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

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 E. coli. These differences have been observed both for the obscuration factor (OBF) and the coincidence probability (COP) 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

Analytics in Microfluidic Systems

Viefhues M. Analytics in Microfluidic Systems. In: Advances in Biochemical Engineering/Biotechnology. Berlin ; Heidelberg: Springer ; 2020.Microfluidic analysis proved to be very sufficient in supporting biotechnological studies. This is due to the wide range of new analysis methods that provide further insight into biotechnological questions but also to intrinsic advantages of the systems themselves. To name two of them, only very small sample amounts are needed, and the analytics are very fast. In this overview paper, microfluidic analysis methods are introduced with a special focus on electric analysis methods. The aim of this work is to shed light on the special advantages of miniaturized electrical analysis in microfluidics; the main theoretical aspects of the methods are given together with the potential scientific insight that can be gained by the respective methods