Isoamyl oleate, a renewable ester with promising biolubricant applications, was synthesized via esterification using Burkholderia cepacia lipase (LBc) immobilized on poly(3-hydroxybutyrate) (PHB). The incorporation of 5% (w/v) polyethylene glycol 1500 (PEG) into the PHB support not only maximized the biocatalyst's activity but also markedly improved its operational stability. Key reaction parameters, including the oleic acid-to-isoamyl alcohol molar ratio, biocatalyst loading, temperature, and water activity, were systematically evaluated. Under optimized conditions (1:4 molar ratio, 100 mg biocatalyst, 60°C) combined with molecular sieves to strictly control water activity, a 94.5% conversion was achieved within 24 h, significantly outperforming the additive-free system (60.5%). Higher water content decreased the ester yield, consistent with an unfavorable shift in the esterification–hydrolysis equilibrium. Apparent thermodynamic analysis confirmed a maximum equilibrium constant and a negative ΔG0app at 60°C. Molecular sieves successfully suppressed the reverse reaction while preserving the enzyme's essential hydration shell. Finally, reusability assays indicated that PEG conferred structural stabilization to the biocatalyst, which preserved useful activity over nine consecutive 24-hour cycles, while the additive-free counterpart became ineffective after four cycles due to pronounced solvent-induced enzyme leaching.
Corrêa et al. (Thu,) studied this question.