| Summary: | 碩士 === 長庚大學 === 生化與生醫工程研究所 === 96 === Carica papaya lipase is a naturally immobilized biocatalyst originated from plant. According to previous reports, this lipase has excellent enantioselectivity when carrying out the hydrolytic resolution of (R,S)-Naproxen esters. Therefore, the purpose of this research is aimed to use the lipase to perform transesterification resolution for a variety of recemic alcohols. We expect to screen suitable alcohol that can be resolved by using this lipase. When (R,S)-2-hydroxyl carboxylic acid esters were selected as the substrates to proceed lipase-catalyzed transesterification resolution, results revealed that the papaya lipase has better enantioselectivity for (R,S)-methyl 3-phenyllactate (E = 35.7). Changing of acyl donor to other vinyl esters of differ alkyl length and apolar solvent did not affect the enzyme performance. In comparison with the results of using the lipase pretreated with isopropyl ether or without the treatment, results revealed that the untreated papaya lipase has the best enantioselectivity for (R,S)-methyl 3-phenyllactate (E = 73.8). For (R,S)-2-hydroxyl carboxylic acid esters of different structures, the results revealed that the kinetic parameter of k2S are notably different for (R,S)-methyl 3-phenyllactate and (R,S)-ethyl 2-hydroxy-4-phenylbutyrate, i.e. 0.289 mmol/h g and 0.0117 mmol/h g, respectively. But the parameter Km of (R,S)-methyl mandelate was much higher than those of others, implying the very low affinity of the substrate to the lipase. The racemic alcohols of different structures were further selected as the substrates to perform the lipase-catalyzed transesterification resolution, with which the low reaction rate of (R,S)-methyl mandelate was elucidated.
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