(254e) Enhanced Lipase-Catalyzed Hydrolysis and Modification of Fats and Oils
AIChE Annual Meeting
Tuesday, October 30, 2018 - 9:40am to 10:00am
The use of microbial lipases for the hydrolysis of natural oils such as triglyceride esters is a green alternative to conventional high temperature, high pressure steam-based technology. Lipases are a group of enzymes whose primary function is to catalyze the hydrolysis of fats and oils at the oil-water interface to yield free fatty acids, diglycerides, monoglycerides and glycerol. The hydrolytic splitting of the esters is necessary for the downstream production of high value chemical products such as coatings, adhesives, and high performance personal care products. Deployment of enzymatic methods enables conversions to be achieved at close to ambient temperature and pressure with positive impacts on energy utilization and product purity. Enzymatic splitting of triglyceride esters is limited often by slow kinetics due to mass transfer limitations and by challenges of economic enzyme recycling. In this study, rates of reaction for the enzymatic hydrolysis of blended vegetable oil in the presence of lipase immobilized onto blended polymer supports and the influence of low voltage steady direct current (DC) electrical field on soluble enzymes were determined. Main advantages of these polymers include high mechanical stability and high enzyme activity at low protein loading. The immobilization criteria used was adsorption, whereby the enzyme adheres to the surface of the support particles by Van der Waals forces of attraction, were based on finding a low cost method of loading enzyme onto the support. Various compositional polymer resins were chosen for this study, includes epoxy, meth acrylic, octodecyl, and three different styrene based resins. All the hydrolysis reactions were carried out by mixing oil, water and immobilized enzyme in 30:10:1 ratio, on a weight basis, in a stirred tank reactor operated at 300 RPM. Epoxy-supported resin, showed more stability and activity compared to the other supports because epoxy groups can react with amino or thiol groups of the enzyme and form strong bonds between enzyme and supports which makes it attractive for recycling. Styrene based resins showed poor immobilization capabilities. Effects of pH and temperature were also studied. The possible effect of electrical charge on the lipase activity has hitherto not been considered. The reactions were conducted in a fixed rectangular geometry batch reactor fitted with planar electrodes. The two immiscible liquid phases, oil and aqueous lipase solution, were located between the electrodes with a quiescent rectangular interface of known area. The rates of conversion to the free fatty acid and glycerol were determined for applied DC voltages in the range 0-30 Volts imposed between the two electrodes. Comparisons with control conditions in the absence of electrical field, in the absence of enzyme and different electrode mesh sizes were also made. The results showed clear evidence of significant increase in the rates of reaction in the presence of the electrical field. These results also show evidence of an optimum voltage since at the upper end of the voltage range there was significant reduction in the rate enhancement compared with observations at lower voltages. It was concluded that the electric field has a positive effect on reaction rate, independent of interfacial area. This suggested possible changes in enzyme structure due the electrical field, modification of the nature of the enzyme binding at the liquid-liquid interface, or possibly intensification of local transport rates of substrates and reaction products close to the interface. The latter could involve phenomena such as electro-kinetic transport or electro-osmosis.
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