The Role Of ROS In Ethanol Stress Of Saccharoniyccs Cerevisiae

Saccharomyces cerevisiae is a strain used to produce ethanol and is applied in the production of ethanol fuel and brewing industry. Saccharomyces cerevisiae is a tranditional yield ethanol strain, but is sensitive to the high concent of ethanol. Excessive accumulation of enthanol could inhibit the growth and activity of cells, induce reactive oxygen species, thereby lead to a damage to yeast cells. Autophagy is an important degradation pathway for maintaining the balance and matter cycle in eukaryotic cells. Although we have a certain amiynt research on ethanol stress, the mechanism of ethanol stress in Saccharomyces cerevisiae, which ROS plays a leading role under ethanol stress, whether autophagy is involved in ethanol strees and what role autophagy has in ethanol. The above problems are not yet clear.To understand which ROS has an important role in ethanol stress, Saccharomyces cerevisiae from Angel Yeast was as the experimental material in this work, we studied the effect of reactive oxygen species (ROS) on Saccharomyces cerevisiae growth and fermentation under ethanol stress, through detecting physiological indicatiors including cell growth, the membrane integrity, superoxide anion(O2·-) conctent, hydrogen peroxide (H2O2)content, malondialdehyde(MDA), carbonyl content and so on. The result showed that ethanol could inhibit the growth of yeast cells in the logarithmic phase, damage the membrance integrity, rise the levels of O2·-and H2O2, increase the content of MDA (the product of Lipid peroxide). We used exogenous Glutathione (GSH), Methionine (Met) and N-acetylcysteine (NAC) treated ethanol stressed Sacchayomycescerevisiae respectively, and found that they could reduced the level O2·-and H2O2, increased cells activity and decreased the concent of MDA. This indicates tha ethanol couldinduce the generation of O2·-and H2O2, leding to the oxidative stress, resulting in the damage to yeast cells. When the growth inhibited serious, ethanol even could lead to the death. GSH and Met, NAC could clear the excess of ROS, reduce the yeast damage caused by ethanol stress and improve the ethanol yield.In order to understand whether autophagy was involved in the ethanol stress in the S. cerevisiae as well as it was related with ROS, we used3-MA (autophagy inhibitor) and rapamycin (autophagy inducer) to treat ethanol-stressed Saccharomyces cerevisiae, the membrane integrity was by PI staining, the level of O2·-and H2O2was detected by ROS fluorescent probe DHE and DCFH-DA staining. The results showed that3-MA could reduce the inhibition of ethanol on yeast cells, improve the membane integrity, reduce the levels of O2·-and H2O2. But rapamycin could further deepen the colony inhibition, reduce the membrane integrity, improve the levels of O2·-and H2O2. This indicates that autophagy involves in Saccharomyces cerevisiae ethanol stress by regulating the level of ROS, and plays a role of maintaining cell survival in ethanol-stressed Saccharomyces cerevisiae.