Covalent immobilization of Candida antarctica lipase on core-shell magnetic nanoparticles for production of biodiesel from waste cooking oil

Abstract

In the present work, lipase from Candida antarctica (CALB) was covalently immobilized on functionalized magnetic nanoparticles (MNPs) to catalyze biodiesel synthesis. Core-shell nanoparticles were synthesized by coating Fe3O4 core with silica shell (Fe3O4@SiO2). The nanoparticles functionalized with (3-glycidoxypropyl)trimethoxylsilane (GPTMS) were used as immobilization matrix. The protein binding efficiency on functionalized Fe3O4@SiO2 was calculated as 84%, preserving 97% of specific activity of the free enzyme. Physical and chemical properties of the nanoparticles and the immobilized lipase were characterized by TGA, XRD, SEM, IR, TEM and DLS. Higher thermal stability and methanol tolerance for immobilized derivatives were obtained compared to the free enzyme. The immobilized lipase was then used to produce biodiesel by transesterification of waste cooking oil with methanol. In an optimization study, the effect of oil to methanol ratio, tert-butanol and molecular sieve as water adsorbent on the yield of biodiesel production were considered. Optimum oil to methanol ratio at 1:3 was observed for immobilized CALB in biodiesel production. Molecular sieve had a great effect on yield, with almost 100% conversion. The immobilized preparation of CALB also presented a good reusability, keeping 100% of its initial activity after 6 cycles of the reaction.