Contact cellulase

One possible explanation is that the mere contact of the cell surface on the insoluble inducer is sufficient to trigger cellulase production. Another explanation is that cellololytic microorganisms have trace quantities of constitutive cellulases which are continuously released. A third possibility is that the cells are able to synthesize cellulases under starvation conditions. 

However, Thomas and Dimnill (1979) studied the effect of shear on catalase and urease activities by using a coaxial cylindrical viscometer that was sealed to prevent any air-liquid contact. They found that there was no significant loss of enzyme activity due to shear force alone at shear rates up to 106 sec-1. They reasoned that the deactivation observed by Charm and Wong (1970) was the result of a combination of shear, air-liquid interface, and some other effects which are not fully understood. Charm and Wong did not seal their shear apparatus. This was further confirmed, as cellulase deactivation due to the interfacial effect combined with the shear effect was found to be far more severe and extensive than that due to the shear effect alone (Jones and Lee, 1988). 

For the enzymatic process, the feedstock is first pretreated with a dilute acid to break down the lignocellu-lose into lignin, hemicellulose, and cellulose. Enzymes called cellulases and xylanases are then used to break down the cellulose and hemicellulose fractions into six- and five- carbon sugars, respectively. Without the dilute acid treatment, the enzymes would not be able to come in efficient contact with the cellulose and hemicellulose. The sugars are then fermented to ethanol using organisms such as E. S. cerevisiaeP ... 

Enzyme s effect mechanism, i.e. enzyme catalysis, operates first of all to form an enzyme substrate complex [14]. Direct physical contact of enzyme and substrate is required to obtain the complex. The current proposed mechanism of cellulase action is illustrated in Fig. 15-1. However, the mechanism of enzymatic hy-... 

The fact that cellulase enzymes act on an insoluble substrate, cellulose, moves the kinetics outside Michaelis-Menten on several counts. First of all, the enzyme can be adsorbed to the substrate or imadsorbed, but only the adsorbed enzyme acts on the cellulose. Even more puzzHng is the substrate concentration. Do we count the entire substrate, or just that in close contact with the enzyme Clearly, we have to start from first principles in characterizing the cellulase/cel-lulose system. 

In qualitative tests, no pectinase was detected in permeate from some runs and detected at what appeared to be low levels in permeate from other runs. Presumably, this indicates pectinase. and therefore cellulase, were concentrated to some extent in the retentate and this may be related to the increase in flux rate with filtering time. Other factors involved may be longer contact time with enzymes, general cell rupture and size reduction caused by pumping shear, or other undetermined factors. 

More than 60% reduction in the degree of polymerization of cellulose (about 1150 to 440) in the first eleven hours of contact with Peni-cillium variable cellulase (Figure 4) has been reported (2). Further depolymerization was very slow, implying that the amorphous portion of the cellulose has reacted rapidly, leaving a more resistant crystalline structure represented by a DP of about 440. These conclusions strongly... 

Loss of Cellulase (Cx) Activity in the Presence of Highly Susceptible Substrate and Absorbent. Temperature and pH affect the inactivation and adsorption losses of T. viride cellulase in contact with Solka Floe and milled Solka Floe (3). Since several saccharification studies were conducted with highly reactive cellulose (Sweco 70 heated), a knowledge of the difference, if any, between adsorption and other losses of T. viride cellulase in contact with such substrates (at 50°C., pH—4.8) was necessary. Accordingly, T. viride cellulase was incubated with Sweco... 

Kim et al. [41] reported that a significant deactivation was observed when cellulase was subjected to shear and/or exposed to air-liquid interface, which was thought to be far more severe and extensive than shear effect alone. By using sufficient additives (surfactants and non-catalytic proteins, e.g., BSA), cellulase deactivation can be, to some extent, prevented, and cellulase can be stabilized. This might be because the addition of non-ionic surfactants could reduce the contact of enzymes with the air-liquid interface because of the surface... 

Hytonen M, Vanhanen M, Keskinen H, et al. (1994) Pharyngeal edema caused by occupational exposure to cellulasa enzyme. AUergy 49 782-784 Kanerva L, Vanhanen M, Tupasela O (1998) Occupational contact urticaria from cellulase enzyme. Contact Dermatitis... 

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