Lipase from Candida rugosa was immobilized on poly(N-vinyl-2-pyrrolidone-co-styrene) hydrogel (poly(VP-co-ST)) with ethylene dimethacrylate and a,a'-azoisobutyronitrile, which act as crosslinker and initiator, respectively. Three different compositions of monomers were used, namely VP(%):ST(%), 10:90, 50:50, and 70:30 (wt(%)/wt(%)). The immobilized lipases were used in the enantioselective esterification of (R,S)-2-(4-chlorophenoxy)-propanoic acid with n-tetradecanol. The optimum reaction condition of the enantioselective esterification for the native lipase and the poly(VP-co-ST) hydrogel immobilized lipases was determined with respect to temperature, solvents, and initial water activity (a(w)). The optimum temperature obtained was 40degreesC, with the poly(VP-co-ST) hydrogel immobilized lipase VP(%)/ST(%):10:90 showing the highest enantiomeric excess. In the solvent effect studies, the best solvents for high enantioselectivity were chloroform and carbon tetrachloride. In the a(w) studies, optimum a(w) for NL, V-P(%):ST(%), 10:90, and 50:50 was 0.328, while for VP(%): ST(%), 70:30, it was 0.55. (C) 2004 Wiley Periodicals, Inc.