Gelatin-Stabilized Water-in-Water Emulsions for Biocatalysis: Interfacial Enzyme Confinement, In Situ Product Extraction, and Cryogenic Recyclability.

Water-in-water (W/W) emulsions offer high biocompatibility for enzymatic processes but are difficult to stabilize with conventional oil-water surfactants due to their ultralow interfacial tension. Here, we design a gelatin-stabilized PEG/dextran (PEG/Dex) emulsion platform enabling integrated "reaction-separation-recovery" biocatalysis. By tuning the pH and polymer concentration, programmable microarchitectures such as core-shell, Janus, or triple-phase droplets were achieved. In cascade oxidation of guaiacol, the compartmentalized system reached an 86% yield of tetraguaiacol─50% higher than isolated phases─due to efficient product partitioning into the PEG phase while enzymes were retained in the gelatin phase. Catalytic efficiency (kcat/Km) increased by 2.20-fold for glucose oxidase and 1.31-fold for horseradish peroxidase compared to buffer. Postreaction cooling (4 °C) triggered Gel gelation, enabling enzyme recovery with >70% activity retained after 3 cycles. This fully aqueous and recyclable platform demonstrates significant potential for enzyme engineering, bioactive compound synthesis, and green manufacturing.