Kinetics of Asymmetric Reduction of Phenylglyoxylic Acid to R-(–)-Mandelic Acid by Saccharomyces Cerevisiae FD11b1

The kinetics of asymmetric production of R-(–)-mandelic acid (R-MA) from phenylglyoxylic acid (PGA) catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of glucose and PGA were controlled respectively with a dual feeding system. When the electron donor glucose was supplied at the rate of 0.0833mmol·gdw−1·h−1, the specific production rate (qp) and the enantiomeric excess of R-MA reached the maximum 0.353mmol·gdw−1·h−1 and 97.1%, respectively. The apparent reduction activity of yeast FD11b was obviously affected by both substrate PGA and product MA. The qp value reached the maximum 0.36—0.38mmol-gdw−1·h−1 when the PGA concentration was controlled between 25 and 35mmol·L−1. The obvious substrate inhibition of bioconversion was observed at the PGA concentrations higher than 40mmol·L−1. The accumulation of product MA also caused a severe feed-back inhibition for its production when the product concentration was above 60mmol·L−1. The kinetic model with the inhibition effect of both substrate and product was simulated by a computer-based least-square arithmatic. The established kinetic model was in good agreement with the experimental data.