Study of the Influence of Microwave and Conventional Heating on the Lipase-Catalyzed Esterification of Lauric Acid with Different Alcohols

In a systematic study, three commercial lipases were used for the esterification of lauric acid with six different alcohols: metha- nol, ethanol, propanol, butanol, pentanol, and allyl alcohol, under con- ventional heating and microwave irradiation. Optimization of reaction conditions included reaction time and effect of temperature under mi- crowave irradiation and conventional heating. The optimum reaction temperature was previously established in enzymatic esterification by conventional heating. Novozyme 435, lipase (Pseudomonas cepacia) immobilized in diatomite (PS-DI) and lipase (P. cepacia) immobilized in ceramic (PS-CI) were used in this study. The latter showed the highest activity, therefore, this enzyme was used to investigate the variation of reaction time under microwave heating. The stability of immobilized lipases under classical heating and under the microwave irradiation was studied by visual analysis of the immobilized matrix by scanning electron microscopy (SEM).