Abstract: Rhodobacter sphaeroide as a new biocatalysts were investigated in the asymmetric reduction of ketones to chiral alcohols. The cells were used in an aqueous system for the asymmetric reduction of acetophenone to prepare (S)-1-phenyl-ethanol by photo-electron-transfer reactions. It is found that higher product yield and product enantiomeric excess could be achieved. The results show that the enantiomer excess of the chiral alcohols was up to 99%(e.e.) and the yield is more than 90%. The effects of DCMU and the optimal reaction conditions on the reaction were investigated. The results show that the reaction was controlled by light completely, the optimal substrate concentration is 17.0 mmol/L, the optimal cell mass concentration is 0.2 g/mL, the optimal pH is 7—8, the optimal reaction time was 72 h.

Key words: Photosynthetic bacteria, Asymmetric reduction, Photo-electron-transfer, Acetophenone, Chiral alcohols