Biocatalytic synthesis of S(−)-1-(1′-naphthyl) ethanol by a novel isolate of Candida viswanathii

A new yeast strain Candida viswanathii MTCC 5158, isolated from soil, is capable of carrying out the enantioselective reduction of 1-acetonaphthone to S(−)-1-(1′-naphthyl) ethanol which is an important synthetic intermediate of mevinic acid analogue, (potential inhibitor of 3-hydroxy methyl glutaryl coenzyme A reductase). Studies on the culture conditions and catalytic performance of this microorganism showed that the carbonyl reductase occurs constitutively in C. viswanathii and its production is enhanced by feeding acetonaphthone (2 mM) during the early period of cultivation. Mannitol (1%, w/v) was found to be beneficial both for growth and enzyme production. Supplementation of the media with yeast extract (0.5%) and Ca2+ (2 mM) enhanced the enzyme production. The optimal temperature and pH for the growth and enzyme production were 25 °C and 10, respectively. The organism produced enantiopure (S)-alcohol with good conversion (>97%) and almost absolute enantioselectivity (ee >99%). Parameters of the bioreduction reaction were optimized and the optimal temperature and pH for the reduction were found to be 25 °C and 8, respectively. The optimized substrate as well as the resting cell concentration was 2 and 200 g/l, respectively. The preparative scale reaction using resting cells of C. viswanathii yielded (S)-alcohol with 97% conversion and >99% ee.