| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 88 === Abstract
Optical active α-amino acids find wide applications in medical, agrochemical and food processing industries. In this study, the stereoselectivity of papain was employed for the optical resolution of phenylglycine (PG) via the esterification of PG and ethanol. The solubility of PG in non-polar organic solvent was greatly enhanced by modifying the amino group of PG with functional groups such as acetyl, Z (benzyloxycarbonyl), benzylcarbonyl and BOC (t-butoxycarbonyl). The effects of operation conditions on the reaction rate and enantioselectivity of papain were studied systematically. The reaction kinetics was also investigated.
The BOC-protected PG was chosen as the substrate in this study since it shows maximum solubility in organic solvent. Under a drying time of 40 minutes, 5 mg papain absorbed on 20 mg micro-porous polypropylene showed maximum activity. The optical operation conditions for the esterification were: enzyme load = 10 mg papain, 10 mM DL-BOC-PG, 500 mM ethanol. After testing various solvents, hexane was chosen as the solvent. As temperature increases, the reaction rate increases while the enanselectivity decreases. The obtained E value was between 35 and 150. Kinetic studies showed that the esterification between PG and ethanol with ethanol in excess amount follows Michaelis-Menten kinetics with substrate inhibition. Kinetic parameters obtained are: (Kmapp)L = 1655.5 mM, (Vmapp)L = 17.12 mmol ester/h.mg pp, (KI)L = 0.11mM.
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