A team of researchers made a discovery that could prove important for producing large quantities of cellulosic ethanol.
Researchers from Dartmouth's Thayer School of Engineering and Mascoma Corporation in Lebanon, N.H., have, for the first time, genetically engineered bacteria to produce ethanol more efficiently from inedible cellulosic biomass, including wood, grass, and various waste materials.
Naturally occurring bacteria require lower temperature and an expensive enzyme called cellulase to produce ethanol, said Lee Lynd, who is a Dartmouth College professore and an author of the study.
The newly engineered bacterium, known as ALK2, can ferment all the sugars present in biomass and can do it at 122 degrees F (50 degrees C), compared with conventional microbes that cannot function above 98.6 degrees F (37 degrees C).
At higher temperatures, the fermentation process required two and a half times less cellulase in one controlled experiment, Lynd said in a telephone interview.
Lynd explains that this discovery is only the first step, a proof of concept, for future development of ethanol-producing microbes that can make ethanol from cellulosic biomass without adding enzymes. Lynd is the corresponding author on the study and the chief scientific officer and co-founder of Mascoma Corporation, a company working to develop processes to make cellulosic ethanol.
All of the ethanol currently used in this country as an additive to gasoline comes from corn. However, it is widely recognized that cellulosic biomass has significant advantages over corn as a raw material for ethanol production, provided that a cost-effective technology for converting cellulosic materials can be developed.
There are several features that make cellulosic ethanol attractive. The raw material, cellulosic biomass, is available on a large scale, does not include food crops, and is cost-competitive with petroleum on both an energy and a mass basis.
The technology to convert cellulosic biomass to ethanol is steadily improving, and it also has the potential to be cost-competitive with gasoline production. Environmental benefits include a sustainable carbon cycle with near-zero net greenhouse gas emissions, because the carbon dioxide captured growing the biomass roughly equals what is emitted while running an engine. In addition, ethanol has excellent performance and compatibility with existing internal combustion engines as well as fuel cell-powered vehicles of the future.
Innovative technology for ethanol production from cellulosic raw materials has been a central focus of Lynd's, who won the inaugural Lemelson-MIT Sustainability Award in 2007, a top honor for inventors.
"I'm not sure if it was a good or a bad sign that I knew alternative energy would be so important today when I started this work 30 years ago," says Lynd. "At that time, tools of molecular biology were in a nascent state of development. Now we can make much faster progress, and I anticipate more exciting advances soon."
Other authors on this study include: A. Joe Shaw, the lead author on the paper, Kara Podkaminer, Sunil Desai, and Stephen Rogers with the Thayer School; and John Bardsley, Philip Thorne, and David Hogsett with Mascoma Corporation.