| Summary: | 碩士 === 國立中正大學 === 化學工程研究所 === 89 === The immobilized 1,3-regiospecific lipase Mucor miehei was employed to catalyze the transesterification reaction of Menhaden oil with n-3 PUFA (n-3 polyunsaturated fatty acid) to enrich the n-3 PUFA content of acylglycerols under supercritical carbon dioxide. In the past, researchers have worked on various efforts to enrich the contents of n-3 PUFA at ambient conditions. However, low reaction rate was found in organic solvent. To corps with this issue, supercritical carbon dioxide was used to shorten the reaction time ,due to its high mass transfer power
The research consists of two parts: one is to investigate the effect of interesterification of Menhaden oil and n-3 PUFA with different parameters, the other is to study the kinetic characteristics in the reaction. Through the saponification of menhaden oil followed by urea inclusion , 80.1% n-3 polyunsaturated fatty acid can be concentrated which containing EPA 29.4% and DHA 41.8% . Rate profiles for the conversion progressively increased at beginning, after five hours conversion approach to lever off. As the pressure raised, reaction rate decreased due to destructive the amino-group of lipase. The enzyme exhibits a good performance and stabilities in the region of 323 k. Ethanol was used as cosolvent and concentration was up to 10 wt%. The substrate ratio of acylglycerols and n-3 PUFA equal to 1:4 by considering the acylglycerols inhibition.The conversion appears 1.3 folds higher in SC-CO2 than in n-hexane in ambient pressure after 5 hours. From the results, supercritical fluids demonstrates a better catalytic abilities and stabilities with respect to conventional organic solvent, including high diffusivities and low viscosities which increase mass transfer of substrate into the catalyst particles. The kinetics of reaction are suggested to fit the Ping-pong Bi-Bi mechanism and the general multi-substrate rate expression which proposed by Alberty. The rate expression was modeled by Michaelis -Menten mechanism. The reaction rate constants Km and Vmax were also evaluated. For the experimental range investigated, there was 7.3% deviation between experimental and modeled data.
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