Multiple effects driven by pulsed electric field to enhance the catalytic efficiency of the mussel-inspired proteolytic membrane in protein hydrolysis

Although the immobilization of enzymes on the membrane is an effective method to improve enzyme stability and reusability, the immobilized enzyme also causes low activity and reduces substrate accessibility. In order to overcome these shortcomings and provide a viable proteolytic membrane with increasing enzyme activity and substrate accessibility, a pulsed electric field (PEF)-assisted proteolytic membrane (PAPM) was constructed by immobilizing PEF-treated pepsin on PDA and PEI co-deposited ultrafiltration membrane. The PEF-treated pepsin endowed high activity (165.33 ± 2.31 %) and charge amount (−3.95 mV), with stable and uniform particle size (39 nm). These phenomena were attributed to the multiple effects driven by PEF, including the diffusion effect, electrolysis reactions, and microstructural regulation. Specifically, PAPM retained 80 % of original pepsin activity and enhanced 25 % pepsin activity compared to the conventional proteolytic membrane (PM). Such improvement can be ascribed to two factors: Firstly, PEF regulated pepsin microstructure to an optimal structure (4.6 % increase of the α-helix and 4.0 % reduction of the random coil) for pepsin immobilization. Secondly, PEF changed pepsin charge properties from positive (+1.62 mV) to negative (−3.95 mV), while substrate charges were positive. Heterogeneous charge interactions between pepsin and substrates increased the accessibility of the substrate to immobilized pepsin, effectively promoting enzymatic reactions. This study offers a feasible method to prepare the proteolytic membrane in protein hydrolysis.