Enzymes can be immobilized in membranes to develop a catalytic membrane capable of producing certain compounds or decreasing fouling during the separation process. Enzyme immobilization on inorganic materials, such as ceramics, generally involves a time-consuming and multistep method, uses toxic solvents, and requires more than one chemical, making the industrial upscaling unattractive. Therefore, the search for simpler and more straightforward immobilization protocols is essential. This study aimed to assess a two-step and a one-step strategy to immobilize the lipase Eversa Transform 2.0 (ET2) on ceramic membranes for treatment of oily wastewater, where hydrolyzation of oil molecules by the immobilized lipase is expected to reduce fouling and provide the membrane with self-cleaning capacity. The results show that the one-step strategy achieved the same enzyme loading, membrane hydrolytic activity, and enzyme specific activity (3.10 ± 0.10 g/m2, 1986.2 ± 40.0 U/m2, and 641.3 ± 17.8 U/g, respectively) as the conventional two-steps method (3.12 ± 0.23 g/m2, 1822.8 ± 77.7 U/m2, and 587.8 ± 59.6 U/g, respectively). The immobilized ET2 by both strategies achieved significant degradation of the oil foulants and hence reduction of fouling, suggesting great potential for its application as a self-cleaning agent in oil-water membrane separation processes. The membrane with lipase immobilized by the one-step approach, however, exhibited better performance with a lower water permeance reduction after emulsion filtration (35%), a greater permeance increase after cleaning (25%), and a higher overall permeance recovery (90%) than the one with immobilized ET2 by the two-step method (40%, 14%, and 74%, respectively). These results show clear advantages of the simpler, more environmentally friendly one-step immobilization strategy.

One-step immobilization of lipase in α-alumina membranes using polydopamine

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