Cloning and characterization of a beta-glucosidase from marine microbial metagenome with excellent glucose tolerance

The demand for beta-glucosidases insensitive to product inhibition is increasing in modern biotechnology, for these enzymes would improve the process of saccharification of lignocellulosic materials. In this study, a beta-glucosidase gene which encodes a 442-amino-acid protein was isolated from a marine microbial metagenomic library by functional screening and named as bgl1A. The protein was identified to be a member of GH1 family, and was recombinantly expressed, purified and biochemically characterized. The recombinant beta-glucosidase, Bgl1A, exhibited high level of stability in the presence of various cations and high concentrations of NaCl. Interestingly, it was activated by glucose at concentrations lower than 400 mM. With glucose further increasing, the enzyme activity of Bgl1A was gradually inhibited, but remained 50% original value in even as high as 1,000 mM glucose. These findings indicate Bgl1A might be a potent candidate for industrial applications.