Butanol, Ethanol from Cellulose--Better Cellulases Needed

Corn (maize) ethanol just is not going to work. Despite the efforts of big agricultural interests to promote corn ethanol, the economics simply does not work. But cellulosic butanol/ethanol could easily work, if the right cellulases are found--to break down cellulose into simple fermentable sugars.

A critical step in producing cellulosic ethanol involves breaking down a plant's cell wall material and fermenting the sugars that are released. Current technologies use microbial enzymes called "cellulases" to digest the cellulose in grasses and such rapidly growing trees as poplars. The microbial enzymes have a structure that makes them very efficient at binding to and digesting plant cell wall material called lignocellulose (a combination of lignin and cellulose).

But now, a new class of plant enzymes with a similar structure has been discovered, potentially offering researchers new properties for producing ethanol even more efficiently.

"The bottleneck for conversion of lignocellulose into ethanol is efficient cellulose degradation," said Jocelyn Rose, Cornell assistant professor of plant biology. "The discovery of these enzymes suggests there might be sets of new plant enzymes to improve the efficiency of cellulose degradation."

The paper appears in the April 20 issue of the Journal of Biological Chemistry. Breeanna Urbanowicz, a graduate student in Rose's laboratory, was the paper's lead author.

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Here is another approach from UCSD:

To help unlock the cellulose bottleneck, a team of scientists has conducted molecular simulations at the San Diego Supercomputer Center (SDSC), based at UC San Diego. By using “virtual molecules,” they have discovered key steps in the intricate dance in which the enzyme acts as a molecular machine -- attaching to bundles of cellulose, pulling up a single strand of sugar, and putting it onto a molecular conveyor belt where it is chopped into smaller sugar pieces.

“By learning how the cellulase enzyme complex breaks down cellulose we can develop protein engineering strategies to speed up this key reaction,” said Mike Cleary, who is coordinating SDSC’s role in the project. “This is important in making ethanol from plant biomass a realistic ‘carbon neutral’ alternative to the fossil petroleum used today for transportation fuels.”

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This field is receiving large infusions of cash, due to the huge potential payoff if biofuels can displace a significant quantity of fossil fuels, in western transportation.