In-situ immobilization of lipase on α-alumina membrane for oil fouling control and cleaning

Abstract

Enzyme immobilization on inorganic membranes is typically a difficult, time-consuming, multi-step process carried out ex-situ (outside the filtration system). To enable process scaling, an in-situ immobilization technique is essential. Therefore, an in-situ method to immobilize the lipase Eversa Transform 2.0 (ET2) on a ceramic membrane was developed using polydopamine as a bonding agent. The in-situ immobilization was successful, and optimum dopamine hydrochloride and ET2 concentrations (0.3 mg·mL−1 and 4 mg·mL−1, respectively) resulted in an enzyme loading of 10 g·m−2 that increased the membrane water affinity and hydrolytic activity towards soybean oil (38 mmol·min−1·m−2). The enzymatic membrane demonstrated great self-cleaning capability (pure water permeance recovery of 97 % after cleaning with deionized water at 40 °C for 6 h) and strong fouling resistance (pure water permeance decline limited to 43 % following oil emulsion filtration). To reuse the membrane after it lost its hydrolytic activity, calcination or in-situ chemical cleaning were tested. There were no morphological or chemical alterations on the membrane surface after five cycles of modification-regeneration. When compared to ex-situ immobilization techniques, in-situ enzyme immobilization and chemical regeneration can save costs, improve the sustainability of the process, and ease scale-up.