A blue-green soup percolates in thick glass bottles under the cool light of red, blue and green LEDs in one of the labs of Himadri B. Pakrasi, PhD, the George William and Irene Koechig Freiberg Professor of Biology in Arts & Sciences and professor of energy in the School of Engineering & Applied Science.
The soup is colored by a strain of cyanobacteria that bubbles off 10 times the hydrogen gas produced by its nearest competitors.
Biohydrogen, like that bubbling up from the microbial soup, is one of the most appealing renewable energy fuels. Produced by splitting water with energy from the sun, it releases mostly water when it burns. It is hard to get any cleaner than that.
The strain of bacteria growing in Pakrasi’s lab is Cyanothece 51142. All cyanobacteria are able to fix carbon from the atmosphere, stuffing it away in starch or glycogen. Cyanothece is among the rarer strains that also can fix nitrogen, converting atmospheric nitrogen to ammonia and eventually to larger nitrogen-rich molecules. As a result, Cyanothece produces copious amounts of hydrogen gas.
When conditions warrant, Cyanothece can survive on air, water and sunlight alone. It is about as self-reliant as an organism can be.
What intrigues Pakrasi most about these microbes is their ingenuity. Their unique metabolism gives them the ability to produce hydrogen, a clean fuel, while disposing of two waste products: glycerol, a byproduct of biodiesel production, and carbon dioxide, a waste product from coal-fired power plants.
“They give you a lot of bang for your buck,” says Pakrasi, who also is director of I-CARES, the International Center for Advanced Renewable Energy and Sustainability.
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