Beyond the oil–water interface: Cooperative alkali–lipase catalysis induces pH-responsive self-assembly in triolein hydrolysis

Lipase-catalyzed and alkaline hydrolysis of triglycerides generate amphiphilic molecules that reorganize oil-water interfaces and form supramolecular assemblies with defined colloidal properties in oil and water. Here, we present a structural and compositional analysis of a biphasic triolein/buffer system subjected to alkaline treatment or enzymatic hydrolysis by Sus scrofa, Rhizomucor miehei, and Thermomyces lanuginosus lipases across a pH range of 7.0-11.0. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) reveal minimal structural changes below pH 9.0. In contrast, at pH 11.0, reaction-driven self-assembly produces water-in-oil emulsions and vesicles in the oil phase. In the aqueous phase, oil-swollen micelles and vesicles form, with size and morphology dependent on the hydrolysis conditions. These nanostructures correlate with variations in product composition and interfacial enrichment, markedly increasing the available interfacial area. While previous studies have examined lipase-catalyzed lipid hydrolysis, the coupled structural evolution of both oil and aqueous under enzymatic and alkaline conditions has, to the best of our knowledge, not been resolved. This study reveals a direct link between hydrolysis, amphiphile generation, and pH-dependent self-assembly beyond the oil-water interfaces. It offers mechanistic insight relevant to lipid digestion, interfacial catalysis, and the design of pH-responsive colloidal materials.