Abstract
The AcrAB-TolC efflux pump is involved in the organic solvent tolerance of Escherichia coli. Most E. coli strains are highly sensitive to organic solvents such as n-hexane and cyclohexane. Here, a recombinant E. coli transformed with an expression plasmid containing acrAB and tolC became tolerant to n-hexane and cyclohexane. The levels of AcrA, AcrB, and TolC in the recombinant increased by 3- to 5-fold compared to those in the control strain without the plasmid for acrAB or tolC. To investigate the usability of the recombinant as a biocatalyst in an aqueous-organic solvent two-phase system, we further introduced xylMA xylene monooxygenase genes from Pseudomonas putida mt-2 into the recombinant and examined the production of styrene oxide from styrene. The resulting recombinant produced 1.8 mg and 1.0 mg styrene oxide mL-1 of medium in a medium overlaid with a 25% volume of n-hexane and cyclohexane containing 10% (wt vol-1) styrene, respectively.
Keywords:
Escherichia coli; AcrAB-TolC efflux pump; Organic solvent; styrene; styrene oxide.
MeSH terms
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Bacterial Outer Membrane Proteins / genetics
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Bacterial Outer Membrane Proteins / metabolism*
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Biocatalysis / drug effects
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cyclohexanes / metabolism*
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Cyclohexanes / pharmacology
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Epoxy Compounds / metabolism*
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Escherichia coli / genetics*
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Escherichia coli / metabolism*
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Escherichia coli Proteins / genetics
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Escherichia coli Proteins / metabolism*
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Hexanes / metabolism*
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Hexanes / pharmacology
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Lipoproteins / genetics
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Lipoproteins / metabolism*
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Membrane Transport Proteins / genetics
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Membrane Transport Proteins / metabolism*
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Multidrug Resistance-Associated Proteins / genetics
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Multidrug Resistance-Associated Proteins / metabolism*
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Oxygenases / genetics
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Plasmids / genetics
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Pseudomonas putida / enzymology
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Pseudomonas putida / genetics
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Solvents / metabolism*
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Solvents / pharmacology
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Styrene / metabolism*
Substances
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AcrA protein, E coli
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AcrAB-TolC protein, E coli
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AcrB protein, E coli
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Bacterial Outer Membrane Proteins
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Carrier Proteins
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Cyclohexanes
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Epoxy Compounds
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Escherichia coli Proteins
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Hexanes
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Lipoproteins
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Membrane Transport Proteins
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Multidrug Resistance-Associated Proteins
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Solvents
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tolC protein, E coli
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n-hexane
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Styrene
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Cyclohexane
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styrene oxide
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Oxygenases
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xylene monooxygenase