Microalgal transformation of progesterone by the terrestrial-isolated cyanobacterium Microchaete tenera

Abstract

A large number of microorganisms including various microalgal strains are able to convert steroid compounds into useful metabolites. In the present study, the ability of Microchaete tenera, a rice paddy field-isolated microalga, was investigated for biotransformation of progesterone. The incubation was carried out at 25°C under continuous illumination in the present of 0.25 g L−1 of progesterone. After 5 days incubation of the microalga in BG-11 liquid medium, the broth was extracted and the products were purified by the aid of chromatographic methods. Structure elucidation of the metabolites was performed by spectral data (13C NMR, 1H NMR, FTIR, and MS) and physical constants (melting points and optical rotations). Eventually, four major steroids including 20β-hydroxypregn-4-en-3-one, 20α-hydroxypregn-4-en-3-one, 6β-hydroxypregn-4-en-3,20-dione and 6α-hydroxypregn-4-en-3,20-dione were the results of this biotransformation. The study also showed that the best concentration of starting material, temperature, photoregime, and the influence of CO2 partial pressure on the production of bioconverted metabolites were 0.25 g L−1, 25°C, continuous light and 2.0 ± 0.1% (v/v), respectively. Highest concentrations of all biotransformed metabolites were obtained in the 5th day.