Isolation and Characterization of a Mutant of Trichoderma reesei Showing Reduced Levels of Extracellular β-Glucosidase

Summary: A mutant (D6-13) of Trichoderma reesei that produced low levels of extracellular β-glucosidase was physiologically and biochemically characterized. The mutant was unable to grow and produced very little cellulase activity on Solka-Floc, Avicel, micro-crystalline cellulose and acid-swollen cellulose. Whereas growth was nearly normal on cellobiose, lactose and glucose, cellulase production was slightly decreased on cellobiose and lactose. The mutant produced nearly normal levels of FPA (filter-paper activity) and endoglucanase on sophorose. A distinct lag and a lowered specific sugar consumption rate was observed for the mutant on 0·3% cellobiose; this appeared to be due to lowered wall-bound β-glucosidase activity. The multiplicity and role of different β-glucosidases in T. reesei is discussed.