An intensified technique for lipase catalysed amide synthesis

The enzymatic synthesis of propyl acetamide under the influence of sonication has been explored. The effect of various reaction parameters that drive the reaction was studied and optimised under solvent free condition to achieve maximum yield. At temperature 60 degrees C, mole ratio of propyl amine to butyl acetate 1:1.5, 3% (w/v) of lipase loading with ultrasound (US) frequency as 22 kHz, 100 W power of ultrasonic bath and with agitation speed of 100 rpm, 98% conversion was obtained in 2 h. Kinetic modeling of lipase catalysed amidation illustrated the substrate inhibition by propylamine and the values determined are V-max = 9.9 M/min/g of catalyst and K-ia = 1.45 M. The thermodynamic study revealed that US lowered the energy of activation thus making it more feasible than the conventional technique. The reusability studies were also performed and immobilised lipase was reusable for 5 successive cycles with 50% loss from its initial activity. Thus, ultrasound successfully intensified the amidation reaction as compared to conventional mechanical stirring by two folds.