title: Green fluorescent protein (GFP) leakage from microbial biosensors provides useful information for the evaluation of the scale-down effect.
abstract: Mixing deficiencies can be potentially detected by the use of a dedicated whole cell microbial biosensor. In this work, a csiE promoter induced under carbon-limited conditions was involved in the elaboration of such biosensor. The cisE biosensor exhibited interesting response after up and down-shift of the dilution rate in chemostat mode. Glucose limitation was accompanied by green fluorescent protein (GFP) leakage to the extracellular medium. In order to test the responsiveness of microbial biosensors to substrate fluctuations in large-scale, a scale-down reactor (SDR) experiment was performed. The glucose fluctuations were characterized at the single cell level and tend to decrease the induction of GFP. Simulations run on the basis of a stochastic hydrodynamic model have shown the variability and the frequencies at which biosensors are exposed to glucose gradient in the SDR. GFP leakage was observed to a great extent in the case of a culture operated in well-mixed fed-batch mode, by comparison with those operated in SDR. GFP leakage seems to be correlated to a higher membrane permeability, confirming previous studies highlighting a better cell viability in cultures operated in a fluctuating environment. Our results suggest that GFP leakage could be used in parallel to the normal GFP biosensor function in order to assess microbial viability in process conditions.
authors.affiliation: Université de Liège, Gembloux Agro-Bio Tech, Unité de Bio-industries/CWBI, Gembloux, Belgium. F.Delvigne@ulg.ac.be
authors.forename: Frank
authors.initials: F
authors.lastname: Delvigne
authors.forename: Alison
authors.initials: A
authors.lastname: Brognaux
authors.forename: Frédéric
authors.initials: F
authors.lastname: Francis
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Twizere
authors.forename: Nathalie
authors.initials: N
authors.lastname: Gorret
authors.forename: Soren J
authors.initials: SJ
authors.lastname: Sorensen
authors.forename: Philippe
authors.initials: P
authors.lastname: Thonart
mesh_terms: D019149:Bioreactors; D015374:Biosensing Techniques; D002463:Cell Membrane Permeability; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000172:deficiency; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000378:metabolism*; D057446:Hydrodynamics; D007218:Industrial Microbiology; D008956:Models, Chemical; D059010:Single-Cell Analysis / Q000379:methods; D013269:Stochastic Processes
chemical_list: D003470:Culture Media; D049452:Green Fluorescent Proteins; D005947:Glucose