Monitoring the Functionality and Stress Response of Yeast Cells Using Flow Cytometry

Abstract

Throughout fermentation, yeast faces continuously changing medium conditions and reacts by adapting its metabolism. The adaptation is a critical process and is dependent on the accurate functioning of the cell. A stable membrane potential, which is, among other roles, responsible for protecting the yeast from low pH, is an important attribute for evaluating functionality. Other factors are storage products such as glycogen, trehalose, and neutral lipids, as well as mitochondrial activity and the integrity of the DNA. These parameters can be complemented by the analysis of viability, cell cycle, intracellular pH, and reactive oxygen species in the cell. The correlation of all these factors provides valuable information for evaluating the performance of a yeast population during fermentation. In order to demonstrate the analytical capabilities of flow cytometry, a Saccharomyces cerevisiae yeast strain was observed in a modified growth medium for 384 h (16 days). The results confirm observations made with other methods and reports from the literature. However, with flow cytometry, it is possible to gain deeper insight into stress response and adaptation behavior of yeast at a cellular level. The causality from the formation of oxygen-radicals to cell death, for example, can be shown, as well as the dependency of the intracellular pH on the stability of the membrane. The proposed bio-monitoring system has the potential to provide applicable information as a process control tool for wineries.

A cytofluorimetric analysis of a Saccharomyces cerevisiae population cultured in a fed-batch bioreactor

“…cerevisiae growth can be efficiently monitored by FCM through the analysis of both the cell size and different cell properties (e.g: viability, vitality, apoptotic index, free radicals production, protein and nucleic acids content). This gives the possibility to correlate cellular attributes to yeast growth performance and predict the overall outcome of the bioprocess of interest [ 20 – 22 ].…”

A cytofluorimetric analysis of aSaccharomyces cerevisiaepopulation cultured in a fed-batch bioreactor

“…It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted February 26, 2021. ; https://doi.org/10.1101/2021.02.26.433019 doi: bioRxiv preprint 3 S. cerevisiae growth can be efficiently monitored by FCM through the analysis of both the cell size and different cell properties (e.g: viability, vitality, apoptotic index, free radicals production, protein and nucleic acids content). This gives the possibility to correlate cellular attributes to yeast growth performance and predict the overall outcome of the bioprocess of interest (20)(21)(22).…”

“…S. cerevisiae growth can be efficiently monitored by FCM through the analysis of both the cell size and different cell properties (e.g: viability, vitality, apoptotic index, free radicals production, protein and nucleic acids content). This gives the possibility to correlate cellular attributes to yeast growth performance and predict the overall outcome of the bioprocess of interest (20–22).…”

Effect of Several Nutrients and Environmental Conditions on Intracellular Melatonin Synthesis in Saccharomyces cerevisiae

“…Several factors, either biotic or abiotic, can affect the yeasts present during alcoholic fermentation, and thus, modify the fermentation performance and the production of bioactive compounds [ 1 , 2 ]. The microbial interactions and responses, such as the synthesis of antimicrobial compounds, competition for nutrients and yeast–yeast cell contact are the main biotic factors [ 3 , 4 ].…”