Co-transformation of Panax major ginsenosides Rb1 and Rg1 to minor ginsenosides C–K and F1 by Cladosporium cladosporioides

Rb 1 and Rg 1 are the major ginsenosides in protopanaxadiol and protopanaxatriol. Their content in ginsenosides was 23.8 and 17.6%, respectively. A total of 22 isolates of β-glucosidase producing microorganisms were isolated from the soil of a ginseng field using Esculin-R2A agar. Among these isolates, the strain GH21 showed the strongest activities to convert ginsenoside Rb 1 and Rg 1 to minor ginsenosides compound-K and F 1 , respectively. Ginsenosides Rb 1 and Rg 1 bioconversion rates were 74.2 and 89.3%, respectively. Meanwhile, the results demonstrated that the ginsenoside Rg 1 could change the biotransformation pathway of ginsenoside Rb 1 by inhibiting the formation of the intermediate metabolite gypenoside-XVII. GH21 was identified as a Cladosporium cladosporioides species based on the internal transcribed spacers (ITS) ITS1-5.8S-ITS2 rRNA gene sequences constructed phylogenetic trees.