Overexpression of pyruvate kinases and phosphoenolpyruvate synthase in Escherichia coli : physiological characterization and application /
Escherichia coli (E. coli) is perhaps the most widely studied
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965761&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Escherichia coli (E. coli) is perhaps the most widely studied prokaryote by both scientists and engineers in the area of biological sciences. On one hand scientists are trying to unravel and understand the biochemical and genetic regulation of various metabolic pathways as has evolved in the bacterial cell, while on the other hand engineers are constantly on the look out for constructing and designing new strains by altering existing pathways for improving production of chemicals. In most cases these engineered strains are quite different from the wild type. Engineers use the insights from the paradigms developed by the scientists to narrow down their choices for manipulating strains for a specific purpose, and the characterization of this engineered strain serves as feedback in the understanding of that paradigm, either strengthening it or invalidating it. In this study a combined attempt is made in which alterations in the central metabolism of E. coli are characterized from a fundamental perspective and then a new central metabolism is created that improves production of 3-deoxy-D-arabino-heptulosonate7- phosphate (DAHP) over an existing industrial strain. The central metabolism is altered by overexpression of a gluconeogenic enzyme, phosphoenolpyruvate synthetase (Pps) under glycolytic conditions and also by overexpression of pyruvate kinases (PykI, Pykll). These three enzymes along with the glucose phosphotransferase system (PTS) contribute significantly in the modulation of the intracellular levels of two key metabolites of the central metabolism, phosphoenolpyruvate (PEP) and pyruvate. Insights obtained from this study were successfully used in directing more carbon flux from PEP towards aromatics production. The following results were obtained: (1) Overexpression of PykH observable effect on the specific growth rate and the glucose consumption rate in E. coli. However, overexpression of Pps increased glucose uptake rate, oxygen consumption rate, fermentation product excretion, and showed activity dependent growth inhibition. (2) Overexpression of Pps in combination with DAHP synthase (AroG) and transketolase (TktA) increases the yield of DAHP production from glucose by almost twofold over the control strains to near theoretical levels. |
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| Item Description: | Vita. "Major Subject: Chemical Engineering". |
| Physical Description: | xiv, 91 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |