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Applied Microbiology and Biotechnology

, Volume 45, Issue 5, pp 612–620 | Cite as

Engineering the homoserine dehydrogenase and threonine dehydratase control points to analyse flux towards L-isoleucine in Corynebacterium glutamicum

  • S. Morbach
  • R. Kelle
  • S. Winkels
  • H. Sahm
  • L. Eggeling
ORIGINAL PAPER

Abstract

 The synthesis of L-isoleucine by Corynebacterium glutamicum involves 11 reaction steps, with at least 5 of them regulated in activity or expression. Using gene replacement we constructed a vector-free C. glutamicum strain having feedback-resistant aspartate kinase and feedback-resistant homoserine dehydrogenase activity. Isogenic strains carrying in addition one or several copies of feedback-resistant threonine dehydratase were made and their product accumulations compared. With strain SM1, with high threonine dehydratase activity, accumulation of 50 mM L-isoleucine was achieved, whereas with the parent strain only 4 mM L-isoleucine was obtained. Applying a closed-loop control fed-batch strategy to strain SM1 a final titre of 138 mM L-isoleucine was achieved with an integral molar yield of 0.11 mol/mol, and a maximal specific productivity of 0.28 mmol (g h)-1. This shows that high L-isoleucine yields can be obtained in the presence of one copy of feedback-resistant homoserine dehydrogenase by applying the appropriate fermentation strategy. In addition, the specific profiles of 2-oxoglutarate and pyruvate accumulation during fermentation revealed a major transition of the metabolism of C. glutamicum during the fermentation process.

Keywords

Fermentation Corynebacterium Glutamicum Molar Yield Final Titre Isogenic Strain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1996

Authors and Affiliations

  • S. Morbach
    • 1
  • R. Kelle
    • 1
  • S. Winkels
    • 1
  • H. Sahm
    • 1
  • L. Eggeling
    • 1
  1. 1.Institut für Biotechnologie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany. Fax: +49 2461 61 2710DE

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