Cellulose Nanocrystal-Immobilized Lipase for Pickering Interface Biocatalysis

Enzymes are promising biocatalysts due to their high efficiency, mild conditions, high specificity, nontoxicity, and environmental friendliness. However, the enzyme suffers from poor stability and reusability. Enzyme immobilization is a commonly used technology to enhance its stability and reusability. In this study, the cellulose nanocrystal (CNC) was chosen as the enzyme immobilization carrier due to its sustainability, high specific surface area, biocompatibility, water dispersibility, and excellent Pickering emulsifying ability. Lipase was immobilized on a polydopamine-coated CNC (PC), and the obtained lipase-immobilized PC (LPC) displayed significantly enhanced stability and higher activity in harsh conditions compared to free lipase. LPC possessed partial wettability with both water and oil phases and a lower absolute value of the zeta potential than CNC, endowing it with a better Pickering emulsifying ability than CNC. LPC was fixed at the oil–water interface of the Pickering emulsion by ultrasonication, and the resulting Pickering emulsion droplets were employed as microreactors for ester hydrolysis and synthesis via Pickering interface biocatalysis. LPC displayed significantly enhanced catalysis activity at the oil–water interface of the Pickering emulsion compared to free lipase in a traditional oil–water biphasic system due to the increased contact area between the enzyme and the substrate, reduced diffusion distance of the substrate, and lipase interface activation effect. Moreover, LPC could be facilely recycled by centrifugation, and the recycled LPC still retains high catalysis activity. This study proposed a facile and sustainable method of enzyme immobilization to enhance its stability and reusability and achieved a significantly increased activity via Pickering interface biocatalysis.