Microbial Conversion of Major Ginsenosides to Minor Pharmacological Ginsenoside Compound-K by Sphingomonas sp. ZY-3

Ginsenoside is the most important secondary metabolite of ginseng, and the metabolite of Ginsenoside Rb1 has various pharmacological activities, such as anti-tumor properties. Although various chemical and biological methods have been reported of preparation for it, enzymatic production by microbial bioconversion is able to produce engineering range metabolite with specific selectivity and high efficiency. In this study, to achieve minor pharmacological ginsenoside Compound-K from major ginsenoside using microbial biotransformation, many soil bacteria which have strong β– glucosidase activity were isolated. The screening was performed on esculin containing 1/10 TSA agar plate and then observed color development. The selected positive isolates were cultured 1000ppm G-Rb1 and the products were analyzed by TLC (thin-layer-chromatography) and HPLC (highperformance liquid chromatography) method. One novel bacterial strain ZY-3 could hydrolyze ginsenoside Rb1 to the active metabolites Compound-K through F2 and Rd. Based on phylogenetical tree, it was found to belong to genus Sphingomonas and was very close to Sphingomonas jaspsi TDMA-16 and Sphingomonas astaxanthinifaciens TDMA-17 (96.8%, 96.5%, similarity based on 16S rRNA sequence). The bioconversion production of Compound-K occurred by consecutive hydrolyses of the terminal sugar moieties at the C20 carbon and hydrolyses of the terminal and inner C-3 carbon of ginsenoside Rb1 showing the biotransformation pathway: Rb1 → Rd → F2→Compound-K. Keywords-ginsenoside; microbial biotransformation; 16S rRNA gene