The combination of a membrane bioreactor using lipase from Serratia marcescens and a crystallizer has been proposed for the production of optically active (2R, 3S)-3-(4-methoxyphenyl) glycidic acid methyl ester ((-)MPGM) from racemic compounds ((+/-)MPGM). The reaction kinetics were investigated with a view toward industrial application of this newly devised bioreactor system. The following results were obtained. (i) The hydrolysis of (+/-)MPGM in the bioreactor system proceeded as a first-order reaction with respect to the substrate amount. (ii) The reaction rate depended on the amount of enzyme loaded onto a membrane module and the initial amount of substrate in the crystallizer. (iii) The reaction rate was not influenced by the rate of substrate circulation between the crystallizer and membrane bioreactor. (iv) Although the level of performance of the bioreactor system with respect to hydrolysis decreased with increasing operation time, it recovered to upon loading of fresh enzyme onto the membrane. This bioreactor system in which an enzymatic reaction and product crystallization occurred simultaneously had a high level of productivity compared with that of the conventional membrane bioreactor using a solubilized (+/-)MPGM substrate.