Energy Efficiency

Bacterium Boosts Ethanol Prospects

Microbe requires far lower level of enzymes to convert cellulosic materials.

As the chemical industry increasingly focuses on the use of renewable feedstocks, production of ethanol from sources such as agricultural wastes, grasses and wood is attracting particular attention ( see the October 2008 Cover story: After all, such cellulosic ethanol avoids concerns about redirecting food crops such as corn to chemicals production and also promises to lower costs. A thermophilic bacterium that converts such materials into ethanol without any detectable organic byproducts may play an important role, hope a team of researchers at Dartmouth College, Hanover, N.H., and Mascoma Corp., Lebanon, N.H.

“In the near term, the thermophilic bacterium we have developed is advantageous because the costly cellulase enzymes typically used for ethanol production can be augmented with the less expensive, genetically engineered new organism,” notes Lee R. Lynd, a professor of environmental engineering design at Dartmouth.
Lee Lynd is part of researcher group that engineered bacterium that enhances production of cellulosic ethanol.
Source: Joseph Mehling, Dartmouth College.

The researchers developed an anerobic bacterium, called ALK2, that works at 50°C to 55°C, versus 32°C to 37°C for conventional ethanol-producing microbes, says Lynd. Because of this, ALK2 requires much less cellulase (a 2.5-fold lower level under test conditions) than the conventional microbes but maintains comparable, near theoretical yield of ethanol, he explains. “Both of these advantages contribute to potentially lower processing costs than can be obtained with conventional biological processes,” adds Jim Flatt, senior vice president of R&D at Mascoma.

Tests have been run over the past two years in test tubes and 1-L. fermentors. The bacterium converted more than 99% of xylose and provided a mean yield of 0.46 g. ethanol/g. xylose, with no deterioration in yield over hundreds of generations in continuous culture. (Further details appear in the September 16 issue of the Proceedings of the National Academy of Science.)

The next step, says Lynd, is to “show the efficacy with real-world substrates in conditions representative of an industrial environment.” He is confident about the prospects.

Mascoma expects to begin pilot-scale trials of an ALK2-based process in 2009, notes Flatt. “In the best case scenario, the ALK2 bacterium would be used commercially beginning in 2012,” he adds. Mascoma will offer the bacterium as part of an overall process package.

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