Isolation and partial characterization of a mutant of trichoderma reesei and its application in solid‐state fermentation of paddy straw alone or in combination with pleurotus sajor‐caju

Abstract

A number of mutant strains overproducing cellulase, ß‐glucosidase, and xylanase enzymes were isolated from the cellulolytic fungus Trichoderma reesei QM 9414 after mutagenesis by chemical treatment. Selection was carried out using agar plates containing microcrystalline cellulose. Cellulase (filter paper hydrolyzing activity) and ß‐glucosidase production by one of the mutants in shake flask cultures was approximately twice as high as the parent strain. Xylanase production was found to be twenty‐five times as high when 1% xylan was used as the carbon source as when 1% cellulose was used. The morphology of the mycelium of the mutants was quite different from that of the parent strain. The mutants, for example, produced mycelium which was highly branched and showed a typical restricted growth pattern when grown on cellulose agar plates. During solid‐state fermentation of paddy straw, maximum degradation was observed in the treatment where a superior mutant of T. reesei was inoculated in combination with Pleurotus sajor‐caju. The two organisms together caused 44.57% cellulose, 58.5% hemicellulose, and 59.2% lignin degradation.