PRODUCTION OF CELLULASE SYSTEMS BY SELECTED MUTANTS OF TRICHODERMA-REESEI IN SOLID-STATE FERMENTATION AND THEIR HYDROLYTIC POTENTIALS

Three mutants of Trichoderma reesei were grown in solid-state fermenta tion (SSF) in flasks and in a pan bioreactor. Mutant strain MCG 80 pro ved to be best at producing an optimal cellulase system using lignocel lulosic material (wheat straw [WS]) as substrate. This preparation exh ibited a beta-glucosidase activity (beta GA) to FPA (FPA) ratio of abo ut 1.0, which is indicative of a high potential for hydrolysis of cell ulose. The yields of cellulase systems and the ratio of beta GA to FPA produced in flasks were comparable to that of the pan bioreactor. The cellulase system of T. reesei MCG 80 having a ratio of beta GA to FPA close to 1.0 gave the most complete (88-95%) hydrolysis of 5% deligni fied wheat straw (DWS). On the other hand, the cellulase system of coc ultures of T. reesei QMY-1 and Aspergillus phoenicis failed to produce high hydrolytic yields in spite of having a very high ratio of beta G A to FPA (3.04). This failure was owing to the fact that coculture con tained the relatively poor-quality cellulase system of the dominant or ganism; A. phoenicis. The resulting fermented WS can be used, as a sou rce of enzyme (unextracted), for hydrolysis of wheat straw, and it giv es increased yields of reducing sugars compared to analogous. extracte d enzyme preparations. The hydrolytic potential of two commercial enzy mes tested were considerably lower than those of the cellulase systems produced on WS. It is evident that a complete cellulase system having a beta GA-to-FPA ratio close to 1.0 and high hydrolytic potential can be produced on lignocellulosic feedstocks in SSF.