| Summary: | 碩士 === 大同大學 === 生物工程學系(所) === 93 === D-Amino acid oxidase (DAO) is an important enzyme used to produce 7-aminocephalosporanic acid (7-ACA), a starting material for the semi-synthesis of cephem antibiotics. Rhodosporidium toruloides DAO CDNA gene was heterlogously expressed in the E. coli strain BL-21(DE3), using four different expression vectors, pET23am, pET24am, pET20b and pET26b in combination with two media, LB and TB and varying concentration of IPTG. With LB medium and using pET23am as the expression vector, the highest intracellular DAO activity, 4294 U/l was obtained〜3 hours after induction with IPTG. When pET24am as the expression vector instead, the highest intracellular DAO activity, 2724 U/l was observed 5 hours after induction. With pET20b and pET26b as the expression vectors, the highest intracellular DAO activities, 571 and 592U/l, respectively appeared 2 hours after induction. As the culture medium replaced by TB, the DAO activity were increased 5-10 times. Using pET23am and pETET24am as the expression vectors, the higher DAO activity, 50592 and 39651U/l were observed 5 and 18 hours, respectively after induction. When pET24a and pET26b used instead, the higher DAO activity, 3241 and 2393U/l were obtained 18 and 8 hours, respectively after induction.
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