Trehalose—A Stress Protectant and Stress Indicator Compound for Yeast Exposed to Adverse Conditions

Abstract

Changes in environmental conditions such as temperature, aeration, nutrient type and availability, and metabolite concentrations can significantly affect yeast performance during fermentation. Alterations in such factors serve to either exert or alleviate stress, thus affecting the overall stress response of the cells. This stress response causes significant changes in the cellular composition that may either directly or indirectly impact on fermentative performance. The effects of various environmental stresses on the cellular composition of the brewing yeast strain, Saccharomyces cerevisiae var. uvarum (AJL 2036), in growing and non-growing states were evaluated. Trehalose was observed to be a very sensitive and responsive compound to stress conditions. All of the stresses applied to the cells evoked a notable response in cellular trehalose content. This response altered depending on the cell growth phase and was related to the sensitivity of the cells to stress. Trehalose was found to be either hydrolyzed and presumably acting as a carbon source or synthesized and accumulated likely to function as a membrane stabilizer and protectant. The cellular trehalose content could be used as a stress indicator compound in this brewing yeast strain. Carbonation was evaluated to induce a stress response in non-growing yeast, indicating that the alleviation of dissolved CO2 in yeast handling is beneficial to cell vitality. The cellular protein content was also observed to possibly have a role in the stress response and tolerance of brewing yeast, particularly in the case of actively growing yeast where stress application led to large changes in the protein content of the cells. The glycogen content decreased in stressed yeast, presumably as it was used for metabolic energy to fuel the stress response.