Yeast Cell Cycle during Fermentation and Beer Quality

Abstract

The yeast cell cycle is divided into four phases, G0/G1, S, G2, and M. Among them, G1 was thought to be the most important phase for fermentation performance because yeast cells undergo many critical preparations before budding. Therefore, it is advantageous to analyze the biochemical changes in the G1 phase to more precisely control the fermentation performance. However, the intracellular transition of yeast cells during the G1 phase has not been studied in detail because there was no method to simultaneously monitor the DNA and RNA contents in individual yeast cells. To solve this problem, we developed a new method for yeast cells by modifying the DNA/RNA double-staining method used for mammalian cells. DNA and RNA of yeast cells were stained with acridine orange under acidic conditions with ethylenediaminetetraacetic acid. The DNA and RNA contents in the yeast cells were measured using a flow cytometer. With this new method, we detected the amount of variation in the DNA and RNA. During the G1 phase, RNA was synthesized before the DNA synthesis that corresponded to yeast cell budding. The DNA/RNA synthesis during the G1 phase correlated with the fermentation performance and beer quality. It is worth noting that the DNA/RNA synthesis timing before the first budding significantly affects the final beer product quality.