Acetone/isooctane mixture at the ratio of 3:1 (v/v) was the suitable organic solvents for monoacylglycerols (MAG) production by glycerolysis of palm olein with immobilized lipase PS on Accurel EP-100 (IM-PS). The optimum condition for MAG production was found to be 10% (w/v) of palm olein in acetone/isooctane mixture, the mole ratio of palm olein to glycerol 8:1, water content in glycerol 10% (w/w) and the amounts of IM-PS used was 50% (w/w) of palm olein. The temperature was controlled at 45degreesC. Under these conditions, the yield of 56% MAG was obtained at 24h. Stability of the IM-PS was also studied. More than 90 and 80% of the hydrolytic activity remained after incubated in mixed solvents for 24 h at 4 and 45degreesC, respectively. The K-m and V-max value of IM-PS for glycerolysis of palm olein in acetone/isooctane mixture were 229.05 and 0.4 mM/min, respectively. (C) 2004 Elsevier Inc. All rights reserved.