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Abstract
Organic mono-phase and organic–aqueous two-phase systems were applied for 17-carbonyl reduction of androst-4-en-3,17-dione to testosterone by whole cells of the microalga Nostoc muscorum (Nostocaceae). To investigate the correlation between solvent hydrophobicity and biotransformation yield in mono- and biphasic systems, a range of 16 organic solvents with log Poctanol values (logarithm of the solvent partition coefficient in the n-octanol/water system) between − 1.1 and 8.8 were examined. Organic solvents with log Poctanol values greater than 7, such as hexadecane and tetradecane, provided the best biocompatibility with the bioconversion by algal cells. The data also indicated that the highest yields were obtained using organic–aqueous (1:1, v/v) biphasic systems. The optimum volumetric phase ratio, reaction temperature and substrate concentration were 1:1, 30°C and 0.5 mg mL−1, respectively. Under the mentioned conditions a fourfold increase in biotransformation yield (from 7.8±2.3 to 33.4±1.8%) was observed.