Characterization of the Acetate-Producing Pathways in Escherichia coli
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- 作者：Cheryl R. Dittrich ; George N. Bennett ; and Ka-Yiu San
- 刊名：Biotechnology Progress
- 出版年：2005
- 出版时间：August 2005
- 年：2005
- 卷：21
- 期：4
- 页码：1062 - 1067
- 全文大小：108K
- 年卷期：v.21,no.4(August 2005)
- ISSN：1520-6033
文摘
Although the bacterium E. coli is chosen as the host in many bioprocesses, theaccumulation of a common byproduct, acetate, is often problematic. Acetate, whenpresent at high levels, will inhibit both cell growth and recombinant proteinproductivity. In addition, products derived from the central aerobic metabolic pathwayoften compete with the acetate-producing pathways poxB and ackA-pta for glucose asthe substrate. As such, a significant portion of the glucose may be excreted as acetate,wasting substrate that otherwise could have been used for the desired product. Wehave created mutant E. coli strains with a deletion of either the poxB or the ackA-ptapathway. These two strains, along with the wild-type strain, have been studied inbatch reactors over a 12 h time period, at pH 7.0 and 6.0. The wild-type strain hasalso been studied using glucose as the carbon source. Data were collected to correlatecellular growth, extracellular metabolite production, enzyme activity, and geneexpression. Results show that the ackA-pta pathway dominates in exponential phase,and the poxB pathway dominates in stationary phase. The ackA-pta pathway isrepressed in acidic environments, whereas the poxB pathway is activated.