| Summary: | 碩士 === 明志科技大學 === 生化工程研究所 === 102 === The synthesis of lipoic acid ester using lipoic acid and phenyl ethanol was catalyzed by commercial lipase enzyme (Novozym 435). A three-level three-variable and central composite designed response surface methodology (RSM) was employed to evaluate the parametric effects on esterification of phenyl ethanol and lipoic acid. The effects of various temperature (40-60°C), molar ratios of lipoic acid to phenyl ethanol (1:1-1:3), amounts of enzyme used (20-40 %) on conversion rates were investigated. The results showed that increasing temperature, lipoic acid/phenyl ethanol molar ratio, enzyme amount increased the production of lipoic acid ester. An empirical model for predicting the conversion was developed. The empirical model was statistically verified with experimental data, indicating its experimental acceptance. Therefore, the model could be successfully employed to determine the optimal reaction conditions for lipoic acid ester synthesis. The optimal conditions derived via RSM for the reaction were temperature of 49°C, lipoic acid/phenyl ethanol molar ratio of 1:2.958, enzyme amount of 40%. The actual conversion reached 70% under optimal conditions, which is close to the predicted value of 77.5%. Finally, the chemical structures of the derived compound was using NMR, and the product was using column chromatography with a 60% yield.
Key words：lipoic acid, phenyl ethanol, Response Surface Methodology、Lipase
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