Abstract: In the present work, we immobilized lipase onto cellulose acetate (CA)-polytetrafluoroethylene (PTFE) composite membrane by a combined method of adsorption and cross-linking. The effects of different immobilization conditions such as immobilization temperature, adsorption time, lipase concentration, cross-linking time and cross-linking agent concentration on lipase immobilization efficiency and catalytic activity were explored. Immobilized lipase was also characterized. The optimal immobilization conditions were reaction temperature of 25 ℃, adsorption time of 2 h, lipase concentration of 0.02 g/mL, crosslinking time of 3 h, and cross-linking agent concentration of 0.2%. Under the optimal immobilization conditions, the maximum activity of immobilized lipase reached up to 17.2 U/cm2. The optimal temperature and pH of immobilized lipase were 35 ℃ and 8.5, respectively, which exhibited a decrease by 5 ℃ and shift to alkaline side by 1.0 when compared with the free enzyme. After repeated use for 10 times for 10 h each time, the residual activity was still up to 55.5%. The SEM micrographs revealed better immobilization of the enzyme on CA-PTFE composite membrane.

Key words: CA-PTFE composite membrane, lipase, immobilization, lipase activity