The nature of fatty acid modifies the equilibrium position in the esterification catalyzed by lipase

The equilibrium position in lipase mediated esterification of various fatty acids and butanol was studied. The influence of the chain length and the p resence of unsaturations in the fatty acids on the equilibrium position was measured and predicted. To predict equilibrium position the program TREP e xtended (TREPEX) based on the UNIFAC group contribution method was used. Us ing an equilibrium constant of 35, calculated on the basis of thermodynamic activities, the equilibrium position between butanol and saturated and/or unsaturated fatty acids with different chain lengths can be predicted. The eater mole fraction at equilibrium increases with the fatty acid chain leng th, and for fatty acids with the same carbon number, the highest values are found for unsaturated fatty acids. For reaction systems containing two sat urated fatty acids, a slightly higher mole fraction is obtained for the fat ty acid with the higher chain length, while for mixtures consisting of satu rated and unsaturated fatty acids, the mole fractions of the unsaturated es ters are lower than those of the saturated ones, regardless the chain lengt h of the fatty acid. These experimental results are in goad agreement with the calculations with TREPEX. (C) 2000 John Wiley & Sons, inc.