Complete conversion of major protopanaxadiol ginsenosides to compound K by the combined use of α-l-arabinofuranosidase and β-galactosidase from Caldicellulosiruptor saccharolyticus and β-glucosidase from Sulfolobus acidocaldarius

•α-l-Arabinofuranosidase and/or β-galactosidase, and β-glucosidase were combined.•The conditions for compound K production of the enzymes were optimized.•The enzymes completely converted major protopanaxadiol ginsenosides to compound K. The ginsenoside compound K has pharmaceutical activities, including anti-tumor, anti-inflammatory, anti-allergic, and hepatoprotective effects. To increase the production of compound K, the α-l-arabinofuranoside-hydrolyzing α-l-arabinofuranosidase (CS-abf) and/or the α-l-arabinopyranoside-hydrolyzing β-galactosidase from Caldicellulosiruptor saccharolyticus (CS-bgal) were mixed with the β-d-glucopyranoside-hydrolyzing β-glucosidase from Sulfolobus acidocaldarius (SA-bglu). The optimum conditions for the production of ginsenoside compound K from ginsenoside Rc or Rb2, or from major protopanaxadiol ginsenosides in ginseng root extract were determined to be pH 6.0 and 75°C with 8mgml−1 ginsenoside Rc, 8mgml−1 Rb2, or 10% (w/v) ginseng root extract; and 10.5Uml−1 CS-abf or CS-bgal supplemented with 4.5Uml−1 SA-bglu, or 10.5Uml−1 CS-abf and 10.5Uml−1 CS-bgal supplemented with 4.5Uml−1 SA-bglu, respectively. Under optimum conditions, ginsenosides Rc and Rb2, and major protopanaxadiol ginsenosides in ginseng root extract were completely converted to compound K after 12, 14, and 20h, respectively, with the respective productivities of 388, 328, and 144mgl−1h−1. This is the first report of the complete conversion of major protopanaxadiol ginsenosides to compound K.