Kinetic model of lipase-catalyzed conversion of ascorbic acid and oleic acid to liposoluble vitamin C ester

The kinetics of L-ascorbyl oleate synthesis catalyzed by immobilized lipase from Candida antarctica in acetone was investigated. Significant inhibition of synthesis with an excess of ascorbic acid was observed. Experimental data were successfully fitted with a ping-pong bi-bi kinetic model with substrate inhibition, and related kinetic constants were determined. The kinetic study was performed at optimum experimental factors (temperature, initial water content, and enzyme concentration), which were determined using response surface methodology. Then, a model for predicting product-time progress curves was developed by expanding the obtained ping-pang model with terms describing ester hydrolysis. Kinetic constants of the reverse reaction were determined, and good congruence between the model and experimental data was achieved. Calculated kinetic constants revealed that lipase has the highest affinity for ascorbyl oleate, slightly lower activity with ascorbic acid, and the lowest activity with oleic acid. The obtained results are valuable for elucidating the reaction mechanism and represent an important contribution for reaction optimization and creating strategies to increase the productivity of vitamin C ester synthesis. (C) 2012 Elsevier B.V. All rights reserved.