Salvation Through Fermentation
Yeasts are single-celled organisms whose voracious appetite for sugar serves us well. For more than 10,000 years, humans have harnessed the fermentative power of yeast to create beer, wine, cheese and bread. But yeasts are also critical to the process of generating other important products, including medicines such as penicillin and biofuels such as ethanol.
Genetically closer to animals than plants, yeasts are living microorganisms that feed on sugar. When yeasts metabolize sugar, they convert it into other compounds. In the case of biofuels, yeasts convert the simple sugars found in plant biomass into ethanol, isobutanol, or other specialty fuels. The efficiency with which a yeast species converts sugar affects the yield of any fermented food or fuel product. As such, yeast performance can be the deciding factor in whether or not a particular product is economically viable. Corn-based ethanol, which is developed by combining a high-efficiency yeast with sugar-rich corn, is one example of a popular product that offers a high return on investment (though, corn production is also heavily subsidized by the U.S. government). Currently, as much as 97 percent of gasoline sold in the U.S. contains ethanol.
Producing economically viable biofuels from biomass other than corn, however, is more complicated. Many biofuels researchers, including those at the Great Lakes Bioenergy Research Center based at the University of Wisconsin-Madison, are now focused on making biofuels from low-input crops such as switchgrass and poplar. These dedicated bioenergy crops, no portion of which are used for food, avoid the conflicts that arise from growing food crops to produce fuel.
Although not yet a market force, cellulosic biofuels, or fuels made from grasses and wood, are routinely factored into future climate mitigation scenarios because of their potential to displace petroleum use and mitigate greenhouse gas emissions. Dedicated bioenergy crops can also be grown on non-agricultural land, require less fertilizer than annual crops such as corn, and boost biodiversity. Ultimately, the Center’s researchers hope to find ways of growing sustainable biomass and converting it to biofuels and bio-products that provide cost-competitive alternatives to petroleum-derived fuels and chemicals.
Getting there, however, will depend on a number of scientific advancements, including finding new ways to harness the power and potential of yeast.