Characterization of a metagenome-derived β-glucosidase and its application in conversion of polydatin to resveratrol

Abstract

For the beneficial pharmacological properties of resveratrol, there is increasingly interest in enzymatic conversion of polydatin to resveratrol. The metagenomic technique provides an effective strategy for mining novel polydatin-hydrolysis enzymes from uncultured microorganisms. In this study, a metagenomic library of mangrove soil was constructed and a novel β-glucosidase gene MlBgl was isolated. The deduced amino acid sequences of MlBgl showed the highest identity of 64% with predicted β-glucosidase in the GenBank database. The gene was cloned and overexpressed in Escherichia coli BL21(DE3). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) assay demonstrated the purified recombinant β-glucosidase r-MlBgl with a molecular weight approximately of 71 kDa. The optimal pH and temperature of purified recombinant r-MlBgl were 7.0 and 40˚C, respectively. r-MlBgl could hydrolyze polydatin effectively. The kcat and kcat/Km values for polydatin were 989 s-1 and 1476 mM-1 s-1, respectively. These properties suggest that -r-MlBgl has potential application in the enzymatic conversion of polydatin to resveratrol for further study.