Optimization of the enzyme catalyzed ultrasound assisted synthesis of cinnamyl butyrate using response surface methodology

The detailed optimization study for the ultrasound assisted lipase catalyzed synthesis of cinnamyl butyrate under solvent free conditions was described using central composite rotatable design and response surface methodology. The statistical analysis shows that three out of the four variables tested, i.e. molar ratio (A), enzyme loading (B), and ultrasound intensity (D) are found to be statistically significant. The mutual interactions between molar ratio-enzyme loading (AB) and temperature-ultrasound intensity (CD) are also found to be significant along with quadratic interactions of all the parameters (A2, B2, C2, D2). The maximum conversion of 93% was obtained at optimal conditions; molar ratio 2.5 (cinnamyl alcohol:butyric acid); enzyme loading 2.8% of the total mass of reactants; reaction temperature 46 °C and ultrasound intensity 105 W (ultrasound intensity is 7412.68 W/m2). Additionally, hydrodynamic parameters have been determined to estimate the effect of external and intraparticle mass transfer diffusion, which do not show any significant influence on the reaction rate. Reusability study of biocatalyst shows that it can be used up to three cycles with minimal loss of its enzymatic activity.