Thermodynamics and kinetics of lipase catalysed hydrolysis of oleyl oleate

The kinetics of enzymatic hydrolysis of oleyl oleate in the boundary layer between stagnant organic and aqueous phases was studied using a commercial lipase preparation which was dissolved in the aqueous phase. Three aspects of the reaction were investigated. (1) The hydrolysis equilibrium in the organic phase cannot be expressed in terms of the concentrations of ester, alcohol and organic acid alone since the activity of the organic compounds changes dramatically with conversion, i.e. with the water content in the organic phase. An empirical correlation that accounts for the water activity and the unknown activity coefficients of the organic compounds is determined. (2) The influence of the interfacial area was examined, and it was found that the amount of ester converted per unit area of interface is independent of the available interfacial area and of the amount of ester. (3) The inhibition of the reaction by the hydrolysis products and by n-alkanes was measured. Both acid and alcohol inhibit the hydrolysis reaction while the influence of long-chained alkanes is very small. It is concluded that the reaction rate is determined by the interfacial concentrations, and that these concentrations differ from the bulk concentrations because of the different surface affinities of the components.