Cell density is one of the most important monitoring parameters in biotechnology. Until today, this parameter is mostly monitored off line or at best at line; sampling is necessary in both cases. Furthermore, such methods do not allow for continuous measurements.
Group of Prof. Wiedemann
Process-monitoring via in situ microscopy
Advantageous for many applications e.g. with respect to process understanding, PAT etc. would be methods that work a) non invasively, b) automated, c) in situ inside the bioreactor and provide a continuous data stream or at least good statistics. In situ microscopy is such a method. Very few functional and readily usable in situ microscopic systems exist worldwide, technically most advanced – at least in our opinion – is the one developed at the Mannheim University of Applied Sciences (Prof. Dr. Hajo Suhr; see also inftech.hs-mannheim.de.)
Cell density and -viability determination of animal cells via in situ microscopy (Partners Mannheim University of Applied Sciences, University of Lille, InVivo Biotech Services, Berlin, and others)
We use a high resolution, sterilisable, mechanically robust in situ microscope with no moving parts and without electronic components within the bioreactor. It is inserted through a standard 25 mm Ingold port; most of its components (camera etc.) can be exchanged during a process if necessary.
The system enables determination of the total cell density (TCD) of animal cells in moving suspensions (e.g. hybridoma, Jurkat, CHO). Substantially more challenging is the determination of the viable cell density (VCD) through intelligent image analysis and without the use of markers / dyes. We repeatedly showed that this is possible (see under publications). Current work looks at simplification of optomechanical components enabling routine application in the field and also at improving viability determination.
In situ microscopy in yeast (S. cerevisiae; cooperation with Universidade Federal de São Carlos / Brazil)
Yeast cells can readily be counted via in situ microscopy but are difficult candidates for subsequent morphological and/or viability assessment. This is due to their comparatively poor display of visible morphological characteristics. Predominant aim of this work is the monitoring of yeast driven fermentation processes for bioethanol production.
Quality control of Erythrocytes (Cooperation with University of Heidelberg, DRK Blutspendedienst Institut Mannheim, KIT)
Erythrozytes are stored in the form of concentrates for several weeks in blood banks. During this time, storage lesions occur on a biochemical and morphological level. Measuring the degree of haemolysis is the gold standard method for routine assessment of such changes. We investigate if an adaptation of in situ microscopy, termed Flow Morphometry, could be of advantage for red blood cell quality control or diagnostic purposes.
In situ microscopy in wastewater treatment (Cooperation with University Duisburg-Essen, Currenta GmbH & Co. OHG, INEOS Cologne GmbH)
Activated sludge processes play an important role in wastewater treatment. Such processes treat organic pollutants by means of microorganisms. Foam development can be problematic in these operations; predominant cause of foam development are filamentous microorganisms. In this project, we investigate in situ microscopy with respect to monitoring of these filamentous microorganisms in wastewater treatment plants.
Further work in the area of in situ microscopy aims at monitoring of aggregates during the expansion of stem cells (cooperation with University of Würzburg)