Effects of physicochemical characteristics of magnetically recoverable biocatalysts upon fatty acid methyl esters synthesis from oils

Abstract

Abstract This study reports the importance of physicochemical characteristics of the core-shell structured polymer-coated Fe3O4 cluster@SiO2 nanocomposite particles for designing the biocatalysts used for transesterification of soybean oil. To demonstrate this issue, two different types of polymer molecules such as polyethylenimine (PEI) and polyacrylic acid (PAA) each with two different molecular weights are employed. The highest fatty acid methyl esters (FAMEs) synthesis yield values are achieved by the lipases immobilized onto the low- and high-molecular-weight PEI-coated particles as compared to those of the low- and high-molecular-weight PAA-coated particles (i.e., ∼64.8% and ∼73.1% versus ∼51.5% and ∼46.4%, respectively). The lipases immobilized onto the PEI-coated particles also exhibit excellent stabilities over five repeated uses. The solvent content assays of the particles immersed in water, methanol and soybean oil reveal that the PEI-coated particles have the highest tendency to absorb the oil and the least ones to absorb water and methanol. Thus, those particles increase the substrate molecules accessibility to the immobilized lipases in the reaction medium, leading to the superior transesterification efficiency. This study provides insight into the highly effective enzymatic production of biodiesel with considering the physicochemical properties of support particles used for enzymes immobilization.