Ethyl oleate synthesis by Porcine pancreatic lipase in organic solvents

The Porcine pancreatic lipase catalysed esterification of oleic acid with ethanol was studied in 10 different solvents with constant initial water content in the reaction mixture. The initial rates of the esterification reaction were attempted to correlate with such solvent properties as hydrophobicity (log P), water solubility (Sw), dielectric constant, electron pair acceptance and donation index (expressed as ENT +DNN), polarisability etc. While significantly good linear correlations with log P and log Sw were obtained, the correlations with the other properties were found to be inferior. The kinetics of the reactions was found to conform to the so-called Ping-Pong-Bi-Bi model with ethanol inhibition effect and the estimated model parameters exhibited statistically significant correlation with log P consistent to its correlation with the initial rate. Assuming that organic solvents do not interfere with the lipase–substrate binding process nor with the catalytic mechanism, the contribution of substrate–solvent interactions to enzyme kinetics was accounted for by replacing the substrate concentrations of the intrinsic kinetic equations by thermodynamic activities. The values of the corrected intrinsic parameters (Km, ksp) and the maximal rate (Vmax) were found to be nearly equal for all the media. © 2002 Elsevier Science B.V. All rights reserved