Sodium Caseinate–Enzyme Conjugates as Biocatalysts for Recyclable Pickering Interfacial Biocatalysis

Stimuli-responsive Pickering interfacial biocatalysis is a prominent topic in biphasic biocatalysis for its high efficiency and flexible tunability. Herein, we designed CO2/N2-responsive sodium caseinate (NaCas)–enzyme conjugates that acted as both catalytic sites and stabilizers to construct a responsive Pickering interfacial biocatalytic system. The conjugates were prepared by a one-step strategy in which amino groups reacted with carboxyl groups between NaCas and enzymes. In the meantime, NaCas, with a disordered structure, could act as a buffer in the microenvironment to improve enzyme stability in harsh environments. The emulsion system stabilized by horseradish peroxidase (HRP)–NaCas displayed a higher catalytic efficiency and conversion rate compared with the conventional two-phase system, and HRP–NaCas could be easily recycled at least five times by bubbling CO2 and N2. Furthermore, the coupled NaCas system was implemented in Candida antarctica lipase B (CaLB), which extended the excellent interfacial characteristics and application field of NaCas.