October 26, 2006

Greenhouse Gases as Feedstock?

Will bacteria play THE major role in the production of biofuels and sequestering of carbon dioxide? Patents already exist for strains of bacteria that can convert syngas into ethanol.

New research being funded by the U.S. Department of Energy to study new roles for bacteria. The challenge is to sequence the DNA of certain cyanobacteria that can extract greenhouse gases from the air and, using sunlight, convert them into "thick mats of green biomass, from which liquid ethanol can be extracted." Sounds similar to the idea of using algae as a "breath mint" for smokestacks - but much more refined.

Here are excerpts form an article that appeared in "Washington University in St. Louis News & Information":

Sequencing The DNA Of Six Photosynthetic Bacteria To Make Biofuel To Warm Homes And Run Cars
by Tony Fitzpatrick

The United States Department of Energy (DOE) has devoted $1.6 million to sequencing the DNA of six photosynthetic bacteria that Washington University in St. Louis biologists will examine for their potential as one of the next great sources of biofuel that can run our cars and warm our houses.

That's a lot of power potential from microscopic cyanobacteria (blue-green algae) that capture sunlight and then do a variety of biochemical processes. One potential process, the clean production of ethanol, is a high priority for DOE.

A natural at fermentation

"The Department of Energy is very interested in the production of ethanol or hydrogen and other kinds of chemicals through biological processes," said Pakrasi, who also is director of the University's Bioenergy Initiative. "Cyanobacteria have a distinct advantage over biomass, such as corn or other grasses, in producing ethanol, because they use carbon dioxide as their primary cellular carbon source and emit no carbons and they naturally do fermentation. In biomass, yeast needs to be added for fermentation, which leads to the production of ethanol. Cyanobacteria can offer a simpler, cleaner approach to ethanol production." Pakrasi heads a group of nearly two dozen researchers who will do a lengthy, painstaking manual annotation of the gene sets of each organism to figure out what each gene of each strain does.

"The diversity in those sequences will give us the breadth of what these organisms do, and then we can pick and choose and make a designer microbe that will do what we want it to do," Pakrasi said. "We want to tap into the life history of these organisms to find the golden nuggets."

One possible way to produce ethanol using Cyanothece strains is a hybrid combination of the microbe and plant matter where the cyanobacteria coexist with plants and enable fermentation. The model exists in nature where cyanobacteria form associations with plants and convert nitrogen into a useful form so that plants can use the nitrogen product.

Extracting ethanol

At Washington University, Pakrasi and his collaborators have designed a photobioreactor to watch Cyanothece convert available sunlight into thick mats of green biomass, from which liquid ethanol can be extracted.

Pakrasi led the sequencing of Cyanothece 54112 as the focus of a Department of Energy "grand challenge project" that resulted in the sequencing and annotation of a cyanobacterium gene that could yield clues to how environmental conditions influence key carbon fixation processes at the gene-mRNA-protein levels in an organism.

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