Fatty acid specificity of immobilized kid goat pre-gastric esterase: Effects of pH

Production of lipolyzed butteroil by a calf pregastric esterase immobilized in a hollow fiber reactor: III. Effect of glycerol

Lipolysis of butter oil in a hollow fiber reactor containing an immobilized calf pregastric esterase was studied at 40 degrees C, a pH of 6.0, and glycerol concentrations of 0, 150, and 500 g/L in the buffer solution. The concentrations of 10 fatty acid species in the lipolyzed product were determined using high-performance liquid chromatography. The rate of loss of enzyme activity and the relative selectivities of this esterase depended on the glycerol concentration. By contrast, the overall rate of release of fatty acids was not affected by the glycerol concentration. Loss of enzyme activity was modeled using first-order kinetics. The models for deactivation and reaction kinetics were fit simultaneously to the data. The model was successful in describing the rates of release of all 10 fatty acid species for a range of space times from 0 to 25 h. The parameters of the model were tested for dependence on glycerol concentration.

Lipolysis of butter oil by immobilized lamb pregastric esterase: I. Uniresponse kinetics-pH and temperature effects

Lamb pregastric esterase, immobilized by physical adsorption on microporous polypropylene in a hollow fiber reactor, has been employed to effect the continuous hydrolysis of the triglycerides in butter oil. Experimental data were obtained at temperatures from 35 to 45 degrees C and pH values from 5.5 to 6.5. The overall rate of hydrolysis was fastest at 40 degrees C and a pH of 6.0. Nonlinear regression methods were employed to determine the kinetic parameters of rate expressions based on a generic Ping-Pong Bi Bi mechanism. The best nonlinear fit of the data was consistent with a mechanism that assumes that acylation of the enzyme is the rate-limiting step in the hydrolysis reaction.

Effect of pH on the production of lipolyzed butter oil by a calf pregastric esterase immobilized in a hollow-fiber reactor: II. Multiresponse kinetics

The lipolysis of butter oil in a hollow-fiber reactor containing an immobilized calf pregastric esterase was studied at 40 degrees C and at pH values of 4.0, 5.0, 6.0, and 7.0. The concentrations of ten fatty acid species in the lipolyzed product were determined using high-performance liquid chromatography (HPLC). The relative specificity of this esterase depended on pH. Three mathematical models derived from a generalized Michaelis-Menten mechanism were tested for their ability to describe the rates of release of individual specific fatty acids. Loss of enzyme activity was modeled using first order kinetics. The models for deactivation and reaction kinetics were fit simultaneously to the data. The parameters of the model were also tested for dependence on pH. The model was successful in describing the rates of release of all ten fatty acid species for a range of space times and pH values.

Effect of pH on the production of lipolyzed butter oil by a calf pregastric esterase immobilized in a hollow-fiber reactor: I. uniresponse kinetics

A calf pregastric esterase immobilized in a hollow-fiber reactor was employed to hydrolyze milkfat, thereby producing a lipolyzed butteroil. The reaction kinetics can be modeled by a two-parameter model of the general Michaelis-Menten form based on a ping-pong bi-bi mechanism; the rate of enzyme deactivation can be modeled as a first-order reaction. The initial concentration of accessible glyceride bonds, [G](O), was estimated by complete saponification of the substrate butteroil as 2400 mM. An extra sum of squares test indicated that not only the parameters of the kinetic generalized Michaelis-Menten model, but also the deactivation-rate constant varied significantly with pH. The optimum pH, for lypolysis is near 6.0 at a temperature of 40 degrees C because at this pH the rate of deactivation of the esterase is minimized.