Kinetic resolution of a chiral alcohol, 4-hydroxy-3-methyl-2-(2[1]-propenyl)-2-cyclopentenone (HMPC), a key intermediate for the production of prallethrin insecticides, was successfully carried out by enantioselective hydrolysis of (RS)-HMPC acetate using calcium alginate gel-entrapped cells of a newly isolated esterase-producing bacterium Acinetobacter sp. CGMCC 0789. When the effect of different cosolvents was investigated, it was found that isopropanol could markedly enhance the activity and enantioselectivity of the immobilized cells. The optimum concentration of isopropanol was 10% (v/v) where immobilized cells still showed good operational stability. After 10 cycles of reaction, no significant decrease in the enzyme activity was observed. The catalytic specificity constants (Vmax/Km) for both enantiomers of the substrate were determined with partially purified enzyme, giving 0.0184 and 0.671 h−1for the (S)- and (R)-ester, respectively.