title: Real-time monitoring of cell viability and cell density on the basis of a three dimensional optical reflectance method (3D-ORM): investigation of the effect of sub-lethal and lethal injuries.
abstract: Cell density and cell viability have been followed on-line by using a three-dimensional optical reflectance method (3D-ORM) probe. This method has allowed to highlight the differences between a well-mixed and a scale-down bioreactor configured in order to reproduce mixing deficiencies during a fed-batch culture of Escherichia coli. These differences have been observed both for the obscuration factor (OBF) and the coincidence probability delivered by the probe. These parameters are correlated to flow cytometry measurement based on the PI-uptake test and cell density based on optical density measurement. This first set of results has pointed out the fact that the 3D-ORM probe is sensitive to sub-lethal injuries encountered by microbial cells in process-related conditions. The effect of lethal injuries has been further investigated on the basis of additional experiments involving heat stress and a sharp increase of the OBF has been observed indicating that cells are effectively injured by the increase of temperature. However, further improvement of the probe are needed in order to give access to single-cell measurements.
authors.affiliation: Gembloux Agro-Bio Tech, Unité de Bio-industries/CWBI, Université de Liège, Passage des Déportés 2, 5030 Gembloux, Belgium.
authors.forename: Alison
authors.initials: A
authors.lastname: Brognaux
authors.forename: Jörg
authors.initials: J
authors.lastname: Bugge
authors.forename: Friedel H
authors.initials: FH
authors.lastname: Schwartz
authors.forename: Philippe
authors.initials: P
authors.lastname: Thonart
authors.forename: Samuel
authors.initials: S
authors.lastname: Telek
authors.forename: Frank
authors.initials: F
authors.lastname: Delvigne
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism; D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D002452:Cell Count / Q000379:methods*; D002463:Cell Membrane Permeability; D002470:Cell Survival; D004926:Escherichia coli / Q000166:cytology* / Q000378:metabolism; D005434:Flow Cytometry; D011419:Propidium / Q000032:analysis / Q000378:metabolism; D059010:Single-Cell Analysis
chemical_list: D001426:Bacterial Proteins; D011419:Propidium