-Glucosidase and cellulase formation by a Trichoderma reesei mutant defective in constitutive -glucosidase formation

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Abstract
A mutant of Trichoderma reesei QM 9414 - T. reesei M8 - was isolated after .gamma.-irradiation. It did not form .beta.-glucosidase during growth on glycerol or glucose, but secreted .beta.-glucosidase upon growth on cellobiose. The mutant was also able to grow on cellulose and secrete .beta.-glucosidase, but with a longer lag. .beta.-Glucosidase activity could be induced in the mutant in a replacement medium by cellobiose and .beta.-methyl D-glucoside. Mycelia lacking .beta.-glucosidase were able to take up both these inducers immediately, indicating the presence of a constitutive permease. The mutant produced cellulases upon growth on lactose and - after a lag - on cellulose. Mycelia of T. reesei M8 pregrown on glycerol or cellobiose could be induced by sophorose to produce cellobiohydrolase I in a replacement system. The findings show that (i) cellobiose and other .beta.-linked disaccharides can be taken up by T. reesei without prior hydrolysis, and (ii) that cellobiose most probably induces .beta.-glucosidase formation during growth on cellulose.
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