Team develops ethanol technique

by Jay Webster | 10/10/10 10:00pm

Researchers in the Thayer School of Engineering have developed a more efficient way of chemically changing plant cellulose into ethanol to be used as fuel, according to Dan Olson '04 Th'06, who led the research team. The new technology will also reduce costs in ethanol fuel production, which will decrease reliance on fossil fuels, according to a Thayer press release.

In a recent article published in the Proceedings of the National Academy of Sciences, Olson and the research team with which he worked described recent advances they have made toward the more efficient mode of ethanol production.

Currently, ethanol is produced by using a "mixture of individual enzymes," Olson said in an interview with The Dartmouth.

"First enzyme A will come in and make a cut, and then a little while later enzyme B will come in and make another cut and then randomly a little later enzyme C will come in," Olson said.

Olson and his research team, on the other hand, have discovered that a particular bacterium Clostridium thermocellum can simultaneously break down all of the bonds that must be broken to convert cellulose into ethanol, rather than waiting for each individual enzyme in the mixture to function, Olson said.

"What I'm looking at is instead of three enzymes that are all floating around, we can use bacteria in nature who are very good at this," he said.

The researchers, who carried out the project in conjunction with Thayer professor Lee Lynd, found that C. thermocellum has a gene that makes it especially efficient at breaking down plant cellulose, according to the press release.

In its most recent research, the team completed an experiment to test the effects of blocking one of the bacterium's enzyme mechanisms, according to the PNAS article. Researchers created a mutant strain of bacteria that had been altered to prevent the production of the enzyme Cel48S, which is one of the enzymes produced most abundantly by the bacteria, in order to test the enzyme's role in processing cellulose.

In the enzyme's absence, the bacteria were still able to break down cellulose, although they did so at a slower rate, according to the article. This led the team to speculate that Cel48S's role is to regulate the process of ethanol production. Determining how the other enzymes are involved in processing cellulose is a "promising direction for future work," according to the paper.

The use of a single bacterium as opposed to a combination of three enzymes will ultimately make the new method of ethanol production more cost-effective than previous technology, according to the press release.

Despite the research's progress, Olson said his project is still in the discovery stages.

"Once the exploratory stage of the research is complete, the goal is to start building cellulosome," he said.

Cellulosome is a structure naturally found in some bacteria that is composed of multiple enzymes, according to the press release.

"[C. thermocellum's] cellulosome is an order of magnitude more efficient at breaking down cellulose than current enzyme technology," the press release stated.

Although Olson's background was in physics and mechanical engineering, he said he became interested in renewable energy while a student at Thayer.

"One day, walking through the halls of Thayer, I came across a newspaper clipping on the wall which was about the research that Lee Lynd was doing," Olson said.

Prior to taking a class with Lynd, Olson said he did not have a background in biology. He said he became interested in researching renewable energy through his connection with Lynd.

In 2005, Lynd founded the Mascoma Corporation, a company devoted to researching and creating cellulosic ethanol, with Thayer professor Charles Wyman, according to the company's website. Olson initially began his research with C. thermocellum while working on researchwith Mascoma, he said.

Olson said it was ethanol's potential as a possible substitute for traditional energy sources that led to his involvement in the project.

"Professor Lynd convinced me that if you want to make a big impact on renewable energy, you need to choose a technology so it can be scaled up and up," Olson said. "It turns out that cellulose, which is plant fibers and woodchips, is abundant all over the globe."

Last year, the United States produced more than 10.6 billion gallons of ethanol to be used for fuel, according to a Renewable Fuels Association press release.

The majority of the funding for the project, which began in December 2008, comes from a U.S. Department of Energy grant, according to Olson.