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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. A recombinant Escherichia coli with enhanced AcrAB-TolC efflux pump level increased production of styrene oxide from styrene in an aqueous-organic solvent two-phase system. [ABSTRACT FROM AUTHOR]