Characterization of β-xylosidase from Thermoanaerobacterium thermosaccharolyticum and its application to the production of ginsenosides Rg1 and Rh 1 from notoginsenosides R 1 and R 2.

β-Xylosidase from Thermoanaerobacterium thermosaccharolyticum was purified by His-trap affinity chromatography giving a specific activity of 5.15 U mg(-1). From gel-filtration chromatography, the purified enzyme was a tetramer with a total molecular mass of 245 kDa. Maximal enzyme activity using o-nitrophenyl(NP)-β-D-xylopyranoside was at pH 6.5 and 60 °C, with a half-life of 50 h. The enzyme had highest activity for oNP-β-D-xylopyranoside among aryl-glycosides, and was only active for notoginsenosides R1 and R2 amongst various ginsenosides. β-Xylosidase completely converted 2 g notoginsenosides R1 and R2 l(-1) to 1.69 g ginsenoside Rg1 l(-1) and 1.63 g ginsenoside Rh1 l(-1) in 4 and 18 h, respectively, with molar conversion yields of 100 % and specific productivities of 0.21 and 0.05 g g-enzyme(-1) h(-1), respectively. To our knowledge, this is the first report on the enzymatic production of ginsenosides Rg1 and Rh1 from notoginsenosides R1 and R2.