Preparation of phytosterol esters based on food-grade Pickering emulsion stabilized by lipase-adsorbed zein-hydroxypropyl chitosan nanoparticles

This study aims to construct a food-grade Pickering emulsion stabilized by zein-hydroxypropyl chitosan composite nanoparticles ( Z -HPCS NPs) adsorbed with lipase CRL (Z-HPCS NPs@CRL) to synthesize phytosterol esters. Uniform spherical Z-HPCS NPs with a strong positive charge (39.2 ± 0.4 mV) were fabricated and complexed with negatively charged lipase CRL to stabilize the emulsion interface. Comprehensive characterization revealed that lipase CRL bound to Z -HPCS NPs through synergistic electrostatic interactions and hydrogen bonding. Furthermore, the unique interfacial characteristics of the Pickering emulsion enable efficient migration of by-product (water) from the oil phase to the aqueous phase, driving the equilibrium towards product formation. The Pickering emulsion system stabilized by Z -HPCS NPs@CRL achieved exceptional phytosterol ester yield (90.9 % in 3 h), surpassing both traditional biphasic systems (15.8 %) and free lipase CRL (82.2 %). This work provides fundamental insights into food-grade Pickering emulsion interfacial biocatalysis for the efficient synthesis of phytosterol esters.