Erythorbyl laurate was continuously synthesized by esterification in a packed-bed enzyme reactor with immobilized lipase from Candida antarctica. Response surface methodology based on a five-level three-factor central composite design was adopted to optimize conditions for the enzymatic esterification. The reaction variables, such as reaction temperature (10-70°C), substrate molar ratio ([lauric acid]/[erythorbic acid], 5-15), and residence time (8-40 min) were evaluated and their optimum conditions were found to be 56.2°C, 14.3, and 24.2 min, respectively. Under the optimum conditions, the molar conversion yield was 83.4%, which was not significantly different (P < 0.05) from the value predicted (84.4%). Especially, continuous water removal by adsorption on an ion-exchange resin in a packed-bed enzyme reactor improved operational stability, resulting in prolongation of half-life (2.02 times longer compared to the control without water-removal system). Furthermore, in the case of batch-type reactor, it exhibited significant increase in initial velocity of molar conversion from 1.58% to 2.04%/min.
Keywords: erythorbyl laurate; immobilized lipase-catalyzed esterification; operational stability; response surface methodology; water removal.
© 2013 American Institute of Chemical Engineers.