Effect Of The Modification Of Lipase By Nonionic Surfactant On The Process Of The Enzymatic Interesterification

The acyl migrations of the interesterification of camellia oil and linoleic acid in organicsolvent by six nonionic surfactant modified porcine pancreas lipases (Tween40-PPLipase,Tween65-PPLipase, Span60-PPLipase, Span80-PPLipase, S1170-PPLipase andS1670-PPLipase) were studied catalysed. Furthermore, the kinetics and thermodynamics ofinteresterification of triolein and stearic acid catalysed by these lipases in organic solventwere also investigated.The modification of the PPLipase by nonionic surfactant modification could increase theinteresterification acitivity in some degree, and decreas the acyl migration during the earlystage of the interesterification. When acyl incorporation was below20%, the acyl migrationsof the interesterification catalysed by modified PPLipase were all not higher than6%. Theacyl migrations of the interesterification catalysed by Span80-PPLipase, S1170-PPLipase andS1670-PPLipase were basically the same and were all under5%. While the system acylmigration rate catalysed by PPlipase was10%maximum. The amount of diacylglycerol hadreached8%and kept constant at the beginning of the reaction.When acyl incorporation belowupon20%, the amount of monoglycerol and acyl migration grew rapidly. The monoglycerolof each reaction reached about12%maximum in5h, and at the same time acyl migration ofeach reaction increased from10%to30%. The acyl migration and the amount of eachcomponent of the system no longer changed after equilibrium.Based on mass balance, the kinetics model of the interesterification of triolein and stearicacid catalyzed by lipase in organic solvent was developed. The equation of each componentconcentration and reaction velocity and time was deduced. The average rate constant [K,L2/(mmol·min·gE)] of each enzymatic interesterification was caculated, K of theinteresterification catalyzed by PPlipase was1.85×10-6, K of the interesterification catalyzedby Tween40-PPlipase was6.22×10-6, K of the interesterification catalyzed byTween65-PPlipase was10.2×10-6, K of the interesterification catalyzed by Span60-PPlipase,11.1×10-6, K of the interesterification catalyzed by Span80-PPlipase was19.7×10-6, K of the interesterification catalyzed by S1170-PPlipase was15.7×10-6, K of the interesterificationcatalyzed by S1670-PPlipase was13.4×10-6.Based on the reaction rate constant k at different temperature ccording to kinetics modeland Arrhenius equation&other thermodynamic equations, the thermodynamic characteristicsof the interesterificaion of glycerol trioleate (OOO) and stearic acid catalyzed by PPLipase,Tween65-PPLipase, S1670-PPLipase and Span80-PPLipase were investigated at differenttemperature. The energy of activation (Ea) of the interesterifications catalyzed by PPLipase,Tween65-PPlipase, S1670-PPlipase and Span80-PPlipase were106.0kJ/mol,79.4kJ/mol,,88.0kJ/mol and,99.7kJ/mol, respectively.The free energy of activation (△G≠, kJ/mol) of theinteresterifications catalyzed by PPLipase, Tween65-PPlipase, S1670-PPlipase andSpan80-PPlipase were110.4,107.1,106.5and105.5, respectively. The enthalpy of activation(△H≠, kJ/mol) of the interesterifications catalyzed by PPLipase, Tween65-PPlipase,S1670-PPlipase and Span80-PPlipase were103.3,76.8,85.4and97.1, respectively. Theentropy of activation (△S≠, kJ/mol) of the interesterifications catalyzed by PPLipase,Tween65-PPlipase, S1670-PPlipase and Span80-PPlipase were-0.023,-0.094,-0.065and-0.025, respectively. The data of△G≠and△S≠were average value of the reactions atdifferent temperature. For lipase catalyzed interesterification, with the temperature increasingin a specicial rang, the reaction velocity could be accelerated and, and then the reaction rateconstant k was improved, but the temperature had no influence on the free energy ofactivation, entropy of activation, enthalpy of activation and energy of activation. The lipasecatalyzed interesterification was endothermic and entropy decreasing reaction, however theenthalpy of activation and entropy of activation of the reaction catalysed by different lipasewere not the same. The reaction rate constant k was affected by Ea and△G≠, the free energyof activation had a lager effect on the reaction rate constant k than energy of activation.