Metabolic flux analysis of Escherichia coli MG1655 under octanoic acid (C8) stress
type: CreativeWork
description: Metabolic engineering has evolved to the point of fulfilling the dream of having industrial chemicals produced renewably. Carboxylic acids [e.g., short chain fatty acids (SCFAs) such as octanoic acid (C8)] are such chemical intermediates that can be produced by Escherichia coli engineered with thioesterases specific for short chain fatty acids. However, C8 is toxic to E. coli at concentration greater than 10 mM. To design a better host strain for the production of large amount of SCFAs, 13C metabolic flux analysis of E. coli was performed for both C8 stress and control condition (without C8). To investigate central carbon metabolism for the culture environmental change, a mixture of labeled and unlabeled glucose was used as the sole carbon source for bacterial growth and proteinogenic amino acid isotopomers were measured using two-dimensional (13C, 1H) HSQC NMR spectroscopy. Notable differences of several amino acids isotopomer abundance were observed between the control condition and C8 stress condition, suggesting that the precursor nodes of these amino acids in metabolic pathways were responding to the stress. More specifically, the difference suggested that the distribution of fluxes among the tricarboxylic acid (TCA) cycle, pentose phosphate pathway, pyruvate node, alpha-ketoglutarate node and oxaloacetate node changed. By comparing the metabolic flux maps of E. coli MG1655 grown at different conditions, pathways that have flux change under stress were identified. Inhibition effect for several pathways, resulting in a reduction in carbon flux, was found under stress: the TCA cycle flux by ~ 44%; the malic enzyme pathway by ~ 80%; the phosphoenolpyruvate carboxylase pathway ~ 60%; the CO2 production rate by 18%; and pyruvate dehydrogenase pathway by ~50%. Meanwhile, a few pathways were activated under C8 stress: the pyruvate dehydrogenase flux (`PoxB') became active; the malate dehydrogenase pathway (`mdh') in TCA cycle increased by ~55%; and the extracellular a…
abstract: Metabolic engineering has evolved to the point of fulfilling the dream of having industrial chemicals produced renewably. Carboxylic acids [e.g., short chain fatty acids (SCFAs) such as octanoic acid (C8)] are such chemical intermediates that can be produced by Escherichia coli engineered with thioesterases specific for short chain fatty acids. However, C8 is toxic to E. coli at concentration greater than 10 mM. To design a better host strain for the production of large amount of SCFAs, 13C metabolic flux analysis of E. coli was performed for both C8 stress and control condition (without C8). To investigate central carbon metabolism for the culture environmental change, a mixture of labeled and unlabeled glucose was used as the sole carbon source for bacterial growth and proteinogenic amino acid isotopomers were measured using two-dimensional (13C, 1H) HSQC NMR spectroscopy. Notable differences of several amino acids isotopomer abundance were observed between the control condition and C8 stress condition, suggesting that the precursor nodes of these amino acids in metabolic pathways were responding to the stress. More specifically, the difference suggested that the distribution of fluxes among the tricarboxylic acid (TCA) cycle, pentose phosphate pathway, pyruvate node, alpha-ketoglutarate node and oxaloacetate node changed. By comparing the metabolic flux maps of E. coli MG1655 grown at different conditions, pathways that have flux change under stress were identified. Inhibition effect for several pathways, resulting in a reduction in carbon flux, was found under stress: the TCA cycle flux by ~ 44%; the malic enzyme pathway by ~ 80%; the phosphoenolpyruvate carboxylase pathway ~ 60%; the CO2 production rate by 18%; and pyruvate dehydrogenase pathway by ~50%. Meanwhile, a few pathways were activated under C8 stress: the pyruvate dehydrogenase flux (`PoxB') became active; the malate dehydrogenase pathway (`mdh') in TCA cycle increased by ~55%; and the extracellular a…
author: Fu, Yanfen
language: en
date published: 2011-01-01
date modified: 2026-07-24T02:38:46Z
provider: Iowa State University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Iowa State University

PropertyValue
property ID: DOI
value: 10.31274/etd-180810-2244