Lipase-catalysed ester synthesis in solvent-free oil system: is it esterification or transesterification?

Area of Science:

• Biocatalysis
• Organic Chemistry
• Enzyme Kinetics

Background:

• Lipase-catalyzed ester synthesis is crucial for various industries.
• Understanding the reaction mechanism in solvent-free systems is essential for process optimization.
• Previous studies have not fully elucidated the mechanism in immobilized lipase systems.

Purpose of the Study:

• To investigate the reaction mechanism of ester synthesis catalyzed by immobilized lipase in a solvent-free system.
• To determine the influence of different alcohol substrates and fatty acids on ester production.
• To explore the role of reactant polarity in lipase activity.

Main Methods:

• Solvent-free ester synthesis using lipase, coconut oil, and ethanol or fusel alcohols.
• Analysis of fatty acid and ester concentrations over time.
• Investigation of the effects of added butyric acid and octanoic acid on ester synthesis.

Main Results:

• Ester formation proceeded via a two-step mechanism: initial hydrolysis followed by esterification, not direct alcoholysis.
• Butyric acid inhibited ester synthesis with ethanol but not with fusel alcohols.
• Octanoic acid did not adversely affect the synthesis of its corresponding esters.
• Lipase activity was found to be dependent on the polarity of the reactants.

Conclusions:

• The study provides the first evidence for a dual mechanism (hydrolysis and esterification) in immobilized lipase-catalyzed ester synthesis in solvent-free media.
• Reactant polarity significantly impacts lipase activity, offering insights for optimizing biocatalytic processes.
• The findings contribute to a deeper understanding of enzyme behavior in non-aqueous environments.