In their recent study Vees et al. (2020), developed a robust CytoSense based method to analyze yeast cells viability and morphology in media with a high particle background (Fig 1). The method was successfully employed as a monitoring tool in fermentation processes of S. cerevisiae in spent sulfite liquor*. The analysis of cell viability is very important for industrial processes where microorganisms are used. A CytoSense in combination with fluorescent viability staining has already shown its potential in previous studies by Veiter & Herwig (2019) and Doppler et al. (2020). More importantly, the data produced by a CytoSense provides an insight into physiology and morphology which is not accessible through common online and offline biomass monitoring methods. Thus, Vees et al. developed a CytoSense based method capable of:
(i) yeast cell quantification against medium background
(ii) determination of yeast viability
(iii) assessment of yeast physiology through morphological analysis of the budding division process.
The method was specifically tailored to measurements in a complex medium with a high particle background. This presents a fast and potent alternative to conventional offline measurements like dry cell weight and optical density which cannot distinguish between viable cells and media background. Additionally, enhanced insight into yeast physiology is generated through the simultaneous use of fluorescent viability staining and morphological assessment: information on overall viability, size distribution of media background and/or yeast cells can be obtained through one single measurement.For more information about the study, click on the following link.
The at-line monitoring method is possible to turn into an ďonlineĒ application through combination with automated sampling and processing. For this purpose, sampling, dilution, and addition of fluorescent dyes need to be performed in a modular process analytical (PAT) system connected with the flow cytometer. For more information on PAT systems and how to combine them with CytoSense, please contact CytoBuoy!
*Spent sulfite liquor is a by‐product obtained in the process of dissolving pulp by the acid sulfite method.The main components present in the spent liquor are sugars, which are used in fermentation for the production of yeast or alcohol.