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 (q p ) and the enantiomeric excess of R-MA reached the maxi-mum 0.353mmol·gdw-1·h-1 and 97.1%, respectively. The apparent reduction activity of yeast FD11b was obviously af-fected 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 estab-lished kinetic model was in good agreement with the experimental data.
