Abstract: Thirty six strains that exhibited the catalytic activity for asymmetric reduction of ethyl pyruvate to (S)-ethyl lactate were isolated from sewage of a chemical factory in Chengdu, China and the neighboring soil. Among them, yeast strain BTY18-6 has high catalytic activity. The asymmetric reduction of ethyl pyruvate to (S)-ethyl lactate catalyzed by BTY18-6 resting cells in an aqueous phase was examined, and the parameters influencing the bio-reduction were optimized. The results showed that, under the optimized conditions of 2.5% glucose as co-substrate, the initial reaction pH = 6.8, the initial cell concentration at 0.175 g/ml (wet mass) cultured for 48 h, the initial ethyl pyruvate concentration at 65 mmol/L, temperature 32 ^oC, and reaction time 48 h, the ethyl pyruvate conversion reached 95.5% with enantiomeric excess of 92.1%.

Key words: yeast resting cell, biological catalysis, ethyl pyruvate, asymmetric reduction, (S)-ethyl lactate