title: Metabolic flux analysis using stoichiometric models for Aspergillus niger: comparison under glucoamylase-producing and non-producing conditions.
abstract: Aspergillus niger AB1.13 cultures with glucoamylase production (with D-glucose as substrate) and without glucoamylase production (with D-xylose as substrate) were characterized by metabolic flux analysis. Two comprehensive metabolic models for d-glucose- as well as for D-xylose-consumption were used to quantify and compare the metabolic fluxes through the central pathways of carbon metabolism at different pH-values. The models consist of the most relevant metabolic pathways for A. niger including glycolysis, pentose-phosphate pathway, citrate cycle, energy metabolism and anaplerotic reactions comprising two intracellular compartments, the cytoplasm and mitochondrion. When D-xylose was used as the sole carbon source, the relative flux of the substrate through the oxidative pentose-phosphate pathway (PPP) via G6P-dehydrogenase was unaffected by the pH-value of the culture medium. About 30% of D-xylose consumed was routed through the oxidative PPP. In contrast, the flux of D-glucose (i.e., under glucoamylase-producing conditions) through the oxidative PPP was remarkably higher and, in addition was significantly affected by the pH-value of the culture medium (40% at pH 5.5, 56% at pH 3.7, respectively). Summarizing, the flux through the PPP under glucoamylase producing conditions was 30-90% higher than for non-producing conditions.
authors.affiliation: Institute of Biochemical Engineering, Technische Universität Braunschweig, Gaussstr. 17, 38106 Braunschweig, Germany. ibvt@tu-bs.de
authors.forename: Guido
authors.initials: G
authors.lastname: Melzer
authors.forename: Alex
authors.initials: A
authors.lastname: Dalpiaz
authors.forename: Andreas
authors.initials: A
authors.lastname: Grote
authors.forename: Martin
authors.initials: M
authors.lastname: Kucklick
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Göcke
authors.forename: Rochus
authors.initials: R
authors.lastname: Jonas
authors.forename: Petra
authors.initials: P
authors.lastname: Dersch
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Franco-Lara
authors.forename: Bernd
authors.initials: B
authors.lastname: Nörtemann
authors.forename: Dietmar C
authors.initials: DC
authors.lastname: Hempel
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology*; D005087:Glucan 1,4-alpha-Glucosidase / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D008954:Models, Biological; D008956:Models, Chemical; D010427:Pentose Phosphate Pathway / Q000502:physiology; D013379:Substrate Specificity; D014994:Xylose / Q000378:metabolism*
chemical_list: D014994:Xylose; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose