Analysis The Mechanism Of Ethanol Tolerance Based On The Differences Of Parental Strain And Ethanol Adapted Strains Of Saccharomyces Cerevisiae

Energy crisis and environmental problems promote the need for alternative renewable energy sources. As a kind of clean and renewable biofuel, bioethanol is a good substitute for traditional fossil fuels, which will help alleviate the problem of environmental pollution and energy crisis. The method of fermentation is widely used in the production of bioethanol. Saccharomyces cerevisiae is the most widely used microbe for industrial ethanol production. However, in the fermentation process, the Saccharomyces cerevisiae cells are often stressed by a variety of environmental factors, such as high temperature, oxidation and the accumulation of ethanol et al. Such stresses can affect cell viability and the final ethanol productivity, and even can cause cell death. Among environmental challengers, the accumulation of ethanol which is fermentation product is the main inhibitor to the integrity of fermentation and ethanol productivity. In response to various environmental stresses, microorganisms including Saccharomyces cerevisiae has evolved a series of mechanisms to deal with environmental perturbations. Understanding the tolerance of Saccharomyces cerevisiae cells in the presence of ethanol, especially in high concentrations of ethanol, contributes to establishing the ethanol yield strainsThe article chose the parental strain, M5which is tolerant of5%ethanol and M10which is tolerant of10%ethanol as the research object. This research which consists of three aspects is concentrating on studying the tolerance mechanism of adapted strains, including ethanol metabolism, the relationship of membrane lipid changes and the tolerance of ethanol, and genomics analyzes of intracellular metabolites.Compared with the parental strain, adapted strains has obvious advantages in the growth rate, survival and production of ethanol, showing superior growth traits. Analysis of the expression of21genes associated with the metabolism of ethanol, in adapted strains EMP enhanced, increasing the fermentation characteristics; TCA cycle enhanced,meaning higher energy productivity which meets the demand of EMP increasing energy consume, consistent with high ethanol tolerance Ethanol adapted strains at a10%ethanol have higher content of ergosterol, trehalose and fatty acid production.These indicate changes in adapted strains membrane and related components, altering membrane fluidity, for the purpose of resisting the stress of ethanol. In the10%ethanol, ethanol adapted strains have a lower rate of cell disruption, demonstrating that the cells has high integrity and the tolerance to10%ethanol is stronger than the original strain.Using the method of metabolomics to analysis the metabolites of cells, comparing to the7control groups of metabolites with significant differences in the comparison, the results showed that compared with the parental strain, the acid metabolites in ethanol adapted strains have significant differences. In addition to acids, in the presence of ethanol, the strains with higher ethanol tolerance seems have more differences in the intracellular carbohydrate metabolites This suggests that ethanol stress can affect the metabolism of cell acids, and high concentration of ethanol have a certain impact on the metabolism of carbohydrate.