Enhanced Steroid Metabolites Production by Resting Cell Phytosterol Bioconversion

X. Gao, J. Feng, X. Wang, Q. Hua and D. Z. Wei

Abstract
The steroid metabolites 9-hydroxy-androstenedione (9-OH-AD), androstadienedione (ADD) and androstenedione (AD) are important steroidal pharmaceuticals. In order to raise the production of steroid metabolites, an efficient resting cell phytosterol bioconversion process was developed to produce 9-OH-AD in the presence of hydroxypropyl-β-cyclodextrin (HP-β-CD). Cell growth medium containing phytosterol as an inducer positively improved cell activity. Under aerobic conditions, bioconversion proceeded at 70 g L–1 phytosterol in the presence of HP-β-CD (the optimized molar ratio of HP-β-CD/phytosterol was 1:1) with 30 g L–1 resting Mycobacterium neoaurum NwIB-yV cells (cell dry mass) in a 5-L bioreactor, where 9-OH-AD production and space-time yield reached 36.4 g L–1 and 9.1 g L–1 d–1, respectively. The recycling of cells and HP-β-CD enables cost-saving and industrial applications. This bioprocess was also applied for the production of ADD and AD. The production of these steroid metabolites was much higher than that reported in previous studies.

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Keywords
phytosterol, steroid metabolites, resting cell bioconversion, hydroxypropyl-β-cyclodextrin, optimisation