Regulation of beta-Disaccharide Accumulation by beta-Glucosidase Inhibitors to Enhance Cellulase Production in Trichoderma reesei

Trichoderma reesei is a high-yield producer of cellulase for applications in lignocellulosic biomass conversion, but its cellulase production requires induction. A mixture of glucose and beta-disaccharide has been demonstrated to achieve high-level cellulase production. However, as inducers, beta-disaccharides are prone to be hydrolyzed by beta-glucosidase (BGL) during fermentation, therefore beta-disaccharides need to be supplemented through feeding to overcome this problem. Here, miglitol, an oc-glucosidase inhibitor, was investigated as a BGL inhibitor, and exhibited an IC50 value of 2.93 mu g/mL. The cellulase titer was more than two-fold when miglitol was added to the fermentation medium of T. reesei. This method was similar to the prokaryotic expression system using unmetabolized isopropyl-beta-D-thiogalactopyranoside (IPTG) as the inducer instead of lactose to continuously induce gene expression. However, cellulase activity was not enhanced with BGL inhibition when lactose or cellulose was used as an inducer, which demonstrated that the transglycosidase activity of BGL is important for the inducible activity of lactose and cellulose. This novel method demonstrates potential in stimulating cellulase production and provides a promising system for T. reesei protein expression.