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Biotechnology
Year: 2008  |  Volume: 7  |  Issue: 2  |  Page No.: 293 - 298

Bioconversion of Hydrocortisone by Unicellular Microalga Oocystis pusilla

Younes Ghasemi, Sara Rasoul-Amini, Mohammad Hossein Morowvat, Seyed Bagher Mosavi Azam, Shadman Shokravi, Abdolali Mohagheghzadeh, Mohammad Bagher Ghoshoon and Mohammad Javad Raee    

Abstract: A unicellular microalga, Oocystis pusilla, was isolated from paddy-field and applied in the biotransformation experiment of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 °C for 14 days incubation. The products obtained were chromatographically purified followed by their characterization using spectroscopic methods. 11β, 17α, 20β, 21-tetrahydroxypregn-4-en-3-one (2), 11β, 17β-dihydroxyandrost-4-en-3-one (3) and 11β-hydroxyandrost-4-en-3, 17-dione (4) were the main byproducts in the hydrocortisone bioconversion. Bioreaction characteristics observed were 20-ketone reduction for accumulation of compound 2 and side chain degradation of the substrate to prepare compounds 3 and 4. Time course study showed the accumulation of the product 2 from the second day of the fermentation and 3 as well as 4 from the third day. All the metabolites reached their maximum concentration in seven days. Optimum concentration of the substrate, which gave maximum bioconversion efficiency, was 0.5 mg mL-1 in one batch. Growth was not influenced by the addition of steroid substrate. Biotransformation was completely inhibited in a concentration above 2.0 mg mL-1.

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