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- Singh, CP, et al.
(författare)
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A comparison between lipase-catalyzed esterification of oleic acid with glycerol in monolayer and microemulsion systems
- 1994
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 71, s. 1405-1409
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper lipase catalyzed synthesis - esterification of oleic acid with glycerol - i8 carried out in L2 microemulsions and in monolayers. The microemulsions were based on isooctane as nonpolar component and various water-glycerol mixtures as polar component. The substrate, oleic acid/sodium oleate, constituted the microemulsion surfactant. The lipase is known to reside mainly in the water pools. Monolayers of oleic acid/sodium oleate were formed on subsolutions of glycerol and water and the enzyme solution was injected under the compressed monolayers. Thus, the arrangement of the reactants at the oil-water interface of the microemulsion can be regarded as analogous to that at the air-water interface of the monolayer. The microemulsion structure was characterized by self-diffusion NMR. It was found that the higher the glycerol to water ratio, the lower are the water D-values. The reactions in microemulsions generally gave a low degree of oleic acid conversion. The yield increased with increasing glycerol to water ratio. Monoglycerides were the main product and no triglyceride could be detected. The monolayer experiments gave a somewhat higher degree of conversion with tri- and diglycerides being the major reaction products. The reason why triglycerides are formed in monolayer experiments but not in microemulsions is believed to be due to an unfavourable partitioning of the diglyceride in the microemulsion systems. Once formed, the diglyceride will partition into the hydrocarbon domain and become inaccessible for reaction with the enzyme-O-acyl intermediate at the oil-water interface. In addition, the interfaces in the two systems are very different. The monolayer interface is static, whereas the microemulsion interface is highly dynamic, and this difference may also influence the product pattern.
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- Singh, CP, et al.
(författare)
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Synthesis of mono- and diglycerides in water-in-oil microemulsions
- 1994
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 71, s. 583-587
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Tidskriftsartikel (refereegranskat)abstract
- Enzyme catalyzed esterification reaction was carried out in single phase, oil-continuous microemulsions. The lipozyme was solubilized, along with glycerol and water, in the aqueous core of water/AOT/hydrocarbon microemulsion system. Upon addition of fatty acid, mono- and diglycerides were formed due to the esterification reaction taking place at the interface of the droplets in the microemulsion. The initial rate of conversion of oleic acid increases with oil chain length of the continuous phase whereas final conversion is maximum for hexane. The percent conversion of stearic acid is 30% whereas the percent conversion of oleic acid is 70%. The percent conversions of various fatty acids under the same continuous medium increases with chain length of fatty acids. The oleic acid/glycerol ratio is an important parameter for the optimum conversion of oleic acid into glycerides. The percent yield can be increased by subsequent addition of glycerol after equilibrium is reached. Temperature has a considerable effect on the synthesis reaction. HPLC analysis of samples from microemulsions show the presence of mono- and diglycerides. Possible mechanisms for the above mentioned effects are discussed.
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