A purified alkaline thermotolerant bacterial lipase of Baciffits coagidans MTCC-6375 was efficiently immobilized onto poly(N-AEAAm-co-AAc-cl-MBAm)-hydrogel at pH 8.5 and at temperature 55 degrees C in 16 h. The hydrogel-bound matrix possessed 1.04 U/g (matrix) lipase activity with a specific activity of 1.8 U/mg of protein. The immobilized lipase resulted in formation of 52.5 rnM of ethyl propionate (52% conversion) at 55 degrees C in 9 h in n-nonane. Ethanol and propionic acid when used in a ratio of 300 : 100 mM, respectively, in ii-nonane along with 10 mg of hydrogel-bound lipase resulted in optimal synthesis of ethyl propionate (82.5 mM). Addition of molecular sieves (3 angstrom, 0.7 g/reaction volume) further enhanced the conversion rate to 82.4% resulting in 83.5 mM of ethyl propionate. Incubation temperature below or above 55 degrees C had a marked effect on the synthesis of ethyl propionate. However, esterification performed in n-heptane at 65 degrees C resulted in 87.5 mM of ethyl propionate with a conversation rate of 89.3%. (c) 2007 Wiley Periodicals, Inc.