Production of aglycone protopanaxatriol from ginseng root extract using Dictyoglomus turgidum β-glycosidase that specifically hydrolyzes the xylose at the C-6 position and the glucose in protopanaxatriol-type ginsenosides

Abstract

The hydrolytic activity of a recombinant β-glycosidase from Dictyoglomus turgidum that specifically hydrolyzed the xylose at the C-6 position and the glucose in protopanaxatriol (PPT)-type ginsenosides followed the order Rf > Rg₁ > Re > R₁ > Rh₁ > R₂. The production of aglycone protopanaxatriol (APPT) from ginsenoside Rf was optimal at pH 6.0, 80 °C, 1 mg ml⁻¹ Rf, and 10.6 U ml⁻¹ enzyme. Under these conditions, D. turgidum β-glycosidase converted ginsenoside R₁ to APPT with a molar conversion yield of 75.6 % and a productivity of 15 mg l⁻¹ h⁻¹ after 24 h by the transformation pathway of R₁ → R₂ → Rh₁ → APPT, whereas the complete conversion of ginsenosides Rf and Rg₁ to APPT was achieved with a productivity of 1,515 mg l⁻¹ h⁻¹ after 6.6 h by the pathways of Rf → Rh₁ → APPT and Rg₁ → Rh₁ → APPT, respectively. In addition, D. turgidum β-glycosidase produced 0.54 mg ml⁻¹ APPT from 2.29 mg ml⁻¹ PPT-type ginsenosides of Panax ginseng root extract after 24 h, with a molar conversion yield of 43.2 % and a productivity of 23 mg l⁻¹ h⁻¹, and 0.62 mg ml⁻¹ APPT from 1.35 mg ml⁻¹ PPT-type ginsenosides of Panax notoginseng root extract after 20 h, with a molar conversion yield of 81.2 % and a productivity of 31 mg l⁻¹ h⁻¹. This is the first report on the APPT production from ginseng root extract. Moreover, the concentrations, yields, and productivities of APPT achieved in the present study are the highest reported to date.