Covalent immobilization of lipase onto aminopropyl-functionalized hydroxyapatite-encapsulated-γ-Fe2O3 nanoparticles: A magnetic biocatalyst for interesterification of soybean oil.

Hydroxyapatite-encapsulated γ-Fe2O3 nanoparticles were prepared, and lipase from Candida rugosa was then covalently bound onto the magnetic materials via covalent linkages. The magnetic carrier and immobilized lipase were characterized by enzyme activity assays, XRD, FT-IR, TEM, VSM and N2 adsorption-desorption techniques. Results demonstrated that γ-Fe2O3 nanoparticles were coated with the hydroxyapatite, and the lipase was indeed tethered to the magnetic carriers without damage to their structure. The immobilized lipase showed a strong magnetic responsiveness and displayed high catalytic activities towards the interesterification of soybean oil. The interesterified products were evaluated for their total fatty acid (FA) composition, slip melting point (SMP), iodine value, triacylglycerols (TAGs) profile and FA composition at sn-2 position in TAGs. The FA positional distributions and TAG species significantly changed after the enzymatic interesterification. Besides this, the interesterified products showed an obvious reduction in their SMP in comparison with the physical blends.