Abstract
The esterification of cinnamic acid (CA) and oleyl alcohol (OA) in organic solvent media by immobilized lipase Novozym 435 was optimized in terms of selected parameters, including the logarithm of the 1βoctanol/water partition coefficient of the organic solvent (log P, 0.29β4.5), initial water activity (a~w~, 0.05β0.75), agitation speed (0β200 rpm), temperature (35β65 Β°C) and ratio of substrates (CA/OA, 1.0:0.5β1.0:6.0). The results showed that the more hydrophobic solvent mixtures and lower initial a~w~ values resulted in a higher enzymatic activity and bioconversion yield. The most appropriate solvent medium and initial a~w~ value was the mixture of isoβoctane/2βbutanone (85:15, v/v) and 0.05, respectively. The results also showed that an agitation speed of 150 rpm and a reaction temperature of 55 Β°C were optimal for the reaction system. The activation energy (E~a~) of the esterification reaction was calculated as 43.6 kJ mol^β1^. The optimal ratio of CA to OA was 1.0:6.0, with the absence of any inhibition by OA. Using the optimized conditions, the maximum enzymatic activity was 390.3 nmol g^β1^ min^β1^, with a bioconversion yield of 100% after 12 days of reaction. In addition, the electrospray ionizationβmass spectroscopy analysis confirmed that the major end product of the esterification reaction was oleyl cinnamate. Copyright Β© 2005 Society of Chemical Industry