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Resting cells of recombinant E. coli show high epoxidation yields on energy source and high sensitivity to product inhibition

Authors

  • Mattijs K. Julsing,

    1. Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Strasse 66, 44227 Dortmund, Germany; telephone: +49-231-755-7384; fax: +49-231-755-7382
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  • Daniel Kuhn,

    1. Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Strasse 66, 44227 Dortmund, Germany; telephone: +49-231-755-7384; fax: +49-231-755-7382
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  • Andreas Schmid,

    1. Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Strasse 66, 44227 Dortmund, Germany; telephone: +49-231-755-7384; fax: +49-231-755-7382
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  • Bruno Bühler

    Corresponding author
    1. Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Strasse 66, 44227 Dortmund, Germany; telephone: +49-231-755-7384; fax: +49-231-755-7382
    • Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Strasse 66, 44227 Dortmund, Germany; telephone: +49-231-755-7384; fax: +49-231-755-7382.
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Abstract

Metabolically active resting (i.e., nongrowing) bacterial cells have a high potential in cofactor-dependent redox biotransformations. Where growing cells require carbon and energy for biomass production, resting cells can potentially exploit their metabolism more efficiently for redox biocatalysis allowing higher specific activities and product yields on energy source. Here, the potential of resting recombinant E. coli containing the styrene monooxygenase StyAB was investigated for enantioselective styrene epoxidation in a two-liquid phase setup. Resting cells indeed showed twofold higher specific activities as compared to growing cells in a similar setup. However, product formation rates decreased steadily resulting in lower final product concentrations. The low intrinsic stability of the reductase component StyB was found to limit overall biocatalyst stability. Such limitation by enzyme stability was overcome by increasing intracellular StyB levels. Beyond that, product inhibition was identified as a limiting factor, whereas complete toxification of the bacterial cells, as it was observed with growing cells, and deactivation of the multicomponent enzyme system did not occur. The resting cell setup allowed high product yields on glucose of more than 5 mol molmath image, which makes the use of resting cells a promising approach for ecologically as well as economically sustainable oxygenase-based whole-cell biocatalysis. Biotechnol. Bioeng. 2012; 109:1109–1119. © 2011 Wiley Periodicals, Inc.

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