The Kinetics of D-malate production from maleate by permeabilized Pseudomonas pseudoalcaligenes was described by assuming competitive product inhibition in addition to biocatalyst inactivation. The kinetic parameters for conversion and inactivation were determined from a simultaneous fit of two independent data sets of substrate concentration vs, time. In order to select appropriate conditions, the effects of pH and temperature on the initial substrate conversion rate (excluding inactivation) were studied first. The pH optimum ranged from 7-8. The temperature optimum was approximately 45 degrees C. The conversion parameters increased with pH and/or temperature. The first-order inactivation rate constant depended on temperature only; it increased strongly between 25-35 degrees C.