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Applied and Environmental Microbiology, May 2009, p. 2784-2791, Vol. 75, No. 9
0099-2240/09/$08.00+0 doi:10.1128/AEM.02713-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands,1 TNO-Quality of Life, Business Unit Food and Biotechnology Innovations, Julianalaan 67, 2628 BC Delft, The Netherlands,2 B-Basic, Julianalaan 67, 2628 BC Delft, The Netherlands,3 Kluyver Centre for Genomics of Industrial Fermentation, P.O. Box 5057, 2600 GA Delft, The Netherlands4
Received 26 November 2008/ Accepted 28 February 2009
The oxidative D-xylose catabolic pathway of Caulobacter crescentus, encoded by the xylXABCD operon, was expressed in the gram-negative bacterium Pseudomonas putida S12. This engineered transformant strain was able to grow on D-xylose as a sole carbon source with a biomass yield of 53% (based on g [dry weight] g D-xylose–1) and a maximum growth rate of 0.21 h–1. Remarkably, most of the genes of the xylXABCD operon appeared to be dispensable for growth on D-xylose. Only the xylD gene, encoding D-xylonate dehydratase, proved to be essential for establishing an oxidative D-xylose catabolic pathway in P. putida S12. The growth performance on D-xylose was, however, greatly improved by coexpression of xylXA, encoding 2-keto-3-deoxy-D-xylonate dehydratase and
-ketoglutaric semialdehyde dehydrogenase, respectively. The endogenous periplasmic glucose dehydrogenase (Gcd) of P. putida S12 was found to play a key role in efficient oxidative D-xylose utilization. Gcd activity not only contributes to D-xylose oxidation but also prevents the intracellular accumulation of toxic catabolic intermediates which delays or even eliminates growth on D-xylose.
Published ahead of print on 6 March 2009.
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