Cellulose cellulase system

Huang, A. A., "Kinetic Studies on Insoluble Cellulose-Cellulase System," Biotechnol. Bioeng. 17 (1975) 1421-1433. 

Cellulose-Cellulase System. In Figure 10 are shown the accessibility curves of the cotton which had been swollen to different extents by phosphoric acid. The fiber saturation point, given by the amount of water inaccessible to a very large molecule, is seen to increase from 0.48 ml./ gram for cotton treated with water alone to 1.40 ml./gram for cotton swollen in 78.8% acid. The median pore size increased from 23 A. to 52 A. 

A Simplified Kinetic Approach to Cellulose-Cellulase System... 

Michaelis-Menten Mechanism Applied to Cellulose-cellulase System... 63... 

The nature of this inhibition has not been explained. Product inhibition in the case of dehydrogenation of dienedol and of hydrocortisone by cells of Septomyxa is also reported (Chen et al., 1962). For product inhibition of cellulose-cellulase system, no linearity is noticeable. Data (Ghose, 1969d) on high rate saccharification of cellulose at lower substrate concentrations are presented in Table 2 and Fig. 3. 

If inhibition is caused by product, then I may be replaced by P and Ki by Kp, The inhibition mechanism may be described as formation of a complex between the enzyme and the inhibitor. This results in the partial loss of the compatibility to form the product In such a situation, therefore, the amount of product expected in the uninhibited reaction is always eater than that in the inhibited regardless of the nature of inhibition. The Eq. (18) should thus represent the model for competitive substrate or product inhibition. The rate of reaction should thus vary with either substrate concentration (in absence of inhibitor or product) or inhibitor (or product) concentration. It is not possible to evaluate the interdependence of the inhibition process between the three independent components the substrates, the products and known inhibitors. The Cellulose-cellulase system is one of competitive inhibition by two products of the process. This follows from the similarity of values of equilibrium constants, Kp for both cellobiose and glucose. The reciprocal plots for no inhibition, glucose and cellobiose inhibition based on the data of Table 4 are presented in Fig. 7. 

Webb, 1963), but, rather, is a more stable species. However, the ES complex does pass through a truly activated state in the course of coupling, and, in the case of a solid system, through a chain of such activated states. In the case of cellulose-cellulase system products (cellobiose or glucose) seem to be unbound to the enzyme but in others the products form complexes which are comparable to the ES complexes. Because cellulose is an insoluble substrate it has not been proven that there exists a product enzyme complex that is comparable to the enzyme substrate complex. The mechanism of the cellulose breakdown is an extremely complex system. 

These workers have also demonstrated the validity of the kinetic equations based on experimental data. However, the mechanism by which the enzyme-forming systems in derepressed cultures are not affected by repressing metabolites could not be explained. But, there exists a scope for verification of these models with the cellulose-cellulase system forming Q and C, complexes. 

A simplified Kinetic Approach to Cellulose-Cellulase System T. K. Ghose and K. Das, New Delhi (India)... 

Pretreatment of Substrate. Several different lignocelluloses were pretreated with NaOH. This pretreatment partially solubilizes the hemicelluloses and lignin and swells the cellulose so that the organism can utilize it for its growth and for production of a cellulase system in SSF. The treated lignocelluloses were not washed. The NaOH treatment is done with a minimum amount of water so that, after the addition of nutrient solution and inoculum, the moisture content is less than 80% wt/wt and there is no free water in the medium. More water was added to make suspensions of different lignocellulosic substrates of the desired concentration (1% or 5%) for liquid-state (submerged) fermentation (LSF). 

Extraction of the cellulase system. The culture of SSF from each flask (originally 5 g of substrate) was mixed well with more water to bring the final weight of the mixture (mycelium plus unutilized lignin, cellulose, and hemicelluloses) to 100 g. Tween 80 was added at a rate of 0.1%. The mixture was shaken for 0.5 h and centrifuged. The supernatant was used for enzyme determination. We estimated that about 7% to 10% cellulases remained adsorbed on the residues (mycelium and unutilized cellulose, hemicelluloses, and lignin) when the residues were suspended in water and Tween 80 as before and the supernatant was tested for cellulase titer. 

R. flavefaciens cells, during growth in pure culture, released cellulase, endoglucanase, and xylanase into the culture fluid. This microorganism hydrolyzed cellulose to yield only cellobiose as a product 49). It had been reported that a ceUobiose phosphorylase and glucokinase were present in R flavefaciens (8). The Ruminococcus cellulase system was repressed by disaccharides such as cellobiose, sucrose, and lactose 50). 

Humans do not produce the enzymes, called cellulases, necessary to digest cellulose. Bacteria possessing cellulase inhabit the digestive tracts of animals such as sheep, goats, and cows giving these animals the ability to digest cellulose. Cellulase bacteria also exist in the digestive systems of... 

As mentioned earlier, Cx enzymes exist in multiple forms in most cellulase systems. As a rule they vary in the degree of randomness of their attack on CM-cellulose, and they may be distinguished by plotting... 

Figure 1. Cooperative action of enzymes of the cellulase system in hydrolytically converting cellulose to glucose...

Since we had been able to purify the enzymes of the cellulase system of T. viride, the purification and identification of the T. reesei system was attempted. It was of interest to compare the enzymes produced during growth on cellulose with those produced in response to sophorose. The... 

The stimulation of the synthesis of the cellulase system of T. reesei QM 9414 by sophorose was established as shown by the results of experiments summarized in Table IV. Other than sophorose, of the glycosides and oligosaccharides tested, only lactose caused even a limited production of the enzymes of the cellulase system. Lactose is not as closely related structurally to sophorose as is, for example, the disaccharide laminaribiose it is more closely related structurally to cellobiose, which, despite being the major product of cellulose breakdown, does not promote enzyme production under the conditions of this experiment. It was noted that both intra- and extracellular constitutive enzyme levels produced by cells growing on glucose (or by resting cells without inducer, Table IV) are less than 0.5% of the fully induced levels and thus are negligible. 

A wide range of prokaryotic and eukaryotic microorganisms have the potential to produce cellulolytic enzymes when cellulose is present in the growth media (20,23,28,30). However, unlike some of the microorganisms that produce an incomplete cellulase system, T. reesei, a true cellulolytic fungus, produces an array of cellulase enzymes, i.e., the cellulase complex, which is able to hydrolyze cellulose to glucose (23). 

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