Lipase immobilization on alumina membranes using a traditional and a nature-inspired method for active degradation of oil fouling

This study compared the traditional method of silanization using 3-aminopropyltriethoxysilane (APTES) with the innovative technique of polydopamine coating (PDA) for lipase immobilization on α-alumina membranes. Three lipases were tested, and Eversa Transform 2.0 (ET2) was chosen to be immobilized in the membrane due to its high hydrolytic activity towards soybean oil. Polydopamine deposition with and without glutaraldehyde activation presented the highest membrane hydrolytic activities (1553 ± 209 and 1845 ± 283 U·m−2, respectively). The membrane without activation maintained 41.1 ± 1.7 % of the free enzyme activity while the one with glutaraldehyde preserved only 23.9 ± 1.0 %. When tested in oil–water separation using a soybean oil emulsion, the membranes with ET2 immobilized by PDA showed water permeance 2-fold higher than the nonactive membranes (300 ± 12 and 156 ± 4 L·h−1·m−2·bar, respectively), showing good fouling-degrading capacity. They also presented self-cleaning properties when activated through the use of proper pH and temperature. The water permeance recovery for the control membrane was 34% while the membranes with immobilized ET2 by PDA and APTES showed recoveries of 69% and 49%, respectively. Permeance recovery for ET2 immobilized by silanization was similar to the PDA-coated membrane with no enzyme (45%).