Microbial oxidation of benzyl sulfides and bibenzyl by Mortierella isabellina and Helminthosporium species

Abstract

The biotransformation of 1,2-diphenylethane by the fungus Mortierella isabellina ATCC 42613, and that of a series of alkyl benzyl sulfides by the fungi M. isabellina and Helminthosporium species NRRL 4671 have been studied. Mortierella hydroxylates 1,2-diphenylethane in low yield, giving (S)-1,2-diphenylethanol with an enantiomeric purity of 33%. Bioconversions of deuterium-labelled and racemic 1,2-diphenylethanol by M. isabellina demonstrate that this organism performs reversible oxidation/reduction of the alcohol. Biotransformations of n-alkyl benzyl sulfides by H. species give predominantly the (S) enantiomer of sulfoxide, with no sulfone formation, but M. isabellina, although showing a general preference for the oxidation of alkyl benzyl sulfides to (R) sulfoxides, also generates sulfones from n-alkyl benzyl sulfides in a time-dependent manner that suggests a stereoselective removal of (R) sulfoxide. The latter microorganism can be used, however, for the production of (R)-benzyl methyl and benzyl isopropyl sulfoxides, and gives (S)-benzyl tert-butyl sulfoxide in low yield. Key words: biotransformation, enzymes, sulfoxides.