Ethanol just might help America break its addiction to fossil fuels — but not if it has to be made from corn, as is typically the case today. That's why researchers and entrepreneurs are rushing to find ways to turn non-food biomass into biofuel. The key trick will be to come up with a cheaper way to produce fuel from cellulosic material, ranging from corncobs to wood waste to switchgrass.
It'd be great if brewer's yeast, the humble one-celled organism that biofuel producers use to make ethanol, could handle cellulose as well as it handles simpler sugars. That would cut down on all the enzymatic processing that's currently required to get the party started.
Well, it turns out that researchers at the University of California at Berkeley are trying to teach that old brewer's yeast new tricks, by inserting genes from a type of fungus that can digest cellulose. The fungus, Neurospora crassa, can't produce alcohol. But the researchers conducted a genome-wide analysis of the critter and found a family of genes that appeared to facilitate the transport of more complex sugars into the cell. When the right genes were spliced into brewer's yeast (Saccharomyces cerevisiae), two of the resulting strains could grow on cellodextrin as well as the usual glucose. One strain produced 60 percent more alcohol than normal yeast when grown on a type of cellodextrin known as cellobiose.
"This improvement over the wild organism is a proof-of-principle that allows us to take the technology to the next level, with the goal of engineering yeast that can digest and ferment plant material in one pot," Jamie Cate, a member of the Berkeley team, said in a news release. Enzymes would still be required to break cellulose down into cellodextrins, but further genetic engineering could conceivably streamline the process further. And Cate pointed out that a wide variety of biofuels could be produced.
"The use of these cellodextrin transporters is not limited to yeast that makes ethanol," Cate said. "They could be used in any yeast that's been engineered to make, for example, other alcohols or jet fuel substitutes."
The Berkeley researchers' report was published today on the journal Science's website and will appear in a future issue. But they're not the only ones working to improve biofuel production through genetic engineering. Heck, that's one of the big reasons why genetic pioneer J. Craig Venter and others are putting so much effort into developing synthetic cells.
Here are links to other reports about yeast re-engineering:
- Chemist blends math and synthetic biology in biofuel research
- Engineer identifies genes for making biofuel more efficiently
- New yeast can ferment more sugar, make more ethanol
- Winemaking yeast could be key to alternative fuel
Some folks are already worried about the potential risks associated with "frankenfuels." The issue is definitely something to think about. If you believe re-engineering yeast to make better biofuel is scary, what would you say to combining genetically engineered yeast with human DNA to create artificial corneas? And it's not just yeast: E. coli bacteria are being tweaked as well, to produce biodiesel.
I'd love to get your honest opinion on bioengineering — so please be frank in your comments below.
Authors of the SciencExpress study, "Cellodextrin Transport in Yeast for Improved Biofuel Production," include Cate as well as Jonathan Galazka, Chaoguang Tian, William Beeson and N. Louise Glass of the University of California at Berkeley, and Bruno Martinez of Lawrence Berkeley National Laboratory.