Phase-Specific Immobilization\nof Phospholipase D as\nan Efficient Pickering Emulsion Interfacial Catalyst for Converting <i>Antarctic Krill</i> Oil Phospholipid

Phosphatidylserine (PS), a rare phospholipid in <i>Antarctic\nkrill</i> oil (AKO) critical for brain development, can be produced\nfrom the abundant phosphatidylcholine (PC) using phospholipase D (PLD)\nin Pickering emulsion interfacial catalysis (PIC) systems. However,\nthe exposure of PLD to organic solvent around the emulsion interface\ndiminished PLD activity, limiting the conversion efficiency of PS.\nIn this study, we proposed a strategy to fabricate a PIC system with\nhigh efficiency and stability by immobilizing PLD in a specific phase\non the emulsion interface, based on investigating the effect of the\ninterfacial microenvironment on PLD activity. Janus-poly(acrylic acid)/polystyrene\n(JPP) and Janus-polyethylenimine/octadecane (JPO) particles were fabricated\nas carriers to realize the specific-phase immobilization of PLD. The\nhighest activity was observed when PLD was immobilized on the hydrophilic\nside of JPP (PLD@JPP(W)), 1.9-fold that of free PLD. The catalytic\nefficiency of PLD@JPP(W) was 1.7-fold that of free PLD, confirmed\nby the <i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub> value enhancement. Immobilization on the hydrophilic side also enhanced\nthe thermal stability of PLD. The half-lives of PLD were extended\nfrom 4 to 36 h at 40 °C and from 6 to 28 days at 4 °C. Importantly,\nPLD@JPP(W) showed excellent catalytic efficiency as a PIC system,\nachieving a PS productivity of 93% within a short time of 2 h at an\nenzyme dosage of 0.05 mg. PLD@JPP(W) exhibited a 3.6 times higher\nyield than free PLD in the production of PS from PC rich in <i>Antarctic krill</i> oil. The strategy in this work could also\nbe applied to other lipases, providing a promising method for the\nefficient conversion of functional lipids.