Preparation of (R)-(-)-mandelic acid by two-step biotransformation of ethyl benzoylformate

(R)-(-)-mandelic acid was synthesized by two-step biotransformation. (R)-(-)-mandelic acid ethyl ester was obtained via asymmetric reduction of ethyl benzoylformate by Saccharomyces cerevisiae CGMCC No. 3361 at the first step. The conversion and enantiomeric excess of R-(-)-mandelic acid ethyl ester reached 99.8% and 100%, respectively. (R)-(-)-mandelic acid was obtained via hydrolysis of (R)-(-)-mandelic acid ethyl ester by Bacillus cereus CGMCC No. 12336 at the second step. The conversion and enantiomeric excess of R-(-)-mandelic acid reached 97.2% and 100%, respectively. Kinetic models were developed for asymmetric reduction of ethyl benzoylformate and hydrolysis of (R)-(-)-mandelic acid ethyl ester. The kinetic models are in good agreement with the experimental data.