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Influence of temperature on nucleus degradation of 4‐androstene‐3, 17‐dione in phytosterol biotransformation by Mycobacterium sp.

One of the steroid intermediates, 4‐androstene‐3, 17‐dione (AD), in the biotransformation of phytosterols is valuable for the production of steroid medicaments. However, its degradation during the conversion process is one of the main obstacles to obtain high yields. In this study, the effect of temperature on nucleus degradation during microbial biotransformation of phytosterol was investigated. The results indicated that microbial degradation of phytosterol followed the AD‐ADD‐‘9‐OH‐ADD’ pathway, and that two important reactions involved in nucleus degradation, conversions of AD to ADD and ADD to 9‐OH‐ADD, were inhibited at 37°C. With a change in the culture temperature from 30 to 37°C, nucleus degradation was reduced from 39·9% to 17·6%, due to inhibition of the putative KstD and Ksh. These results suggested a simple way to decrease the nucleus degradation in phytosterol biotransformation and a new perspective on the possibilities of modifying the metabolism of strains used in industrial applications.