The action of cellulolytic enzymes from Myrothecium verrucaria

Publisher Website
Google Scholar
Abstract
The action of cell-free filtrates from Myrothecium verrucaria was examined on various forms of insoluble cellulose and on the soluble cellulose derivative, carboxymethylcellulose. Unlike the parent organism which completely solubil-izes undegraded forms of cellulose (de-waxed cotton fibres), cell-free culture medium has a negligible effect (4% solubilization) on the same substrate unless this is first swollen with phosphoric acid. After such treatment of cellulose, cellulolytic filtrates produce as much as 90% solubilization of swollen cellulose powder or of swollen de-waxed cotton fibres. Conditions governing the activity of the cell-free filtrates on swollen cellulose powder are described. The preparation has an optimum activity on swollen, cellulose powder at about pH 5. Values of 1 g of swollen cellulose powder/1 and of 0-5 g of carboxymethylcellulose /I were obtained for the Michaelis constants. At pH 5-5 and temperatures between 20[degree] and 54[degree] the cell-free filtrate loses cellulase slightly'' more rapidly than carboxymethylcellulase activity. In contrast, under the appropriate assay conditions for the two activities, carboxymethylcellulase is denatured more rapidly than cellulase. Agitation of cell-free filtrates in presence of cellulose has no marked effect on the degree of cellulolysis. With carboxymethylcellulose as substrate, however, agitation produces 70% inhibition. Glucose, cellobiose or reaction products of enzymic cellulolysis fail to retard enzymic solubilization of cellulose unless present in amounts comparable with the initial weight of cellulose. Cellulase in cell-free filtrates is strongly adsorbed on its insoluble substrate and is only slowly released as the cellulose itself is solubilized.