Biotransformation of Phytosterols to 9α-Hydroxyandrostenedione by Mycobacteriumsp.in Oil-Water Emulsion System

A simple oil-water emulsion system was developed for highly efficient biotransformation of phytosterols to 9α-hydroxyandrost-4-ene-3,17-dione(9-OH-AD).Results indicated that mechanical shearing force generating shear force and addition of Tween 80 as dispersant were the essential factors to form a stable emulsion system.And the ratio of cereal oil was related to the effective load of system for phytosterols concentration.In the emulsion system,a higher biomass was got at an evenly dispersed state.Application of the emulsion system accelerated biotransformation process at higher phyosterols concentration of 20g/L phytosterols with 64.06% molar yield and 1.28g/(L·d)productivity of 9-OHAD.After biotransformation,the major by-products partitioned in the oil phase would be removed with oil,and the purity of 9-OH-AD by the chromatography area normalizing increased from 66%to 90%.