The aim of this master thesis is to test whether flow cytometry can replace established methods for monitoring the kinetics of alcoholic fermentation in winemaking. We monitored alcoholic fermentation by the release of CO2 in pure and mixed cultures of indogenous strains and commercial strains in sterile YM medium, white must and red broth. At selected time points during the process, we took samples and checked the population composition of yeasts and viability by plating on WL medium, by flow cytometry and by automated counting under the microscope. Using flow cytometry and by indirect determination of colony units on agar plates, we checked the correlation between the results of yeast concentration measurements. After alcoholic fermentation, we performed an analysis of physicochemical parameters using enzyme assays. Alcoholic fermentation with a commercial strain was the fastest and the wine had the highest content of desirable yeast cell products. Live cell concentrations were comparable for all three methods at the beginning of alcoholic fermentation and differed more towards the end of the process, which can be attributed to the different proportions of dead cells in the different methods. We have confirmed that flow cytometry is a faster and more accurate method than conventional methods as it also detects VBNC cells. Yeast Brettanomyces bruxellensis is a known wine spoilage that is difficult or costly to detect by conventional method. At elevated concentrations, the yeast forms an undesirable 4-ethylphenol that gives it its characteristic Brett aroma. Through experimental work, we have demonstrated that flow cytometry is a faster, more accurate, more robust and specific method for detecting Brettanomyces yeast cells compared to a conventional method.
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