Asymmetric oxidation of prochiral sulfides is a direct means for production of enantiopure sulfoxides which are important in organic synthesis and the pharmaceutical industry. In the present study, Streptomyces glaucescens GLA.0 was employed for stereoselective oxidation of prochiral sulfides. Growing cells selectively catalyzed the oxidation of phenyl methyl sulfide to the corresponding sulfoxide. Only very little overoxidation was observed, resulting in minor amounts of the unwanted sulfone. Addition of isopropyl alcohol as a co-solvent, time of substrate addition and composition of the reaction media resulted in enhanced phenyl methyl sulfide biotransformation. The concentration of the undesired by-product (sulfone) was as low as 4% through the reaction course under optimal reaction conditions. The results show that S. glaucescens GLA.0 is a promising whole-cell biocatalyst for preparing highly enantiopure (R)-phenyl methyl sulfoxide in high yield (90%) with an enantiomeric excess (ee) exceeding 99%.
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