Objective: The aim of this study was to provide a new approach to synthesize hydroperoxylated products of 20 (S) -protopanaxadiol

and to optimize the microbial transformation conditions by Mucor racemosus AS 3.205. Method: Biotransformation conditions were optimized by altering several influencing factors. The yields of two hydroperoxylated products of 20 (S) -protopanaxadiol were evaluated. Result: Two metabolites were isolated and identified as 25

26-en-24 (R)-hydroperoxyl-20 (S) -protopanaxadiol and 23

24-en-25-hydroperoxyl-20 (S) -protopanaxadiol. The optimal transformation condition was as following:an inoculation amount at 10%

substrate concentration at 0.25 mmol·L-1

sample injected after inoculated 48 h

transformation time of 5 d

culture temperature at 28 ℃

and shaking speed at 150 r·min-1. Conclusion: Microbial transformation system by M. racemosus AS 3.205 can be used to obtain hydroperoxylated products of 20 (S) -protopanaxadiol. The yields of two hydroperoxylated products could be greatly increased under the optimized condition.