Frog’s foam fashions fuel

Krista D. Zanolli, Contributing Editor, krista.zanolli@photonics.com

With the inevitable decline of fossil fuels, the race is on to discover renewable energy solutions. As an alternative, researchers from the University of Cincinnati have found a way to convert solar energy and carbon dioxide into sugars to create new forms of biofuel.

The natural process of photosynthesis involves plants taking energy from the sun and carbon from the air and converting them into sugars. It’s those converted sugars that make biofuels like ethanol and bioethanol viable alternatives to fossil fuels. The problem is that the cost of growing and processing crops for biofuel production reduces efficiency rates to as low as 5 percent.

University of Cincinnati researchers are finding ways to take energy from the sun and carbon from the air to create new forms of biofuel, thanks to a semitropical frog species. Courtesy of the University of Cincinnati.

The researchers now say that they have fashioned an artificial photosynthetic material that can convert solar energy and carbon dioxide into sugars with an efficiency rate approaching 96 percent. And, oddly enough, they owe their inspiration to the nesting habits of a subtropical frog – the Tungara.

The female Tungara generates a resistant biofoam nest to protect her fertilized eggs from sunlight, temperature and pathogens until the eggs hatch. The foam is effective because it allows light and air to penetrate while still concentrating the reactants. The foam nests are also resistant to bacteria and fungus and can last up to two weeks. Similarly, the artificial photosynthetic material, which uses plant, bacterial, frog and fungal enzymes trapped within a foam housing, produces sugars from sunlight and carbon dioxide.

The artificial material’s major foam-forming ingredient is the Tungara frog’s surfactant protein Ranaspumin-2. Unlike chemical detergents, the Rsn-2 protein surfactant enables foam formation in low concentrations without disrupting cell membranes.

According to the study published online in Nano Letters, the foam converts light into adenosine triphosphate or ATP (considered the major energy currency of a cell) and then carbon dioxide into sugar using the Calvin-Benson-Bassham cycle. The ATP synthesis is initiated by the lipid vesicles’ exposure to green light.

“The advantage for our system compared to plants and algae is that all of the captured solar energy is converted to sugars, whereas these organisms must divert a great deal of energy to other functions to maintain life and reproduce,” said David Wendell, research assistant professor and co-author of the study, along with Carlo Montemagno, dean of the college of engineering and applied science, and student Jacob Todd. “Our foam also uses no soil, so food production would not be interrupted, and it can be used in highly enriched carbon dioxide environments, like the exhaust from coal-burning power plants, unlike many natural photosynthetic systems.”

Wendell added that too much carbon dioxide shuts down photosynthesis in natural plant systems, “but ours does not have this limitation due to the bacterial-based photocapture strategy.”

“The system that we have takes carbon out of the atmosphere and uses the sunlight to go and remold the molecules into a fuel – so it’s carbon neutral,” said Montemagno in an interview with Cincinnati public radio station WVXU. “I think the features of what we’ve done allow it to be scalable and commercially deployed. For me the real underlying advantage of this is that we’re demonstrating that we are able to incorporate life processes and make it intrinsic, and that’s what is really magical about this.”

“You can convert the sugars into many different things, including ethanol and other biofuels,” Wendell said. “And it removes carbon dioxide from the air but maintains current arable land for food production.”

“This new technology establishes an economical way of harnessing the physiology of living systems by creating a new generation of functional materials that intrinsically incorporates life processes into its structure,” Montemagno said. “Specifically, in this work it presents a new pathway of harvesting solar energy to produce either oil or food with efficiencies that exceed other biosolar production methodologies. More broadly, it establishes a mechanism for incorporating the functionality found in living systems into systems that we engineer and build.”

The team says the next step will be to try to make the technology feasible for large-scale applications like carbon capture and coal-burning power plants.

“This involves developing a strategy to extract both the lipid shell of the algae (used for biodiesel) and the cytoplasmic contents (the guts), and reusing these proteins in foam,” Wendell said. “We are also looking into other short carbon molecules we can make by altering the enzyme cocktail in the foam.”

“It is a significant step in delivering the promise of nanotechnology,” Montemagno added.