Enhanced Production of Protopanaxatriol from Ginsenoside Re and Rg1 Using a Recombinant Bacterial β-glucosidase

20(S)-protopanaxatriol (PPTA), an aglycone of ginseng saponins, is rarely found and is present in a limited amount; it exhibits various pharmaceutical activities, including memory improvement, and anti-diabetic and anti-cancer effects. An enzymatic method was developed to improve 20(S)-protopanaxatriol aglycone [20(S)-PPTA] production using recombinant β-glucosidase (BgpA) cloned from Terrabacter ginsenosidimutans Gsoil 3082^T. The optimal hydrolytic activity was obtained at pH 7.0 and 37°C. The enzyme could hydrolyze the rutinoside and glucose moieties at the C6 and C20 positions, respectively, of ginsenosides Re and Rg1 to produce 20(S)-PPTA through the formation of ginsenoside F1 as an intermediate. For gram-scale production, the enzyme reaction was performed in a 10-L fermenter for 48 h at a substrate concentration of 10 mg/mL. Finally, 5.45 g 20(S)-PPTA was produced from 36 g PPT type ginsenoside mixture with 95% purity by chromatography. This study thus reveals an industrial application of a minor component, 20(S)-PPTA.