Investigation of factors affecting biotransformation of phytosterols to 9-hydroxyandrost-4-ene-3,-17-dione based on the HP-β-CD-resting cells reaction system

Abstract

Based on the hydroxypropyl-β-cyclodextrin-resting cells reaction system, high substrate concentration and improved reaction rate were achieved in a bioprocess of microbial side-chain cleavage of phytosterols to 9-OH-AD. Investigation of the kinetics of biotransformation showed that the initial reaction rate was strongly inhibited by a substrate concentration greater than 8 g/L. The oxygen transfer rate was also a critical parameter that could influence the rate of reaction. The results highlighted the importance of dissolved oxygen, particularly at high substrate concentration. Finally, analysis of metabolites showed that the main loss of process yield was due to by-product (16.3%) and nucleus degradation (8–11%) in the biotransformation. Investigation of the kinetics of metabolite formation provided fundamental knowledge on the biochemical reaction which was critical for understanding how to develop the biotransformation into an industrial application.

Keywords::

• Biotransformation
• hydroxypropyl-β-cyclodextrin
• Mycobacterium
• phytosterols
• rate limitation

Declaration of interest: The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

This paper is supported by the National Natural Science Foundation of China (General Program, No. 21276083).