Nutritional and Cultural Studies for Optimal Conversion of β-sitosterol to Testosterone by Rhizopus oryzae nrc11
Publication Date : 31/12/2016
A strain of Rhizopus oryzae nrc11 was evidenced to have ability to convert β-sitosterol to testosterone in a single fermentation step. Productivity of testosterone was studied in five different fermentation media. Testosterone yield varied considerably in different media and the highest yield was attained in nutrient broth medium. Augmentation of medium with different carbon and nitrogen sources was accompanied with increase in hormone yield in mostly all tested sources. The optimal yield was in case of corn steep liquor (280 µg/flask). Further enrichment of the medium with cane molasses (20 gm/l) resulted in an impressive elevation in the yield to reach the value of 370 µg/flask. The results showed also that the role of nutritional requirements was critically controlled by initial pH value of the medium. The fermentation medium was best suited to biotransformation process at neutral pH value (pH 7) and slight change in initial pH away from value of 7 was accompanied with drastic decrease in testosterone concentration. Slight increase in yield could be attained by increasing agitation of culture to 200 rpm. However, comparable yield outputs were obtained under static and agitated culture which may be beneficial when considering costs of agitation in large scale processes. The effects of some additives like surfactant, oxidation-reduction agents and protective agents of steroidal nucleus were studied and there was no further optimization in the yield which proved that improvement done has reached the ultimate optimization under tested nutritional and cultural condition.
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