Gaseous environments modify physiology in the brewing yeast Saccharomyces cerevisiae during batch alcoholic fermentation.

AIMS: To investigate the impact of different gaseous atmospheres on different physiological parameters in the brewing yeast Saccharomyces cerevisiae BRAS291 during batch fermentation. METHODS AND
RESULTS: Yeasts were cultivated on a defined medium with a continuous sparging of hydrogen, helium and oxygen or without gas, permitting to obtain three values of external redox. High differences were observed concerning viable cell number, size and metabolites produced during the cultures. The ethanol yields were diminished whereas glycerol, succinate, acetoin, acetate and acetaldehyde yields were enhanced significantly. Moreover, we observed major changes in the intracellular NADH/NAD(+) and GSH/GSSG ratio.
CONCLUSIONS: The use of gas led to drastic changes in the cell size, primary energy metabolism and internal redox balance and E(h). These changes were different depending on the gas applied throughout the culture. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, our study describes the influence of various gases on the physiology of the brewing yeast S. cerevisiae. These influences concern mainly yeast growth, cell structure, carbon and redox metabolisms. This work may have important implications in alcohol-related industries, where different strategies are currently developed to control better the production of metabolites with a particular attention to glycerol and ethanol.