Cellulase in Degradation of Lignocellulosic Wastes
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Cellulosic ethanol
Degradation
Summary Cellulose is the most abundant carbon source in nature but it is very difficult to degrade because of its insolubility, quasi-crystalline structure and its presence in plant cell walls in a matrix with other polymers that limit access to the cellulose surface. Most cellulose in soils is degraded by cellulolytic microorganisms that use a number of different approaches to overcome the recalcitrance of cellulose in plant cell walls. All of these approaches involve multiple cellulases and, since cellulose is insoluble and microorganisms cannot ingest particles, the cellulases are present outside of the cell although they can be attached to its outer surface. An impressive article by Tolonen et al. in this issue of Molecular Microbiology shows that deletion of the single family 9 cellulase gene in Clostridium phytofermentans prevents growth on cellulose although the mutant strain grows perfectly well on glucose and its other cellulase genes are transcribed normally. These results show for the first time that a single cellulase can be essential for cellulose degradation by an organism despite the presence of several other cellulases. It will be interesting to learn the detailed mechanism that C. phytofermentans uses to degrade cellulose.
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Degradation
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In this paper,recent research progress on the mechanism of cellulose degradation by cellulase is studied.The new theory points out that overlooking of cellulose's sup-molecular structure may be the main reason for difficulties in degrading cellulose.The paper briefly describes the research progress on the factors that would influence cellulose degradation by cellulases,such as temperature,pH,time of enzyme reaction and inhibitor,activator.Also,the paper identifies the problems existing in the degradation of cellulose by cellulase and suggests its research direction for the future work.
Degradation
Cellulosic ethanol
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Cellulose in jujube powder was hydrolyzed by HCl,NaOH and cellulase of different concentration at different temperature for different time to determine the optimal hydrolysis condition.The optimal concentration of HCl,NaOH and cellulase was 0.05 mol/L,0.5 mol/L and 0.1×10-6 g/g respectively.The optimal temperature for HCl,NaOH and cellulase was 30,30 and 40 ℃ respectively.The optimal time for HCl,NaOH and cellulase was 20 min.There was no significant difference among three methods for cellulose hydrolysis.
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Cellulosic ethanol
Degradation
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Living organisms produce a wide variety of polymeric carbohydrates, of which cellulose is the most abundant. The main deterioration of cellulose is caused by microorganisms, and the biological degradation of cellulosic substances is an extremely important process for the maintenance of the carbon balance in nature. Since crystalline cellulose is an insoluble substance with a supramolecular structure, the enzymological approaches to this substrate are rather complicated and difficult . In most cellulolytic microorganisms, several cellulase components together constitute a "cellulase system" and cellulosic materials are converted to soluble sugars by their synergistic action . To understand completely the biodegradation mechanism of cellulose, therefore, the strict purification and characterization of each cellulase component is absolutely necessary . This review describes the cellulolytic enzymes and focuses on the mechanism of their action . It is divided into seven sections and includes the historical background of cellulase . Our recent findings concerning the enzyme mechanisms involved in native cellulose degradation are also described.
Cellulosic ethanol
Degradation
Cellulosome
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Abstract Up to now, experimental limitations have prevented researchers from achieving the molecular‐level understanding for the initial steps of the enzymatic hydrolysis of cellulose, where cellulase breaks down the crystal structure on the surface region of cellulose and exposes cellulose chains for the subsequent hydrolysis by cellulase. Because one of these non‐hydrolytic enzymatic steps could be the rate‐limiting step for the entire enzymatic hydrolysis of crystalline cellulose by cellulase, being able to analyze and understand these steps is instrumental in uncovering novel leads for improving the efficiency of cellulase. In this communication, we report an innovative application of the microcantilever technique for a real‐time assessment of the morphological change of cellulose induced by a treatment of sodium chloride. This sensitive nanomechanical approach to define changes in surface structure of cellulose has the potential to permit a real‐time assessment of the effect of the non‐hydrolytic activities of cellulase on cellulose and thereby to provide a comprehensive understanding of the initial steps of the enzymatic hydrolysis of cellulose. Biotechnol. Bioeng. 2010;107: 190–194. © 2010 Wiley Periodicals, Inc.
Enzymatic Hydrolysis
Limiting
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In the cellulase-cellulose reaction system, the adsorption of cellulase on the solid cellulose substrate was found to be one of the important parameters that govern the enzymatic hydrolysis rate of cellulose. The adsorption of cellulase usually parallels the rate of hydrolysis of cellulose. The affinity for cellulase varies depending on the structural properties of cellulose. Adsorption parameters such as the half-saturation constant, the maximum adsorption constant, and the distribution coefficient for both the cellulase and cellulsoe have been experimentally determined for several substrates. These adsorption parameters vary with the source of cellulose and the pretreatment methods and are correlated with the crystallinity and the specific surface area of cellulose substrates. The changing pattern of adsorption profile of cellulase during the hydrolysis reaction has also been elucidated. For practical utilization of cellulosic materials, the cellulose structural properties and their effects on cellulase adsorption, and the rate of hydrolysis must be taken into consideration.
Cellulosic ethanol
Enzymatic Hydrolysis
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The technological conditions of degrading cellulose of haulm by cross experiments were studied with cellulase.The experimental results showed by cross experiments that the influential extent of affecting factors to degrading cellulose of haulm is:A(Enzyme amount)B(Substrate concentration)E(Reaction time)C(Reaction temperature)D(pH).The best combination of degrading cellulose of haulm with cellulase is A3B1E3C3D2,that is,the optimal conditions of degrading cellulose are 0.2% of cellulase,5.0% of haulm,at 50℃ and pH 5.0 for 2.0hrs.The ratio of cellulose to glucose reached 22.3% within only two hours which the time is shortened 12-30 times compared with the traditional enzymatic way.
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Cellulosic superabsorbents (SAP) are produced by using cellulose and cellulose derivative blends with different binding methods, generally. But cellulose in SAP leads decrease in water absorption and water bonding ability because of nonreactive character of cellulose based on its chemical structure. The oxidative pretreatments of cellulose were attempted for the resolve of disadvantage of cellulose in SAP, in this study. Hydrogen peroxide and TEMPO (2,2,6,6- tetramethylpiperidine-1-oxyl) were used for oxidative pretreatments of cellulose. Oxidized cellulose and carboxymethylcellulose (CMC) blended and cross-linked by epicholohydrin for cellulosic SAP production. Water absorption capacity of cellulosic SAP were determined in pH:2, 7 and 10. The results show that the oxidative pretreatments of cellulose had affirmative effect of water absorption capacity of cellulosic SAP according to control samples.
Cellulosic ethanol
Cellulose fiber
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