Induction and the Regulation of Production of Cellulase by Fungi

SYNTHESIS of cellulases by fungi is considered to be induced by cellulose substrates, or more specifically by their water soluble short chain depolymerization products such as cellobiose1, and occasionally by other disaccharides such as sophorose2 or lactose3. Glucose is considered to invoke an inducer-represser mechanism of regulation of enzyme production when added to cellulose, for it represses the induction of cellulase unless present in extremely small amounts4. But fungi which grow on cellulose alone must also utilize glucose, for the monomer is often reported to be the final product of cellulose depolymerization5,6. The production of cellulase would not be expected to be repressed in these conditions because the organism's rate of glucose utilization would usually be restricted by the relatively slow rate of release of monomer from cellulose. Thus, if glucose were supplied to laboratory cultures as their sole source of carbohydrate at a limited rate, comparable with its slow rate of release from cellulose, then production of the enzyme might well be promoted. We have experimental support for this hypothesis, showing that the production of cellulase is controlled by the organismapos;s rate of metabolism when regulated, for example, by carbohydrate uptake. We have also found that neither cellulose, cellobiose, nor any other sugar is required per se for production of the enzyme.