Biotransformation of Phytosterols to Androstenedione in Two Phase Water-oil Systems

S. Stefanov, D. Yankov and V. Beschkov

Abstract
The microbial transformation of phytosterols to androstenedione (androst-4-ene-3,17-dione, AD) and androstadienedione (androsta-1,4-diene-3,17-dione, ADD) in two-phase water-oil systems by means of the strain Mycobacterium sp. MB3683 has been studied. The effect of some process conditions, like the agitation speed, the age and amount of inoculum, the temperature and some additional carbon sources have been investigated. The highest conversion rates were attained with 10–15 % of inolucum of age t = 16–20 h at T = 34–35 "C and n = 400 min–1. Media containing high concentrations of carbohydrates have a negative impact on the process, while the natural nitrogen sources influence beneficially the bioconversion. The use of silicon oil and polypropylene-glycol as solubilizing agents was found suitable for the above-mentioned biotransformation and permitted to increase considerably the amount of the substrate in the system. On the other hand, the biotransformation rate depended on the amount of the oils, because they inhibited the microbial cells growth.

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Keywords
phytosterol, androst-4-ene-3, 17-dione, Mycobacterium, two-phase water-oil systems