Acoustic cavitation promoted lipase catalysed synthesis of isobutyl propionate in solvent free system: Optimization and kinetic studies

The present work highlights the effect of ultrasound on enzymatic synthesis of isobutyl propionate, a rum flavor by esterification of isobutanol and propionic acid in non-aqueous, solvent free system (SFS) using Fermase CALB™10000. The optimization study for different variables in presence of ultrasound showed a maximum conversion of 95.14% at 60 °C temperature, 4% w/w enzyme dose, 1:3 acid:alcohol ratio, 40 W power, 25 kHz frequency, 50% duty cycle and 150 rpm speed in 3 h as compared to 10 h of conventional method. The optimal enzyme loading was reduced to 4% w/w using ultrasound irradiation compared to 5% w/w of conventional. The efficiency of enzyme improved notably and can be reused up to seven cycles preserving its former activity. The application of ultrasound greatly enhanced esterification reactions by maintaining enzyme stability and improving the production yield. Moreover, owing towards a green approach, the synthesis is carried out in SFS for development of lucrative flavor ester. Bisubstrate kinetic models like random bi-bi, ping pong bi-bi and ordered bi-bi were applied to the experimental data using non-linear regression analysis. The experimental data and kinetic study revealed that reaction obeyed Ping-Pong bi-bi model with kinetic parameters, Vmax = 50.0 M/min/g catalyst, KA = 4.87 × 10−2 M, KB = 9.06 × 10−4 M, KiA = 9.8 × 10−1 M, KiB = 1.05 × 10−3 M & SSE = 2.74 × 10−4 for lipase catalysed synthesis of isobutyl propionate under ultrasound with inhibition by both acid and alcohol.