Enhanced Stability and Catalytic Performance of pH-Responsive Pickering Interface Biocatalysis via Electrostatically Mediated Immobilized Enzymes

A novel pH-responsive Pickering interfacial biocatalysis (PIB) system has been constructed. The oil-in-water emulsion was stabilized by immobilized enzyme CL@HMSS-DMAEMA, which was obtained through physical adsorption of lipase CL onto hollow mesoporous silicon spheres modified with 2-[dimethylamino]ethyl methacrylate (HMSS-DMAEMA). Within the pH response range of 3.0–11.0, the zeta potentials of the carrier and lipase exhibited opposite charges and almost mirror-symmetrical configuration, thereby ensuring electrostatic attraction throughout the demulsification/emulsification process. This strategy significantly enhanced enzyme loading, thermal stability, enzyme activity, and pH-responsive resilience. The pH-responsive PIB system achieved a 95.0% conversion rate for retinol fatty acid esters, with a catalytic efficiency (CE) 14.8 times higher than that of the PE system (CL@HMSS) and 25.2 times higher than that of free enzymes, while maintaining over an 80.0% conversion rate after 10 cycles. These findings underscore the importance of electrostatic interactions in enzyme immobilization, thereby improving the reliability of pH-responsive PIB platforms. The present study also proposes a novel design concept for the stimulus-response PIB system.