Abstract
BackgroundEscherichia coli has been explored as a platform host strain for biofuels production such as butanol. However, the severe toxicity of butanol is considered to be one major limitation for butanol production from E. coli. The goal of this study is therefore to construct butanol-tolerant E. coli strains and clarify the tolerance mechanisms.ResultsA recombinant E. coli strain harboring σ70 mutation capable of tolerating 2 % (v/v) butanol was isolated by the global transcription machinery engineering (gTME) approach. DNA microarrays were employed to assess the transcriptome profile of butanol-tolerant strain B8. Compared with the wild-type strain, 329 differentially expressed genes (197 up-regulated and 132 down-regulated) (p < 0.05; FC ≥ 2) were identified. These genes are involved in carbohydrate metabolism, energy metabolism, two-component signal transduction system, oxidative stress response, lipid and cell envelope biogenesis and efflux pump.ConclusionsSeveral membrane-related proteins were proved to be involved in butanol tolerance of E. coli. Two down-regulated genes, yibT and yghW, were identified to be capable of affecting butanol tolerance by regulating membrane fatty acid composition. Another down-regulated gene ybjC encodes a predicted inner membrane protein. In addition, a number of up-regulated genes, such as gcl and glcF, contribute to supplement metabolic intermediates for glyoxylate and TCA cycles to enhance energy supply. Our results could serve as a practical strategy for the construction of platform E. coli strains as biofuel producer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0527-9) contains supplementary material, which is available to authorized users.
Highlights
Escherichia coli has been explored as a platform host strain for biofuels production such as butanol
Several transcription factors, including sigma factor, CRP, Spt15, H-NS and Hha, have been successfully engineered to improve organic solvent tolerance of various microbial strains [12,13,14,15]. σ70 is a subunit of RNA polymerase encoded by rpoD, which regulates over 1000 genes in E. coli
Our findings suggest that the butanol tolerance mechanism of △yghW and △yibT are related to membrane fatty acid composition
Summary
Escherichia coli has been explored as a platform host strain for biofuels production such as butanol. Results: A recombinant E. coli strain harboring σ70 mutation capable of tolerating 2 % (v/v) butanol was isolated by the global transcription machinery engineering (gTME) approach. Escherichia coli, as an important platform microorganism, has been widely engineered as an alternative host for the production of. Most industrial biofuel-producing strains were obtained through solvent stress adaptation, genetic and metabolic engineering and traditional mutagenesis [6,7,8,9]. Global transcription machinery engineering (gTME) emerged as a promising strategy and has been widely used to evolve the desired phenotypes in recent years [10, 11]. Our group previously isolated an E. coli harboring σ70 mutant C9, which could grow in the presence of 69 % (v/v) of cyclohexane [19]
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