Effect of Fermentation Temperature and Culture Medium on Glycerol and Ethanol during Wine Fermentation

Abstract

Yeast strain BH8, which exhibited significant differences from nine other yeast strains studied for glycerol production, was selected to investigate the effect of fermentation temperature (13 and 25°C) and culture medium (synthetic medium and grape must) on fermentation kinetics, yeast growth, and glycerol and ethanol synthesis at three different stages of wine fermentation. Yeast viability was better at 13°C than at 25°C in both growth media, and the more complex grape must enabled yeast cells to reach a higher population density. The accumulation of glycerol, glycerol-3-phosphate dehydrogenase (GPD) activity, and the level of expression of the GPD1 gene were highest in the initial stages of fermentation, which potentially counteracted the hyperosmotic stress caused by the high concentration of sugar in the media. More glycerol was produced during fermentation at 25°C than at 13°C and in grape must compared to the synthetic medium at both temperatures. Ethanol production was mainly affected by fermentation temperature. More ethanol was produced at 13°C than at 25°C, with lower expression of the ADH1 gene and level of ADH activity. The expression of the HSP104 and ALD6 genes was induced by ethanol stress in the final stages of fermentation. The amount of glycerol produced was not correlated to the production of acetic or succinic acid.