June 14, 2013
Leaf-Cutter Ants Lend A Hand In Biofuel Research
Brett Smith for redOrbit.com — Your Universe Online
As gardeners around the United States tend to their flowers or herbs, leaf-cutter ants are actively cultivating gardens of fungus and bacteria as a source of food and shelter.
"All the enzymes that we found are similar to known enzymes, but they are completely new; no one had identified or characterized them until now,” said co-author Frank Aylward, a graduate student with the Great Lakes Bioenergy Research Center (GLBRC).
In their study, the research team used genome sequencing technology to understand the unique roles played by both the fungi and the bacterium that co-exist in these ant gardens.
"We really tried as thoroughly as possible to characterize the biomass degrading enzymes produced," Aylward says. "Identifying all these new enzymes really opens the door to technological applications, because we could potentially mix and match them with others that we already know about to achieve even better biomass degradation."
They identified one symbiotic fungus, Leucoagaricus gongylophorous, that provides food for leaf-cutter ants by developing fruiting bodies rich in fat and nutrients. To produce these fruiting bodies, the fungus generates enzymes that break the leaf´s cellulose apart into glucose subunits, which are then metabolized.
The team also identified bacteria that may help boost the fungus's productivity. The bacteria appear to be providing key nutrients and assisting the fungus by breaking apart plant polymers that encase the cellulose.
"We think there could potentially be a division of labor between the fungus and bacteria," said co-author Garret Suen, University of Wisconsin, Madison assistant professor of bacteriology and Wisconsin Energy Institute researcher.
Enzymes that allow for the access and deconstruction of cellulose are of major interest to the GLBRC researchers who want to ferment the stored sugars to ethanol and other biofuels. Understanding how these enzymes work could help researchers fashion comparable methods for processing biofuel raw materials, such as corn stalks and grasses.
Unfortunately, the complexity of the ant gardens makes for a difficult puzzle to solve, especially if the goal is to create a viable process.
"We are interested in the whole fungus garden community, because a lot of plant biomass goes in and is converted to energy for the ants," Aylward said.
"In an industrial setting, you need a system that's reproducible, sustainable, controlled – and that produces a consistent level of ethanol," Suen explained.
Instead of recreating the entire fungus garden to extract the natural processes, researchers said they hope to duplicate and purify the desired enzymes synthetically. However, the process of determining which enzymes are the most effective can be time-consuming and costly.
To expand their search, the researchers plan to study other insects that also create fungal communities, including certain species of termites and beetles.
"It's difficult to think that we can actually find a process that improves on nature," Aylward said, "so it probably makes sense to learn from it."