Natural shellac nanoparticles stabilized Pickering emulsion: pH and CO2/N2 dual responsive behavior and its application in biocatalytic synthesis of phosphatidylserine.

This study developed a pH and CO₂/N₂ dual-responsive Pickering emulsions stabilized by natural shellac nanoparticles (SNs), eliminating the need for complex synthetic stabilizers. Dynamic interfacial tension analysis reveals pH-dependent adsorption kinetics and interfacial rearrangement behavior of the SNs. Leveraging pH- or CO₂/N₂-regulated protonation-deprotonation transitions, the system could easily achieve O/W emulsion demulsification or emulsification while maintaining exceptional solvent universality and cycling stability (at least fifty cycles). The dual-responsive emulsion was further used as an interfacial catalytic platform for phospholipase D-mediated synthesis of phosphatidylserine (PS), which showed a 56 % increase in phosphatidylcholine conversion and a 98 % increase in PS yield compared with the traditional solvent system. The CO₂/N₂-triggered demulsification enabled green product/catalyst recovery, and the catalytic efficiency remains over 80 % of its original level after 5 cycles. These advancements originated from the synergistic stabilization of the nanoparticles with enzymes. This work establishes a zero-chemical-modification strategy for constructing intelligent emulsions from natural biomacromolecules, and expands its potential application in high value-added substance synthesis.