Bibliografias temáticas / Cellulose

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Literatura científica selecionada sobre o tema "Cellulose"

Autor: Grafiati

Publicado: 4 de junho de 2021

Última modificação: 31 de julho de 2024

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Artigos de revistas sobre o assunto "Cellulose"

Deng, Yijie, e Shiao Y. Wang. "Sorption of Cellulases in Biofilm Enhances Cellulose Degradation by Bacillus subtilis". Microorganisms 10, n.º 8 (26 de julho de 2022): 1505. http://dx.doi.org/10.3390/microorganisms10081505.

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Biofilm commonly forms on the surfaces of cellulosic biomass but its roles in cellulose degradation remain largely unexplored. We used Bacillus subtilis to study possible mechanisms and the contributions of two major biofilm components, extracellular polysaccharides (EPS) and TasA protein, to submerged biofilm formation on cellulose and its degradation. We found that biofilm produced by B. subtilis is able to absorb exogenous cellulase added to the culture medium and also retain self-produced cellulase within the biofilm matrix. The bacteria that produced more biofilm degraded more cellulose compared to strains that produced less biofilm. Knockout strains that lacked both EPS and TasA formed a smaller amount of submerged biofilm on cellulose than the wild-type strain and also degraded less cellulose. Imaging of biofilm on cellulose suggests that bacteria, cellulose, and cellulases form cellulolytic biofilm complexes that facilitate synergistic cellulose degradation. This study brings additional insight into the important functions of biofilm in cellulose degradation and could potentiate the development of biofilm-based technology to enhance biomass degradation for biofuel production.

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Kumar, Amit. "Dissolving pulp production: Cellulases and xylanases for the enhancement of cellulose accessibility and reactivity". Physical Sciences Reviews 6, n.º 5 (30 de abril de 2021): 111–29. http://dx.doi.org/10.1515/psr-2019-0047.

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Abstract Dissolving pulps are high-grade cellulose pulps that have minimum amount of non-cellulosic impurities. Dissolving pulps are the basic source for the manufacturing of several cellulosic products such as viscose, lyocell, cellulose acetates, cellulose nitrates, carboxymethyl-cellulose, etc. Dissolving pulps are mainly manufactured by pre-hydrolysis kraft and acid sulphite pulping. A high reactivity of dissolving pulps is desirable for its eco-friendly utilization for several purposes. Several approaches including mechanical, chemical, ultrasonic, and enzymatic treatments have been employed for the improvement of pulp reactivity. This review mainly focussed on pulp reactivity improvement through enzymatic approaches. Cellulases and xylanase have been proved effective for the improvement of pulp reactivity of dissolving pulp from different sources. The different combinations of cellulase, xylanase, and mechanical refining have been tested and found more effective rather than the single one.

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Hetzler, Stephan, Daniel Bröker e Alexander Steinbüchel. "Saccharification of Cellulose by Recombinant Rhodococcus opacus PD630 Strains". Applied and Environmental Microbiology 79, n.º 17 (21 de junho de 2013): 5159–66. http://dx.doi.org/10.1128/aem.01214-13.

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ABSTRACTThe noncellulolytic actinomyceteRhodococcus opacusstrain PD630 is the model oleaginous prokaryote with regard to the accumulation and biosynthesis of lipids, which serve as carbon and energy storage compounds and can account for as much as 87% of the dry mass of the cell in this strain. In order to establish cellulose degradation inR. opacusPD630, we engineered strains that episomally expressed six different cellulase genes fromCellulomonas fimiATCC 484 (cenABC,cex,cbhA) andThermobifida fuscaDSM43792 (cel6A), thereby enablingR. opacusPD630 to degrade cellulosic substrates to cellobiose. Of all the enzymes tested, five exhibited a cellulase activity toward carboxymethyl cellulose (CMC) and/or microcrystalline cellulose (MCC) as high as 0.313 ± 0.01 U · ml−1, but recombinant strains also hydrolyzed cotton, birch cellulose, copy paper, and wheat straw. Cocultivations of recombinant strains expressing different cellulase genes with MCC as the substrate were carried out to identify an appropriate set of cellulases for efficient hydrolysis of cellulose byR. opacus. Based on these experiments, the multicellulase gene expression plasmid pCellulose was constructed, which enabledR. opacusPD630 to hydrolyze as much as 9.3% ± 0.6% (wt/vol) of the cellulose provided. For the direct production of lipids from birch cellulose, a two-step cocultivation experiment was carried out. In the first step, 20% (wt/vol) of the substrate was hydrolyzed by recombinant strains expressing the whole set of cellulase genes. The second step was performed by a recombinant cellobiose-utilizing strain ofR. opacusPD630, which accumulated 15.1% (wt/wt) fatty acids from the cellobiose formed in the first step.

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Hall, J., G. W. Black, L. M. A. Ferreira, S. J. Millward-Sadler, B. R. S. Ali, G. P. Hazlewood e H. J. Gilbert. "The non-catalytic cellulose-binding domain of a novel cellulase from Pseudomonas fluorescens subsp. cellulosa is important for the efficient hydrolysis of Avicel". Biochemical Journal 309, n.º 3 (1 de agosto de 1995): 749–56. http://dx.doi.org/10.1042/bj3090749.

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A genomic library of Pseudomonas fluorescens subsp. cellulosa DNA, constructed in lambda ZAPII, was screened for carboxymethyl-cellulase activity. The pseudomonad insert from a recombinant phage which displayed elevated cellulase activity in comparison with other cellulase-positive clones present in the library, was excised into pBluescript SK- to generate the plasmid pC48. The nucleotide sequence of the cellulase gene, designated celE, revealed a single open reading frame of 1710 bp that encoded a polypeptide, defined as endoglucanase E (CelE), of M(r) 59663. The deduced primary structure of CelE revealed an N-terminal signal peptide followed by a 300-amino-acid sequence that exhibited significant identity with the catalytic domains of cellulases belonging to glycosyl hydrolase Family 5. Adjacent to the catalytic domain was a 40-residue region that exhibited strong sequence identity to non-catalytic domains located in two other endoglucanases and a xylanase from P. fluorescens. The C-terminal 100 residues of CelE were similar to Type-I cellulose-binding domains (CBDs). The three domains of the cellulase were joined by linker sequences rich in serine residues. Analysis of the biochemical properties of full-length and truncated derivatives of CelE confirmed that the enzyme comprised an N-terminal catalytic domain and a C-terminal CBD. Analysis of purified CelE revealed that the enzyme had an M(r) of 56000 and an experimentally determined N-terminal sequence identical to residues 40-54 of the deduced primary structure of full-length CelE. The enzyme exhibited an endo mode of action in hydrolysing a range of cellulosic substrates including Avicel and acid-swollen cellulose, but did not attack xylan or any other hemicelluloses. A truncated form of the enzyme, which lacked the C-terminal CBD, displayed the same activity as full-length CelE against soluble cellulose and acid-swollen cellulose, but exhibited substantially lower activity than the full-length cellulase against Avicel. The significance of these data in relation to the role of the CBD is discussed.

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Brumm, Phillip, Phillip Brumm, Dan Xie, Dan Xie, Larry Allen, Larry Allen, David A. Mead e David A. Mead. "Hydrolysis of Cellulose by Soluble Clostridium Thermocellum and Acidothermus Cellulolyticus Cellulases". Journal of Enzymes 1, n.º 1 (26 de abril de 2018): 5–19. http://dx.doi.org/10.14302/issn.2690-4829.jen-18-2025.

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The goal of this work was to clone, express, characterize and assemble a set of soluble thermostablecellulases capable of significantly degrading cellulose. We successfully cloned, expressed, and purified eleven Clostridium thermocellum (Cthe) cellulases and eight Acidothermuscellulolyticus(Acel) cellulases. The performance of the nineteen enzymes was evaluated on crystalline (filter paper) and amorphous (PASC) cellulose. Hydrolysis products generated from these two substrates were converted to glucose using beta-glucosidase and the glucose formed was determined enzymatically. Ten of the eleven Cthe enzymes were highly active on amorphous cellulose. The individual enzymes all produced <10% reducing sugar equivalents from filter paper. Combinations of Cthe cellulases gave higher conversions, with the combination of CelE, CelI, CelG, and CelK converting 34% of the crystalline cellulose. All eight Acel cellulases showed endo-cellulase activity and were highly active on PASC. Only Acel_0615 produced more than 10% reducing sugar equivalents from filter paper, and a combination of six Acel cellulases produced 32% conversion. Acel_0617, a GH48 exo-cellulase, and Acel_0619, a GH12 endo-cellulase, synergistically stimulated cellulose degradation by the combination of Cthe cellulases to almost 80%. Addition of both Acel enzymes to the Cthe enzyme mix did not further stimulate hydrolysis. Cthe CelG and CelI stimulated cellulose degradation by the combination of Acel cellulases to 66%.

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Chatterjee, Soumya, Sonika Sharma, Rajesh Kumar Prasad, Sibnarayan Datta, Dharmendra Dubey, Mukesh K. Meghvansi, Mohan G. Vairale e Vijay Veer. "Cellulase Enzyme based Biodegradation of Cellulosic Materials: An Overview". South Asian Journal of Experimental Biology 5, n.º 6 (11 de março de 2016): 271–82. http://dx.doi.org/10.38150/sajeb.5(6).p271-282.

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Cellulose, a macromolecule of β -D- anhydroglucopyranose units linked by β (1,4)-glycosidic bonds, is the world’s most abundant organic polymer and is the main component of plant biomass that provides stability. Due to its sta-ble fibrous property, it has become one of the most important commercial raw materials for many industries. However, accumulation of waste cellulose due to natural and/or anthropogenic sources is a matter of concern in terms of environmental pollution. Wastes cellulosic substrates can be utilized as sources of energy through controlled hydrolysis using cellulases- a complex group of enzymes capable of degrading all types of cellulosic waste materials. A number of bacteria, fungi and insects are having the capability to degrade cellulose by production of cellulase enzymes. Further, the symbiotic insect-microbe relationships present in the insect gut microbiome for the production of cellulolytic system is of immense importance as this would lead to applications in different fields like biodegradation of cellulosic wastes, pollution reduction, biofuel production, insect/pest control etc. Cel-lulase gene can also be improved by genetic or protein engineering methods using recent technological advances. This review deals with the advances of cellulase enzymes and its utilization for different application.

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Pratama, Rahadian, I. Made Artika, Tetty Chaidamsari, Herti Sugiarti e Soekarno Mismana Putra. "Isolation and Molecular Cloning of Cellulase Gene from Bovine Rumen Bacteria". Current Biochemistry 1, n.º 1 (2 de setembro de 2017): 29–36. http://dx.doi.org/10.29244/cb.1.1.29-36.

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Cellulases are the enzymes that hydrolyze cellulosic biomass and are produced by the microorganisms that grow over cellulosic matters. The objective of this research was to isolate and clone cellulase gene from cellulose-degrading bacteria of bovine rumen. Cellulose-degrading bacteria was isolated from rumen fluid using a selective medium. Total RNA was isolated from selected colony having cellulose degrading activity and was used as a template for cDNA construction using reverse transcriptase polymerase chain reaction (RT-PCR) technique. The resulted cDNA was employed as a template for PCR amplification of cellulase gene using specific primers. The cellulase gene candidate obtained was cloned into the pGEM-T-Easy vector followed by determination of its nucleotide sequence. The sequence was then aligned with sequences of cellulase genes from GenBank. Results showed that a number of isolates of rumen bacteria exhibit cellulase activity and the CR-8 isolate was selected for further analysis. The successful isolation of total RNA from CR-8 was indicated by the presence of two intense bands of ribosomal RNA (23S and 16S). The reverse transcription process was successful and the amplification of cellulase gene using the specific primers F1 and R1 resulted in a DNA fragment of 1900 bp as a candidate of cellulase gene. The fragment was successfully cloned into the pGEM-T-Easy vector, and the resulted recombinant plasmid was successfully introduced into the E. coli cells. Nucleotide sequence analysis suggested that the cloned gene is cellulase gene and shares 99% homology with the endo-1,6-beta-glucanase of T. harzianum.

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Li, Xia, Xiaoyan Geng, Lu Gao, Yanfang Wu, Yongli Wang, Alei Geng, Jianzhong Sun e Jianxiong Jiang. "Optimized expression of a hyperthermostable endoglucanase from Pyrococcus horikoshii in Arabidopsis thaliana". BioResources 14, n.º 2 (19 de fevereiro de 2019): 2812–26. http://dx.doi.org/10.15376/biores.14.2.2812-2826.

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Manufacturing microbial cellulase in plants is an attractive strategy for the cost-effective production of cellulosic ethanol, especially the expression of thermostable cellulase, which causes no negative effects on plant growth and development. The beta-1,4-endogenous cellulase from Pyrococcus horikoshii (EGPh) is considered one of the most promising glycosyl hydrolase in the biofuel and textile industry for its hyperthermostability and its capability to hydrolyze crystalline celluloses, which has been researched extensively during recent years. In this study, the coding sequence of EGPh was expressed in Arabidopsis thaliana under the control of a CaMV35S promoter after codon optimization, with the addition of a eukaryotic Kozak sequence. The expression of EGPh caused no deleterious effects to the growth and development of transgenic A. thaliana. The heterologous EGPh showed relatively high activities, up to 111.69 and 13.35 U.mg-1 total soluble protein against soluble cellulose carboxymethyl cellulose (CMC) and insoluble microcrystalline cellulose (Avicel), respectively. The subcellular localization analysis showed that the EGPh protein was targeted to the plasma membrane and cell wall. Based on these results, it is proposed that EGPh is an ideal candidate for the commercial production of hyperthermostable endoglucanase using plants as biofactories.

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Mizuno, Masahiro, Shuji Kachi, Eiji Togawa, Noriko Hayashi, Kouichi Nozaki, Toshiyuki Itoh e Yoshihiko Amano. "Structure of Regenerated Celluloses Treated with Ionic Liquids and Comparison of their Enzymatic Digestibility by Purified Cellulase Components". Australian Journal of Chemistry 65, n.º 11 (2012): 1491. http://dx.doi.org/10.1071/ch12342.

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In this study, regenerated celluloses were prepared from microcrystalline cellulose (MCC) by treatment with three ionic liquids (ILs) having 1-ethyl-3-methylimidazolium (Emim) as the cation, and the IL N-(2-methoxyethyl)-N,N-diethyl-N-methylammonium alanine ([N221ME][Ala]), where the amino acid moiety is the anion. The crystal form of cellulose was transformed from cellulose I to cellulose II by dissolution with an IL and regeneration with anti-solvent. However, the crystallinity of the regenerated cellulose was different; the disordered chain region was increased in the order of [N221ME][Ala] < [Emim][OAc] < [Emim][DEP] < [Emim][Cl]. The monocomponent cellulase, especially endoglucanase, showed high hydrolyzing activity for regenerated cellulose compared with untreated cellulose. Furthermore, the degree of increase of hydrolyzing activity was almost coincident with the order of crystallinity. For the effective hydrolysis of cellulose treated with an IL, it is necessary to prepare the cellulase mixture containing an adequate ratio of each cellulase component according to crystal allomorph and the crystallinity of regenerated cellulose.

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Bu, Yingjie, Bassam Alkotaini, Bipinchandra K. Salunke, Aarti R. Deshmukh, Pathikrit Saha e Beom Soo Kim. "Direct ethanol production from cellulose by consortium of Trichoderma reesei and Candida molischiana". Green Processing and Synthesis 8, n.º 1 (28 de janeiro de 2019): 416–20. http://dx.doi.org/10.1515/gps-2019-0009.

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Abstract Industrial cellulosic ethanol production is a challenge due to the high cost of cellulases for hydrolysis when lignocellulosic materials are used as feedstock. In this study, direct ethanol production from cellulose was performed by consortium of Trichoderma reesei and Candida molischiana. Cellulose was hydrolyzed by a fully enzymatic saccharification process using Trichoderma reesei cellulases. The produced reducing sugar was further utilized by Candida molischiana for ethanol production. Because the optimal temperature for the cellulase system is approximately 50°C, the effect of temperature rise from 30°C to 50°C on cellulose hydrolysis was investigated. The results showed that the temperature rise from 30°C to 50°C after 36 h of cultivation was the best for reducing sugar and glucose production. Under these conditions, the maximum concentrations of reducing sugar and glucose produced by T. reesei were 8.0 g/L and 4.6 g/L at 60 h, respectively. The maximum production of ethanol by C. molischiana was 3.0 g/L after 120 h.

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Mais fontes

Teses / dissertações sobre o assunto "Cellulose"

Ravachol, Julie. "Rôle des glycosides hydrolases de famille 9 dans la dégradation de la cellulose et exploration du catabolisme de xyloglucane chez Ruminiclostridium cellulolyticum". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4054.

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R. cellulolyticum est une bactérie mésophile, anaérobie stricte et cellulolytique, qui sécrète des macro-complexes multienzymatiques (cellulosomes) très performants dans la dégradation des polysaccharides de la paroi végétale. Les Glycoside Hydrolases de famille 9 (GH9) sont toujours surreprésentées chez les bactéries à cellulosomes. Le génome de R. cellulolyticum code 13 GH9 dont 12 participent aux cellulosomes. Mon travail de thèse a consisté à étudier l’ensemble des GH9 de R. cellulolyticum, en déterminant leurs activités à l’état libre et en complexes, afin d’élucider leurs rôles dans la dégradation de la cellulose. Les GH9 ont chacune des activités et des spécificités de substrats différentes. Deux GH9 présentent des activités atypiques, puisque l’une d’elles est inactive et l’autre est une xyloglucanase. Les caractérisations en complexes ont souligné l’importance de la diversité des GH9 et ont montré qu’elles agissent en synergie dans la dégradation de la cellulose. De plus, l’élargissement du panel des GH9 de R. cellulolyticum par l’introduction d’une cellulase exogène de Lachnoclostridium phytofermentans a permis d’améliorer les capacités cellulolytiques de la clostridie. L’activité xyloglucanase d’une des GH9 m’a poussé à étudier le catabolisme du xyloglucane chez R. cellulolyticum. Ce travail a mis en exergue la présence d’un équipement spécialisé dans l’utilisation de ce sucre. Ainsi, après une dégradation du xyloglucane par les enzymes cellulosomales en xyloglucane dextrines, ces dernières sont importées dans le cytoplasme par un transporteur ABC spécifique puis hydrolysées séquentiellement par les enzymes cytoplasmiques en mono et disaccharides assimilables
Ruminiclostridium cellulolyticum is a mesophilic and strictly anaerobic bacterium. It produces multienzymatic complexes called cellulosomes which efficiently degrade the plant cell wall polysaccharides. Family-9 Glycoside Hydrolases (GH9) are plethoric in cellulosome-producing bacteria. The genome of R. cellulolyticum thus encodes for 13 GH9 enzymes, 12 of them participate to the cellulosomes.My Ph. D. aimed at characterizing all GH9 enzymes from R. cellulolyticum, by determining their activities in a free and complexed states, in order to elucidate their role in cellulose degradation. All GH9 enzymes exhibit various activities and substrate specificities. Two of them have atypical activities, since one is inactive and one is a xyloglucanase. Results obtained when all GH9 are in complex highlighted the importance of GH9 diversity and revealed they act synergistically in cellulose depolymerization. Moreover, expanding the panel of GH9 enzymes by introducing an exogenous cellulase from Lachnoclostridium phytofermentans improved the cellulolytic capacities of R. cellulolyticum. The xyloglucanase activity of one GH9 enzyme prompted me to investigate the xyloglucan catabolism in R. cellulolyticum. This work uncovered the presence of a specialized equipment for xyloglucan utilization. After extracellular digestion of xyloglucan by cellulosomal enzymes, xyloglucan dextrins are imported into the cytoplasm via a specific ABC-transporter and sequentially hydrolyzed by cytoplasmic enzymes into fermentable mono and disaccharides

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Cervin, Nicholas. "Porous Cellulose Materials from Nano Fibrillated Cellulose". Licentiate thesis, KTH, Fiberteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104196.

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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99 %) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can also be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle.In the second part of the work a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified NanoFibrillated Cellulose (NFC). Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped NFC nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 % and a density of 30 mg cm-3. These porous cellulose materials have a higher Young’s modulus than other cellulose materials made by freeze drying and a compressive energy absorption of 56 kJ m-3 at 80 % strain. Measurements with an autoporosimeter reveal that most pores are in the range of 300 to 500 μm.

QC 20121107

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Peri, Suma Lee Yoon Y. "Kinetic investigation and modeling of cellulase enzyme using non-crystalline cellulose and cello-oligosaccharides". Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/PERI_SUMA_47.pdf.

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Mokatse, Khomotso. "Production, characterization and evaluation of fungal cellulases for effective digestion of cellulose". Thesis, University of Limpopo (Turfloop Campus), 2013. http://hdl.handle.net/10386/1129.

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Thesis (M.Sc. (Microbiology)) --University of Limpopo, 2013
The production of cellulase is a key factor in the hydrolysis of cellulosic materials and it is essential to make the process economically viable. Cellulases are the most studied multi- enzyme complex and comprise of endo-glucanases (EG), cellobiohydrolases (CBH) and β- glucosidases (BGL). The complete cellulase system; comprising CBH, EG and BGL components thus acts synergistically to convert crystalline cellulose to glucose. Cellulases are currently the third largest industrial enzyme worldwide. This is due to their wide applications in cotton processing, paper recycling, juice extraction, as detergent enzymes and additives in animal feed. In this study, production of cellulase by five fungal isolates (BTU 251-BTU 255) isolated from mushrooms, was investigated and optimised. Internal transcribed spacer regions (ITS1 and ITS4) were applied to identify the five fungal microorganisms. Isolates were identified as follows: BTU 251 as Aspegillus niger,BTU 253 as Penicillium polonicum, and BTU 255 as Penicillium polonicum. Cellulase was produced in shake flask cultures using Mandel’s mineral solution medium and Avicel as a carbon source. Cellulase activity was tested using 3, 5-Dinitrosalicylic acid assay and zymography, A. niger BTU 251 showed five activity bands ranging from 25- 61 kDa had an average nkat of 7000. Cultures from BTU 252 were the least active with an average nkat/ml of 200 and one activity band of 25 kDa. P. polonicum BTU 253 showed three activity bands ranging between 45 and 60 kDa and had an average nkat/ml of 2200. BTU 254 showed five activity bands ranging from 22- 116 kDa and had average nkat of 350. P. polonicum BTU 255 produced the highest cellulase activity of 8000 nkat/ml and with three activity bands estimated at 45-60 kDa on zymography. The optimal temperature for activity of the cellulases was between 55-70°C and enzymes were most active within a pH range of 4-6. Optimal pH for production of cellulases by P. polonicum BTU 255, P. polonicum BTU 253 and A. niger BTU 251 was 4 while optimal temperature for production of the cellulases was between 50-55°C. Total cellulase activity was determined using Whatman No.1 filter paper as a substrate and β- glucosidase production was determined in polyacrylamide gels using esculin as a substrate. In the hydrolysis of crystalline cellulose (Avicel), a combination of A. niger BTU 251 and P. polonicum BTU 255 (1:1), (1:9), (1:3), and (1:2) produced maximum glucose as follows: 1:1 (0.83g/L), 1:9 (10.4g/L), 1:3 (0.77g/L) and 1:2 (0.73g/L). Cellulases from P. polonicum BTU 255 were partially purified using affinity precipitation and analysed using MALDI- TOF/TOF. Peptide sequences of P. polonicum obtained from MALDI-TOF/TOF analysis were aligned by multiple sequence alignment with C. pingtungium. Conserved regions were identified using BLAST anaylsis as sequences of cellobiohydrolases. More research is required in producing a variety of cellulases that are capable of hydrolysing crystalline cellulose, the current study contributes to possible provision of locally developed combinations of cellulases that can be used in the production of bioethanol.

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Schult, Tove. "Properties of acid sulfite cellulose for cellulose derivatives". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1508.

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Linder, Markus. "Structure-function relationships in fungal cellulose-binding domains /". Espoo, Finland : VTT, Technical Research Centre of Finland, 1996. http://www.vtt.fi/inf/pdf/publications/1996/P294.pdf.

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Gal, Laurent. "Etude du cellulosome de Clostridium cellulolyticum et de l'un de ses composants : la cellulase CelG". Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11071.

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Le cellulosome de la bacterie cellulolytique clostridium cellulolyticum atcc 35319 a ete etudie. C'est un complexe de 600 kda, en moyenne, qui degrade efficacement la cellulose cristalline. Il est constitue de plusieurs proteines de masse moleculaire relative variant entre 170 et 30 kda. L'utilisation du minicipc1 biotinyle a permis de montrer qu'au moins treize d'entre elles possedaient une dockerine. Parmi celles-ci, les proteines cela, celc, cele, celf et celg, dont les genes sont clones et sequences, ont ete identifiees. Afin de rechercher de nouveaux genes cel codant pour des proteines possedant une dockerine, une marche sur le chromosome en aval de cele a ete entreprise. Elle a revele l'existence de trois nouveaux genes impliques dans la cellulolyse : cipx, celh et celj. - cipx est une proteine tres originale constituee d'un domaine de type linker et d'une cohesine. - celh et celj, tout comme celg, possedent un domaine catalytique de la famille 9 de la classification des glycosyl-hydrolases, suivi d'un domaine de type cbd de la famille iii et enfin d'une dockerine c-terminale. Pour tenter de comprendre le role joue par ce dernier type de proteines dans la cellulolyse, la caracterisation biochimique de celg a ete entreprise. Le gene celg a ete surexprime chez escherichia coli et la proteine recombinante correspondante a ete purifiee. Celg est une endoglucanase qui degrade efficacement la cmc et le glucane d'orge. Elle est egalement active sur la cellulose amorphe et degrade les cellodextrines ayant un degre de polymerisation superieur ou egal a trois. Contrairement aux autres endoglucanases caracterisees jusqu'a present chez c. Cellulolyticum, celg degrade les celluloses cristallines, et en particulier la bmcc de maniere tres efficace. Pour etudier l'influence relative de chacun des domaines de celg dans ce mecanisme, differentes constructions genetiques, permettant la synthese du domaine catalytique seul ou du domaine de type cbd fusionne derriere la glutathion-s-transferase, ont ete realisees. Dans tous les cas, les proteines recombinantes ne presentent ni activite catalytique ni proprietes d'adhesion a la cellulose. L'ensemble de ces resultats suggere qu'a la difference de la plupart des cellulases, les differents domaines constitutifs de celg ne sont pas independants. La presence d'au moins deux autres proteines homologues a celg (celh et celj) au sein du systeme cellulolytique de c. Cellulolyticum suggere que ces proteines jouent un role fondamental dans les mecanismes de degradation de la cellulose chez cet organisme.

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Lane, J. M. "Solid state NMR studies of cellulose and cellulose acetate". Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374690.

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Hu, Gang. "Adsorpton and Activity of Cellulase Enzymes on Various of Cellulose Substrates". NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-04222009-234535/.

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The objective of this research is to understand the interfacial behavior of cellulase enzymes and its effect on cellulose hydrolysis. This research began with an in-situ monitoring of cellulose hydrolysis using a piezoelectric based quartz crystal microbalance. The time-course kinetics was modeled using a dose response model. The adsorption indicated by the frequency drop followed a Langmuir model as cellulase enzyme increased. Another important part of this research is the development of a new cellulase activity assay based on the piezoelectric technique. This assay provides an easier and more user friendly method for cellulase enzyme activity measurement. It also helps to clarify an element of the interpretation of frequency drops after the injection of cellulase solutions in the hydrolysis of cellulose film, which has been neglected in previous research. Interfacial adsorption of cellulase protein was also investigated using the depletion method. The effects of substrate properties, primarily the crystallinity, which was characterized using X-ray diffraction, were investigated. The effect of surface area, which was measured using both laser light scattering and BET adsorption, on cellulase adsorption were also investigated. It was found that crystallinity played a more important role in cellulase adsorption than surface areas of cellulosic substrate. In characterization of cellulosic substrates, the water retention value (WRV) was also investigated. The results indicated that lower crystallintiy substrates have higher water retention ability. The cellulase adsorption, as well as desorption, was also studied by using sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The adsorption results followed the same trend as indicated by the depletion methods. The various isozymes demonstrated a uniform adsorption in proportion to their concentrations. Desorption appeared uniform. Higher pH was found to create higher desorption for a particular cellulase from a particular substrates. It was also found that cellulase from Trichoderma reesei had higher affinity to cellulosic substrates used in this work than the one from Aspergillus niger.

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Qian, Chen. "Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42496.

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Adsorption of xyloglucan (XG) onto thin desulfated nanocrystalline cellulose (DNC) films was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring (QCM-D), and atomic force microscopy (AFM) measurements. These studies were compared to adsorption studies of XG onto thin sulfated nanocrystalline cellulose (SNC) films and regenerated cellulose (RC) films performed by others. Collectively, these studies show the accessible surface area is the key factor for the differences in surface concentrations observed for XG adsorbed onto the three cellulose surfaces. XG penetrated into the porous nanocrystalline cellulose films. In contrast, XG was confined to the surfaces of the smooth, non-porous RC films. Surprisingly surface charge and cellulose morphology played a limited role on XG adsorption. The effect of the non-ionic surfactant Tween 80 on the adsorption of cellulase onto alkane thiol self-assembled monolayers (SAMs) on gold was also studied. Methyl (-CH3), hydroxyl (-OH) and carboxyl (-COOH) terminated SAMs were prepared. Adsorption of cellulase onto untreated and Tween 80-treated SAMs were monitored by SPR, QCM-D and AFM. The results indicated cellulase adsorption onto SAM-CH3 and SAM-COOH were driven by strong hydrophobic and electrostatic interactions, however, hydrogen bonding between cellulase and SAM-OH was weak. Tween 80 effectively hindered the adsorption of cellulase onto hydrophobic SAM-CH3 substrates. In contrast, it had almost no effect on the adsorption of cellulase onto SAM-OH and SAM-COOH substrates because of its reversible adsorption on these substrates.
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Livros sobre o assunto "Cellulose"

Yaser, Abu Zahrim, Mohd Sani Sarjadi e Junidah Lamaming. Cellulose. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084.

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Clarke, Anthony J. Biodegradation of cellulose: Enzymology and biotechnology. Lancaster, Pa: Technomic Pub. Co., 1996.

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Khan, Sher Bahadar, e Tahseen Kamal. Bacterial Cellulose. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9781003118756.

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Oksman, Kristiina, e Mohini Sain, eds. Cellulose Nanocomposites. Washington, DC: American Chemical Society, 2006. http://dx.doi.org/10.1021/bk-2006-0938.

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Heinze, Thomas J., e Wolfgang G. Glasser, eds. Cellulose Derivatives. Washington, DC: American Chemical Society, 1998. http://dx.doi.org/10.1021/bk-1998-0688.

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Heinze, Thomas, Omar A. El Seoud e Andreas Koschella. Cellulose Derivatives. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-73168-1.

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Fan, Liang-tseng, Mahendra Moreshwar Gharpuray e Yong-Hyun Lee. Cellulose Hydrolysis. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72575-3.

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Hamad, Wadood Y. Cellulose Nanocrystals. Chichester, UK: John Wiley & Sons, Ltd, 2017. http://dx.doi.org/10.1002/9781118675601.

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Muthu, Subramanian Senthilkannan, e R. Rathinamoorthy. Bacterial Cellulose. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-9581-3.

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Kumar, Vinod, Saurabh Saran, Ashok Pandey e Carlos Ricardo Soccol. Bacterial Cellulose. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003355434.

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Capítulos de livros sobre o assunto "Cellulose"

Kopp, Victória Vieira, Vânia Queiroz, Mariliz Gutterres e João Henrique Zimnoch dos Santos. "Application of Cellulose in Leather". In Cellulose, 277–85. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-19.

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Indarti, Eti, Zalniati Fonna Rozali, Dewi Yunita, Laila Sonia e Marwan Mas. "Characteristics of Cellulose Nanocrystals from Sugarcane Bagasse Isolated from Various Methods". In Cellulose, 201–15. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-14.

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Yahya, Mohammad Harris M., e Noor Azrimi Umor. "Challenges and State of the Art of Allium Pulp Development for Papermaking". In Cellulose, 269–76. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-18.

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Meng, Tan Kean, Muaz Mohd Zaini Makhtar, Muhammed Aidiel Asyraff Mohmad Hatta e Mohd Asyraf Kassim. "Biorefinery of Biofuel Production". In Cellulose, 45–70. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-4.

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Aziz, Siti Ayu, e Mohd Sani Sarjadi. "A Brief Overview of the Use of Bamboo Biomass in the Asian Region's Energy Production". In Cellulose, 7–26. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-2.

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Raymond, Rozelyn Ignesia, e Khim Phin Chong. "Review on the Current Updates on Palm Oil Industry and Its Biomass Recycling to Fertilizer in Malaysia". In Cellulose, 71–81. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-5.

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Promie, Ahsan Rajib, Afroza Akter Liza, Md Nazrul Islam, Atanu Kumar Das, Md Omar Faruk, Sumaya Haq Mim e Kallol Sarker. "Cellulose-Based Bioadhesive for Wood-Based Composite Applications". In Cellulose, 163–73. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-11.

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Umor, Noor Azrimi, Nurul Hidayah Adenan, Nadya Hajar, Nurul Ain Mat Akil, Nor Haniah A. Malik, Shahrul Ismail e Zaim Hadi Meskam. "Comparing Properties and Potential of Pinewood, Dried Tofu, and Oil Palm Empty Fruit Bunch (EFB) Pellet as Cat Litter". In Cellulose, 301–7. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-21.

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Aziz, Siti Ayu, Sabrina Soloi, Mohd Hafiz Abd Majid, Juferi Idris, Md Lutfor Rahman e Mohd Sani Sarjadi. "Pre-Treatment of Oil Palm Empty Fruit Bunches with Sea Water Improves the Qualities of Lignocellulose Biomass". In Cellulose, 27–43. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-3.

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Tanpichai, Supachok. "All-Cellulose Composites". In Cellulose, 145–62. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003358084-10.

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Trabalhos de conferências sobre o assunto "Cellulose"

Ding, H., e F. Xu. "CELLULOSE-ACCESSIBILITY OF CELLULASES". In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.770.

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Zhang, P. F., e Z. J. Pei. "Effects of Ultrasonic Treatments on Cellulose in Cellulosic Biofuel Manufacturing: A Literature Review". In ASME 2010 International Manufacturing Science and Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/msec2010-34180.

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Cellulosic biofuels are one type of renewable energy, and have been proposed to replace traditional liquid transportation fuels. Cellulosic biomass is the feedstocks in cellulosic biofuel manufacturing. Cellulose accounts for approximately 30% of the total weight in cellulosic biomass. Glucose, one type of monosaccharide convertible to ethanol, can be obtained by hydrolyzing the polymeric structure of cellulose. Currently enzymatic methods are the most common for the hydrolysis of cellulose. However, the low efficiency of enzymatic hydrolysis increases production cost and hinders the large-scale manufacturing of cellulosic biofuels. Ultrasonic treatments applied on cellulosic biomass were found to improve the efficiency of hydrolysis and subsequently increase the sugar yield of hydrolysis. To understand the effects of ultrasonics on cellulose, investigations have been conducted on the effects on cellulose characteristics caused by ultrasonic treatments during hydrolysis. This paper reviews the effects of ultrasonic treatments on cellulose during hydrolysis in terms of sugar yield and some characteristics of cellulose, such as accessibility, crystallinity, degree of polymerization, and morphological structure.

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Atalla, Rajai H. "Studies of Polymorphy in Native Cellulose". In Papermaking Raw Materials, editado por V. Punton. Fundamental Research Committee (FRC), Manchester, 1985. http://dx.doi.org/10.15376/frc.1985.1.59.

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Our studies of cellulose structure based on X-ray diffractometry, Raman spectroscopy, and Solid State ¹³C-NMR have led us to a model which addresses questions of structure at two levels. The first is that of the organization of individual chains. Two stable ordered states of cellulose chains are postulated, together with a disordered state in which there is less coherence between the orientations of adjacent anhydroglucose rings. The ordered states are identified as kᵢ and kᵢᵢ based on their predominance in celluloses I and II, respectively; both conformations are based on the dimeric anhydrocellobiose as the basic repeat until in the ordered chain. The disordered state is identified as kₒ. The second level of organization is that of aggregation of chains into three-dimensionally ordered crystalline domains. At this level our model recognizes two crystalline forms within the native state. These are identified as Iα and Iß, the first found to be dominant in bacterial and algal celluloses, the second dominant in celluloses from higher plants. These two forms are found to contain chains possessing the same molecular conformation ᵏI, but the patterns of hydrogen bonding are found to be different. Cellulose II, which is derived from the native state by mercerization or regeneration at low temperatures, is found to consist predominantly of chains in the ᵏII conformation in yet a third distinct crystalline lattice.

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Graham, William D., Stephanie L. Mathews, Christina Stolarchuk, Andrew Moore, Sunkyu Park, Joel J. Pawlak e Amy Grunden. "Investigation into the Structural and Thermal Behavior of Bacterial Cellulose Fbers after Biologically Relevant Puriﬁcation". In Advances in Pulp and Paper Research, Cambridge 2013, editado por S. J. I’ Anson. Fundamental Research Committee (FRC), Manchester, 2013. http://dx.doi.org/10.15376/frc.2013.2.785.

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Cellulose is the most abundant biopolymer on the planet. Historically rooted in the paper industry, advancements in colloidal chemistry, polymer chemistry, and the development of novel saccharification techniques have expanded the commercial applications of cellulose to include the production of liquid crystal displays, use in high strength composites, and biofuels. Despite this renewed interest in cellulosic products, the establishment of cellulose as a global commodity is significantly hindered by the inefficiencies in cellulose liberation and processing. The current model associated with cellulose liberation from lignin and hemicellulose relies on the use of highly basic reagents resulting in significant alterations to cellulose native structure. Laboratory techniques have been developed to attempt to isolate cellulose, while leaving it in its native structure. In this work, we demonstrate how even mild laboratory isolation techniques significantly influence cellulose structure in bacterial cellulose. Furthermore, we propose that bacteria cellulose serves as a model for cellulose as found in plants and animals.

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SINGH ROHEWAL, SARGUN SINGH, JIHO SEO, NIHAL KANBARGI e AMIT K. NASKAR. "RECYCLABLE CELLULOSE FIBER REINFORCED VITRIMER COMPOSITE". In Proceedings for the American Society for Composites-Thirty Eighth Technical Conference. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/asc38/36699.

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Vitrimer is an innovative class of polymeric materials which demonstrates traditional thermoset-like mechanical and chemical resilience while still being able to flow on demand like a traditional thermoplastic through covalently adaptive dynamic linkages. Herein, high-performance cellulose fiber reinforced vitrimer composites are developed using an epoxy-based vitrimer and natural cellulose paper. The reinforced vitrimer composite was fabricated by impregnating the porous structure of cellulose paper with two curable monomers, followed by in-situ polymerization of the monomers inside the fibrous scaffold. The introduction of hydroxyl group present on the cellulosic framework assisted in a faster topological rearrangement of the crosslinked matrix through transesterification exchange reaction, thus imparting various sought-after properties like shape recovery and recyclability via simple thermal reprocessing. Moreover, the reinforced vitrimer composite exhibits superior tensile properties as high as 90 MPa with 15-25 volume% vitrimer loading due to the interfacial adhesion via ester exchange reaction between the epoxy matrix and functionalities on the cellulosic fibers. Noteworthily, the key ingredients of the resulting composite (i.e., epoxy-based vitrimer and cellulose fibers) can be comfortably recycled without using aggressive chemical treatment, enabling composite to be easily recycled or disposed of at the end of service life and assist in reducing the subsequent manufacturing cost. This study would shed light on the development of a recyclable polymer composite with exceptional mechanical properties while simultaneously demonstrating self-healing and shape memory capabilities.

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Hospodarova, Viola, Nadezda Stevulova, Vojtech Vaclavik, Tomas Dvorsky e Jaroslav Briancin. "Cellulose Fibres as a Reinforcing Element in Building Materials". In Environmental Engineering. VGTU Technika, 2017. http://dx.doi.org/10.3846/enviro.2017.104.

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Nowadays, construction sector is focusing in developing sustainable, green and eco-friendly building materials. Natural fibre is growingly being used in composite materials. This paper provides utilization of cellulose fibres as reinforcing agent into cement composites/plasters. Provided cellulosic fibres coming from various sources as bleached wood pulp and recycled waste paper fibres. Differences between cellulosic fibres are given by their physical characterization, chemical composition and SEM micrographs. Physical and mechanical properties of fibre-cement composites with fibre contents 0.2; 0.3and 0.5% by weight of filler and binder were investigated. Reference sample without fibres was also produced. The aim of this work is to investigate the effects of cellulose fibres on the final properties (density, water absorbability, coefficient of thermal conductivity and compressive strength) of the fibrecement plasters after 28 days of hardening. Testing of plasters with varying amount of cellulose fibres (0.2, 0.3 and 0.5 wt. %) has shown that the resulting physical and mechanical properties depend on the amount, the nature and structure of the used fibres. Linear dependences of compressive strength and thermal conductivity on density for plasters with cellulosic fibres adding were observed.

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Chen, Xiao-Quan, Xue-Yan Deng, Wen-Hao Shen e Meng-Yu Jia. "Preparation and Characterization of Spherical Nanosized Cellulose by Enzymatic Hydrolysis of Pulp Fibers". In Advances in Pulp and Paper Research, Oxford 2017. Fundamental Research Committee (FRC), Manchester, 2017. http://dx.doi.org/10.15376/frc.2017.2.785.

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In this work, the pulp fibers were enzymolyzed to prepare the nano-sized cellulose (NC). The as-prepared samples were characterized by optical microscopy, electron microscopy, and Raman spectra. The experimental results indicated that enzymatic hydrolysis of pulp fibers could produce the spherical NC with a mean particle size of about 30 nm, which has the excellent monodispersity and uniformity. When the concentration of complex enzymes was 20 u/mL (cellulase: xylanase = 9:1), the yield of NC was 13.6%. The single cellulase was used, even if the concentration and time reached up to 200 u/mL, only a mixture of trip and granular flocculation were obtained. The positive synergistic effect between xylanase and cellulase could be due to the enzymolysis of hemicellulose located on the cellulose microfibers to favorable of cutting and splitting of the microfibers by the endoglycannase in cellulase. Otherwise, the additive copper sulfate could decrease formation of reducing sugar effectively.

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Liu, Yu-San, Yonghua Luo, John O. Baker, Yining Zeng, Michael E. Himmel, Steve Smith e Shi-You Ding. "A single molecule study of cellulase hydrolysis of crystalline cellulose". In BiOS, editado por Jörg Enderlein, Zygmunt K. Gryczynski e Rainer Erdmann. SPIE, 2010. http://dx.doi.org/10.1117/12.840975.

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Yu, Laipu, e Gil Garnier. "Mechanism of Internal Sizing with Alkyl Ketene Dimers: The Role of Vapour Deposition". In The Fundamentals of Papermaking Materials, editado por C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.2.1021.

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The role played by AKD vapours during internal sizing was investigated using commercial AKD waxes and model surfaces. The model surfaces consist of cellulose and cellulose acetate films deposited on smooth glass slides. These cellulosic films were exposed to AKD vapours at temperatures ranging from 80 degrees C to 175 degrees C for different periods of time. The extent of sizing was followed by measuring the advancing contact angle of water over the treated surfaces. A simple model, considering both physisorption and chemical reaction, was developed and validated with experimental data. The energy of activation of 61 .4 kJ/mole was derived from the Arrhenius plot . From a series of indirect techniques, it is concluded that the establishment of a covalent bond between cellulose and AID is essential in order to introduce permanent hydrophobicity to cellulosic surfaces. The effect of “sizing promoters” on the reaction rate was also examined. Both NaHC03 and cationic PEI failed to catalyze sizing between cellulose and AKD vapours. The mechanism proposed and the model will shed new light on the phenomena of AKD sizing treatment and sizing migration.

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Lindström, Tom. "Some Fundamental Chemical Aspects on Paper Forming". In Fundamentals of Papermaking, editado por C. F. Baker e V. Punton. Fundamental Research Committee (FRC), Manchester, 1989. http://dx.doi.org/10.15376/frc.1989.1.311.

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The fundamental physico-chemical aspects of retention chemistry are reviewed in the light of basic concepts in colloid chemistry. Special emphasis has been paid to the surface chemistry of cellulose and cellulosic materials, their origin of charge, dispersion force interactions as well as the implication of certain aspects of peculiar cellulosic surfaces, e.g. the influence of their porosity on polymer adsorption. Charge neutralization, patch flocculation, heterocoagulation, bridging and complex flocculation phenomena are discussed as well as polymer adsorption phenomena at the cellulose/water interface

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Relatórios de organizações sobre o assunto "Cellulose"

Morrison, Mark, e Joshuah Miron. Molecular-Based Analysis of Cellulose Binding Proteins Involved with Adherence to Cellulose by Ruminococcus albus. United States Department of Agriculture, novembro de 2000. http://dx.doi.org/10.32747/2000.7695844.bard.

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At the beginning of this project, it was clear that R. albus adhered tightly to cellulose and its efficient degradation of this polysaccharide was dependent on micromolar concentrations of phenylacetic acid (PAA) and phenylpropionic acid (PPA). The objectives for our research were: i) to identify how many different kinds of cellulose binding proteins are produced by Ruminococcus albus; ii) to isolate and clone the genes encoding some of these proteins from the same bacterium; iii) to determine where these various proteins were located and; iv) quantify the relative importance of these proteins in affecting the rate and extent to which the bacterium becomes attached to cellulose. BARD support has facilitated a number of breakthroughs relevant to our fundamental understanding of the adhesion process. First, R. albus possesses multiple mechanisms for adhesion to cellulose. The P.I.'s laboratory has discovered a novel cellulose-binding protein (CbpC) that belongs to the Pil-protein family, and in particular, the type 4 fimbrial proteins. We have also obtained genetic and biochemical evidence demonstrating that, in addition to CbpC-mediated adhesion, R. albus also produces a cellulosome-like complex for adhesion. These breakthroughs resulted from the isolation (in Israel and the US) of spontaneously arising mutants of R. albus strains SY3 and 8, which were completely or partially defective in adhesion to cellulose, respectively. While the SY3 mutant strain was incapable of growth with cellulose as the sole carbon source, the strain 8 mutants showed varying abilities to degrade and grow with cellulose. Biochemical and gene cloning experiments have been used in Israel and the US, respectively, to identify what are believed to be key components of a cellulosome. This combination of cellulose adhesion mechanisms has not been identified previously in any bacterium. Second, differential display, reverse transcription polymerase chain reaction (DD RT-PCR) has been developed for use with R. albus. A major limitation to cellulose research has been the intractability of cellulolytic bacteria to genetic manipulation by techniques such as transposon mutagenesis and gene displacement. The P.I.'s successfully developed DD RT- PCR, which expanded the scope of our research beyond the original objectives of the project, and a subset of the transcripts conditionally expressed in response to PAA and PPA have been identified and characterized. Third, proteins immunochemically related to the CbpC protein of R. albus 8 are present in other R. albus strains and F. intestinalis, Western immunoblots have been used to examine additional strains of R. albus, as well as other cellulolytic bacteria of ruminant origin, for production of proteins immunochemically related to the CbpC protein. The results of these experiments showed that R. albus strains SY3, 7 and B199 all possess a protein of ~25 kDa which cross-reacts with polyclonal anti-CbpC antiserum. Several strains of Butyrivibrio fibrisolvens, Ruminococcus flavefaciens strains C- 94 and FD-1, and Fibrobacter succinogenes S85 produced no proteins that cross-react with the same antiserum. Surprisingly though, F. intestinalis strain DR7 does possess a protein(s) of relatively large molecular mass (~200 kDa) that was strongly cross-reactive with the anti- CbpC antiserum. Scientifically, our studies have helped expand the scope of our fundamental understanding of adhesion mechanisms in cellulose-degrading bacteria, and validated the use of RNA-based techniques to examine physiological responses in bacteria that are nor amenable to genetic manipulations. Because efficient fiber hydrolysis by many anaerobic bacteria requires both tight adhesion to substrate and a stable cellulosome, we believe our findings are also the first step in providing the resources needed to achieve our long-term goal of increasing fiber digestibility in animals.

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Delmer, Deborah, Nicholas Carpita e Abraham Marcus. Induced Plant Cell Wall Modifications: Use of Plant Cells with Altered Walls to Study Wall Structure, Growth and Potential for Genetic Modification. United States Department of Agriculture, maio de 1995. http://dx.doi.org/10.32747/1995.7613021.bard.

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Our previous work indicated that suspension-cultured plant cells show remarkable flexibility in altering cell wall structure in response either to growth on saline medium or in the presence of the cellulose synthesis inhibitor 2,-6-dichlorobenzonitrile (DCB). We have continued to analyze the structure of these modified cell walls to understand how the changes modify wall strength, porosity, and ability to expand. The major load-bearing network in the walls of DCB-adapted dicot cells that lack a substantial cellulose-xyloglucan network is comprised of Ca2+-bridged pectates; these cells also have an unusual and abundant soluble pectic fraction. By contrast, DCB-adapted barley, a graminaceous monocot achieves extra wall strength by enhanced cross-linking of its non-cellulosic polysaccharide network via phenolic residues. Our results have also shed new light on normal wall stucture: 1) the cellulose-xyloglucan network may be independent of other wall networks in dicot primary walls and accounts for about 70% of the total wall strength; 2) the pectic network in dicot walls is the primary determinant of wall porosity; 3) both wall strength and porosity in graminaceous monocot primary walls is greatly influenced by the degree of phenolic cross-linking between non-cellulosic polysaccharides; and 4) the fact that the monocot cells do not secrete excess glucuronoarabinoxylan and mixed-linked glucan in response to growth on DCB, suggests that these two non-cellulosic polymers do not normally interact with cellulose in a manner similar to xyloglucan. We also attempted to understand the factors which limit cell expansion during growth of cells in saline medium. Analyses of hydrolytic enzyme activities suggest that xyloglucan metabolism is not repressed during growth on NaCl. Unlike non-adapted cells, salt-adapted cells were found to lack pectin methyl esterase, but it is not clear how this difference could relate to alterations in wall expansibility. Salt-adaped cell walls contain reduced hyp and secrete two unique PRPP-related proteins suggesting that high NaCl inhibits the cross-linking of these proteins into the walls, a finding that might relate to their altered expansibility.

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Bartscherer, K. A., J. J. de Pablo, M. C. Bonnin e J. M. Prausnitz. Purification of aqueous cellulose ethers. Office of Scientific and Technical Information (OSTI), julho de 1990. http://dx.doi.org/10.2172/6084196.

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Alan R. White e Ann G. Matthysse. Cellulose Synthesis in Agrobacterium tumefaciens. Office of Scientific and Technical Information (OSTI), julho de 2004. http://dx.doi.org/10.2172/840242.

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Cuzens, J. E. Conversion of bagasse cellulose into ethanol. Office of Scientific and Technical Information (OSTI), novembro de 1997. http://dx.doi.org/10.2172/674641.

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Stipanovic, Arthur. The Effect of Cellulose Crystal Structure and Solid-State Morphology on the Activity of Cellulases. Office of Scientific and Technical Information (OSTI), novembro de 2014. http://dx.doi.org/10.2172/1163897.

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Barnes, Eftihia, Jennifer Jefcoat, Erik Alberts, Hannah Peel, L. Mimum, J, Buchanan, Xin Guan et al. Synthesis and characterization of biological nanomaterial/poly(vinylidene fluoride) composites. Engineer Research and Development Center (U.S.), setembro de 2021. http://dx.doi.org/10.21079/11681/42132.

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The properties of composite materials are strongly influenced by both the physical and chemical properties of their individual constituents, as well as the interactions between them. For nanocomposites, the incorporation of nano-sized dopants inside a host material matrix can lead to significant improvements in mechanical strength, toughness, thermal or electrical conductivity, etc. In this work, the effect of cellulose nanofibrils on the structure and mechanical properties of cellulose nanofibril poly(vinylidene fluoride) (PVDF) composite films was investigated. Cellulose is one of the most abundant organic polymers with superior mechanical properties and readily functionalized surfaces. Under the current processing conditions, cellulose nanofibrils, as-received and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized, alter the crystallinity and mechanical properties of the composite films while not inducing a crystalline phase transformation on the 𝛾 phase PVDF composites. Composite films obtained from hydrated cellulose nanofibrils remain in a majority 𝛾 phase, but also exhibit a small, yet detectable fraction of 𝛼 and ß PVDF phases.

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Heintz, C. E., K. A. Rainwater, L. M. Swift, D. L. Barnes e L. A. Worl. Enzymatic degradation of plutonium-contaminated cellulose products. Office of Scientific and Technical Information (OSTI), junho de 1999. http://dx.doi.org/10.2172/350862.

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Wood, Devon, Hang Liu e Carol J. Salusso. Production and characterization of bacterial cellulose fabrics. Ames: Iowa State University, Digital Repository, novembro de 2015. http://dx.doi.org/10.31274/itaa_proceedings-180814-130.

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Harmon, Jennifer. Homegrown: Investigating Design Potential of Bacterial Cellulose. Ames: Iowa State University, Digital Repository, 2017. http://dx.doi.org/10.31274/itaa_proceedings-180814-216.

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