title: Chemostat cultivation and transcriptional analyses of Clostridium acetobutylicum mutants with defects in the acid and acetone biosynthetic pathways.
abstract: Clostridium acetobutylicum is a model organism for the biotechnologically important acetone-butanol-ethanol (ABE) fermentation. With the objective to rationally develop strains with improved butanol production, detailed insights into the physiological and genetic mechanisms of solvent production are required. Therefore, pH-controlled phosphate-limited chemostat cultivation and DNA microarray technology were employed for an in-depth analysis of knockout mutants with defects in the central fermentative metabolism. The set of studied mutants included strains with inactivated phosphotransacetylase (pta), phosphotransbutyrylase (ptb), and acetoacetate decarboxylase (adc) encoding genes, as well as an adc/pta double knockout mutant. A comprehensive physiological characterization of the mutants was performed by continuous cultivation, allowing for a well-defined separation of acidogenic and solventogenic growth, combined with the advantage of the high reproducibility of steady-state conditions. The ptb-negative strain C. acetobutylicum ptb::int(87) exhibited the most striking metabolite profile: Sizable amounts of butanol (29 ± 1.3 mM) were already produced during acidogenic growth. The product patterns of the mutants as well as accompanying transcriptomic data are presented and discussed.
authors.affiliation: Lehrstuhl für Mikrobiologie, Technische Universität München, Emil-Ramann Straße 4, 85354, Freising, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hönicke
authors.forename: Tina
authors.initials: T
authors.lastname: Lütke-Eversloh
authors.forename: Ziyong
authors.initials: Z
authors.lastname: Liu
authors.forename: Dörte
authors.initials: D
authors.lastname: Lehmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Liebl
authors.forename: Armin
authors.initials: A
authors.lastname: Ehrenreich
mesh_terms: D000096:Acetone / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000235:genetics*; D000440:Butanols / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000172:deficiency; D002264:Carboxylic Acids / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000235:genetics* / Q000254:growth & development*; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D010709:Phosphate Acetyltransferase / Q000172:deficiency
chemical_list: D000440:Butanols; D002264:Carboxylic Acids; D000096:Acetone; D010709:Phosphate Acetyltransferase; D002262:Carboxy-Lyases; C023743:acetoacetate decarboxylase