| As one of important types of additives, vitamin A lactate is widely used in cosmetics, medicine and other chemical industries. Enzyme-catalyzed production of vitamin A lactate boasts many advantages such as mild reactions, good catalysis effects and low energy consumption. In this paper, the synthesis of vitamin A lactate by immobilized lipase Novozym 435 was investigated.Firstly,the influences of solvent, the molar ratio of substrates, the reaction temperature and time were optimized and the best result was obtained by transesterification from 0.167 g vitamin A acetate and 0.150g lactic acid ,at 35 °C, in 5 ml solvent ,with 25mg lipase. In these conditions ,52.19 % of vitamin A acetate was converted into vitamin A lactate. The immobilized lipase was reused 5 batches, the yield of ester high than 45% was achieved.Secondly, Response Surface Methodology based on a five-variable central composite rotatable design was used to determine the effect of reaction time , temperature, enzyme amount, acid concentration and agitation speed on the esterification reaction. The mathematical model for the process was established.Finally, Kinetics of lipase-catalyzed esterification of lactic acid and Vitamin A have been investigated. The reaction rate could be described in terms of the Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism. Response surface methodology (RSM) was used for the prediction of the kinetic constants of the reaction. The relationships between the kinetic constants(Vmax, Kma and Kmb) and the reaction parameters were obtained as follows:To assess the accuracy of the RSM approach for determining Vm ,Kma and Kmb , a detailed validation experiments were carried out by the conventional approach at three different reactiontemperature (27°C;35°C;38°C) . The results indicated that the RSM approach gave the reasonable results for the determination of Vm ,Kma and Kmb in the range of tested parameters.
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