Biofuels may soon be produced quickly, efficiently, and at a cost comparable to gasoline thanks to a discovery from researchers at the Great Lakes Bioenergy Research Center. The research team has identified several genes that improve yeast’s ability to digest the natural sugar xylose. This means that it will soon be possible to efficiently produce bio-ethanol from cellulosic biomass–waste matter such as the stalks, leaves, and husks of plants, wood chips, sawdust, and dead trees–as opposed to land-intensive crops like corn. The unlikely source of the genes: fungus living symbiotically with bark beetles.
Cellulosic materials cost about half as much as corn per ton, but are historically more difficult than corn to convert to ethanol. Current strains of yeast used industrially for the purpose of converting cellulosic biomass to ethanol have difficulty fermenting the plant sugar xylose, and can do so only after all glucose is exhausted. As xylose makes up nearly half of all available plant sugars, this marks a great loss in ethanol yield.
The team chose bark beetles on account of their woody, xylose-rich habitat. By comparing the sequencing of two xylose-fermenting fungi that live alongside the beetles–Spathaspora passalidarum and Candida tenuis–the researchers was able to identify several genes that effectively increase fermentation of the sugar.
Ethanol can be used as a fuel for cars, but is usually used as a gasoline additive to increase octane and improve vehicle emissions. Production of corn-based ethanol in the United States is just over three billion gallons per year. While biodiesel offers a fossil energy ratio of 5.54 to 1, there is still apprehension about its production and use. These concerns are linked to increased food prices because of the large amount of arable land required for crops as well as the energy-intensive production process (especially corn-based fuels). With available US cropland diminishing, the ability to convert woodier waste will be an important factor in keeping bio-ethanol part of the alternative fuels discussion.
As bark beetles and their related fungi are devastating forests from the northern Rockies to the Czech Republic, it’s nice to know they may provide some great ecological benefit alongside the destruction.
Article by Allison Leahy, appearing courtesy Earth & Industry.