In situ dark field microscopy for on-line monitoring of yeast cultures
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A new-type in situ probe has been developed to acquire dark field images of yeast in bioreactors. It has been derived from an in situ bright field microscope that is able to measure cell density in bioreactors during fermentation processes. The illumination part of the probe has been replaced with a dark field device, in which an aspheric condenser is used, so that high contrast dark field images can be obtained. The technique of second imaging is implemented to improve the sharpness of the images by means of a relay lens. This new in situ probe is expected to enable the evaluation of the cell viability without staining owing to modern image processing.
KeywordsDark field microscopy Aspheric lens Fermentation Yeast Cell density Biomass Viability
The authors thank Thomas Scheper, Technical Chemistry Institute (Institut für Technische Chemie) of Hannover University, Germany for providing the prototype of the probe, including the mechanical parts, software for controlling the electro-mechanical elements. Gratitude is also shown to the Graduate College of Bioinformatics (Graduiertenkolleg Bioinformatik) of Bielefeld University and German Research Foundation (Deutsche Forschungsgemeinschaft) for funding this project.
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