Characterization of cellulolytic enzyme complexes obtained from mutants of Trichoderma reesei with enhanced cellulase production

Abstract

The cellulolytic enzyme complexes secreted by the fungus Trichoderma reesei QM 9414 and its mutants M 5, M 6, MHC 15, and MHC 22 were characterized by determining their specific filter-paper (FP)-, carboxymethylcellulase (Cx)-and β-glucosidase (βG)-activities. They were characterised further by measuring their Cx and βG profiles after separation on an isoelectrofocusing column over the pH range 3–10. While the overall FP-activity was roughly equal in all preparations, the specific β-glucosidase activity was highest in mutants MHC 15 and MHC 22 which are distingiushed morphologically from the parent strain, QM 9414, by a higher degree of branching of their hyphae. Two peaks of β-glucosidase activity were detected by isoelectric focusing in preparations from QM 9414 and M 6, none in the enzyme from the mutant M 5 while 3 and 4 peaks respectively were found in preparations from morphological mutants MHC 15 and MHC 22. The higher β-glucosidase activity in these last two preparations was also reflected in the higher glucose to cellobiose ratio in the initial stages of cellulose hydrolysis by the individual enzyme preparations.