Pickering gel emulsion stabilized by enzyme immobilized polymeric nanoparticles: a robust and recyclable biocatalyst system for biphasic catalysis

Abstract

Despite the rapid development of Pickering interfacial catalysis (PIC) at oil–water interfaces with chemocatalysts, highly efficient Pickering interfacial biocatalyst systems, having a high oil/water ratio, super-stability and recyclability, are still urgently desired. In this study, a Pickering gel emulsion stabilized by enzyme-decorated copolymeric nanoparticles is developed for biphasic biocatalysis. The nanoparticles are synthesized by surfactant-free emulsion polymerization and covalently decorated with a model lipase Candida antarctica lipase B (CALB). An oil-in-water Pickering gel emulsion with an oil/water ratio of 3 could then be prepared by homogenizing heptane into the CALB decorated nanoparticle aqueous dispersion. The catalysing efficiency is evaluated by just allowing the Pickering gel system to stand at room temperature and studying the enzymatic esterification of hexanoic acid with hexanol in the oil phase. It is found that CALB immobilized on the nanoparticles in the Pickering gel emulsion shows a highly enhanced enzyme activity compared with free CALB, with a conversion rate of up to 96.5%. In addition, the Pickering gel emulsion maintains 92.5% residual activity after 10 reaction cycles, in each cycle the oil and aqueous phases are separated simply by centrifugation. This approach herein opens the door to the development of a Pickering interfacial biocatalyst system with a high water/oil volume ratio, super-stability, and easy recyclability for sustainable applications in biphasic enzyme catalysis.