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Extremophile Bacteria Transform CO2 and Light Into Fuel Better Than Photosynthesis


Someone has to fund experiments in this world, to accelerate the rhythm of their success, and that is currently ARPA-E. The “electrofuels” program is something they have been focusing on lately. The idea behind electrofuels is finding methods of producing biofuels with an efficiency higher than that of photosynthesis, using plants and algae.

Extremophiles are the right answer to that, and Metallosphaera sedula is an extremophile – a bacterium that naturally lives in harsh conditions, at high temperatures and acidic environments, doesn’t feed with organic matter, but rather with inorganic matter (such as CO2) to synthesize its enzymes that keep it alive, neither they use light to live.

Pairing these organisms with solar cells, that produce electricity, seems to be a good idea, as recent research points out. Bruce Logan, from Penn State University fabricated methane using microorganisms from sunlight and CO2, for example.

Metallosphaera sedula can draw energy from a copper-iron sulfide called chalcopyrite, the black substance shown here. As it feeds, it produces copper ions (green), iron oxide (orange), and sulfur (yellow). The organism uses the energy from the sulfides to produce acetyl-CoA, a fundamental building block in cells. Researchers have been able to engineer organisms to convert acetyl-CoA into butanol and other liquid fuels. “It oxidizes the metal sulfide, and that’s how it gets energy and electrons for cellular processes,” says Robert Kelly, director of the North Carolina State biotechnology program.

These organisms have long been studied for the enzymes they produce, since these enzymes can survive at high temperatures, and thus could be useful for industrial processes. But in recent years, researchers’ access to the genomes of organisms has allowed them to identify entire metabolic pathways–series of reactions undertaken by organisms–for converting carbon dioxide into various organic molecules. It may be possible to modify these pathways so that these organisms produce fuels.

The researchers don’t know yet if these extremophiles could capture CO2 and transform it into fuels as well or even better than naturally-occurring photosynthetic processes, but they try finding alternatives to that, though artificial photosynthesis. “There’s a lot of ‘white space’ here. This is not an area that has been investigated as a possible route toward biofuels. And this is what Arpa-e is supposed to do–try new things,” says Eric Toone, the project director in charge of the electrofuels program.

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