Abstract

Yeasts used in fermentation processes are subject to different stress conditions, including low pH, high initial substrate concentration, accumulation of toxic compounds (e.g. ethanol), and temperature fluctuations. The fermentation of mescal is conducted under variable environmental conditions throughout the year. One of the most important environmental factors is temperature, as autumn and winter fermentations occur at low temperatures, but fermentation temperatures are much higher in summertime. The aim of this work was to compare the response of Saccharomyces cerevisiae strains isolated from agave fermentations to different stress conditions and two different medium culture one mimicking mezcal production, using agave must and other synthetic must development for analysis in wine industry. The strains isolated from agave were compared with a commercial strain used in wine elaboration, which exhibits good tolerance to the different stresses found in industrial fermentations. All strains grew in the presence of glucose and fructose irrespective of the sugar concentration, and low pH did not affect the formation of colonies. Differences in growth were observed among the strains at low temperature and high concentrations of ethanol. Only 28% of the tested strains exhibited good tolerance to high ethanol concentrations, a desirable trait for avoiding stuck fermentations. The strain ITD00185 was able to grow in alcoholic stress condition, consuming sugar and producing ethanol in agave must. This strain shows tolerance to the different stress conditions and may be a useful starter culture for agave fermentation, the potential of the native strains to be used to improve other industrial fermentation processes that involve low temperatures and high ethanol yields.

Key words: Ethanol, tolerance, Mescal, native strains.