A novel beta-glucosidase-encoding gene, bgl-gs1 which was identified from a positive fosmid clone in a metagenomic library of the gut of Globitermes sulphureus, encodes a 455 amino acid polypeptide that contains a catalytic domain belonging to glycoside hydrolase family 1 (GH1). It was expressed in Escherichia coli BL21 (DE3) and the expression product showed a molecular mass of similar to 51.7 kDa by SDS-PAGE. The optimal temperature and pH for the activity of the purified recombinant enzyme Bgl-gs1 with p-nitrophenyl-beta-D-glucoside (pNPG) were 90 C and 6.0, respectively. The specific activities of Bgl-gs1 on pNPG and salicin were 110 and 14 U/mg of protein, respectively, and its K-m values were 0.18 and 2.59 mM, respectively. The residual activity of Bgl-gs1 was maintained above 70% after the recombinant enzyme was incubated at 75 degrees C and pH 6.0 for 2 h, and its half-life at 90 degrees C was approximately 1 h in the presence of 4 mM pNPG. Bgl-gs1 showed synergistic effect with either a crude enzyme mixture of the fungal strain Trichoderma reesei Rut-C30 or a fusion protein (TcE1) created from the cellobiohydrolase cbh1 gene of T. reesei and endoglucanase from Acidothermus cellulolyticus; 87 and 137% increases in hydrolytic efficiency were noted on microcrystalline cellulose, respectively. These results suggest that the thermostable beta-glucosidase Bgl-gs1 is a likely candidate for industrial applications. (C) 2012 Elsevier Inc. All rights reserved.