Two local companies are using genetically engineered microorganisms to convert agricultural waste into ethanol.

Constanza Villalba

During last night’s State of the Union address, President George Bush announced plans to replace 20 percent of the gasoline the country uses with renewable fuels, primarily ethanol. It was the third year in a row he mentioned ethanol is his address, and the second one in which he pointed specifically to ethanol made from wood chips, grasses, and agricultural waste.

The president’s endorsement of ethanol derived from cellulose has fueled intense interest in this renewable energy source. Two Cambridge-based companies, Celunol and Mascoma, are building or expanding their pilot plants in a bid to make it commercially viable.

Ethanol is already being mixed with gasoline to power cars, particularly in Brazil and the midwestern United States. The United States makes about four billion gallons of ethanol a year, mostly by fermenting cornstarch. But critics of corn ethanol say that the harvesting, fertilization, and processing of corn requires almost as much, if not more, energy than the amount produced when burning the ethanol.

One could tip that balance and get more ethanol out of the existing corn crop by breaking down and fermenting the corn stalks and other plant waste material. Some researchers project that this new source of ethanol could more than quadruple the number of gallons produced yearly, replacing about 10 percent of the fossil fuel consumed in the U.S.

The problem is that the production of ethanol from plant waste material—breaking down cellulose and hemicellulose into simpler, fermentable sugars—is costly and technically difficult. Cellulose and hemicellulose are hard to extract. Once extracted, enzymes can convert cellulose into glucose that microbes can easily ferment. But hemicellulose breaks down primarily into xylose, a sugar that traditional fermenting organisms cannot convert to ethanol.

Microbe makeover

To make cellulosic ethanol cost-efficient and competitive with other fuels, manufacturers have to squeeze as much ethanol as possible out of every leaf and stalk. That means finding a way to ferment xylose. For that, Celunol and Mascoma have turned to academic collaborators who engineer microbes to do their bidding.

Celunol is working with Lonnie Ingram, a microbiology professor at the University of Florida, whose lab created a bacterial strain called KO11. While its unengineered predecessor converts xylose into a mixture of acids, alcohol, and gases, KO11 turns xylose into ethanol.

Since November, KO11 and another organism from the Ingram lab have been hard at work at Celunol’s pilot plant in Jennings, LA. The existing facility can make only about 50,000 gallons of ethanol per year, but by the end of this summer, the company hopes to be producing about 1.5 million gallons a year. That’s still not commercial scale, but it will give the company a chance to test its technology further.

Mascoma is also engineering organisms to ferment xylose. But Lee Lynd, chief scientific officer of Mascoma and an engineering professor at Dartmouth College, says Mascoma sees a much larger payoff from developing organisms that can ferment cellulose without the need for enzymes. That way, he says, they can reduce the number of steps in the process, making it more efficient and less costly.

Michael Ladisch, director of the Laboratory of Renewable Resources Engineering at Purdue University, says it may be five to 10 years before such a do-it-all organism can be optimized for use in an industry setting.

Since its founding in 2005, Mascoma has secured $39 million in funding and an additional $14.8 million to build a pilot facility in Rochester, NY. The company hopes to begin construction this year.

The two companies also face a leading competitor. A Canadian company called Iogen has been operating a precommercial plant since 2004.