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Characterization of the Acetate‐Producing Pathways in Escherichia coli
Author(s) -
Dittrich Cheryl R.,
Bennett George N.,
San KaYiu
Publication year - 2008
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp050073s
Subject(s) - escherichia coli , biochemistry , enzyme , metabolic pathway , mutant , chemistry , strain (injury) , biosynthesis , metabolite , substrate (aquarium) , extracellular , biology , gene , ecology , anatomy
Although the bacterium E. coli is chosen as the host in many bioprocesses, the accumulation of a common byproduct, acetate, is often problematic. Acetate, when present at high levels, will inhibit both cell growth and recombinant protein productivity. In addition, products derived from the central aerobic metabolic pathway often compete with the acetate‐producing pathways poxB and ackA ‐ pta for glucose as the 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. We have created mutant E. coli strains with a deletion of either the poxB or the ackA‐pta pathway. These two strains, along with the wild‐type strain, have been studied in batch reactors over a 12 h time period, at pH 7.0 and 6.0. The wild‐type strain has also been studied using glucose as the carbon source. Data were collected to correlate cellular growth, extracellular metabolite production, enzyme activity, and gene expression. Results show that the ackA ‐ pta pathway dominates in exponential phase, and the poxB pathway dominates in stationary phase. The ackA ‐ pta pathway is repressed in acidic environments, whereas the poxB pathway is activated.