Abstract
Abstract This study aims at clean production of 2-ethylhexyl palmitate catalyzed by lipase Fermase CALB 10000 in a solvent-free system using ultrasound technology. The central composite design (CCD) of response surface methodology with 4 factors at 3 levels consisting of acid to alcohol molar ratio (1:3-1:7), enzyme loading (3 %-7% (w/w)), ultrasound power (60 - 100 W) and duty cycle (30%-70 %) was used for optimization of the reaction. All the reactions were carried out at a fixed temperature of 60°C, 200 rpm and reaction time (120 min). The statistical software, Design-Expert 9.0, was used for regression analysis and graphical analysis of the responses obtained by running the set of designed experiments. The polynomial equation of quadratic order was employed to fit the experimental data. The operating conditions for optimum synthesis of 2-ethylhexyl palmitate were molar ratio of 1:5.5, 5.61 % (w/w) of the enzyme with ultrasound power 79.54 W and duty cycle 48.04 %, leading to a reaction conversion as high as 96.56% in 120 min. The operational stability of the enzyme was maintained at >70% conversion up to 5 cycles. Thus, ultrasound is a promising green technology for the lipase catalyzed synthesis of ethylhexyl esters.
Highlights
This study aims at clean production of 2-ethylhexyl palmitate catalyzed by lipase Fermase CALB 10000 in a solvent-free system using ultrasound technology
In the present study, the application of low-intensity ultrasound may reduce the reaction time to 120 min. This indicated that ultrasound may deliver better mixing of substrate solution which increased the interaction between the substrate and enzyme
The optimization of the process was performed by Response surface methodology (RSM) using central composite design in a solvent free condition
Summary
This study aims at clean production of 2-ethylhexyl palmitate catalyzed by lipase Fermase CALB 10000 in a solvent-free system using ultrasound technology. The operating conditions for optimum synthesis of 2-ethylhexyl palmitate were molar ratio of 1:5.5, 5.61 % (w/w) of the enzyme with ultrasound power 79.54 W and duty cycle 48.04 %, leading to a reaction conversion as high as 96.56% in 120 min. Ultrasound radiations enhance the diffusion of reactants into the enzymes as well as renew the interface by jets formed during cavitation It reduces the transportation barrier so that the enzyme reaches its target site and gives higher conversion in a smaller time span. Response surface methodology (RSM) and central composite design (CCD) on the other hand enable one to elucidate the response or conversion by using various combinations of process parameters This method brings about proper optimization of the reaction under study (Bezerra et al, 2008; Khan et al, 2016). The reusability of Fermase CALB 10000 under optimum reaction conditions was analyzed up to 5 cycles
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