Transformation of Reichstein's compound S into prednisolone by immobilized mixed cultures

Abstract Reichstein's compound S was transformed into prednisolone in a single‐step fermentation using immobilized mixed cultures, entrapped in different gels or adsorbed on clay particles. Calcium alginate at a gel concentration of 2% gave the highest transformation activities and prednisolone yields. The entrapped mixed cultures could be repeatedly used in batch‐wise transformation for at least six times when suspended in diluted nutrient medium and for three times when suspended in distilled water; in the latter case the entrapped cultures required to be reactivated in nutrient medium for further reuse. Mixed cultures adsorbed on clay particles were successfully reused 18 times, with reactivation after the 9th and 15th uses. Continuous transformation of substance S into prednisolone by mixed cultures adsorbed on clay particles was more efficient than batch‐wise reused adsorbed cultures and was dependent on the daily working medium volume.