Green synthesis of the flavor ester butyl butyratecatalyzed by Novozyme 435: a statistical approach

Abstract

Butyl butyrate (C8H16O2) is one of esters of short chain fatty acids and alcohols that are important components for flavoring having fruity aromas. Adhering to green chemistry, enzymatic synthesis was performed for the production of butyl butyrate catalyzed by recombinantCandida Antarctica expressed inAspergillusniger. The acrylic resin immobilized commercial lipase (Novozyme435) was the biocatalysts of choice to catalyze the esterification reaction to produce butyl butyrate. The enzymeassisted esterification was optimized using the statistical approach of Response Surface Methodology by the Box-Behnken Design (BBD). In this study, the reaction parameters evaluated were substrate molar ratio, time and temperature, while the response of each parameter was measured as percentage conversion yields. UsingtheDesign Expert 7.1.6 optimization function, the conditions with the highest desirabilityand percentage conversionvalues were selected to obtain the optimized conditions for the Novozyme 435 catayzed esterification reaction. Two sets of optimum conditions were selected and afforded the highest conversions of 99.62% and 99.55% using (i) molar ratio butyric acid:butanol 1:3.93, 9.93 h at 56.09°C and (ii)  molar ratio butyric acid:butanol1:3.35, 9.79 h at 53.90°C, respectively. The esterification of butanol and butyric acid to produce butyl butyrate was monitored using Thin Layer chromatography (TLC). The production of butyl butyrate was confirmed by various methods which include FTIR Spectroscopy: Attenuated Total Reflectance (ATR) and Gas chromatography (GC).