초록
<P><B>Abstract</B></P> <P>β-glucosidase (BGL), an important component in cellulase complex, plays a crucial role in cellulose hydrolysis. However, its activity in cellulase system of <I>Trichoderma reesei</I>, the conventional cellulase producer, is extremely low. In this study, β-glucosidase gene (<I>bgl</I>) from <I>Aspergillus niger</I> was cloned and achieved secreted expression in <I>Pichia pastoris</I>. High-level production of BGL (129 IU/mL) was achieved in a 1 m<SUP>3</SUP> fermenter by using an optimized mixed-feed strategy, in which glycerol/methanol at the ratio of 1:5 and 30 g/L corn steep powder were fed to maintain the methanol concentration of 0.7% (v/v). The obtained BGL was then used to catalyze the synthesis of sophorose, a strong inducer for cellulase production, from glucose via a transglycosylation reaction. When used the resultant glucose-sophorose mixture (GSM) containing 7.08% sophorose as both carbon source and inducer, the cellulase yield produced by <I>Trichoderma reesei</I> was high up to 95.23 IU/mL (filter paper activity), which was 2.1-fold of that achieved by lactose. These results indicated that the BGL is potential for application in the cost-effective and highly efficient production of <I>Trichoderma reesei</I> cellulase.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Recombinant <I>P. pastoris</I> was constructed for β-glucosidase (BGL) overexpression. </LI> <LI> High activity BGL was obtained under fed-batch process using mixed feeding medium. </LI> <LI> Sophorose was synthesized from glucose by BGL-mediated transglycosylation. </LI> <LI> A novel glucose-sophorose mixture (GSM) boosted cellulase activity. </LI> <LI> GSM showed stronger induction capability than lactose in cellulase production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>