Researchers used bacteria to convert solar energy into liquid fuel in what they have called a "bionic leaf."
We all know that leaves convert solar energy into their own fuel through photosynthesis, and now scientists may have figured out a way to do the same, Harvard Medical School reported. The new work includes an "artificial leaf" that uses a catalyst to make sunlight split water into hydrogen and oxygen. The technique also employs bacteria to convert carbon dioxide and hydrogen into the liquid fuel isopropanol. The leaf is also made from materials that are relatively inexpensive and accessible.
"This is a proof of concept that you can have a way of harvesting solar energy and storing it in the form of a liquid fuel. Dan's formidable discovery of the catalyst really set this off, and we had a mission of wanting to interface some kinds of organisms with the harvesting of solar energy. It was a perfect match," said Pamela Silver, the Elliott T. and Onie H. Adams Professor of Biochemistry and Systems Biology at HMS, who worked on the project with Daniel Nocera, the Patterson Rockwood Professor of Energy at Harvard University.
In the new system, the "leaf" produces oxygen and hydrogen; the hydrogen is then fed to the bacterium Ralstonia eutropha, which uses an enzyme to convert it back into protons and electrons. This process prompts the creation of more cells by combining the digested protons and electrons with carbon dioxide. Additionally, the pathways in the bacterium have been engineered to create isopropanol.
"The advantage of interfacing the inorganic catalyst with biology is you have an unprecedented platform for chemical synthesis that you don't have with inorganic catalysts alone," said Brendan Colón, a graduate student in systems biology in the Silver lab and a co-author of the paper. "Solar-to-chemical production is the heart of this paper, and so far we've been using plants for that, but we are using the unprecedented ability of biology to make lots of compounds."
The researchers' goal is to surpass nature's ability to convert solar energy to biomass at an efficiency of 1 percent. In the future, they hope to achieve as high as 5 percent efficiency.
"We're almost at a 1 percent efficiency rate of converting sunlight into isopropanol," Nocera said. "There have been 2.6 billion years of evolution, and Pam and I working together a year and a half have already achieved the efficiency of photosynthesis."
The findings were published in a recent edition of the Proceedings of the National Academy of Sciences.
