Evaluation of reaction parameters and kinetic modelling for Novozym 435 catalysed synthesis of isoamyl butyrate.

BACKGROUND The work describes the synthesis of isoamyl butyrate, a fruity banana flavour using immobilised lipase [ EC 3.1.1.3] as a biocatalyst in a solvent-free system, under mild optimised reaction conditions. Kinetic modelling with Ping Pong Bi Bi models, and thermodynamic parameters were evaluated at different temperatures. RESULT The optimised parameters of temperature, mole ratio and enzyme loading attained 96% maximum conversion of ester in 10 h. Novozym 435 was successively recycled nine times with 33% loss of initial enzyme activity. The kinetic parameters were found as: maximum rate constant ( V_max) = 28.027 mmol min⁻¹ g⁻¹ (of catalyst), rate constant for acid ( K_a) = 0.636 mol L⁻¹, rate constant for alcohol ( K_b) = 0.657 mol L⁻¹, rate constant for alcohol inhibition ( K_ib) = 0.022 mol L⁻¹ at optimum conditions by varying initial concentration of acid from 1.5 to 8.3 mol L⁻¹ and concentration of alcohol from 2.12 to 7.9 mol L⁻¹. The possibility of mass transfer resistance was investigated using an effectiveness factor which was determined as 1. CONCLUSION From kinetic modelling, the esterification reaction was found to obey the Ping Pong Bi Bi mechanism with substrate inhibition. From thermodynamic evaluation the activation energy (E_a) for reaction, Gibbs free energy change (ΔG), and the enthalpy change ( ΔH) was obtained as 16 kJ mol⁻¹, 71 kJ mol⁻¹ and 13 kJ mol⁻¹, respectively. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]