The hydrolysis of phosphatidylcholine by an immobilized lipase: Optimization of hydrolysis in organic solvents

Abstract

The ability of a commercial immobilized lipase preparation (Lipozyme) to hydrolyze the fatty acyl ester bonds of soybean phosphatidylcholine in organic media was investigated. Response surface methodology, based on a Modified Central Composite design, was employed to examine the effects on hydrolysis of solvent polarity, water, pH, duration and temperature of incubation, and the amounts of substrate and catalyst. A second-order regression model was developed, which allows evaluation of the effects of these parameters, alone or in combination. Hydrolysis increased in a relatively straightforward manner in response to increases in incubation time and the amount of catalyst and was approximately constant over the range of substrate amounts studied. Solvent polarity had a profound effect on the degree of hydrolysis, and the qualitative and quantitative degrees of this effect were dependent upon the values of the other parameters studied. Conditions were identified where enzyme activity was strong in either nonpolar or polar solvents, with activity increasing as the polarity of the medium increased. Enzyme activity was minimum at about 37°C, increasing below and above this temperature. Activity was not affected by the presence of acid or base in the reactions. Increasing amounts of water stimulated enzyme activity in solvents more polar than hexane, while in less polar solvents water inhibited activity.