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Bacteria Turn Sunlight to Liquid Fuel in ‘Bionic Leaf’

Researchers have paired a solar-powered catalyzing device with genetically engineered bacteria to convert water and carbon dioxide into an alcohol-based liquid fuel. The system, dubbed a "bionic leaf," is described in the Proceedings of the National Academy of Sciences.

The process is modeled after the way in which plants use photosynthesis to turn CO2, H2O and other ingredients into energy, but with some novel chemical twists. One of the researchers, Harvard's Dan Nocera, has been working on artificial leaf systems for more than a decade. "The catalysts I made are extremely well-adapted and compatible with the growth conditions you need for living organisms like a bacterium," Nocera said in a news release.

The catalyst uses sunlight to split water into hydrogen and oxygen. Then a strain of bacteria known as Ralstonia eutropha combines the hydrogen with carbon dioxide to make isopropanol — which can be burned as fuel but is better-known as the main ingredient in rubbing alcohol.

Another member of the research team, Harvard Medical School's Pamela Silver, said the experiment was a "proof of concept" for solar-to-chemical conversion. The next step is to boost the system's energy efficiency rate from its current level of nearly 1 percent to a goal of 5 percent.

Invasive bacteria becomes biofuels 5:22

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Harvard Medical School's Joseph Torella and Harvard's Christopher Gagliardi are co-first authors of "Efficient Solar-to-Fuels Production From a Hybrid Microbial-Water-Splitting Catalyst System." In addition to Silver and Nocera, the other authors include Harvard Medical School's Janice Chen and Brendan Colon, Harvard's D. Kwabena Bediako and Jeffery Way of the Wyss Institute for Biologically Inspired Engineering at Harvard University. The research was supported by the Air Force Office of Scientific Research, the Office of Naval Research and the National Science Foundation.