Cellulases characterization

Li, J., Y. M. Du, and H. B. Liang. 2006a. Low molecular weight water-soluhle chitosans Preparation with the aid of cellulase, characterization, and solubihty. J. Appl. Polym. Sci. 102 1098-1105. 

Functional screening of a soil metagenomic library for cellulases revealed a total of eight cellulolytic clones, one of which was purified and characterized [58]. Despite the fact that this library had been generated from a soil sample collected from a... 

Three regulators were identified by genetic analysis. The main repressor, KdgR, controls the transcription of pectinase genes, the intracellular catabolic pathway and the secretion machinery. The PecS repressor controls the production of pectate lyases and cellulases, the secretion machinery and the biosynthesis of a blue pigment. PecT acts as a repressor of the production of some pectate lyases. Other proteins are involved in the regulation of pectinase s5mthesis but their role is not well characterized. 

Our early studies dealt with characterization of cellulase from Clostridium thermocellum (4, 5), the first described thermoanaerobe. More recently, we have characterized the saccharidases in three new non-cellulolytic thermoanaerobic species (6-12). Table II compares the general properties of thermophilic saccharidases identified in C. thermosulfurogenes strain 4B (6), C. thermohydrosulfuricum strain 39E (7), and Thermoanaerohacter strain B6A (13). It is worth noting here that... 

The classification of cellulase sequences into domains allows the further recognition of distinct sequences that characterize each family. To make these sequences evident, one must use multiple sequence alignments of the members of each individual family. We have concentrated on the Microhispora bispora endoglucanase, and present some initial multiple sequence alignments of the catalytic and binding domain families of which it is a member. 

For Trichoderma reesei the cellulases most thoroughly investigated with respect to their structural properties are CBH I and CBH II and to a lesser extent the two en-doglucanases (EG I and EG III) 11 (Table I). For most other cellulases structural characterizations are confined to the amino add sequence as deduced from the base sequence of the respective genes and to sequence related investigations such as hydro-phobic cluster analysis 10 or computer aided molecular modelling and homology... 

A given microorganism may produce one or more enzymes of each type. An understanding of the role of each enzyme in cellulose biodegradation requires their purification and characterization, and an analysis of the ways in which they interact with the substrate and with each other. However, it is often quite difficult to determine the number and type of truly different enzymes produced by an organism. Many cellulolytic microorganisms secrete proteases, which may degrade some or all of the cellulases to smaller,... 

Index Entries Trichoderma reesei fermentation cellulase growth characterization cellulose hydrolysis. 

The objective of the current work was to characterize carefully the dynamics of cellulase production and metabolic activity following cellulose addition in a batch cultivation of the strain T. reesei Rut-C30. Cells were initially grown on glucose as the carbon source, and after its depletion, cellulose was added. Since it is difficult to follow the growth directly after addition of a solid substrate, on-line measurements of C02 evolution were used to follow the metabolic activity of the cells. Frequent samples were also taken to measure enzyme activity and sugar concentrations. 

Fungal cellulase enzyme systems capable of efficiently catalyzing the hydrolytic degradation of crystalline cellulose are typically composed of endo-acting cellulases (EGs), exo-acting cellulases (CBHs), and at least one cellobiase (1-6). The CBHs are typically the predominant enzymes, on a mole fraction basis, in such systems (7). Consequently, the CBHs have been the focus of many studies (8). The three-dimensional structure of prototypical CBHs is known (9-12) and their specificities are, in general, well characterized (13,14). However, mechanism-based kinetic analyses of CBH-catalyzed cellulose saccharification are rather limited (15,16). Studies of this latter type are particularly difficult owing to the inherent complexity of native cellulose substrates. 

Kadam, K. and Knutsen, J. (2001), Saccharification Experiments 6-9 Characterization of Cellulase Adsorption onto Pretreated Corn Stover, National Renewable Energy Laboratory, Golden, CO. 

Sheir-Neiss, G. and Montenecourt, B. S., Characterization of the secreted cellulases of Trichoderma reesei wild type and mutants during controlled fermentations. Appl. Microbiol. Biotechnol. 1984, 20, 46-53. 

Beldman, G., Searle-Van Leeuwen, M., Rombouts, F., and Voragen, F., The cellulase of Trichoderma viride Purification, characterization and comparison of all detectable endoglucanases, exoglucanases and B-glucosi-dases. EurJ. Biochem 1985, 146, 301-8. 

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