Immobilization of pregastric esterases in a hollow fiber reactor for continuous production of lipolysed butteroil

Characterization of an anion-exchange porous polypropylene hollow fiber membrane for immobilization of ABL lipase

Hollow fiber membrane offers the advantage to integrate catalytic conversion, product separation and catalyst recovery into a single separation process compared to conventional systems. Polypropylene (PP) hollow fiber membrane is a chemically inert and stable membrane with high potential for enzyme immobilization. The surface properties of polypropylene have been modified by radiation induced graft polymerization. Samples were prepared by grafting of glycidylmethacrylate (GMA) using gamma radiation, at different monomer concentrations and irradiation dose. The resulting epoxy was converted into a diethylamino group as an anion-exchange medium to bind the lipase molecules. Surface properties of the grafted and amine treated samples were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements. AFM revealed higher surface roughness for grafted samples than that of virgin polymer. SEM micrographs illustrated that the porous network was retained at high degree of grafting. Contact angle measurements showed excellent wetting properties with water for the grafted and amine treated membranes. Thermal properties were studied using differential scanning calorimeter (DSC) and thermogravimetic analysis (TGA). It was observed that grafting occurred mainly in the amorphous region of the membranes. Activity and operational stability of ABL lipase, isolated from Arthobacter sp. were assayed after immobilizing it to the modified PP hollow fiber. Immobilized lipase retained 20U/g activity after ten hydrolysis cycles and 68% residual activity after 12 weeks of storage.

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.

Biotechnology for the production of nutraceuticals enriched in conjugated linoleic acid: II. Multiresponse kinetics of the hydrolysis of corn oil by a Pseudomonas sp. lipase immobilized in a hollow-fiber reactor

The hydrolysis of corn oil in the presence of a lipase from Pseudomonas sp. immobilized within the walls of a hollow-fiber reactor was studied at 30 degrees C. To assess the selectivity of this immobilized enzyme, the effluent concentrations of five different free fatty acids were measured using high-performance liquid chromatography (HPLC). Several rate expressions associated with a generic ping-pong bi-bi mechanism were used to fit the experimental data for this lipase-catalyzed reaction. A multiresponse nonlinear regression method was employed to determine the kinetic parameters associated with these rate expressions. Quasi-optimum operating conditions corresponded to 30 degrees C and a buffer pH value of 7.0. Under these conditions, the concentration of free linoleic acid (C18:2) (the fatty acid of primary interest) in the effluent oil stream for a fluid residence time of 6 h was approximately 0.5 M.

Kinetics and mechanisms of reactions catalyzed by immobilized lipases*

This review focuses on the kinetics of several modes of immobilization of lipases, on the mechanisms of reactions of activation of immobilized lipases, and on the kinetics and mechanisms of reactions catalyzed by immobilized lipases. A comprehensive overview of the state of the art pertaining to structural features of lipases is provided as an aid to understand immobilization, interfacial activation, and catalytic performance. General rate expressions are duly derived; more frequent simplifying assumptions are stated and the results thereof listed. Physicochemical and statistical significance of parameters in rate expressions fitted to experimental data are also discussed whenever possible.

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.

Biotechnology for the production of nutraceuticals enriched in conjugated linoleic acid: I. Uniresponse kinetics of the hydrolysis of corn oil by a pseudomonas sp. lipase immobilized in a hollow fiber reactor

The kinetics of the hydrolysis of corn oil in the presence of a lipase from Pseudomonas sp. immobilized within the walls of a hollow fiber reactor can be modeled in terms of a three-parameter rate expression. This rate expression consists of the product of a two-parameter rate expression for the hydrolysis reaction itself (which is of the general Michaelis-Menten form) and a first-order rate expression for deactivation of the enzyme. Optimum operating conditions correspond to 30 degrees C and buffer pH values of 7.0 during both immobilization of the enzyme and the hydrolysis reaction. Under these conditions, the total fatty acid concentration in the effluent oil stream for a fluid residence time of 4 h is approximately 1.6 M. This concentration corresponds to hydrolysis of approximately 50% of the glyceride bonds present in the feedstock corn oil. The fatty acid of primary interest in the effluent stream is linoleic acid. Copyright 1999 John Wiley & Sons, Inc.

Hydrolysis of menhaden oil by a Candida cylindracea lipase immobilized in a hollow-fiber reactor

A lipase from Candida cylindracea immobilized by adsorption on microporous polypropylene fibers was used to selectively hydrolyze the saturated and monounsaturated fatty acid residues of menhaden oil at 40 degrees C and pH 7.0. At a space time of 3.5 h, the shell and tube reactor containing these hollow fibers gives a fractional release of each of the saturated and monounsaturated fatty acid residues (i.e., C14, C16, C16:1, C18:1) of ca. 88% of the corresponding possible asymptotic value. The corresponding coproduct glycerides retained over 90% of the initial residues of both eicosapentaenoic (EPA; C20:5) and docosahexaenoic (DHA; C22:6) acids. The half-life of the immobilized lipase was 170 h when the reactor was operated at the indicated (optimum) conditions. Rate expressions associated with a generic ping-pong bi-bi mechanism were used to fit the experimental data for the lipase catalyzed reaction. Both uni- and multiresponse nonlinear regression methods were employed to determine the kinetic parameters associated with these rate expressions. The best statistical fit of the uniresponse data was obtained for a rate expression, which is formally equivalent to a general Michaelis-Menten mechanism. After reparameterization, this rate expression reduced to a pseudo-first-order model. For the multiresponse analysis, a model that employed a normal distribution of the ratio of Vmax/Km with respect to the chain length of the fatty acid residues provided the best statistical fit of the experimental data.

Lipase catalyzed modification of milkfat

Decreasing consumption of high fat milk and dairy products is driving the dairy industry to seek other uses for increasing surplus of milkfat. Enzyme catalyzed modification of milkfat using lipases is receiving particular attention. This review examines lipase-mediated modification of milkfat. Especial attention is given to industrial applications of lipases for producing structured and modified milkfat for improved physical properties and digestibility, reduced caloric value, and flavor enhancement. Features associated with reactions such as hydrolysis, transesterification, alcoholysis and acidolysis are presented with emphasis on industrial feasibility, marketability and environmental concerns. Future prospects for enzyme catalyzed modification of milk fat are discussed.