HYDROLYSIS OF BUTTEROIL BY IMMOBILIZED LIPASE USING A HOLLOW-FIBER REACTOR .4. EFFECTS OF TEMPERATURE

A lipase from Aspergillus niger, immobilized by adsorption on microporous polypropylene hollow fibers, was used to effect the hydrolysis of the glycerides of melted butterfat at pH 70 at 40, 50, 55, and 60-degrees-C. McIlvane buffer was pumped upward through the lumen, and melted butterfat was pumped upward through the shell side of a hollow fiber reactor. Nonlinear regression methods were employed to determine the kinetic parameters of models based on combinations of three nested rate expressions for the hydrolysis reaction with three nested rate expressions for thermal deactivation of the enzyme. A rate expression containing four lumped parameters is sufficient to model the release of free fatty acids as a function of reactor space time and time elapsed after immobilization. Nonlinear regression methods were also employed in global fits of the data to rate expressions containing an explicit dependence on temperature. For the reaction conditions used in this research, a 14-parameter rate expression is necessary to accurately model the overall release of free fatty acids as a continuous function of the absolute temperature, initial substrate concentration, reactor space time, and time elapsed after immobilization of the lipase.