title: Studies on substrate utilisation in L-valine-producing Corynebacterium glutamicum strains deficient in pyruvate dehydrogenase complex.
abstract: The pyruvate dehydrogenase complex was deleted to increase precursor availability in Corynebacterium glutamicum strains overproducing L: -valine. The resulting auxotrophy is treated by adding acetate in addition glucose for growth, resulting in the puzzling fact of gluconeogenic growth with strongly reduced glucose uptake in the presence of acetate in the medium. This result was proven by intracellular metabolite analysis and labelling experiments. To increase productivity, the SugR protein involved in negative regulation of the phosphotransferase system, was inactivated, resulting in enhanced consumption of glucose. However, the surplus in substrate uptake was not converted to L-valine; instead, the formation of up to 289 microM xylulose was observed for the first time in C. glutamicum. As an alternative to the genetic engineering solution, a straightforward process engineering approach is proposed. Acetate limitation resulted in a more efficient use of acetate as cosubstrate, shown by an increased biomass yield Y(X/Ac) and improved L-valine formation.
authors.affiliation: Institute of Biotechnology 2, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bartek
authors.forename: Christiane
authors.initials: C
authors.lastname: Rudolf
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kerssen
authors.forename: Bianca
authors.initials: B
authors.lastname: Klein
authors.forename: Bastian
authors.initials: B
authors.lastname: Blombach
authors.forename: Siegmund
authors.initials: S
authors.lastname: Lang
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
authors.forename: Marco
authors.initials: M
authors.lastname: Oldiges
mesh_terms: D003352:Corynebacterium / Q000145:classification* / Q000378:metabolism*; D024861:Genetic Enhancement / Q000379:methods*; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D014633:Valine / Q000096:biosynthesis*
chemical_list: D011768:Pyruvate Dehydrogenase Complex; D014633:Valine