Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with co-expressed propionate permease (prpP), Beta-ketothiolase B (bktB) and propionyl-CoA synthase (prpE) in Escherichia coli
| Autor: | Chih-Ta Huang, 黃志達 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 Polyhydroxyalkanoates (PHA) are biocompatible and biodegradable polymers produced by some natural bacteria. Different PHA mono-molecule synthesized polymers are with its special thermal and mechanical properties. Previously studies showed that the poly 3-hydroxybutyrate could be produced and accumulated in Escherichia coli engineered by transformation of PHA synthetic operon (phaCAB). However, this recombinant E. coli could not accumulate poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) in regular culture medium. In order to produce PHBV and enhance 3-hydroxyvalerate (3-HV) fraction in PHBV, the strategy was suggested to intensify 3-HV synthesis pathway. In this study, propionate permease (prpP), propionyl-CoA synthesis (prpE), or beta-ketothiolase B (bktB) genes are over-expressed in E. coli, respectively. The result showed the recombinant strain only contained prpE gene produced the higher HV fraction in PHBV. The HV fraction rations are 4.62%, 22.81% and 5.4% in strains CT-2, CT-2E and CT-2-BP, respectively. After simple purified, the material properties of PHBV showed, the molecular weight is increased from 3.42×105 to 9.56×105 and crystallization temperature is decreased from 67.3 oC to 58.6 oC in CT-2-BP strain. The material properties of CT-2E strain showed, the molecular weight is increased from 3.42×105 to 8.47×105, crystallization temperature was not detectable under -40 oC and ΔH is decreased from 71.6 J/g to 51 J/g. Together these results, bioengineering the 3-HV synthesis genes in E. coli could be easier machining and synthesize different kind of polymers. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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