Abstract
This study investigated the kinetic and thermodynamic parameters of the synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase (CALB) immobilized on magnetic poly(styrene-co-divinylbenzene) (STY-DVB-M). The influence of acid/alcohol molar ratio and temperature on oleic acid conversion, ester concentration, and productivity was also assessed. Excess of one of the reagents resulted in high conversions, but the highest productivities were obtained at the stoichiometric ratio. Thus, a 1:1 molar ratio was considered optimal. Thermodynamic parameters calculated from the van’t Hoff equation (ΔS = + 850.64 J mol−1 K−1, ΔH = + 273.78 kJ mol−1) revealed that the reaction is endothermic with a positive entropy change. Temperatures below 45 °C negatively affected reaction kinetics, explained by the positive ΔG values. CALB-STY-DVB-M showed a hydrolytic activity of 522.97 ± 19.14 U g−1 and was about 1.7 times more thermally stable at 60 °C than the free enzyme. In an operational stability test, conducted for 7 consecutive cycles of 24 h, the biocatalyst had a half-life of 739 h. CALB-STY-DVB-M showed satisfactory performance in the synthesis of 2-ethylhexyl oleate, providing oleic acid conversions close to 100%, ester concentration of 450 g L−1, and productivity of 0.5 mmol g−1 h−1. The biocatalyst holds promise for industrial applications.
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