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2 results on '"Ellen Van Horen"'

1. Dynamic Metabolic Flux Analysis Demonstrated on Cultures Where the Limiting Substrate Is Changed from Carbon to Nitrogen and Vice Versa

Author

Ellen Van Horen, Erick Vandamme, Jo Maertens, Wim Soetaert, Gaspard Lequeux, Joeri Beauprez, and Peter A. Vanrolleghem

Subjects
Work (thermodynamics), Time Factors, Article Subject, Nitrogen, Health, Toxicology and Mutagenesis, Lag, lcsh:Biotechnology, Cell Culture Techniques, chemistry.chemical_element, lcsh:Medicine, Biology, lcsh:Chemical technology, lcsh:Technology, Substrate Specificity, chemistry.chemical_compound, Adenosine Triphosphate, Oxygen Consumption, Phase (matter), Metabolic flux analysis, lcsh:TP248.13-248.65, Genetics, Escherichia coli, lcsh:TP1-1185, Biomass, Molecular Biology, lcsh:T, Hydrolysis, lcsh:R, Substrate (chemistry), General Medicine, Carbon Dioxide, Carbon, Biochemistry, chemistry, Carbon dioxide, Molecular Medicine, Biological system, Flux (metabolism), Metabolic Networks and Pathways, Biotechnology, Research Article
Abstract

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 onEscherichia colicultivations 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.

Published
2010

2. Comparison of Different Strategies to Reduce Acetate Formation in Escherichia coli.

Author

Marjan De Mey, Gaspard J. Lequeux, Joeri J. Beauprez, Jo Maertens, Ellen Van Horen, Wim K. Soetaert, Peter A. Vanrolleghem, and Erick J. Vandamme

Subjects
ACETATES, ESCHERICHIA coli, GENE expression, RECOMBINANT proteins
Abstract

E. colicells produce acetate as an extracellular coproduct of aerobic cultures. Acetate is undesirable because it retards growth and inhibits protein formation. Most process designs or genetic modifications to minimize acetate formation aim at balancing growth rate and oxygen consumption. In this research, three genetic approaches to reduce acetate formation were investigated:  (1) direct reduction of the carbon flow to acetate (ackA-pta, poxBknock-out); (2) anticipation on the underlying metabolic and regulatory mechanisms that lead to acetate (constitutive ppcexpression mutant); and (3) both (1) and (2). Initially, these mutants were compared to the wild-type E. colivia batch cultures under aerobic conditions. Subsequently, these mutants were further characterized using metabolic flux analysis on continuous cultures. It is concluded that a combination of directly reducing the carbon flow to acetate and anticipating on the underlying metabolic and regulatory mechanism that lead to acetate, is the most promising approach to overcome acetate formation and improve recombinant protein production. These genetic modifications have no significant influence on the metabolism when growing the micro-organisms under steady state at relatively low dilution rates (less than 0.4 h-1). [ABSTRACT FROM AUTHOR]

Published
2007

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