Enhancing n -Butanol Tolerance of Escherichia coli by Overexpressing of Stress-Responsive Molecular Chaperones
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Enhancing n-Butanol Tolerance of Escherichia coli by Overexpressing of Stress-Responsive Molecular Chaperones Guochao Xu 1 & Lin Xiao 1 & Anning Wu 1 & Ruizhi Han 1 & Ye Ni 1 Received: 26 February 2020 / Accepted: 23 June 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Microbial tolerance to organic solvents is critical for efficient production of biofuels. In this study, n-butanol tolerance of Escherichia coli JM109 was improved by overexpressing of genes encoding stress-responsive small RNA-regulator, RNA chaperone, and molecular chaperone. Gene rpoS, coding for sigma S subunit of RNA polymerase, was the most efficient in improving n-butanol tolerance of E. coli. The highest OD600 and the specific growth rate of JM109/pQE80L-rpoS reached 1.692 and 0.144 h–1 respectively at 1.0% (v/v) n-butanol. Double and triple expression of molecular chaperones rpoS, secB, and groS were conducted and optimized. Recombinant strains JM109/pQE80L-secBrpoS and JM109/pQE80L-groS-secB-rpoS exhibited the highest n-butanol tolerance, with specific growth rates of 0.164 and 0.165 h–1, respectively. Membrane integrity, potentials, and cell morphology analyses demonstrated the high viability of JM109/pQE80L-groSsecB-rpoS. This study provides guidance on employing various molecular chaperones for enhancing the tolerance of E. coli against n-butanol. Keywords Molecular chaperone . n-Butanol tolerance . Escherichia coli . RpoS . Coexpression
Introduction Biofuels are promising alternatives for traditional fossil fuels [1]. Especially, biobutanol (n-butanol), a clear and neutral C4 primary alcohol with low viscous, has many attractive features as a biofuel. In addition, biobutanol could be more compatible with the traditional fossil fuels than ethanol, etc. [2, 3]. Escherichia coli Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12010-02003417-4) contains supplementary material, which is available to authorized users.
* Ye Ni [email protected]
1
The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
Applied Biochemistry and Biotechnology
is generally accepted as a platform microorganism for producing valuable biofuels [4, 5]. Enormous efforts have been committed to design and develop novel pathways, circuits, modules, and synthetic genes for enhanced productivity [6–8]. Nevertheless, severe toxicity of the biofuel products (such as ethanol, n-butanol) is one serious limitation for the application of E. coli in biofuels production. It was reported that the growth of E. coli could be significantly influenced under merely 1.0% (v/v) n-butanol [9]. To achieve the production of biobutanol at high titers, process engineering and host engineering are two alternative and effective strategies. Process engineering, such as membrane separation, adsorption gas, and extraction of newly produced n-butanol is passive method to alleviate n-butanol toxicity [10, 11]. However, ho
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