circuit

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Avakian, A. "3D-bioprinting system for fabrication of alginate microfibers." Thesis, АНПРЭ, ХНУРЭ, Издательство «Точка», 2017. http://openarchive.nure.ua/handle/document/4074.

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Abstract:

The given work is devoted to the theme of 3D-printing of alginate microfibers with encapsulated stem cells which are used for the nerve regeneration. The motorized printing device is developed and tested. The appropriate software controls the device and allows to design the printing structures.

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Dissertations / Theses on the topic 'Alginate'

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