Lee Lynd, an environmental engineer at Dartmouth, says the concept of engineering sugar-fermenting microbes so they’ll also produce enzymes “is widely regarded as the most promising approach” for converting cellulosic materials into ethanol. Many researchers are working on consolidating ethanol processing steps, he says, and some have achieved better results in some parts of the process. But Lynd says this is the first time, as far as he knows, that someone has cloned these transporters.
“These advances are relevant, demonstrate in principle the promise of engineering microbes for improved biomass processing, and could be applied commercially,” Lynd says. “However, the advances are not enabling by themselves, and represent a relatively early step on a long path.”
The technique doesn’t address much of the processing involved in ethanol production. Ethanol makers would still need to use enzymes to break the cellulose down to an intermediate stage called cellodextrin. But the yeast can work with this, instead of waiting for it to be broken down all the way to glucose, removing steps that cost time and money.
For their research, the group used a strain of yeast commonly studied in laboratories. The genes will have to be inserted into strains bred to withstand the demands of industrial ethanol production. Scientists at the University of Illinois, part of the Energy Biosciences Institute that funded the research, will work on that. Meanwhile, Cate will continue to study Neospora to see if he can find an even better combination of genes. “We’re still going to be poking and prodding at Neospora to see what other tricks it might have for us,” he says.
It could be five years before the modified yeast is ready for use in a demonstration-scale ethanol plant, and perhaps a decade before ethanol made this way winds up in gas tanks, Cate says. Researchers won’t know for some time how much of a boost in yield the modified yeast will produce until it is tried in a production setting.
“We make a 10 to 20 percent improvement, other companies make a 10 to 20 percent improvement in their enzymes, and all of a sudden we’ve brought down the cost to where it can start to be competitive with oil,” says Cate.