Method development of flow cytometry analysis of yeast and lactic acid bacteria viability for alcohol fermentation

Abstract: The usage of yeast in conventional brewing techniques involving alcoholic fermentation is an age-old process. Analyzing the viability and obtaining physiological information regarding the microbial diversity of the fermentation samples plays a pivotal role in obtaining real-time information as well as developing a more efficient process design. While traditionally, methods like methylene blue cell staining and/or colony counting techniques provide viability information, their arduous nature and general inconvenience has resulted in the adoption of flow cytometry to not only analyze individual cells but also in-depth cell physiological information in a matter of minutes. The primary focus of this project was to develop a method which utilized flow cytometry to monitor the microbial diversity of the complicated fermentation matrix, in particular the cell concentration and viability of the yeast Saccharomyces cerevisiae and Lacticaseibacillus casei. The developed method offers the quantitative viability analysis of rehydrated freeze-dried yeast and potential lactic acid bacteria present in the fermentation matrix through flow cytometry and better understand the microbial interactions within the fermentation tanks.