Enzymatic esterification of isoamyl alcohol obtained from fusel oil: Optimization by response surface methodolgy

Optimization of lipase-catalyzed production of industrially important isoamyl acetate was carried out by response surface methodology (RSM). Isoamyl alcohol which was distillated from fusel oil and acetic acid were used as the substrates. Immobilized lipase from Candida antarctica (Novozym 435) was catalyzed to this reaction in the solvent-free system. RSM based on five-level, four variable central composite rotatable design was used to evaluate the effects of important parameters on the production of isoamyl acetate. The parameters are acid/alcohol mole ratio (0.2–0.8), enzyme amount (4–12%, w/w), temperature (30–50 °C) and reaction time (4–8 h). It was found that the most effective parameter was acid/alcohol mole ratio. The model indicated the optimum conditions for maximum esterification (4.4 mmol ester/g mixture) in the acid/alcohol mole ratio of 0.8 for 12% (w/w) enzyme at 30 °C and after 8 h, which were in good agreement with the experimental value. The coefficient of determination (R2) for the model is 0.9968. Probability value (P < 0.0001) demonstrates a very high significance for the regression model.