Substrate specificity and kinetics of Candida rugosa lipase in organic media

The fatty acid specificity of lipase from Candida rugosa during the esterification of saturated fatty acids and sulcatol in toluene has been studied. The true kinetic parameters are obtained by fitting the experimental data to a Ping-Pong kinetic model that includes alcohol inhibition. The fitted parameter values are compared with apparent values that would be obtained from restricted data sets in which one of the substrate concentrations was kept constant. It has been found that in reactions inhibited by alcohol the true Ping-Pong parameters can be significantly different from the apparent ones. Corrections for solvation are made by using activities instead of concentrations to fit the kinetic parameters. Though activity coefficients, estimated using the UNIFAC group contribution method, vary by over 25% for changing concentrations in the same solvent, their use did not improve the fit to the data. This contrasts with what has been found in comparisons of different solvents, where the differences in activity coefficients are much larger.