Dynamic metabolic flux analysis demonstrated on cultures where the limiting substrate is changed from carbon to nitrogen and vice versa.
The main requirement for metabolic flux analysis (MFA) is that the cells are in a pseudo-steady state, that there is no accumulation or depletion of intracellular metabolites. In the past, the applications of MFA were limited to the analysis of continuous cultures. This contribution introduces the concept of dynamic MFA and extends MFA so that it is applicable to transient cultures. Time series of concentration measurements are transformed into flux values. This transformation involves differentiation, which typically increases the noisiness of the data. Therefore, a noise-reducing step is needed. In this work, polynomial smoothing was used. As a test case, dynamic MFA is applied on Escherichia coli cultivations shifting from carbon limitation to nitrogen limitation and vice versa. After switching the limiting substrate from N to C, a lag phase was observed accompanied with an increase in maintenance energy requirement. This lag phase did not occur in the C- to N-limitation case.
Lequeux
Gaspard
G
Department of Applied Mathematics, Biometrics and Process Control, Ghent University, Coupure Links 653, 9000 Gent, Belgium. gaspard.lequeux@biomath.ugent.be
Beauprez
Joeri
J
Maertens
Jo
J
Van Horen
Ellen
E
Soetaert
Wim
W
Vandamme
Erick
E
Vanrolleghem
Peter A
PA
D000255:Adenosine Triphosphate / Q000378:metabolism; D018533:Biomass; D002244:Carbon / Q000378:metabolism / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods*; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D006868:Hydrolysis / Q000187:drug effects; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D009584:Nitrogen / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D013379:Substrate Specificity / Q000187:drug effects; D013997:Time Factors
D002245:Carbon Dioxide; D002244:Carbon; D000255:Adenosine Triphosphate; D009584:Nitrogen
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