Metabolic flux analysis using stoichiometric models for Aspergillus niger: comparison under glucoamylase-producing and non-producing conditions.
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.
Melzer
Guido
G
Institute of Biochemical Engineering, Technische Universität Braunschweig, Gaussstr. 17, 38106 Braunschweig, Germany. ibvt@tu-bs.de
Dalpiaz
Alex
A
Grote
Andreas
A
Kucklick
Martin
M
Göcke
Yvonne
Y
Jonas
Rochus
R
Dersch
Petra
P
Franco-Lara
Ezequiel
E
Nörtemann
Bernd
B
Hempel
Dietmar C
DC
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*
D014994:Xylose; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose