May 9, 2008 -- By decoding the genome of a green fungus with a hunger for fibrous plants, scientists hope to boost the supply of cellulose-based ethanol, leaving more food for consumption and driving down transportation costs.
"People have had the idea for many years to use the inedible portion of food and turn it into fuel," said Diego Martinez, a scientist at Los Alamos National Laboratory and study author.
"Right now it's too pricey," he explained. "We want to bring down that cost."
The high cost of cellulose-based ethanol comes from the expensive enzymes, derived from the fungus Tricoderma reesei, which are used to break down trees, corn stalks, paper, and other wood or pulp-based items.
For years, scientists have tried to economically produce enough enzymes to break cellulose down into simple sugars that can then be fermented into ethanol, but to no avail.
Having the genome of T. reesei "gives you a tool kit with all the tools, where before you were trying to blindly match things up," said Jason Stajich, a researcher at the University of California, Berkeley, and co-author of the blog fungalgenomes.org. Stajich was not involved in the new study.
Now that scientists have all the tools, it will be "easier to tinker with the genetic machinery to make it efficiently produce more enzymes to bring down the cost," said Martinez.
Currently, most bioethanol is made out of sugar derived from corn kernels (at least in the United States) in large bioreactors -- vats filled with microorganisms that convert sugar to fuel.
Turning corn kernels into fuel has several disadvantages, most notably it drives up food prices, thereby weakening the food supply to vulnerable regions.
Whoever cracks the cellulose code stands to circumvent those problems, and make a lot of money, by potentially turning everything from corn stalks, sawgrass, paper, and other cellulose-based items into fuel.
The enzymes produced by T. reesei are most effective at breaking cellulose down, so scientists expected a large portion of the fungus' genome to be devoted to this process.
But the scientists got a surprise: Only about 5 to 6 percent of T. reesei's genome appeared to be involved.
The next step is to figure out how the fungus manages the conversion so efficiently. Understanding the process could help streamline ethanol production.
"It's a really cool mystery," said Stajich.
The research is reported in the current issue of Nature Biotechnology.
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