The role of cellulase concentration in determining the degree of synergism in the hydrolysis of microcrystalline cellulose

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Abstract
Microcrystalline cellulose (10 mg of Avicel/ml) was hydrolysed to glucose by different concentrations of the purified cellulase components endoglucanase (EG) II and cellobiohydrolases (CBH) I and II, alone and in combination with each other, in the presence of excess .beta.-glucosidase. At a concentration of 360 .mu.g/ml (160 .mu.g of EG II/ml, 100 .mu.g of CBH I/ml and 100 .mu.g of CBH II/ml) the degree of synergism among them was negligible. As the concentration of cellulase decreased, the degree of synergism increased, reaching an optimum at 20 .mu.g/ml (5 .mu.g of EG II/ml, 10 .mu.g of CBH I/ml and 5 .mu.g of CBH II/ml). There was no apparent relationship between the ratio of the components and the degree of synergism. The latter is probably due, though it could not be proved, to the level of saturation of the substrate with each component. Inhibition of Avicel hydrolysis was observed when the substrate was incubated with saturating and non-saturating concentrations of a mixture of EG II and CBH I respectively. A similar result was also observed with a combination of EG I and EG II.