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Matak, Kristen Erica. "Lactose Hydrolysis by Fungal and Yeast Lactase: Influence on Freezing Point and Dipping Characteristics of Ice Cream". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/30998.
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Two studies were conducted to examine the effects of lactose hydrolysis on freezing point and dipping characteristics of ice cream. The overall research objective was to determine changes in freezing point, texture and ease of dipping ice cream as a result of lactose hydrolysis. It was also the goal of this research to relate observations from the sensory dippability study with hardness and yield stress data to determine if the latter methods could be used as an alternative to human testing of dippability.
In the first experiment, ice cream mixes were treated with lactase (EC 3.2.1.23) to cause 0 to 83% lactose hydrolysis. Lactose hydrolysis decreased the freezing point from -1.63oC in the control (0% hydrolysis) to -1.74oC in the 83% hydrolyzed sample (p < 0.05). Firmness decreased from 0.35 J in the control sample to 0.08 J in the 83% hydrolyzed sample. Lactose hydrolyzed samples melted at a faster rate than the control. There was a difference (p < 0.05) in ease of dipping between samples treated with lactase and the control. There were no perceived differences in sweetness and coldness.
In the second study, ice cream mixes were treated with lactase (EC 3.2.1.23) from the microbial sources Kluyveromyces lactis and Aspergillus oryzae to cause 0 to 100% lactose hydrolysis. Compression measurements and yield stress as measured by the vane method were both affected by the temperature of the samples. R2 values for compression measurements as related to lactose hydrolysis were higher then those obtained for yield stress measurements. Human evaluation determined a difference (p < 0.05) between the control samples (0% hydrolyzed) and the treatment groups (80% and 100% hydrolyzed).
This research demonstrated a relationship between lactose hydrolysis and ease of dipping ice cream. The results implied that the effect of lactose hydrolysis on the dipping characteristics could be evaluated successfully by three different methods: the vane method, compression measurements, and human evaluation. Changes in freezing point due to lactose hydrolysis were minimal, implying that monitoring freezing point is not enough to determine textural characteristics.Master of Science
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Kreft, Mary Ellen. "Lactose hydrolysis by sonicated cultures of Lactobacillus delbrueckii subsp. bulgaricus 11842". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60448.pdf.
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Chaudhary, Manoja Nand, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty y School of Food Science and Technology. "An evaluation of nanofiltration and lactose hydrolysis of milk UF permeate for use in ice cream". THESIS_FSTA_FST_Chaudhary_M.xml, 1997. http://handle.uws.edu.au:8081/1959.7/741.
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This study aimed to obtain 15% total solids and reduced mineral content in milk UF permeate by nanofiltration, hydrolysing the lactose content of nano-concentrate enzymically, partially substituting sucrose in ice cream formulations with hydrolysed lactose nano-concentrate (HLNC), and investigating the effects of HLNC on the physio-chemical and sensory characteristics of ice cream. The desired 15% total solids in the nano-concentrate was achieved after three fold concentration of milk UF permeate. The colour of milk permeate changed, pH and mineral content decreased, and crude protein content, lactose content and titratable acidity increased. The lactose content was hydrolysed by enzyme lactase. HLNC was used to replace 25% and 50% of sucrose in ice cream formulations. Springiness, cohesiveness, chewiness, adhesiveness, hardness, iciness, Ph and colour were not significantly affected. Viscosity, freezing point, glass transition temperature, melting temperature, gumminess and sweetness were significantly decreased, whereas freezing time, saltiness and cooked flavour were significantly increased. The overall acceptability of ice cream significantly decreased at 50% but was insignificantly affected at the 25% level. These results indicate that about one quarter of sucrose could be replaced by HLNC.Master of Science (Hons) (Food Technology)
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Bury, Dean. "Growth and disruption of Lactobacillus delbrueckii spp. bulgaricus for lactose hydrolysis applications". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0009/MQ60097.pdf.
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Ribeiro, Cátia Vanessa Carvalho. "Ensaios de fabrico de queijo fresco com teor reduzido de lactose". Master's thesis, ISA, 2013. http://hdl.handle.net/10400.5/6463.
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Mestrado em Engenharia Alimentar - Instituto Superior de AgronomiaIt can be stated that one third of Portugal’s population suffer of lactose intolerance. The main objective of this study was the development of a new product in our market, originated in Portugal, low lactose fresh cheese. Were tested various enzymatic hydrolysis methodologies, in order to know what is the enzyme’s actuation time on milk or cheese required to hydrolyze the biggest lactose content. The enzyme was added 3 and 18 hours at 6C and 1 hour at 30C, before the beginning of manufacture, and, added at the time of addition of the remaining ingredients, during cheese manufacture. Have also been developed assays with the addition of different amounts of salt, to minimize the predictable effects of lactose hydrolysis, like the increase of sweetness. After 3-4 days of conservation, was achieved a degree of lactose hydrolysis above 90% (93- 97%). Upon reaching concentrations levels less than 0,5g of lactose per 100g of cheese (0,5%, m/m), the product may be considered as low lactose fresh cheese. The different methodologies of manufacture didn’t affect the positive opinion of the tasters, during the sensory evaluation.
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Trevisan, Ana Paula. "INFLUÊNCIA DE DIFERENTES CONCENTRAÇÕES DE ENZIMAS LACTASE E TEMPERATURAS SOBRE A HIDRÓLISE DA LACTOSE EM LEITE PASTEURIZADO". Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/5654.
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The intolerance to lactose is the most common intolerance to carbohydrates among people of all ages and it affects about 70% of the adult population worldwide. Due to the
prevalence of this condition on the world population, the commercial interest on milk and derivatives with reduced amount of lactose has increased. Such product can be obtained through lactose hydrolysis, mainly through the enzymatic method, using lactase enzyme. The level of lactose hydrolysis depends on the dosage of J-galactosidase in milk, as well as on its processing conditions and, for this reason, it is extremely important to evaluate the influence of such conditions concerning obtainment of milk with reduced amount of lactose, such as temperature during hydrolysis and lactase concentration, over the efficiency of the hydrolysis process and over the physical, chemical and microbiological characteristics of the fina product. The aim of the present study was to observe the influence of different temperatures
and concentrations of lactase enzymes over the lactose hydrolysis in pasteurized milks. Samples of pasteurized milks from the Usina Escola de Laticínios (UFSM) were used.
Lactase enzyme, supplied by two companies, was added to the milk in different quantities (0.1g/L; 0.2g/L; 0.5g/L; 0.8g/L e 0.9g/L) and hydrolysis was accomplished in different temperatures (7.9ºC; 12ºC; 22ºC; 32ºC e 36.1ºC). These two variables were combined through Response Surface Methodology (RSM) by rotational composed central delineation. Hydrolysis was followed by crioscopy until it reached stabilization. Physical, chemical and microbiological analysis were carried out before and after lactose hydrolysis, and sensorial analysis was carried out after hydrolysis. Lactase enzyme input modified physical and chemical properties and characteristics of milk, reducing pH, crioscopy, fat and lactose levels and increasing density, total dry extract (TDE), free-fat dry extract (FDE), glucose and protein levels. There was a difference between the efficiency of the two enzymes on the reduction of the lactose level. Lactose hydrolysis reached values in between 80% and 100%, reducing
lactose level to less than 1g/100g, thus enabling milk ingestion by individuals who are intolerant to this carbohydrate. Higher percentages of hydrolysis and, consequently, lower lactose levels were verified in temperatures in between 15 and 30°C, using enzyme
concentrations in between 0.6 and 1.0 g/L. The average total count after hydrolysis was beyond the limit established by law, but concerning the count per milk sample, using enzyme 1 and 2, treatments three and seven did not exceed this limit, respectively. Higher values of total count were found at the highest temperatures and using lowest enzyme concentrations. Differences among milk samples with different lactose levels were not sensorially perceived through triangular test.A intolerância à lactose é a intolerância a carboidrato mais comum entre pessoas de todas as faixas etárias e afeta cerca de 70% dos adultos do mundo. Devido à prevalência desta condição na população mundial, tem aumentado o interesse comercial nos leites e derivados com teor reduzido de lactose. E isto pode ser obtido através da hidrólise da lactose, principalmente pelo método enzimático, com a utilização da enzima lactase. O grau de hidrólise da lactose depende da dosagem da J-galactosidase no leite e das condições de processamento e por isto, é extremamente importante avaliar a influência dessas condições para obtenção do leite com teor reduzido de lactose, como temperatura durante a hidrólise e concentração da lactase, sobre a eficiência do processo de hidrólise e sobre as características físico-químicas e microbiológicas do produto final. O objetivo do presente estudo foi observar a influência de diferentes temperaturas e concentrações de enzimas lactase sobre a hidrólise da lactose em leites pasteurizados. Foram utilizadas amostras de leite pasteurizado, proveniente da Usina Escola de Laticínios (UFSM). A enzima lactase, fornecida por duas empresas, foi adicionada ao leite em diferentes concentrações (0,1g/L; 0,2g/L; 0,5g/L; 0,8g/L e 0,9g/L) e a hidrólise foi realizada a diferentes temperaturas (7,9ºC; 12ºC; 22ºC; 32ºC e 36,1ºC), sendo estas duas variáveis combinadas entre si através da Metodologia de Superfície de Resposta (MSR) por delineamento central composto rotacional. A hidrólise foi acompanhada por crioscopia até que esta se estabilizasse. Foram realizadas análises físicoquímicas e microbiológicas antes e após a hidrólise da lactose e análise sensorial após. A adição da enzima lactase modificou características e propriedades físico-químicas do leite, reduzindo pH, crioscopia, teores de gordura e lactose e aumentando densidade, extrato seco total (EST), extrato seco desengordurado (ESD), teores de proteína e glicose. Houve diferença entre a eficiência das duas enzimas na redução do teor de lactose. A hidrólise da lactose atingiu valores de 80% a 100%, reduzindo o teor de lactose para menos de 1g/100g, possibilitando a ingestão do leite por indivíduos intolerantes a este carboidrato. As maiores porcentagens de hidrólise e, conseqüentemente, os menores teores de lactose foram verificados em temperaturas de 15 a 30ºC e com o uso de concentrações de enzima de 0,6 a 1,0 g/L. A média da contagem total após a hidrólise ultrapassou o limite estabelecido pela legislação, porém, nas contagens realizadas por amostra de leite, com o uso da enzima 1, três tratamentos não excederam esse limite e com o uso da enzima 2, sete. Os maiores valores de contagem total foram encontrados nas maiores temperaturas e com o uso de menores concentrações de enzimas. As diferenças entre amostras de leite com teores de lactose diferentes, não foram sensorialmente percebidas através do teste triangular.
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Freitas, Maria de FÃtima Matos de. "ProduÃÃo de β-galactosidase por Kluyveromyces lactis NRRL Y1564 em soro de leite e imobilizaÃÃo em quitosana". Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9396.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorNeste trabalho, a enzima β-galactosidase, que catalisa a hidrÃlise da lactose em glicose e galactose, foi produzida pelo cultivo do micro-organismo Kluyveromyces lactis NRRL Y1564 em soro de leite suplementado com extrato de levedura. A enzima à um metabÃlito intracelular, sendo a liberaÃÃo da enzima para o meio uma condiÃÃo essencial, por isso estudaram-se diferentes mÃtodos quÃmicos e mecÃnicos de extraÃÃo como, agitaÃÃo com pÃrolas de vidro, ruptura em ultrassom com pÃrolas de vidro, adiÃÃo de etanol e tolueno, observando tambÃm, seus efeitos na atividade enzimÃtica. Posteriormente, realizaram-se ensaios para estudar a influÃncia da temperatura (30, 34, 37 e 40 ÂC) na produÃÃo da enzima a partir do soro de queijo. Na extraÃÃo da enzima, o uso de esferas de vidro em vÃrtex foi o mÃtodo mais eficiente quando comparado com os outros avaliados. A enzima, nÃo sofreu inibiÃÃo ou desnaturaÃÃo quando incubadas com etanol, tolueno ou etanol-tolueno. A temperatura Ãtima de produÃÃo da enzima por K. lactis NRRL Y1564 foi 30 ÂC, com atividade enzimÃtica de 4418,37 U/g de cÃlulas em 12 h de fermentaÃÃo. A enzima produzida foi imobilizada em quitosana 2,0% m/v. Diferentes protocolos de ativaÃÃo usando glutaraldeÃdo, epicloridrina ou glicidol foram avaliados. Estudou-se tambÃm, o tempo de contato enzima-suporte (3, 5 e 10 horas) a fim de se obter um biocatalisador que apresentasse alto rendimento, atividade recuperada e tempo de meia-vida, visando a hidrÃlise da lactose em reator batelada e leito fixo. A influÃncia da temperatura e do pH na hidrÃlise da lactose foi avaliada, usando como substrato uma soluÃÃo sintÃtica (lactose 5,0% (m/v) e leite desnatado, contendo 4,3% m/v de lactose. O suporte que apresentou melhores resultados nos parÃmetros de imobilizaÃÃo foi a quitosana 2% reticulada com glutaraldeÃdo no tempo de imobilizaÃÃo de 5 horas. O biocatalisador produzido nesse estudo apresentou um fator de estabilidade de 17,37 vezes maior que a enzima solÃvel, com uma estabilidade de armazenamento de 100% quando armazenada a 4 ÂC por 90 dias. A temperatura Ãtima de hidrÃlise da lactose foi de 40 ÂC e o pH Ãtimo foi 7,0 . A conversÃo da lactose a 40 ÂC para este derivado (3,0 U/g) foi em mÃdia 53% em 10 ciclos (bateladas consecutivas). Em reator batelada, a conversÃo em glicose a partir da hidrÃlise da lactose, usando soluÃÃo sintÃtica, foi aproximadamente 86 % para a enzima solÃvel (3,8 U/mL) e 83 % para a enzima imobilizada (3,8 U/g). A conversÃo obtida na hidrÃlise do leite desnatado foi de 17 % para a enzima solÃvel e 20 % para a enzima imobilizada.
In this work, the enzyme β-galactosidase which catalyzes the hydrolysis of lactose to glucose and galactose, was produced by cultivating the micro-organism Kluyveromyces lactis NRRL Y1564 in whey supplemented with yeast extract. The enzyme is an intracellular metabolite, the release enzyme is very important, therefore were studied various chemical and mechanical methods of extraction and stirring with glass beads, sonication, addition of ethanol and toluene, noting also their effects on enzymatic activity. Subsequently, trials were carried out to study the influence of temperature (30, 34, 37 and 40 Â C) in the production of the enzyme from the cheese whey. In the enzyme extraction, using glass beads by a vÃrtex was more efficient method compared to others evaluated. The enzyme not presented inhibited or denatured when incubated with ethanol, toluene or ethanol-toluene. The optimum temperature for enzyme production by K. lactis NRRL Y1564 was 30 ÂC with enzymatic activity of 4418.37 U/g of cells at 12 h of fermentation. The enzyme produced was immobilized on chitosan 2.0% w/v. Different activation protocols using glutaraldehyde, epichlorohydrin or glycidol were evaluated. Was also studied, the contact time the enzyme-carrier (3, 5, and 10 hours) to obtain a biocatalyst to produce high yield, recovered activity and half-life in order to hydrolysis of lactose in batch reactor and fixed bed. The influence of temperature and pH on the hydrolysis of lactose was evaluated using as substrate a synthetic solution (lactose 5.0% (w/v) in potassium phosphate buffer 100 mM with 0.1 mM MnCl2) and skimmed milk containing 4.3% w/v lactose. The support shows better results in the parameters of immobilization was chitosan 2% actived with glutaraldehyde and contact time of 5 hours. The biocatalyst produced in this study showed a stability factor of 17.37 and a storage stability of 100% when stored at 4 ÂC for 90 days. Temperature optimum hydrolysis of lactose was 40 ÂC and the optimal pH 7.0. The conversion of lactose to 40 ÂC for this derivative (3.0 U/g) was on average 53% in 10 cycles (consecutive batches). In batch reactor, the conversion to glucose by the hydrolysis of lactose using synthetic solution was approximately 86% for the soluble enzyme (3.8 U/mL) and 83% of the immobilized enzyme (3.8 U/g). The conversion obtained in the hydrolysis of skim milk was 17% for the soluble enzyme and 20% for the immobilized enzyme.
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Davidson, Richard H. "Culture enumeration, lactose hydrolysis and sensory changes in stored frozen yogurt fermented with two culture systems". Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/45071.
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Mioro, Miriam Kanyua. "Designing a Two Component System for Enzyme Immobilization Using a Modified Chitosan Support". Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu15946615388307.
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West, Christopher Michael. "Bioreaction and separation in preparative batch chromatographic columns : the hydrolysis of lactose to yield glucose, galactose and oligosaccharides". Thesis, Aston University, 1997. http://publications.aston.ac.uk/9614/.
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The initial aim of this project was to improve the performance of a chromatographic bioreactor-separator (CBRS). In such a system, a dilute enzyme solution is pumped continuously through a preparative chromatographic column, while pulses of substrate are periodically injected on to the column. Enzymic reaction and separation are therefore performed in a single unit operation. The chromatographic columns used were jacketed glass columns ranging from 1 to 2 metres long with an internal diameter of 1.5 cm. Linking these columns allowed 1, 2, 3 and 4 metre long CBRS systems to be constructed. The hydrolysis of lactose in the presence of β~galactosidase was the reaction of study. From previous work at Aston University, there appeared to be no difficulties in achieving complete lactose hydrolysis in a CBRS. There did, however, appear to be scope for improving the separative performance, so this was adopted as an initial goal. Reducing the particle size of the stationary phase was identified as a way of achieving this improvement. A cation exchange resin was selected which had an average particle size of around half that previously used when studying this reaction. A CBRS system was developed which overcame the operational problems (such as high pressure drop development) associated with use of such a particle size. A significant improvement in separative power was achieved. This was shown by an increase in the number of theoretical plates (N) from about 500 to about 3000 for a 2 metre long CBRS, coupled with higher resolution. A simple experiment with the 1 metre column showed that combined bioreaction and separation was achievable in this system. Having improved the separative performance of the system, the factors affecting enzymic reaction in a CBRS were investigated; including pulse volume and the degree of mixing between enzyme and substrate. The progress of reaction in a CBRS was then studied. This information was related to the interaction of reaction and separation over the reaction zone. The effect of injecting a pulse over a length of time as in CBRS operation was simulated by fed batch experiments. These experiments were performed in parallel with normal batch experiments where the substrate is mixed almost instantly with the enzyme. The batch experiments enabled samples to be taken every minute and revealed that reaction is very rapid. The hydrodynamic characteristics of the two injector configurations used in CBRS construction were studied using Magnetic Resonance Imaging, combined with hydrodynamic calculations. During the optimisation studies, galactooligosaccharides (GOS) were detected as intermediates in the hydrolysis process. GOS are valuable products with potential and existing applications in food manufacture (as nutraceuticals), medicine and drug targeting. The focus of the research was therefore turned to GOS production. A means of controlling reaction to arrest break down of GOS was required. Raising temperature was identified as a possible means of achieving this within a CBRS. Studies were undertaken to optimise the yield of oligosaccharides, culminating in the design, construction and evaluation of a Dithermal Chromatographic Bioreactor-separator.
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Huet, Laurent. "Réactions radicalaires multicomposant appliquées à la synthèse de lactones et pipéridinones fonctionnalisées". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14262/document.
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L'élaboration de squelettes de pipéridinones et lactones a été accomplie de manière très efficace en alliant processus radicalaires et ioniques. La synthèse d'oximes SEM-protégées par un assemblage multicomposant radicalaire permet, après hydrolyse de la fonction oxime, d'obtenir rapidement un aldéhyde fonctionnalisé. Ce composé est ensuite transformé en lactone ou pipéridinone désirée par un processus ionique.Une approche minimisant le nombre d'étapes élémentaires a été développée autorisant ainsi un accès rapide et convenable à une grande diversité de structures. Ces processus peuvent impliquer jusqu'à cinq composantsThe construction of piperidinone and lactone scaffolds has been performed efficiently, combining radical and ionic processes. The synthesis of SEM-protected oximes by a multicomponent radical reaction enables, after hydrolysis of the oxime functional group, the access to a functionalized aldehyde. This compound is then converted into a lactone or a piperidinone by a ionic process.An approach minimizing the number of steps has been developed, thus allowing a rapid and convenient access to a large diversity of structures. These processes may involve up to five components
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Campello, Graciella da Silva. "Imobilização de B-galactosidade (LACTOZYM®) em EUPERGIT® C e sua caracterização". reponame:Repositório Institucional da FURG, 2010. http://repositorio.furg.br/handle/1/2584.
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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, 2010.Submitted by Caroline Silva (krol_bilhar@hotmail.com) on 2012-08-19T20:33:18Z No. of bitstreams: 1 dissertao graciella campello.pdf: 486302 bytes, checksum: 0f3c85b47643a8359572feee54269a00 (MD5)
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Este trabalho teve como objetivo principal investigar a imobilização da enzima β- galactosidase comercial de Kluyveromyces lactis (Lactozym®), bem como caracterizar a enzima livre e imobilizada visando sua aplicação na reação de hidrólise da lactose. Foram feitos testes preliminares com três suportes diferentes para a imobilização (alginato, quitosana e Eupergit® C), sendo que os valores de recuperação da atividade enzimática foram, respectivamente, 2,43%, 6,27% e 41,86%, selecionando-se o suporte Eupergit® C como o mais promissor. Um planejamento Plackett-Burman, correspondente a 12 ensaios mais 3 réplicas no ponto central, foi proposto a fim de verificar os efeitos das variáveis temperatura, pH, força iônica, tempo de imobilização, concentração de galactose, concentração de íons Mg2+ e volume de enzima na imobilização de β-galactosidase em Eupergit® C. A força iônica e o pH foram as variáveis que apresentaram efeito significativo (p<0,1) na imobilização, sendo que o aumento da força iônica de 0,1 M para 1,5 M e o aumento do pH de 6,6 para 7,4 representaram aumento de 30,0% e redução de 17,3% na recuperação da atividade enzimática, respectivamente. À temperatura de 25°C, pH 6,6, concentração salina de 1,5 M, tempo de imobilização de 8 h, concentração de Mg2+ de 1 mM e 0,4 mL de enzima adicionada, atingiu-se 85% de recuperação da atividade enzimática. As enzimas livre e imobilizada, nas melhores condições em Eupergit® C, foram caracterizadas quanto aos perfis de pH e temperatura, estabilidade térmica, parâmetros cinéticos e termodinâmicos. Quanto aos perfis de pH e temperatura, foram obtidos, para ambas, valores máximos de atividade enzimática em pH 6,6 e 45°C. Houve um ganho de estabilidade térmica com a imobilização enzimática, tendo-se observado um aumento de cerca de 4 vezes no tempo de meia-vida da enzima imobilizada a 45oC, em relação à livre, o que pode representar vantagens na utilização da enzima imobilizada em escala comercial. Os valores de energia de ativação para as enzimas livre e imobilizada foram, respectivamente, iguais a 35,28 kJ.mol-1 e 29,46kJ.mol-1; e os valores de energia de ativação da reação de desnaturação para as enzimas livre e imobilizada foram iguais, respectivamente, a 266,12 kJ.mol-1 e 198,77 kJ.mol-1. Foram determinados os parâmetros cinéticos para as enzimas livre e imobilizada, sendo que os valores de Km, 30,33 mM e 104,00 mM, respectivamente, representaram uma diminuição da afinidade da enzima pelo substrato com a imobilização, possivelmente devido a fatores estéricos e conformacionais. Parâmetros termodinâmicos foram calculados, evidenciando novamente a maior estabilidade térmica da enzima imobilizada e indicando que a perda de estabilidade de ambas as enzimas, livre e imobilizada, parece não estar associada a alterações relevantes na estrutura terciária.
Immobilization of b-galactosidase (Lactozym®) on Eupergit® C and its characterization This study aimed to investigate the immobilization of commercial β-galactosidase from Kluyveromyces lactis (Lactozym®) and characterize the free and immobilized enzymes for their application in lactose hydrolysis. Three preliminaries tests were carried out with three different supports for immobilization (alginate, chitosan and Eupergit® C), and the values for recovery of enzyme activity were, respectively, 2.43%, 6.27% e 41.86%, selecting Eupergit® C as the most promising. A Plackett-Burman design, composed of 12 assays over 3 central points was proposed in order to verify the effects of temperature, pH, ionic strength, reaction time, galactose concentration, Mg2+ concentration and enzyme volume on β-galactosidase immobilization using Eupergit® C support. The ionic strength and pH were the variables that presented significant effect (p<0.1) on immobilization. The increase in the ionic strength from 0.1 to 1.5 M and the decrease in pH from 6.6 to 7.4 represented an increase of 30.0% and a reduction of 17.3% in the recovery of enzyme activity, respectively. At 25°C, pH 6.6, salt concentration of 1.5 M, immobilization for 8 h, 1 mM Mg2+ and 0.4 mL of enzyme added, reached 85% recovery of enzymatic activity. The free and immobilized enzyme on Eupergit® C were characterized,determining pH and temperature profiles, thermal stability, kinetic and thermodynamic parameters. pH and temperature profiles showed maximum activity at pH 6.6 and 45°C. There was a gain in thermal stability with the enzyme immobilization and there was an increase of about 4 times in the half-life of immobilized enzyme at 45°C, which may represent advantages when using in a commercial scale. The values of activation energy for free and immobilized enzymes were, respectively, equal to 35.28 kJ.mol-1 and 29.46 kJ.mol-1, and the values of activation energy of denaturation reaction for free and immobilized enzymes were equal, respectively, to 266.12kJ.mol-1 and 198.77 kJ.mol-1. Kinetic parameters were determined for the immobilized and free enzyme. Km values of 30.33 mM and 104.00 mM, respectively, represented a decrease of the affinity of the enzyme by the substrate with immobilization, possibly due to steric and conformational factors. Thermodynamic parameters were calculated, showing the higher thermal stability of the immobilized enzyme and indicating that the loss of stability of both enzymes, immobilized and free, does not seem to be associated with significant changes in tertiary structure.
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Vieira, Aline Alves Melo Tostes. "Estudo da hidrólise enzimática do soro de queijo utilizando as lactases Lactozym® e Prozyn®". Universidade Federal de Uberlândia, 2006. https://repositorio.ufu.br/handle/123456789/15120.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoThe study of the enzymatic hydrolysis of the lactose has been of great importance, due to absence or lack of the enzyme present lactase in the process digestive human. The enzyme β-galactosidase is very used in the processing of milk products by being of low cost and enough studied all over the world. The use of this enzyme in the dairy products prevents the crystallization of the products and it provides to the intolerant people the lactose better life quality. The objective of this work was accomplish a comparative study of the hydrolysis of the cheese whey usig two different maufactures β-galactosidase Prozyn and Lactozym, respectively, Kluyveromyces lactis and Kluyveromyces fragilis, of origin of yeasts. The tests of hydrolysis of the cheese whey were accomplished in a reactor with agitation control and temperature. The cheese whey concentration was of 60 g/L, temperatures of 43, 45 and 48°C, concentration of the enzyme of 4 g/L, pH 6,0 and 6,5 and agitation 300 rpm. Both enzymes obteined better result to 45 °C, however the enzyme Prozyn converts the lactose in smaller time. An analysis was accomplished to verify the concentration of total sugar of the cheese whey, 75%, to evaluate the hydrolysis, obtaining the glucose concentration in function of the time for each studied condition. The influence of the lactose concentration was verified in the enzyne, using lactose solution in erlenmeyer. The enzymatic activity was growing of the concentration 10 g/L up to 120 g/. The enzyatic stability in relation to the pH presented better result pH 6,5 for both enzymes Prozyn and Lactozym. The thermal stability of the free enzyme was certain for the time of half life. The enzyme Prozyn to temperature of 50°C it presented time of life 4,62 min and to 55°C was 2,77 min and enzyme Lactozym to the 50°C was 6,32 min and to 45°C was 115,52 min. In the determination of the enzymatic activity the method of the initial rates of the reaction of hydrolysis of the cheese whey was used. The obteined enzymatic activity was 75,03.10-3 mol/(genzyme.h) and 44,6.10-3 mol/(genzyme.h) for Prozyn and Lactozym, respectively.
O estudo da hidrólise enzimática da lactose tem sido de grande importância, devido a ausência ou carência da enzima lactase presente no processo digestivo humano. A enzima β-galactosidase é a mais utilizada no processamento de produtos lácteos por ser de baixo custo, eficiente e bastante estudada em todo o mundo. A utilização desta enzima nos laticínios previne a cristalização da lactose dos produtos e proporciona às pessoas intolerantes a lactose melhor qualidade de vida. O objetivo deste trabalho foi realizar um estudo comparativo da hidrólise da lactose presente no soro de queijo, utilizando β- galactosidase originária das leveduras Kluyveromyces lactis e Kluyveromyces fragilis adquiridas da Prozyn e Lactozym. Os ensaios de hidrólise do soro de queijo foram realizados em um reator com controle de agitação e temperatura. A concentração de soro foi de 60 g/L, temperaturas de 43, 45, 48 e 53°C, concentração da enzima de 4 g/L, pH 6,0 e 6,5 e agitação 300 e sem agitação mecânica. Ambas as enzimas forneceram melhor resultado à 45 °C, no entanto, a enzima Prozyn converte a lactose em menor tempo. O teor de lactose presente no soro de queijo com concentração 60 g/L foi de 75%. A concentração de glicose em função do tempo determinou a duração da hidrólise, onde a lactose foi quebrada pela enzima e resultou na formação de glicose e galactose em quantidade equimolar. Verificou-se a influência da concentração de lactose na enzima, utilizando solução de lactose na faixa de 10 a 120 g/L em solução tampão láctico pH 6,5 e temperatura 30°C. A atividade enzimática foi crescente da concentração 20 g/L até 100 g/L. A estabilidade enzimática em relação ao pH apresentou melhor resultado em pH 6,0 para a Prozyn e pH 6,5 para a Lactozym. A estabilidade térmica da enzima livre foi determinada pelo tempo de meia vida. A enzima Prozyn à 50°C, apresentou tempo de meia vida de 4,62 min e à 55°C, 2,77 min e a enzima Lactozym à 50°C, 6,30 min e à 45°C, 115,52 min. Na determinação da atividade enzimática utilizou-se o método das taxas iniciais da reação de hidrólise do soro. A atividade enzimática obtida foi 75,03.10-3 mol/(genz..h) e 44,6.10-3 mol/(genz..h) para Prozyn e Lactozym, respectivamente.
Mestre em Engenharia Química
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Stievenard, Sylvain. "Hydrolyse industrielle du lactose : mise au point au stade laboratoire d'un réacteur à lactase immobilisée". Lille 1, 1986. http://www.theses.fr/1986LIL10172.
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L'existence d'une activité lactasique chez un micro-organisme non pathogène nous a conduit à envisager la mise au point d'un procédé d'hydrolyse industrielle du lactose contenu dans le lait et les lactosérums. Notre démarche s'est appuyée sur plusieurs points : le procédé doit être facile à mettre en oeuvre industirellement et doit pouvoir se réaliser en continu. Il doit être en outre peu coûteux et conforme à la législation. La purification de la lactase est procédé qui s'est révélé être trop onéreux et déstabilisateur de l'activité enzymatique. Les cellules de ce microorganisme ont été incluses à l'intérieur d'un polymère d'origine naturelle. Nous avons comparé les paramétres enzymatiques de l'enzyme "libre" et "immobilisée". Le procédé mis au point au laboratoire est décrit, ses performances sont comparées à celles des autres systèmes existant déjà sur le marché.
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Pickens, Tara L. L. "Immobilization of Beta-Glycosidase BglX from Escherichia coli on Chitosan Gel Beads". Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1535472543349818.
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Gregianin, Dóris de Oliveira. "DESENVOLVIMENTO DE BEBIDA MISTA DE SORO DE LEITE COM TEOR DE LACTOSE REDUZIDO E EXTRATO HIDROSSOLÚVEL DE SOJA". UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/714.
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Previous issue date: 2014-08-28The increased incidence of cardiovascular disease and various cancers have been the cause of searching for changing habits in a large portion of the population, seeking the physical activity in conjunction with the consumption of healthier foods with higher nutritional content. Considering the high biological value of the proteins of sweet whey and the recognized effect in reducing risk of cardiovascular disease of soy protein, the aim of this study was to develop a mixed chocolate-soluble soybean extract dissolved in sweet whey. The different proportions of carrageenan stabilizers, pectin and tapioca starch were defined by the experimental design of mixtures simplex centroid. By optimizing the response surface was definitely the best formulation in relation to the physic-chemical and sensory parameters. The simultaneous optimization of response variables indicated that the optimal formulation should contain 46% carrageenan and 54% pectin and 0% starch, with a desirability index of 0.929. The formulation indicated for the desirability function was made with water soluble soy extract dissolved in sweet whey and; on sweet whey with reduced lactose content. Serum was hydrolyzed by the action of lactase from Kluyveromyces lactis yeast enzyme at a concentration of 2500 NLU / L in reaction 4 hr at 37 ° C. The sensory attributes were evaluated by nine points hedonic scale and attitude scale in purchase intent. For overall impression, the formulations presented average value of 7.11 ±1.09, while purchase intent the average value was 3.99 ± 1.28, and the multiple regression models proved to be predictive. The most widely accepted formulations were those who had lower viscosity and instrumental containing pectin in its constitution. The results obtained indicate that the combination of sweet whey and soy aqueous extract is a viable option for the preparation of a chocolate beverage. It was also observed that the use of cassava starch as a thickener does not interfere negatively on the rheological and sensory characteristics and; that the combined carrageenan and pectin concentrations defined predictive model ensures greater acceptability of the product.
O aumento da incidência de doenças cardiovasculares e diversos tipos de câncer tem sido a causa da procura por mudanças de hábitos em grande parte da população, buscando-se a prática de atividades físicas em conjunto com o consumo de alimentos mais saudáveis, com maior valor nutricional. Considerando o alto valor biológico das proteínas do soro de leite doce e o reconhecido efeito na diminuição de risco de doenças cardiovasculares da proteína de soja, o objetivo deste trabalho foi desenvolver um achocolatado misto de extrato hidrossolúvel de soja dissolvido em soro de leite doce. As diferentes proporções dos estabilizantes carragena, pectina e amido de mandioca foram definidas pelo planejamento experimental de misturas simplex centróide. Através da otimização da Superfície de Resposta foi definida a melhor formulação em relação aos parâmetros físico-químicos e sensoriais. A otimização simultânea das variáveis de resposta indicou que a formulação ideal deveria conter 46% de carragena e 54% de pectina e 0% de amido, com um índice de desejabilidade de 0,929. A formulação indicada pela função de desejabilidade foi elaborada com extrato hidrossolúvel de soja dissolvido em soro de leite doce e; em soro doce com teor de lactose reduzido. O soro foi hidrolisado pela ação da enzima lactase proveniente da levedura Kluyveromyces lactis, na concentração de 2.500 NLU/L numa reação de 4 horas à temperatura de 37°C. Os atributos sensoriais foram avaliados pela escala hedônica de nove pontos e escala de atitude na intenção de compra. Para impressão global as formulações apresentaram valor médio 7,11 ±1,09, enquanto que para intenção de compra o valor médio foi de 3,99 ±1,28, sendo que os modelos de regressão múltipla mostraram-se preditivos. As formulações mais aceitas foram aquelas que apresentaram menor viscosidade instrumental e que continham pectina em sua constituição. Os resultados obtidos indicam que a combinação do soro doce de leite e extrato aquoso de soja é uma opção viável para a elaboração de uma bebida achocolatada. Também foi possível observar que o uso do amido de mandioca como espessante não interfere negativamente nas características reológicas e sensoriais do produto e; que a carragena e pectinas combinadas, nas concentrações definidas pelo modelo preditivo, garantem maior aceitabilidade ao produto.
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Chaudhary, Manoja Nand. "An evaluation of nanofiltration and lactose hydrolysis of milk UF permeate for use in ice cream : thesis submitted in fulfilment of the requrement for the degree of Master of Science (Hons.) in Food Technology /". Richmond, N.S.W. : Faculty of Science, Technology and Agriculture, University of Western Sydney, 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030528.125302/index.html.
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Hediger, Thomas. "Die enzymatische Hydrolyse der Lactose mit Hohlfaserreaktoren /". [S.l.] : [s.n.], 1985. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7933.
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Dragana, Ilić-Udovičić. "Optimizacija tehnološkog procesa proizvodnje napitaka od enzimski hidrolizovanog permeata mleka". Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=95728&source=NDLTD&language=en.
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Valorizacija permeata kao sporednog proizvoda industrije mleka je od izuzetnog ekološkog, ekonomskog i tehnološkog značaja.Cilj doktorske disertacije je razvoj tehnološkog procesa prerade permeata, kao sporednog proizvoda dobijenog nakon ultrafiltracije mleka tokom proizvodnje feta sira i svežeg („mladog“) sira. Ispitana je mogućnost enzimske hidrolize laktoze u permeatu korišćenjem enzima β-galaktozidaze izolovanog iz Kluyveromyces lactis u koncentraciji 0,1, 0,3 i 0,5 g/100g na temperaturama 20º, 30º i 40 ºC. Praćene su promene sadržaja laktoze, D–galaktoze i D–glukoze u vremenskim intervalima tokom 60 minuta. Posebna faza istraživanja obuhvatila je matematičko modelovanje i kinetiku procesa hidrolize laktoze u permeatu pod dejstvom β –galaktozidaze i primenu hidrolizovanog permeata u proizvodnji mlečnih napitaka po odabranoj formulaciji. Predložen je tehnološki proces proizvodnje napitka na bazi hidrolizovanog permeata sa dodatkom voćnih baza. Utvrđeni su parametri kvaliteta i trajnosti napitaka tokom 60 dana skladištenja.Na temperaturi 40°C dodatkom enzima β -galaktozidaze u koncentraciji 0,1g/100g za 60 minuta postiže se 100% stepen hidrolize prisutne laktoze u permeatu. Sa većom koncentracijom enzima, 0,3 g/100g odnosno 0,5g/100g, na istoj temperaturi, isti efekat se postiže za 20 minuta.Ispitivanjem kinetike hidrolize laktoze potvrđena je kinetika prvog reda. Generalno posmatrano visoki koeficijenti determinacije pokazuju dobro poklapanje eksperimentalnih rezultata i matematičkog modela reakcije prvog reda. Vrednosti se kreću od 0,974 (temperatura 20°C) do preko 0,990 (na temperaturama 30°C i 40°C) pri koncentraciji enzima 0,1g/100g.Proizvedeni napici od hidrolizovanog permeata su delaktozirani i ne sadrže mlečnu mast. Od ukupnih šećera u svim napicima više od 50% čini glukoza: 50,16% - napitak šumsko voće, 50,42% - napitak pomorandža/šargarepa, 54,65% - napitak multivitamin, odnosno 55,13% - napitak crveno voće.Najveći sadržaj vitamina C nakon proizvodnje imao je napitak sa dodatkom voćne baze multivitamin 0,3972 mg/100g, zatim šumsko voće 0,2887 mg/100g i pomo-randža/šargarepa 0,1999 mg/100g.Najveću vrednost antioksidativne aktivnosti nakon proizvodnje pokazali su uzorci napitka sa multivitaminom i šumskim voćem. Tokom perioda skladištenja dolazi do smanjenja DPPH vrednosti. Najmanji pad je u napitku sa pomorandžom / šargarepom (smanjenje za 17%), a najveći u napitku sa šumskim voćem (za 39%). Analizirani uzorci sadrže ukupnih polifenola u intervalu od 47,84 do 120,38 mg GAE/l u zavisnosti od vrste napitka, odnosno dodatih voćnih baza.Generalno može se zaključiti da se prime-njenim tehnološkim procesom dobijaju napici stabilnog fizičko-hemijskog sastava tokom 60 dana skladištenja, visoke nutritivne i niske energetske vrednosti.Valuation of the permeate as a by-product of the dairy industry is of great ecological, economic and technological importance.The aim of the PhD thesis is the development of the technological process of refining permeate, as a by-product obtained after ultrafiltration of milk during the production of feta cheese and fresh cheese. The possibility of enzymatic hydrolysis of the lactose in the permeate using the enzyme β-galactosidase isolated from Kluyveromyces lactis in a concentration of 0.1, 0.3 and 0.5 g / 100 g at a temperature of 20°, 30° and 40° C was examined. Changes in the content of lactose, D-galactose and D-glucose at intervals of 60 minutes were monitored. A special stage of the research included mathematical modeling and kinetics of lactose hydrolysis in the permeate under the influence of β-galactosidase and application of hydrolyzed permeate in the production of dairy products under the selected formulation. A technological process of producing a beverage on the basis of hydrolyzed permeate with the addition of fruit bases was suggested. Quality and durability parameters were determined for drinks during the 60 days of storage.Addition of the enzyme β-galactosidase at a concentration of 0.1 g / 100 g for 60 minutes at a temperature of 40 ° C a 100% degree of hydrolysis of lactose is achieved, present in the permeate. With a higher concentration of enzyme, 0.3 g / 100 g or 0.5 g / 100g, at the same temperature, the same effect can be achieved in 20 minutes.By examining the kinetics of lactose hydrolysis the first order kinetics was confirmed. Generally high coefficients of determination show good correspondence between the experimental results and the mathematical model of the first order reaction. Values range from 0.974 (at a temperature of 20° C) up to over 0.990 (at temperatures 30° C and 40° C) at a an enzyme concentration of 0.1g / 100g.Beverages produced from hydrolyzed permeate are lactose-free and fat-free products. More than half of the total sugar content in all beverages consists of glucose: 50.16%-forest fruit beverage, 50.42%-beverage orange/carrot, 54.65% beverage multivitamin and 55.13% - beverage red fruit.The highest vitamin C content after production was in a beverage with the addition of fruit base multivitamin (0.3972 mg/100g), followed by forest fruit (0.2887 mg/100g) and orange/carrot (0.1999 mg/100g).Beverage samples with multivitamin and forest fruits showed the highest value of antioxidant activity after production. During the storage period there is a reduction of DPPH values. The smallest decrease was in the beverage with orange/carrot (decreased 17%), and the biggest in the beverage with forest fruit (39%). The content of polyphenols in analyzed samples ranges from 47.84 to 120.38 mg GAE/L depending on the type of beverage and added fruit base.Overall it can be concluded that the applied technological process gives beverages of stable physical and chemical content during the 60 days of storage, of high nutritional value and low energy.
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Simonpieri, Véronique. "Mise au point d'un procédé d'hydrolyse du lactose du lait UHT demi-écrémé à l'aide d'une culture mixte de levures". Dijon, 1987. http://www.theses.fr/1987DIJOS044.
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L'hydrolyse du lactose est réalisée durant 24 heures a 30°C par la levure kluyveromyces lactis. Une concentration cellulaire initiale dense provenant d'une préculture sur substrat lacté, et une culture en conditions aérées et agitées favorisent le processus d'hydrolyse. L'action de kluyveromyces lactis sur certains éléments du lait (matière grasse, fraction protéique, calcium et phosphore) a été précisée. La nature de l'acidité qui apparait corrélativement au développement de la levure a été caractérisée. Une désacidification est possible en introduisant la levure. Candida utilis D 5754 en fin d'hydrolyse. Cette levure n'utilise pas le lactose mais assimile de nombreux acides organiques dont l'acide lactique et se développe bien dans le lait UHTdemi-écrémé dont elle élève le ph
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Fouque, Elie. "Synthèse itérative de lactones α, β-ethyléniques à cycle moyen : hydrolyse enzymatique de lactones saturées". Paris 11, 1989. http://www.theses.fr/1989PA112246.
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Dans ce mémoire de thèse, nous proposons une nouvelle voie d'accès aux lactones alpha, bêta-éthyléniques à cycle moyen par une méthode d'agrandissement de cycle, qui, utilisée de façon récurrente permet à chaque itération d'incorporer dans le squelette laconique un atome de carbone porteur ou non d'un substituant. Dans le premier chapitre, après un exposé concernant la préparation des éthers d'énols triméthylsilyliques de lactones, nous étudions la réaction de ces énoxysilanes avec trois chlorocarbénoïdes différents. Les adduits cyclopropaniques ainsi obtenus, conduisent thermiquement aux lactones alpha, bêta-éthyléniques d'agrandissement de cycle. A l'aide de cette méthode, nous avons préparé avec des rendements satisfaisants des lactones alpha, bêta éthyléniques non substituées, méthylées ou fluorées en alpha, de taille comprise entre 7 et 10 maillons. Dans le second chapitre, nous étudions les propriétés spectroscopiques ainsi que quelques propriétés chimiques de ces lactones insaturées à cycle moyen. Nous mettons en évidence les différences importantes existant entre les composés de stéréochimie E et Z. Par hydrogénation catalytique en phase hétérogène, nous préparons les lactones saturées correspondantes, réalisant ainsi la dernière étape de la séquence et rendant la méthode itérative. Dans le troisième chapitre, nous présentons une nouvelle méthode de préparation des lactones à cycle moyen optiquement actives méthylées en alpha de l'atome d'oxygène, par dédoublement cinétique catalysée par des hydrolases. En utilisant l'estérase de foie de porc (PLE) ou l'estérase de foie de cheval (HLE) sous forme de leur extrait acétonique, en milieu aqueux, l'hydrolyse de ces alkanolides procède de façon hautement énantiosélective. Ainsi le (S)-(+) octanolide-7, le (S)-(+)-nonanolide-8 et le (S)-(+)-décanolide-9 ((S)-(+)-phoracantholide I) ont été isolés avec un bon rendement et un excès énantiomérique supérieur à 95%In this thesis, we report a new method for the preparation of alpha,beta-ethylenic medium ring lactones involving a ring enlargement method which can be used in an iterative way allowing, at each iteration, the incorporation of a carbon atom, substituted or not, in the lactonic skeleton. In the first chapter, is reported the preparation of trimethylsilyl enol ethers of lactones, then the reaction of these enoxysilanes with three different chlorocarbenoids. The cyclopropane adducts so obtained, are thermally transformed into alpha, beta-ethylenic ring expanded lactones. By this way we have prepared in satisfactory yields alpha unsubstituted, alpha methylated or alpha fluorinated 7 to 10 membered alpha,beta-ethylenic lactones. In the second chapter, we study spectroscopic and chemical properties of these unsaturated medium ring lactones. We outline large differences between E and Z isomers. By catalytic heterogeneous hydrogenation we prepare the corresponding saturated compounds, allowing thus the last step of this iterative method. In the third chapter, we present a new method for the preparation of optically active medium ring lactones, methylated in the alpha position of the oxygen atom, by an hydrolase-catalyzed kinetic resolution. Using pig liver esterase (PLE) or horse liver esterase (HLE) (acetone powder), in aqueous phase the hydrolysis is performed with a high enantioselectivity. Thus, (S)-(+)-7- octanolide, (S)-(+)-8-nonanolide and (S)-(+)-9-decanolide ((S)-(+)-phoracantholide I) have been isolated in good yield and enantiomeric excess (over 95%)
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Belbella, Abdelàaziz. "Contribution à l'étude de la dégradation de vecteurs collodaux polymères constituéd de poly(DL-lactide) et de poly(DL-lactide-CO-glycolide". Paris 11, 1995. http://www.theses.fr/1995PA114815.
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Zuñiga, de Lopez Raquel. "Étude structurale et texturale de laits acidifiés par hydrolyse de Glucono-Delta-Lactone et contenant des polysaccharides". Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL071N.
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Le développement des laits fermentes acides avec de nouvelles textures peut être réalisé en exploitant les interactions entre les protéines du lait et les polysaccharides. L’incorporation de ces macromolécules dans le lait peut provoquer une perturbation du système qui est amplifiée lors d'une fermentation. La structure qui en résulte peut avoir une forte incidence sur les propriétés mécaniques et texturales du produit. Afin d'étudier ces différents points, nous avons entrepris ce travail dont l'objectif était de relier la (micro)structure (met, meb, microscospie optique a contraste de phases) des gels de lait non homogénéisés contenant du xanthane et/ou de la gomme de caroube à leurs propriétés mécaniques à large déformation (extrusion capillaire) et aux propriétés d'écoulement des gels de laits homogénéisés. Dans les deux premières parties, l'influence du xanthane et/ou de la gomme de caroube sur la structure de gels de lait non brasses et sur leurs propriétés d'extrusion est montrée. Les profils d'extrusion obtenus ont été analysés mathématiquement en faisant appel au concept de la géométrie fractale et de l'analyse de Fourier. Enfin dans une troisième partie, l'influence de ces polysaccharides sur les propriétés thixotropes des gels homogénéisés est présenté. Il est apparu que l'utilisation de faibles quantités de xanthane ou de gomme de caroube ne modifie pas la microstructure des gels de lait non brassés et tend à augmenter la valeur des paramètres d'extrusion ; elle améliore aussi considérablement les propriétés texturales (augmentation des paramètres calculés à partir des courbes d'écoulement) des gels homogénéisés. En revanche, l'emploi de quantités plus importantes des polysaccharides, modifie complètement la microstructure et les propriétés d'extrusion des gels non homogénéisés et dégradé les propriétés texturales des gels homogénéisés. Une relation semble apparaitre entre le niveau de perturbation de la microstructure initiale des gels, leurs propriétés mécaniques à large déformation et les propriétés d'écoulement des gels homogénéisés.
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Desobry-Banon, Sylvie. "Modification de la structure des micelles de caséine lors de l'acidification par hydrolyse de Glucono-Delta-Lactone". Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_DESOBRY_BANON_S.pdf.
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La synthèse bibliographique, constituant la première partie de ce travail, se divise selon trois thèmes : la structure, les propriétés colloïdales et le comportement en milieu acide des micelles de caséine du lait. L'acidification par hydrolyse de Glucono-Delta-Lactone conduit à la gélification du lait. Le suivi optique de ce processus (chapitre II) dans diverses conditions de température et de concentrations en GDL aboutit à la validation d'une méthode turbidimétrie basée sur la réflexion de la lumière. Le comportement des micelles de caséine durant l'acidification est étudié (chapitre III) grâce à diverses techniques colloïdales telles la viscosimétrie capillaire, la granulométrie laser ou la mobilité électrophorétique (potentiel zéta). Confortée par de nombreux travaux de la littérature, une représentation schématique des mécanismes micellaires conduisant à la gélification du lait est finalement proposée. Ainsi la neutralisation des forces de répulsion électrostatiques des micelles provoquerait une contraction de l'enveloppe protéique et une fragilisation de leur structure interne. Soumises à l'agitation Brownienne, les collisions entre ces particules déstabilisées résulteraient en leur floculation. La formation d'agrégats caséiques est finalement (chapitre IV) traitée selon la théorie des fractals. Les valeurs de dimension fractale (D) obtenues par spectrophotométrie sont en accord avec celles de la littérature. La dépendance de D avec la température d'acidification mettrait en évidence une structure plus compacte avec les basses températures
25
Lopes, Fialho Tatiana. "Lactose hydrolyzed milk powder : optimization of the drying process and study of structural and functional properties". Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R013/document.
Texto completoResumen
La technologie de production du lait en poudre hydrolysé au lactose a été développée pour répondre aux besoins des consommateurs intolérants au lactose. Bien que le produit soit actuellement commercialisé dans certains pays, le secteur est confronté à des problèmes technologiques lors de la production et du stockage de la poudre, tels que l'agglomération, la prise en masse, le brunissement, une hygroscopicité élevée, un faible rendement de production et une perte de propriétés technofonctionnelles. Dans ce contexte, deux objectifs principaux ont été assignés aux travaux de cette thèse: (i) optimiser le processus de séchage du lait en poudre hydrolysé au lactose; (ii) comprendre l'impact de l'hydrolyse du lactose sur la structure interne du lait en poudre hydrolysé au lactose à l'échelle moléculaire. Afin d’optimiser le processus de séchage du lait en poudre hydrolysé au lactose, les échantillons de poudre ont été soumis à diverses conditions de séchage: débits de lait concentré variant de 0,3 à 1,5 kg and h -1 et température d’entrée de l’air allant de 115 à 160 °C. Ensuite, une caractérisation thermodynamique du processus de séchage a été réalisée en utilisant les équations de bilan massique et énergétique. Pour comprendre l'impact de l'hydrolyse du lactose sur la structure interne de la poudre après séchage et pendant le stockage, nous avons analysé l'organisation et la dynamique des molécules dans le lait en poudre hydrolysé au lactose en examinant l'aspect et la structure des échantillons de poudre et leurs propriétés techno-fonctionnelles. Tout au long des expériences, le lait en poudre traditionnel a été utilisé comme témoin. Dans cette étude, il a été observé que les paramètres idéaux pour la production de lait en poudre hydrolysé au lactose étaient les suivants: température de l'air entrant à 145 ° C et débit de 1,0 kg h-1. Cette découverte renforce l'idée selon laquelle les conditions de séchage du lait en poudre hydrolysé au lactose sont différentes de celles utilisées pour la fabrication du lait en poudre traditionnel. Il a également été observé que les molécules présentes dans le lait en poudre hydrolysé au lactose présentaient une organisation moléculaire plus homogène par rapport au lait en poudre traditionnel et permettaient une plus grande interaction protéine-sucre. Dans des conditions de vieillissement accéléré de la poudre hydrolysée, la glycation des protéines était le processus initial qui a déclenché les principales modifications observées dans le lait en poudre hydrolysé au lactose pendant le stockageThe production technology of lactose hydrolyzed milk powder has been developed to meet the needs of lactose intolerant consumers. Although the product is currently marketed in some countries, the industry faces technological issues during the production and storage of the powder such as agglomeration, caking, browning, high hygroscopicity, low production yield and loss of techno-functional properties. In this context, two main objectives were assigned to the work of this thesis: (i) to optimize the drying process of lactose hydrolyzed milk powder; (ii) to understand the impact of lactose hydrolysis on the internal structure of lactose hydrolyzed milk powder on a molecular scale. In order to optimize the drying process of lactose hydrolyzed milk powder, powder samples were subjected to various drying conditions: concentrated milk flow rates varying from 0.3 to 1.5 kg∙h -1 and inlet air temperature ranging from 115 to 160 °C. Then, a thermodynamic characterization of the drying process was carried out using the equations of mass and energy balance. To understand the impact of lactose hydrolysis on the internal structure of the powder after drying and during storage, the organization and dynamics of the molecules in lactose hydrolyzed milk powder were analyzed by examining appearance and structure of the powder samples and their techno-functional properties. Throughout the experiments, traditional milk powder was used as a control. In this study, it has been observed that the ideal parameters for lactose hydrolyzed milk powder production were: inlet air temperature at 145 ° C and 1.0 kg ∙ h-1 flow rate. This finding reinforces the idea that the drying conditions of lactose hydrolyzed milk powder are different from those used to make traditional milk powder. It was also observed that molecules present in milk powder hydrolyzed with lactose presented a more homogeneous molecular organization compared to traditional milk powder and allowed for greater protein-sugar interaction. Under accelerated aging conditions of the hydrolyzed powder, the protein glycation was the initial process that triggers the main modifications observed in lactose hydrolyzed milk powder during storage
26
Edreder, Elmahboub A. "Modelling and optimisation of batch distillation involving esterification and hydrolysis reaction systems : modelling and optimisation of conventional and unconventional batch distillation process : application to esterification of methanol and ethanol using acetic acid and hydrolysis of methyl lactate system". Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4296.
Texto completoResumen
Batch distillation with chemical reaction when takes place in the same unit is referred to as batch reactive distillation process. The combination reduces the capital and operating costs considerably. Among many different types of batch reactive distillation column configurations, (a) conventional (b) inverted (c) semi-batch columns are considered here. Three reaction schemes such as (a) esterification of methanol (b) esterification of ethanol (c) hydrolysis of methyl lactate are studied here. Four different types of dynamic optimisation problems such as (a) maximum conversion (b) maximum productivity (c) maximum profit and (d) minimum time are formulated in this work. Optimal design and or operation policies are obtained for all the reaction schemes. A detailed rigorous dynamic model consisting of mass, energy balances, chemical reaction and thermodynamic properties is considered for the process. The model was incorporated within the dynamic optimisation problems. Control Vector Parameterisation (CVP) technique was used to convert the dynamic optimisation problem into a nonlinear programming problem which was solved using efficient SQP (Successive Quadratic Programming) method available within the gPROMS (general PROcess Modelling System) software. It is observed that multi-reflux ratio or linear reflux operation always led to better performance in terms of conversion, productivity for all reaction schemes compared to that obtained using single reflux operation. Feed dilution (in the case of ethanol esterification) led to more profit even though productivity was found to be lower. This was due to reduction in feed price because of feed dilution. Semi-batch reactive distillation opertation (for ethanol esterification) led to better conversion compared to conventional batch distillation, however, the total amount of acetic acid (reactant) was greater in semi-batch operation. Optimisation of design and operation (for ethanol esterification) clearly showed that a single cloumn will not lead to profitable operation for all possible product demand profile. Also change in feed and /or product price may lead to adjust the production target to maximise the profitability. In batch distillation, total reflux operation is recommended or observed at the begining of the operation (as is the case for methnaol or ethanol esterification). However, in the case of hydrolysis, total reflux operation was obseved at the end of the operation. This was due to lactic acid (being the heaviest) was withrawn as the final bottom product.
27
Edreder, E. A. "Modelling and optimisation of batch distillation involving esterification and hydrolysis reaction systems. Modelling and optimisation of conventional and unconventional batch distillation process: Application to esterification of methanol and ethanol using acetic acid and hydrolysis of methyl lactate system". Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4296.
Texto completoResumen
Batch distillation with chemical reaction when takes place in the same unit is referred to
as batch reactive distillation process. The combination reduces the capital and operating
costs considerably. Among many different types of batch reactive distillation column
configurations, (a) conventional (b) inverted (c) semi-batch columns are considered
here.
Three reaction schemes such as (a) esterification of methanol (b) esterification of
ethanol (c) hydrolysis of methyl lactate are studied here. Four different types of
dynamic optimisation problems such as (a) maximum conversion (b) maximum
productivity (c) maximum profit and (d) minimum time are formulated in this work.
Optimal design and or operation policies are obtained for all the reaction schemes.
A detailed rigorous dynamic model consisting of mass, energy balances, chemical
reaction and thermodynamic properties is considered for the process. The model was
incorporated within the dynamic optimisation problems. Control Vector
Parameterisation (CVP) technique was used to convert the dynamic optimisation
problem into a nonlinear programming problem which was solved using efficient SQP
(Successive Quadratic Programming) method available within the gPROMS (general
PROcess Modelling System) software.
It is observed that multi-reflux ratio or linear reflux operation always led to better
performance in terms of conversion, productivity for all reaction schemes compared to
that obtained using single reflux operation.
Feed dilution (in the case of ethanol esterification) led to more profit even though
productivity was found to be lower. This was due to reduction in feed price because of
feed dilution. Semi-batch reactive distillation opertation (for ethanol esterification) led
to better conversion compared to conventional batch distillation, however, the total
amount of acetic acid (reactant) was greater in semi-batch operation. Optimisation of
design and operation (for ethanol esterification) clearly showed that a single cloumn
will not lead to profitable operation for all possible product demand profile. Also
change in feed and /or product price may lead to adjust the production target to
maximise the profitability.
In batch distillation, total reflux operation is recommended or observed at the begining
of the operation (as is the case for methnaol or ethanol esterification). However, in the
case of hydrolysis, total reflux operation was obseved at the end of the operation. This
was due to lactic acid (being the heaviest) was withrawn as the final bottom product.Libyan Petroleum Institute
28
David, Hamon Catherine. "Synthese asymetrique de lactones : application a la serie des acides meviniques, inhibiteurs de la biosynthese du cholesterol". Poitiers, 1988. http://www.theses.fr/1988POIT2203.
Texto completoResumen
La compactine et la mevinoline sont des inhibiteurs de l'hmg-coa reductase, enzyme qui transforme l'hmg-coa en acide mevalonique dans une des premieres etapes de la biosynthese du cholesterol. Ces inhibiteurs sont caracterises par un squelette decalinique lie a un systeme lactonique dont la presence est indispensable a l'activite biologique. La preparation d'analogues necessite de disposer d'un synthon chiral qui peut etre obtenu a partir d'un sucre de la serie d. Plusieurs methodes de desoxygenation en positions 2 et 4 a partir de sucres divers (glucose, mannose, galactose) ont ete etudiees. Elles reposent sur l'hydrogenolyse de derives halogenes ou soufres. C'est ainsi qu'en utilisant l'anhydro-1,6 d-glucose la lactone recherchee est tenue en seulement 6 etapes
29
Leke, Lokombé. "Valorisation d'un hydrolysat de protéine obtenu à partir de l'hémoglobine bovine : Etudes expérimentales, immunochimiques et essais cliniques". Compiègne, 1994. http://www.theses.fr/1994COMP775S.
Texto completoResumen
L'objectif de ce travail est d'évaluer la valeur biologique et l'efficacité nutritionnelle de l'hydrolysat pepsique d'hémoglobine bovine produit à l'échelle pilote. Les études biochimiques révèlent un déficit en isoleucine et cystéine nécessitant un enrichissement préalable avant tout usage à visé&e nutritionnelle, un rapport en acide aminés essentiels à 49,7 %) et un taux d'acides aminés libres inférieur à 1%. La spectrométrie de masse situe le poids moléculaire des peptides entre 600 et 1650 daltons. La détermination de l'immunogénicité et de l'antigénicité de l'hémoglobine bovine native et de son hydrolysat a été réalisé par la méthode ELISA et le test d'inhibition ELISA chez la souris. Cette capacité est retrouvée uniquement pour l'hémoglobine bovine native. L'hydrolyse enzymatique semble diminuer ou détruire les propriétés immunogènes et antigéniques de l'hémoglobine. Les Coefficients d'Utilisation Digestives (C. U. D. ) et d'efficacité protéique étudiés chez le rat montrent des valeurs similaires à celles observées avec la caséine. Chez le prématuré, on obtient une rétention azotée et une croissance identiques lorsque les enfants sont alimentés au lait humain enrichi avec l'hydrolysat d'hémoglobine ou avec un lait conçu spécialement pour les prématurésThe aim of the present study was to evaluate the biological value and the nutritive efficiency of a peptic haemoglobin hydrolyse produced at a pilot –plant scale. The analysis revealed a deficiency in isoleucine and cysteine demanding an enrichment before utilisation, a ratio of essential amino acids : total nitrogen of 3,16 (amount of essential amino acids mg/g protein 49,7 %) and less than 1 % of free amino acids. Mass Spectrometry estimated the mass molecular of peptides between 600 – 1650 dalton. The evaluation of immunogenicity and antigenicity of native haemoglobin and its hydrolysate was done by ELISA and inhibition ELISA in mice : enzymatic hydrolysis seems to decrease or destroy the immogenic and antigenic activities of haemoglobin. The true digestibility and the protein efficiency studied in rats showed similar values as those observed with casein hydrolysate. Feeding of the premature child with breast milk enriched by haemoglobin hydrolysate allow to maintain an adequate growth and a better nitrogen tetention
30
Miao, Lei. "Synthesis of Amphibian Alkaloids and Development of Acetaminophen Analogues". ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/985.
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The focus of these studies has been toward the development of new synthetic methods and procedures for the synthesis of novel compounds with unique biological properties. This research has led to the development of two new synthetic strategies for the construction of two novel amphibian alkaloids. In addition, the efforts have led to the large-scale process for the preparation of a novel analgesic compound. The regioselective ring opening of lactones (δ-valerolactone and γ-butyrolactone) with aryllithium reagents is reported for the construction of a series of δ-hydroxyarylketones and γ-hydroxyarylketones. Both the R and S enantiomers of the amphibian alkaloid noranabasamine were prepared in >30% overall yield with 80% ee and 86% ee, respectively. An enantioselective iridium-catalyzed N-heterocyclization reaction with either (R)- or (S)-1-phenylethylamine and 1-(5-methoxypyridin-3-yl)-1, 5-pentanediol was employed to generate the 2-(pyridin-3-yl)-piperidine ring system in 69-72% yield. A cis-2, 5-disubstitued pyrrolidine building block derived from (-)-Cocaine•HCl was prepared. We utilized this compound as a chiral building block for the formal synthesis of (+)-gephyrotoxin. Using this pyrrolidine building block, Kishi's intermediate was obtained enantiospecifically in 15 steps and 9.4% overall yield. A large-scale process for the preparation of the analgesic compounds SCP-123 and its sodium salt, SCP-123ss•monohydrate has been developed. The process for the preparation of SCP-123 required three synthetic steps with no chromatography, while the process for the preparation of SCP-123ss required four synthetic steps and no chromatography. The overall yields for both SCP-123 and SCP-123ss were 47% and 46%, respectively, and both compounds were obtained in exceptionally high purity (>99%).
31
Peterson, Ralph Scott. "Lactose hydrolysis by immobilized beta-galactosidase in a capillary bed reactor". 1987. http://catalog.hathitrust.org/api/volumes/oclc/16704043.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1987.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 235-245).
32
Bakken, Andrew Peter. "Novel immobilized [beta]-galactosidase reactors for hydrolysis of lactose in skim milk". 1990. http://catalog.hathitrust.org/api/volumes/oclc/23174620.html.
Texto completoResumen
Thesis (Ph. D.)--University of Wisconsin--Madison, 1990.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 275-287).
33
Scott, Timothy Charles. "Hydrolysis of lactose in permeate from the ultrafiltration of cottage cheese whey using immobilized beta-galsctosidase". 1985. http://catalog.hathitrust.org/api/volumes/oclc/12136891.html.
Texto completoResumen
Thesis (Ph. D.)--University of Wisconsin--Madison, 1985.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 366-372).
34
Chaudhary, Manoja N. "An evaluation of nanofiltration and lactose hydrolysis of milk UF permeate for use in ice cream". Thesis, 1997. http://handle.uws.edu.au:8081/1959.7/741.
Texto completoResumen
This study aimed to obtain 15% total solids and reduced mineral content in milk UF permeate by nanofiltration, hydrolysing the lactose content of nano-concentrate enzymically, partially substituting sucrose in ice cream formulations with hydrolysed lactose nano-concentrate (HLNC), and investigating the effects of HLNC on the physio-chemical and sensory characteristics of ice cream. The desired 15% total solids in the nano-concentrate was achieved after three fold concentration of milk UF permeate. The colour of milk permeate changed, pH and mineral content decreased, and crude protein content, lactose content and titratable acidity increased. The lactose content was hydrolysed by enzyme lactase. HLNC was used to replace 25% and 50% of sucrose in ice cream formulations. Springiness, cohesiveness, chewiness, adhesiveness, hardness, iciness, Ph and colour were not significantly affected. Viscosity, freezing point, glass transition temperature, melting temperature, gumminess and sweetness were significantly decreased, whereas freezing time, saltiness and cooked flavour were significantly increased. The overall acceptability of ice cream significantly decreased at 50% but was insignificantly affected at the 25% level. These results indicate that about one quarter of sucrose could be replaced by HLNC.
35
Zamecnik, John Roby. "Investigation of the kinetics of the reaction network involving the hydrolysis of lactose and oxidation of the hydrolysis products in nitric acid solution". 1987. http://catalog.hathitrust.org/api/volumes/oclc/16793842.html.
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Chen, Jun Qi y 陳駿奇. "Synthesis, characterization and hydrolysis of poly(L-lactide) copolymers". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/64560360887789864268.
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Chen, Jiuun-Chi y 陳駿奇. "Synthesis,Characterization and Hydrolysis of Poly(L-lactide) Copolymers". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/08915252329667828727.
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碩士國立臺灣科技大學
纖維工程技術系
82
Two new types of boidegradable polymer materials, copoly(L- lactic acid/succinic anhydride/ethylene gl- ycol) and copoly(L- lactic acid/succinic anhydride/po- lyethylene glycol),was synthesized by means of direct copolycondensation of EG or PEG( molar mass=200) with diacid, synthesized from L-lactic acid and succinic anhydride,in the presence of a Ti(OBu) or SnOc cata- lyst. The copolymers were characterized by GPC , IR , H- NMR and contact angle.The first-order kinetics is used to caculate the rate constants of hydrolysis reaction.The results indicate that the lower reaction pressure,the higher molecular weight of copolymers.T- here is no discernible difference between the Ti(OBu) and SnOc catalysts in polymerization,as far as mole- cular weight of products and yield of reaction is concerned. The rate constant for more hydrophilic copoly( LA/SA/PEG) is higher than copoly(LA/SA/EG).Ta- king into account the rate constants of PLLA,PEG/PLLA triblock copolymers in the previous study and copoly- mers in this study that the rate constants of hydrol- ysis for lactic acid biodegradble polymers is correl- ated with the ratio of no. of ester to no. of carbon on main chain.
38
Picardo, Clive Michael. "The hydrolysis of 5-HETE lactone by paraoxonase 1 and its stability in serum". 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=789022&T=F.
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劉興鑑. "The hydrolysis kinetics and crystalline properties in polyethylene glycol/poly(L-lactide)block copolymers". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/46719635574241960016.
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邱齡誼. "The effect of substituents on the acidic hydrolysis of 4 substituted-��,��,�奠�,�奠�-tetrabromo-0-xylene to form lactone". Thesis, 1989. http://ndltd.ncl.edu.tw/handle/87895012249776961562.
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41
Edreder, E. A., M. Emtir y Iqbal M. Mujtaba. "Energy saving in conventional and uncoventional batch reactive distillation: application to hydrolysis of methyl lactate system". 2014. http://hdl.handle.net/10454/10623.
Texto completoResumen
NoIn this work, energy consumption in a middle vessel batch reactive distillation (MVBRD) column is considered for the production of lactic acid via hydrolysis of methyl lactate. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time which consequently minimizes the total energy consumption. The problem is subject to constraints on the amount and purity of lactic acid. The optimisation variables are reflux ratio and/or reboil ratio which are treated as piecewise constant. The earlier work of the authors on energy consumption in conventional batch reactive distillation column (CBRD) for the same reaction system is used for comparative analysis with the energy consumption in MVBRD. As an example, for a given separation task, the optimization results show that MVBRD is capable of saving over 23 % energy compared to energy consumption in CBRD column for the same task.
42
Samarajeewa, Sandani. "Poly(lactide)-containing Multifunctional Nanoparticles: Synthesis, Domain-selective Degradation and Therapeutic Applicability". Thesis, 2013. http://hdl.handle.net/1969.1/149300.
Texto completoResumen
Construction of nanoassemblies from degradable components is desired for packaging and controlled release of active therapeutics, and eventual biodegradability in vivo. In this study, shell crosslinked micelles composed of biodegradable poly(lactide) (PLA) core were prepared by the self-assembly of an amphiphilic diblock copolymer synthesized by a combination of ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Enzymatic degradation of the PLA cores of the nanoparticles was achieved upon the addition of proteinase K (PK). Kinetic analyses and comparison of the properties of the nanomaterials as a function of degradation extent will be discussed.
Building upon our findings from selective-excavation of the PLA core, enzyme- and redox-responsive nanoparticles were constructed for the encapsulation and stimuli-responsive release of an antitumor drug. This potent chemotherapeutic, otherwise poorly soluble in water was dispersed into aqueous solution by the supramolecular co-assembly with an amphiphilic block copolymer, and the release from within the core of these nanoparticles were gated by crosslinking the hydrophilic shell region with a reduction-responsive crosslinker. Enzyme- and reduction-triggered release behavior of the antitumor drug was demonstrated along with their remarkably high in vitro efficacy.
As cationic nanoparticles are a promising class of transfection agents for nucleic acid delivery, in the next part of the study, synthetic methodologies were developed for the conversion of the negatively-charged shell of the enzymatically-degradable shell crosslinked micelles to positively-charged cationic nanoparticles for the complexation of nucleic acids. These degradable cationic nanoparticles were found to efficiently deliver and transfect plasmid DNA in vitro. The hydrolysis of the PLA core and crosslinkers of the nanocarriers may provide a mechanism for their programmed disassembly within endosomes, which would in-turn promote endosomal disruption by osmotic swelling, and release of active therapeutics from the polymeric assemblies.
In the last part, a comparative degradation study was performed between the anionic and cationic micellar assemblies in the presence of two model enzymes, and electrostatic interaction-mediated preferential hydrolysis was demonstrated between the oppositely-charged enzyme-micelle pairs. These findings may be of potential significance toward the design of charge-mediated enzyme-responsive nanomaterials that are capable of undergoing environmentally-triggered therapeutic release, disassembly or morphological alterations under selective enzyme conditions.
43
Ramachandran, Karthik. "Bioresorbable Vascular Scaffolds Gain Ductility, Resistance to Hydrolysis, and Radial Strength via a Unique Poly L-lactide Microstructure". Thesis, 2019. https://thesis.library.caltech.edu/11276/3/Movie%20S5-1.mov.
Texto completoResumen
Advances in tissue engineering over the past few decades are poised to revolutionize drug delivery and biomedical implants. Bioresorbable vascular scaffolds (BVS), which are made from the semicrystalline polymer poly (L-lactide), are an example of polymers saving and improving the quality of human life. BVSs are emerging as a promising alternative to metal stents for the treatment of coronary heart disease (CHD), one of the leading causes of death in the world. In contrast to permanent stents, BVSs are designed to have a limited lifespan in the body; they restore blood flow through the occluded artery by lending it support for 3-6 months, but are completely resorbed in 2-3 years, leaving behind a healthy artery. This transient character of BVS restores vasomotion in the treated artery and can eliminate the risk of thrombosis, a dreaded complication regarded as the bane of stenting.
The promising success of the first and currently only clinically-approved BVS (FDA-approval in 2016) provides an impetus to continue its development. The struts of the BVS (~ 150μm) are nearly two times thicker than in metal stents (~ 80μm). A thicker device is challenging to implant and is unable to treat smaller and tortuous arteries. Furthermore, clinicians speculate that irregular blow flow over thicker struts may contribute towards thrombosis. An added complication of working with BVSs is that they are difficult to visualize with X-rays owing to the low atomic mass of polymers. The need for a BVS that is thinner, stronger, and radio-opaque is the motivation for this thesis, which aims to extend the benefits of transient implants to a broader patient population. Chapter I provides a brief chronological overview of the evolution of cardiovascular therapeutics to combat CHD. Chapters II and III elucidate micron-scale gradients in the PLLA microstructure of the clinically-approved BVS that overcome PLLA’s inherent brittleness and provide lasting radial support to the artery. Chapter IV discusses the fabrication of novel instrumentation to establish structure-property relationships for scaffolds, and Chapter V explores polylactide nanocomposites that not only increase radial strength in a thinner profile but also provide radio-opacity.
44
"Characterization of the mechanism of sweet almond beta-glucosidase and a novel assay of the rate of hydrolysis of glucono-1,5-lactone". Tulane University, 2007.
Buscar texto completoResumen
Sweet almond beta-glucosidase was used to catalyze the hydrolysis of paranitrophenol-beta-D-glucopyranoside (pNPG) and methyl-beta-D-glucopyranoside (methyl-glc). The second order rate constants (kcat/Km) were determined over the range of pLs (pL = pH or pD) at which the enzyme is active, resulting in bell shaped plots of rate constants versus pL. k cat/Km represents the mechanistic steps up through and including the first irreversible step (leaving group dissociation). The second order limiting rate constants (kcat/Km)lim show a small solvent kinetic isotope effect (SKIE H2O(V/K) lim/D2O(V/K)lim), 1.15 (+/- 0.03) with pNPG and 1.05 (+/- 0.08) with methyl-glc. The observed acid dissociation constants (pKas) of the enzymic carboxylic acids for methyl-glc are ∼1 pH unit more acid than those for pNPG. These results support that enzyme catalyzed hydrolysis of methyl-glc hydrolysis is dependent on the pKa of an additional anionic residue The inhibitory effects of glucose on the enzyme catalyzed reaction of pNPG were monitored in H2O and D2O. Glucose showed negligible change in binding affinity with pH or substitution of D2O for H 2O, indicating no change in the ability of the glycon moiety of the substrate (and possibly the substrate itself) to bind to the enzyme. The shifts seen in kcat/Km are representative of a shift in k cat A new method of determining the rate of hydrolysis of glucono-1,5-lactone is introduced. The method is applicable at pHs 6 to over 7, where the rate of hydrolysis depends on solvent conditions. The assay is a low cost, efficient and easy method to obtain the rate of hydrolysisacase@tulane.edu
45
Edreder, E. A., Iqbal M. Mujtaba y M. Emtir. "Comparison of Conventional and Middle Vessel Batch Reactive Distillation Column: Application to Hydrolysis of Methyl Lactate to Lactic Acid". 2013. http://hdl.handle.net/10454/9643.
Texto completoResumen
NoComparison of optimal operation between conventional batch reactive distillation column (CBRD) and middle-vessel batch reactive column (MVBRD) for the production of lactic acid via hydrolysis of methyl lactate has not been considered in the past. Therefore, it is the main focus in this work. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time subject to constraints on the amount and purity of lactic acid. Control variables (reflux ratio or/and a reboil ratio) are treated as a piecewise constant. Optimization results indicate that MVBRD is more effective than CBRD in terms of saving in batch time which can be as high as of 20 %.