Enhanced enzyme stability at the interphase of water-oil for continuous-flow olefin epoxidation.

The practical applications of enzymes often require their immobilization for multiple recycling or long-term running. However, practically efficient enzyme immobilization methods are lacking. Herein, we present an enzyme immobilization approach by engineering a porous "interphase" between water and oil around the surfaces of Pickering emulsion droplets. The designed "interphase" consists of a porous, nanometer-thick silica shell serving as a scaffold to incorporate enzymes. Within this "interphase", enzymes can simultaneously be in contact with enzyme-preferred aqueous microenvironment and the oil phase containing organic reactants. The porous "interphase" with its tunable structure and properties allows modulation of transport of reactants, crudely akin to a cell membrane, and of local concentration of reactants. As a proof of the concept, we showcase that our "interphase" strategy is very effective in immobilization of Candida antarctica lipase B (CALB) for continuous-flow olefin epoxidation. Long-term stabilization (800 h), 16-fold increase in catalysis efficiency relative to batch reactions, and 99% H2O2 utilization efficiency are achieved. The integration of unique microenvironment and hydrophobic pores of the "interphase" is found to be crucial for such excellent performances, practically providing the most efficient enzymatic epoxidation system. This strategy opens an avenue for the design of efficient and sustainable biocatalytic processes.