Objective To engineer Pichia pastoris for heterologous production of cellulase from Musca domestica and explore its potential for industrial applications. Results A new beta-glucosidase gene (bg), encoding 562 amino acids, was cloned from M. domestica by using rapid amplification of cDNA ends. The gene bg was linked to pPICZ alpha A and expressed in P. pastoris with a yield of 500 mg l(-1). The enzyme has the maximum activity with 27.6 U mg(-1) towards cellulose. The beta-glucosidase has stable activity from 20 to 70 degrees C and can tolerate one-mole glucose. It has the maximum activities for salicin (25.9 +/- 1.8 U mg(-1)), cellobiose (40.1 +/- 2.3 U mg(-1)) and cellulose (27.6 +/- 3.5 U mg(-1)). The wide-range substrate activities of the beta-glucosidase were further verified by matrix-assisted laser desorption/ionization mass spectra. Structural analysis shows that the beta-glucosidase belongs to glycoside hydrolase family I and possesses O-glycosylation sites. Conclusions Thus, a multifunctional beta-glucosidase was expressed from M. domestica and provides a potential tool for industrial application of cellulose.