The effect of reaction parameters on lipase-mediated chemo-enzymatic epoxidation of linoleic acid was investigated. Hydrogen peroxide was found to have the most significant effect on the reaction rate and degree of epoxidation. Excess of hydrogen peroxide with respect to the amount of double bonds was necessary in order to yield total conversion within a short time period, as well as at temperatures above 50 7C to compensate for hydrogen peroxide decomposition. However, prolonged incubation with high excess of hydrogen peroxide leads to the accumulation of peracids in the final product. The reaction rate increased also with increasing hydrogen peroxide concentration (between 10 and 50 wt-%); however, at the expense of enzyme inactivation. Linoleic acid was completely epoxidized when used at a concentration of 0.5-2 M in toluene at 30 7C, while in a solvent-free medium, the reaction was not complete due to the formation of a solid or a highly viscous oily phase, creating mass transfer limitations. Increasing the temperature up to 60 7C also improved the rate of epoxide formation.
An environmentally benign and volume efficient process for enzymatic production of alkanolamides is described. Immobilized Candida antarctica lipase B, Novozym435, was used to catalyze the condensation of lauric acid with monoethanolamine. The reaction temperature of 90 degrees C was required to keep the reactants in a liquid state. Stepwise addition of the amine minimized problems caused by the formation of a highly viscous amine/fatty acid ion-pair. The enzyme was both very active and stable under the reaction conditions, with about half of the activity remaining after 2 weeks. The maximum amide yield obtained when using equimolar amounts of the reactants was 75%, which could be increased to 95% upon water removal. Special precautions to avoid co-distillation of the amine were required. Two different strategies to avoid the amine loss are presented.
The incorporation of caproic acid in the sn-1 position of phosphatidylcholine (PC) catalyzed by lipase from Rhizopus oryzae was investigated in a water activity-controlled organic medium. The reaction was carried out either as esterification or transesterification. A comparison between these two reaction modes was made with regard to product yield, product purity, reaction time, and byproduct formation as a consequence of acyl migration. The yield in the esterification and transesterification reaction was the same under identical conditions. The highest yield (78%) was obtained at a water activity (a(w)) of 0.11 and a caproic acid concentration of 0.8 M. The reaction time was shorter in the esterification reaction than in the transesterification reaction. The difference in reaction time was especially pronounced at low water activities and high fatty acid concentrations. The loss in yield due to acyl migration and consequent enzymatic side reactions was around 16% under a wide range of conditions. The incorporation of a fatty acid in the sn-1 position of PC proved to be thermodynamically much more favorable than the incorporation of a fatty acid in the sn-2 position.
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