Improved acylation of phytosterols catalyzed by Candida antarctica lipase A with superior catalytic activity

This work reported a novel approach to synthesize phytosterol (β-sitosterol as a model) fatty acid esters by employing Candida antarctica lipase A (CAL A) which shows a superior catalytic activity to other lipases. A series of β-sitosteryl fatty acid esters (C2–C18) have been successfully prepared with structural identification of products by 1H NMR and Fourier transform-infrared spectroscopy (FTIR). Compared to other immobilized lipases, CAL A achieves 6–14 times faster esterification of β-sitosterol with myristic acid. CAL A shows low activity toward short chain fatty acids (C2–C6), and remarkably high activity for medium and long chain ones (≥C8). Reaction time, temperature, enzyme load, substrate ratio and concentration, and solvent property are found to profoundly influence reaction rates. A pronounced correlation between enzyme activities and log P values of solvents, among the solvents with a broad spectrum of log P values, was observed. 93–98% yield of β-sitosteryl esters could be achieved with hexane as solvent, fatty acid (C8–C18)/β-sitosterol (1:1, mol:mol), 5–10% CAL A load at 40–50 °C for 24 h. This work demonstrated the promising potential of CAL A in bioprocess of phytosterols for value-added application.

Candida antarctica lipase A (CAL A) shows a superior activity in catalyzing syntheses of phytosteryl fatty acid (medium/long chain) esters, in which 93–98% yields could be achieved in 24 h.Figure optionsDownload as PowerPoint slideHighlight
► β-Sitosteryl fatty acid esters (C2–C18) synthesized and identified by 1H NMR and FTIR.
► CAL A shows superior activity in catalyzing acylation of phytosterol to other lipases.
► CAL A achieves 6–14 times faster reaction rate over other lipases.
► 93–98% yield of β-sitosteryl esters achieved at 40–50 °C for 24 h.