Expression of a secretory β-glucosidase from Trichoderma reesei in Pichia pastoris and its characterization

A beta-glucosidase gene (bglI) from Trichoderma reesei was cloned into the pPIC9 vector and integrated into the genome of Pichia pastoris GS115. Under the control of the methanol-inducible alcohol oxidase (AOX) promoter and using Saccharomyces cerevisiae secretory signal peptide (alpha-factor), the recombinant beta-glucosidase was expressed and secreted into the culture medium. The maximum recombinant beta-glucosidase activity achieved was 60 U/ml, and beta-glucosidase expression reached 0.3 mg/ml. The recombinant 76 kDa beta-glucosidase was purified 1.8-fold with 26% yield and a specific activity of 197 U/mg. It was optimally active at 70A degrees C and pH 5.0.