Article (Scientific journals)
Bioreactor mixing efficiency modulates the activity of a prpoS::gfp reporter gene in E. coli
Delvigne, Frank; Boxus, Mathieu; Ingels, Sophie et al.
2009In Microbial Cell Factories, 8 (15)
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Keywords :
scale-down; recombinant protein; stress
Abstract :
[en] ABSTRACT: BACKGROUND: Extensive studies have shown that up-scaling of bioprocesses has a significant impact on the physiology of the microorganisms. Among the factors associated with the fluid dynamics of the bioreactor, concentration gradients induced by loss of the global mixing efficiency associated with the increasing scale is the main phenomena leading to strong physiological modifications at the level of the microbial population. These changes are not fully understood since they involve complex physiological mechanisms. In this work, we intend to investigate, at the single cell level, the expression of the rpoS gene associated with the stress response of E. coli. The cultures of the reporter strain have been performed in a small scale reactor as well as in a series of scaled-down bioreactors able to induce extracellular perturbations with increasing level of magnitude. RESULTS: The rpoS level has been monitored by the aim of a transcriptional reporter gene based on the synthesis of the green fluorescent protein (GFP). It has been observed that the level of GFP increases during the transition from batch to fed-batch phase. After this initial increase, the GFP content of the cell drops, primarily due to the dilution by cell division. However, a significant drop of the GFP content has been observed if using a partitioned bioreactor, for which the mixing conditions are very bad, leading to the exposure of the cells to cyclic and stochastic extracellular fluctuations. If considering the flow cytometric profile of the cell to cell GFP content, this drop has to be attributed to the appearance of segregation at the level of the GFP content among the microbial population. CONCLUSION: The generation of extracellular perturbations (in the present case, at the level of the sugar concentration and the dissolved oxygen level) has led to a drop at the level of the rpoS expression level. This drop has to be attributed to a segregation phenomenon in microbial population, with a major sub-population exhibiting a low expression level and a minor sub-population keeping its initial elevated expression level. The intensity of the segregation, as well as its time of appearance during the culture can be related to the bioreactor mixing efficiency.
Disciplines :
Biotechnology
Author, co-author :
Delvigne, Frank  ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech
Boxus, Mathieu ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech
Ingels, Sophie
Thonart, Philippe ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech - Biochimie et microbiologie industrielles
Language :
English
Title :
Bioreactor mixing efficiency modulates the activity of a prpoS::gfp reporter gene in E. coli
Publication date :
2009
Journal title :
Microbial Cell Factories
eISSN :
1475-2859
Publisher :
BioMed Central
Volume :
8
Issue :
15
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 17 September 2009

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