Ultrasound assisted enzyme catalysed synthesis of butyl caprylate in solvent free system

The present study focuses on ultrasound assisted enzyme catalysed synthesis of pleasing flavour and fragrances ester product from caprylic acid and butanol with immobilised Novozym 435 as a catalyst. The maximum conversion of 95.33% in the presence of ultrasound was obtained at molar ratio 1:2 with caprylic acid to n butanol, enzyme loading 1% (w/v), temperature 60 degrees C, agitation speed 150 rpm, ultrasonic power 75 W, frequency 22 kHz and duty cycle 80%. The use of ultrasound reduced the reaction time from 5 to 3.5 h with minimum enzyme loading as compared to conventional synthesis (in the absence of ultrasound). The reusability of the enzyme was examined up to eight successive cycles with 30% loss of enzyme activity as compared to initial activity. Also, the addition of molecular sieves was shown effective. This proved that ultrasound assisted system helps to improve the enzyme catalysed synthesis of flavours. Here, the enzyme loading, reaction time and ultrasound power have found to be significant parameters for maximum ester conversion.