Synthesis of biofuel esters catalyzed by lipase B from Candida antarctica immobilized on a magnetic lignin-based support derived from cashew apple bagasse

Abstract

This study investigated the biosynthesis of ethyl oleate (EO), the main constituent of biodiesel, via the esterification of oleic acid with ethanol, catalyzed by Candida antarctica lipase B (CALB) immobilized on a low-cost support derived from cashew apple bagasse (CAB) lignin. Cashew apple bagasse lignin extraction was carried out through an acid-alkali process and used to produce the CAB-lignin conjugated with magnetite (Lig-MNP) composite, which served as the support for enzyme immobilization. The biocatalyst (Lig-MNP/CALB), obtained through the immobilization process, exhibited an activity of 13 U g⁻¹ and was subsequently applied in esterification reactions to evaluate its catalytic efficiency in comparison to the free enzyme. Acid-to-alcohol molar ratio, temperature, and catalytic load were evaluated. Under optimal conditions – 40 mg mL⁻¹ catalyst load, 40 °C, and a 1:2 molar ratio – Lig-MNP/CALB achieved a maximum EO conversion of 90%. The immobilized enzyme demonstrated operational stability over multiple cycles and was easily recovered through magnetic separation. The purified biofuel reached approximately 90% purity in ethyl oleate and 98% in total esters content. These results highlight the potential of the biocatalyst for sustainable biofuel production.