The advancement of membrane research closely relates to the activities of 'immobilization of enzymes'. The modification of polymeric membrane surfaces according to tailor-made specifications is considered an art and useful in this arena. In this study, lipase is immobilized on Polyvinyl alcohol photomodified Polysulfone (PS-PVA) membranes. The maximum immobilization (1.48 mg/cm(2)) for PS-PVA membranes is achieved. The amount of immobilized lipase directly relates on the PVA content on the membrane. Scanning Electron Microscope and X-ray diffraction patterns show the evidences of lipase immobilization on membranes. The hydrolytic performances of lipase immobilized PS and PS-PVA-glu membranes for olive oil are studied. The free fatty acid (FFA %) and acid value (AV) parameters are determined by titrimetic analysis (1.53 and 3.04 for PS-PVA-glu) and compared with esterification GC-mass analysis data. The K (m) and V (max) values are 105 mM and 0.9 mM/min for lipase immobilized on PS-PVA-glu and 153.8 mM and 0.51 mM/min for lipase on PS. The reusability feature shows the lipase immobilized on PS-PVA-glu matrix have better stability (10.7% decrease) compared to lipase immobilized on PS matrix (33.3% decrease) after five cycles.