Abstract
BackgroundEscherichia coli has emerged as a promising platform microorganism to produce biofuels and fine chemicals of industrial interests. Certain obstacles however remain to be overcome, among which organic-solvent tolerance is a crucial one.ResultsWe used global transcription machinery engineering (gTME) to improve the organic-solvent tolerance (OST) of E. coli JM109. A mutant library of σ70 encoded by rpoD was screened under cyclohexane pressure. E. coli JM109 strain harboring σ70 mutant C9 was identified with capability of tolerating 69 % cyclohexane. The rpoD mutant contains three amino-acid substitutes and a stop-codon mutation, resulting a truncated sequence containing regions σ1.1 and σ1.2. Total protein difference produced by E. coli JM109 strain harboring C9 was examined with 2D-PAGE, and 204 high-abundant proteins showed over twofold variation under different solvent stress.ConclusionsOur results show that several genes (gapA, sdhB, pepB and dppA) play critical roles in enhanced solvent tolerance of E. coli, mainly involving in maintaining higher intracellular energy level under solvent stress. Global transcription machinery engineering is therefore a feasible and efficient approach for engineering strain with enhanced OST-phenotype.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0368-4) contains supplementary material, which is available to authorized users.
Highlights
Escherichia coli has emerged as a promising platform microorganism to produce biofuels and fine chemicals of industrial interests
It is of great importance to develop organic-solvent tolerant (OST) E. coli strains for industrial applications
We evaluated the efficacy of global transcription machinery engineering (gTME) in E. coli by screening rpoD mutant library under cyclohexane pressure
Summary
Escherichia coli has emerged as a promising platform microorganism to produce biofuels and fine chemicals of industrial interests. Certain obstacles remain to be overcome, among which organic-solvent tolerance is a crucial one. Escherichia coli as one of the most important platform microorganisms, could be applied as a whole-cell biocatalyst, which provides safe intracellular environment for enzymes [2]. In whole-cell biocatalysis, nonaqueous system (such as organic solvents) is often adopted to facilitate the solubility of hydrophobic substrates and (or) products [3]. Organic solvents are toxic to most microorganisms. E. coli was reported to barely tolerate organic solvents with LogP values lower than. Toluene is toxic to E. coli cells even at concentrations as low as 0.1 % [5]. It is of great importance to develop organic-solvent tolerant (OST) E. coli strains for industrial applications
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