beta-D-xylosidase, an important glycoside hydrolase, hydrolyzes xylo-oligosaccharides to yield xylose and biotransforms specific saponins by cleaving beta-xylose at the non-reducing end. It is extensively employed in renewable resources, including fuels, food, and pharmaceuticals, as a xylanolytic enzyme. In this study, a 1197 bp beta-xylosidase gene (BaXyl5B) derived from Bifidobacterium adolescentis was cloned and expressed in E. coli BL21. Following purification, the recombinant beta-xylosidase exhibited a distinct band on SDS-PAGE; its molecular weight was determined to be 46.4 kDa. The optimal activity of BaXyl5B was observed at a pH of 6.0 and a temperature of 30 degrees C. Purified BaXyl5B demonstrated multifunctional activities involving p-nitrophenyl-beta-D-xylopyranoside (pNP beta Xyl), p-nitrophenyl-alpha-L-arabinopyranoside (pNP alpha Arap), and p-nitrophenyl-beta-D-glucopyranoside (pNP beta Glc). A significant finding of this study was that BaXyl5B exhibited high selectivity towards ginsenoside Rb3, which could hydrolyze xylose at the C-20 position of Rb3 to yield Rd and F2. Overall, this research explored a novel beta-xylosidase, BaXyl5B, that could serve as a valuable biocatalyst for converting ginsenosides and synthesizing active glycosides and aglycones, making it a promising enzyme for further exploration and utilization.
