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Abstract
Steroids can be ranked among the most widely marketed products from the pharmaceutical industry specially cortisol which is an effective anti-inflammatory drug and one of the important precursors of many other steroid drugs. Introducing a hydroxyl
group in the 11β-position of cortexolone (Reichstein’s Substance S)
by a microbial catalyst is of a commercial value in the production of
pharmaceutical corticosteroid (cortisol).
Screening of microorganisms for their capability to transform cortexolone was carried out. It was found that Curvularia lunata RCMB 019002 transform cortexolone to yield cortisol and other
products with the highest yield of cortisol. The conditions for cultivation of this fungus with the maximum bioconversion activity(maximum yield of cortisol) were investigated. Based on the results, Curvularia lunata RCMB 019002 was cultivated with a medium
composed of (g/l): yeast extract, 5; peptone, 5; glucose, 20; NaCl, 5;
K2HPO4, 5, at pH 6.5 , 30±2°C ,150 rpm for 48 hrs with induction of the hydroxylase enzymes and use of EDTA disodium salt as an additive. The cultivation of fungal cells under the later conditions afforded cortisol in a yield of 50%.
Curvularia lunata RCMB 019002 cells immobilized by entrapment in calcium alginate gel (concentration 3 %) were used for bioconversion of cortexolone to cortisol. The bioconversion efficiency of the immobilized cultures was higher than that obtained with the free cells. The repeated batch biotransformation with the immobilized fungal cells could be successfully maintained for ten cycles (30 days). During the first two cycles of operation, the bioconversion efficiency reached 84.4%.