Protective Role of Reserved Carbohydrates and Glutathione in Yeast Pachysolen tannophilus under Ethanol-induced Stress

Yeast cells constantly sense and adapt to various types of stress by manipulating their reserved carbohydrates and glutathione amounts. The induction of oxidative stress has been reported under several physiological conditions as well as industrial conditions such as fermentation for ethanol production. Therefore, values of trehalose, a common marker of general physiological stress, glutathione, a redox buffer, and oxidized products of both lipids and proteins were examined in exponentially growing Pachysolen tannophilus cells after exposure to ethanol (10%, vol/vol) . The cell viability decreased dramatically under ethanol stress. An increase in trehalose content and a decrease in reduced/oxidized glutathione ratio was observed after exposure of the yeast cells to ethanol. These findings suggest the protective roles of trehalose and glutathione in the pentose-utilizing yeast P. tannophilus . The increased levels of protein carbonyls and lipid-oxidized products suggest the involvement of oxidative stress due to the toxicity of ethanol.