Immobilization of Candida rugosa lipase on magnetic poly(allyl glycidyl ether-co-ethylene glycol dimethacrylate) polymer microsphere for synthesis of phytosterol esters of unsaturated fatty acids

In this article, magnetic microspheres were prepared by suspension polymerization of allyl glycidyl and ethylene glycol dimethacrylate in the presence of vinylphosphonic acid-coated Fe3O4 nanoparticle. Candida rugosa lipase (CRL) was immobilized on the hydrophobic magnetic microspheres via the active epoxy groups. The resulting immobilized CRL had better resistance to pH and temperature inactivation in comparison to free CRL, the adaptive pH and temperature ranges of lipase were widened, and it exhibited good thermal stability and reusability. The immobilized CRL was used as biocatalyst for enzymatic esterification of phytosterols with unsaturated fatty acids (UFAs) to produce the corresponding phytosterol esters. The phytosterols linolenate esterification degree of 93.5% was obtained under the optimized condition: 100 μmol/mL phytosterols, 200 μmol/mL linolenic acid, 15 mg/mL immobilized CRL at 160 rpm and 55 °C for 15 h in 10 mL of isooctane. Phytosterols esters could also be converted in high yields to the corresponding long-chain acyl esters via transesterification with methyl esters of fatty acids (55.3%) or triacylglycerols (above 78.1%) using magnetic immobilized CRL as biocatalyst.