Enzymatic acyl modification of phosphatidylcholine using immobilized lipase and phospholipase A₂

Abstract

Ethanol-soluble (ES) lecithin mainly contains phosphatidylcholine (PC). The incorporation of caprylic acid into PC using immobilized phospholipase A₂ (PLA₂) and lipase was investigated. The Rhizomucor meihei lipase and the porcine pancreatic PLA₂ were immobilized on the hydrophobic resin Diaion HP-20 and the modification was carried out in hexane as solvent. HPTLC with densitometer technique was successfully used for monitoring the production of structured phospholipids (PL) (ML-type PC, MM-type PC, and lysophosphatidylcholine; L: long-chain fatty acid, M: medium-chain fatty acid). The various parameters such as the effects of reaction temperature, enzyme loading, and the effect of molar proportion of substrate were studied in order to determine the optimum reaction conditions for the acidolysis reaction. The optimal operating conditions for the PLA₂-catalyzed reaction were obtained as 50°C temperature, 50% (wt/wt of substrate) enzyme loading, and a 1:12 molar proportion of PC/caprylic acid. For the lipase-catalyzed reaction, the optimized temperature was the same as for PLA₂, but the enzyme loading and molar proportion were slightly lower, i.e., 40 % w/w of substrate and 1:9 PC/caprylic acid, respectively. The effects of these parameters on the production of structured PL were compared. Under these optimal conditions, the ML-type PC content was higher in the PLA₂-catalyzed reaction, i.e., 45.29 mol%, and in the lipase-catalyzed reaction it was 38.74 mol%.