Researchers identify genes in yeast that increase ethanol tolerance; may boost cellulosic ethanol production
Research published in the journal Genetics identifies new genes that improve ethanol tolerance in yeast cells, with the goal of generating higher ethanol concentrations for biofuel production. Industrial stresses, including ethanol stress, limit microbial fermentation and hinder cost-competitiveness with fossil fuels. Improved ethanol tolerance, for example, allows yeast to produce more ethanol from the same amount of nutrients.
This study shows how genetically altered yeast cells survive higher ethanol concentrations, addressing a bottleneck in the production of ethanol from cellulosic material in quantities that could make it economically competitive with fossil fuels.
Our hope is that this research will take us closer to the goal of producing cheap, efficient, and environmentally friendly cellulosic ethanol. At the same time, we’ve learned a lot about how cells respond to alcohol stress. So the project has been very productive from multiple angles.—Audrey P. Gasch, Ph.D., Assistant Professor of Genetics, University of Wisconsin-Madison
To make this discovery, scientists turned to nature, studying how natural strains of the yeast Saccharomyces cerevisiae respond to ethanol treatment. They concluded that many wild strains of yeast respond to ethanol much differently than do traditional laboratory strains. When these wild yeast cells were treated with a low dose of ethanol, they mounted a response to become super-tolerant to high doses.
By comparing and contrasting strains with different responses to ethanol, the researchers were able to quickly identify the specific genes responsible for the increased ethanol tolerance. They identified all genes in the yeast genome whose expression was affected when cells responded to ethanol. Comparing the responses of wild strains and a laboratory strain pointed the researchers to genes involved in high ethanol tolerance. The researchers were able to coax super ethanol tolerance in the laboratory strain by increasing expression of these genes.
We used this information to identify genes required for acquisition of ethanol tolerance in wild strains, including new genes and processes not previously linked to ethanol tolerance, and four genes that increase ethanol tolerance when overexpressed. Our approach shows that comparative genomics across natural isolates can quickly identify genes for industrial engineering while expanding our understanding of natural diversity.—Lewis et al.
Jeffrey A. Lewis, Isaac M. Elkon, Mick A. McGee, Alan J. Higbee, and Audrey P. Gasch (2010) Exploiting natural variation in Saccharomyces cerevisiae to identify genes for increased ethanol resistance. Genetics, Vol. 186, 1197-1205, doi: 10.1534/genetics.110.121871