Characteristics of Anaerobic Bacteroides fragilis CMLF03 and Its Enzymes Involved in the Transformation of Panax notoginseng Saponins

Abstract Panax notoginseng saponins (PNS) are bioactive constituents that can be biotransformed by gut microbiota. Anaerobic Bacteroides bacteria are considered the next-generation probiotics. However, little is known about PNS biotransformation by Bacteroides bacteria. The study identified a nonenterotoxigenic Bacteroides fragilis capable of biotransforming PNS. Three family 3 glycoside hydrolases from the strain were heterologously expressed and identified as β-glucosidases GE-270 and GE-710 and β-xylosidase GE-616. The two β-glucosidases catalyzed the conversion of the abundant protopanaxadiol-type ginsenosides Rb2, Rb3, and Rc present in P. notoginseng flowers and leaves to the rare ginsenoside compounds O, Mx1, and Mc1, respectively, and also converted ginsenoside Rb1 to F2. Furthermore, GE-270 converted the protopanaxadiol-type ginsenoside Rg3 to Rh2 and the protopanaxatriol-type notoginsenoside R1 to ginsenoside Rg1. The β-xylosidase GE-616 could convert the ginsenoside Rb3 to Rd. This research provides a novel anaerobic bacterium and its enzymes for PNS biotransformation.