11 β-Hydroxylation of cortexolone using immobilized Cunninghamella elegans protoplasts

Abstract

Transformation of cortexolone to cortisol and prednisolone by the filamentous fungus Cunninghamella elegans protoplasts as a research tool was studied. The immobilized protoplasts of the fungus hydroxylated cortexolone at 11β -position had significantly higher activity than the free protoplasts. Sucrose as an osmotic stabilizer was found to be best at 0.6 M level. Relatively higher cortexolone bioconversion was obtained on using 3 ml of protoplasts (1.2iN107 protoplasts/ml) entrapped in 3% calcium alginate gel after 18 h incubation. The addition of some supplements was also investigated. The highest bioconversion efficiency was recorded with sodium citrate (1 g/L) and sodium benzoate (1 g/L). Similarly, the bioconversion process was fairly enhanced in the presence of Tween 20, 60 and the tested vitamins supplements. The entrapped protoplasts proved to be able to maintain the bioconversion process for repeated 13 cycles over 252 h. Sodium citrate and sodium benzoate, folic acid, riboflavin, menadione, vitamin B12 and ascorbic acid relatively were able to increase bioconversion efficiency. Key words : Cortexolone, 11£β-hydroxylation, immobilization, Cunninghamella elegans, protoplasts.