Lipase has been immobilized onto different films, polypropylene and poly(tetrafluoroethylene-perfluroro-propyl vinyl ether) using glutalaradehyde as a crosslinker. Differential scanning calorimetery, Fourier transform infrared spectroscopic, x-ray diffraction, and scanning electron microscopy measurements were carried out to confirm the structure of the polymer films as well as the immobilization process of the enzyme onto the polymeric carrier. The activity and stability of the resulting biopolymers produced by lipase have been compared to those for the native lipase. The experimental results showed that the optimum temperature and pH were 40degreesC and 8.0, respectively. The activity of the immobilized lipases varied with lipase concentration and with the yield of grafting. Subjecting the immobilized enzymes to a dose of gamma-radiation of (0.5-10 Mrad) showed complete loss in the activity of the free enzyme at a dose of 5 Mrad. A leakage of the enzyme from the irradiated membranes was not observed in the repeated batch enzyme reactions. The operational stability of the free and immobilized lipase in n-hexane showed that the immobilized enzyme was much more stable than the free one. (C) 2003 Wiley Periodicals, Inc.