Abstract
Electrochemical impedance spectroscopy is a powerful tool in life science for cell and pathogen detection, as well as for cell counting. The measurement principles and techniques using impedance spectroscopy are highly diverse. Differences can be found in used frequency range (β or α regime), analyzed quantities, like charge transfer resistance, dielectric permittivity of double layer capacitance and in off- or online usage. In recent contributions, applications of low-frequency impedance spectroscopy in the α regime were tested for determination of cell counts and metabolic burden in Escherichia coli and Saccharomyces cerevisiae. The established easy to use methods showed reasonable potential in the lab scale, especially for S. cerevisiae. However, until now, measurements for cell counts in food science are generally based on Thoma cell counting chambers. These microscopic cell counting methods decelerate an easy and quick prediction of yeast viability, as they are labor intensive and result in a time delayed response signal. In this contribution we tested our developed method using low frequency impedance spectroscopy locally at an industrial brewery propagation site and compared results to classic cell counting procedures.
Highlights
Cultivation technology using microorganisms, like bacteria and yeasts, is applied in pharmaceutical technology, and in branches like food and bulk chemical production and highly emerging in waste-to-value concepts [1]
As control and analytical tools aiming for biomass determination are often cost intensive, they are used for high value products like in the pharmaceutical biotech, by default
As process analytics in Stiegl brewery rely on cell counting methods, we evaluated our cell numbers in the broth using flow cytometry as explained in the material part
Summary
Cultivation technology using microorganisms, like bacteria and yeasts, is applied in pharmaceutical technology, and in branches like food and bulk chemical production and highly emerging in waste-to-value concepts [1]. For these systems complex raw material—like molasses or sulfur spent liquor—are used as they are considered as waste and low in price These materials have the further drawback that no accurate determination of biomass using offline and online methods is possible anymore, since the media is optical dense and has a high number of particles inside [2]. The use of accurate and reliable biomass measurement systems [3,4], especially of viable cell concentrations (VCCs), would enable proper process control tools This would enhance the robustness of the bioprocess and reduce the batch to batch variations. Many biosensors use a change of an electrical signal for analysis Many applications in this branch use impedance spectroscopy or cyclovoltammetry for detection of low amounts of a target proteins, cells, virus, etc. Application of the system for cell number even in industrial-scale applications
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