March 14, 2007

Yeast research may boost ethanol production

by K.C. Jaehnig

CARBONDALE, Ill. — With a bit of tweaking, the kind of yeast brewers use to give beer its buzz could boost America's ethanol production.

"Yeast is a very easy organism to play with," said Ahmad M. Fakhoury, a plant pathologist at Southern Illinois University Carbondale interested in fungal genetics and the industrial applications of microbes.

"We have a lot of ways to manipulate the genes, to control things in the organism, because a lot is known about its biology and the things that regulate different mechanisms in it."

Beer and ethanol don't differ that much in the way they're made. Both result from fermentation — the process yeast uses to turn plant sugars into alcohol. Because yeast plays such a key role in the brewing business, brewers have developed several strains especially for making beer. These yeasts tolerate the high concentrations of alcohol, the high temperatures and the fairly acidic environment of the fermenting equipment better than the strains used for, say, baking bread.

But while these yeasts can produce more than enough beer, they can't generate enough ethanol to meet the expected growth in demand. High alcohol levels and acidity both decrease yeast's fermentation.

"There's a point where the yeast says, 'Too much ethanol — I won't produce any more,'" Fakhoury said.

"It doesn't want to waste energy producing more than it needs, so it slows or stops production."

As for acidity, brewers rely on it to kill bacteria that produce toxins that kill yeast.

"You can add antibiotics to kill the bacteria, but that's expensive and may add to the antibiotic load if you use the corn left after fermentation as livestock feed," Fakhoury said.

To a fungal geneticist, the solution is obvious: Develop a new, improved strain of yeast that keeps going and going and going no matter how much alcohol or acid it encounters. A two-year, $40,000 grant from the Illinois Council on Food and Agricultural Research is allowing Fakhoury to try to do just that. Because he works on the molecular level, he can do it more quickly than can brewers, who must rely on natural selection over generations of yeast strains.

"We already have a few 'mutants' that seem to be more tolerant (of acid)," Fakhoury said.

"The next step is to work with the National Corn to Ethanol Research Center in Edwardsville to see how they perform fermentation-wise."

Fakhoury hopes results from this preliminary study will prove compelling enough to win support for further research from federal agencies interested in alternative fuels.

"We are now so dependent on oil and fossil fuels, it affects every aspect of our lives," Fakhoury said.

"People have this mindset that there's nothing we can do about it, but there are options, and now there seems to be the political will to come up with solutions. The changeover may not be that difficult."