Biotransformation of electron-poor alkenes by yeasts: Asymmetric reduction of (4S)-(+)-carvone by yeast enoate reductases

Within the framework of a large-scale screening carried out on 146 yeasts of environmental origin. 16 strains (11% of the total) exhibited the ability to biotransform (4S)-(+)-carvone Such positive yeasts, belonging to 14 species of 6 genera (Candida. Cryptococcus. Hanseniaspora, Kluyveromyces, Pichia and Saccharomyces), were thus used under different physiological state (growing, resting and lyophilised cells) Yields (expressed as% of biotransformation) varied from 0 14 to 3004%. in dependence of both the strain and the physiological state of the cells Products obtained from reduction of(4S)-(+)-carvone were 1S,4S- and 1R,4S-dihydrocarvone. (1S,2S,4S)-, (1S,2R,4S)- and (1R,2S,4S)-dihydrocarveol. Only traces of (1R,2R,4S)-dihydrocarveol were observed in a few strains As far as the stereoselectivity of the biocatalysis. with the sole exception of a few strains, the use of yeasts determined the prevalent accumulation of 1S,4S-isomers [(1S,4S)-dihydrocarvone + (1S,2S,4S)-dihydrocarveol + (1S,2R,4S) dihydrocarveol]. The addition of glucose (acting as auxilary substrate for cofactor-recycling system) to lyophilised yeast cells determined a considerable increase of biocatalytic activity in particular, two strains showed a surprising increase of the% of biotransformation of (4S)-(+)-carvone to values >98%). (C) 2009 Elsevier Inc All rights reserved