Termite Guts May Hold the Key to More Efficient Biofuels
Termite poop and biofuels — what's the connection? New research into termites' intestinal comings and goings describes a process that may speed the development and lower the cost of fuels made from plant matter.
Energy sources are a big deal, and the global economy currently turns on the price of oil. Countries wage wars over it, and burning it tarnishes the air. Biofuels pose a tantalizing prospect — an energy source made from renewable resources without that dirty fossil fuel buildup of carbon in the air.
While there are trade-offs in exactly how much biofuels reduce environmental impact and carbon footprints, there is no debate that fossil fuels are an exhaustible resource. The sooner we develop efficient, less-polluting energy sources to replace fossil fuels, the better.
As discussion and development of biofuels advance, science is looking for ways to deliver on the promise.
Well-known types of alternative energy include those driven by wind, sun, water, heat, and biofuels. Coal, oil, and natural gas are all fossil fuel products, while biofuels are energy resources made from plant or vegetative matter called biomass.
A critical factor in the use of biomass for biofuels is the breakdown of the tough, fibrous part of any plant known as lignin, which fills in the structure of plants — from trees to straw. While lignin plays an important role providing a framework, it also promotes movement of water through a plant. When the plant dies, lignin breaks down slowly, holding nutrients and returning them to the soil during the process of decay.
In a study published in the journal Proceedings of the National Academy of Sciences, researchers at the University of Wisconsin-Madison took a close look at how tiny termites might break down a tough industrial problem — lignin.
Looking for clues about how to more quickly decompose lignin, scientists turned to termites. Because termites eat decomposing wood, they have firsthand experience with breaking apart lignin. And scientists have discovered that they get help from fungal friends to convert the lignin into food for their colony.
The researchers were surprised to learn that after feasting on poplar wood, young termites needed only 3.5 hours to digest lignin before eliminating it as poop. A pretty impressive feat considering lignin goes into the termite as wood, and about 60% of the lignin is broken down by the time it comes out as feces.
Since the termites are eating wood, they're able to process lignin more efficiently than other herbivores that consume softer plant material like leaves and grasses. In some tropical areas, termites occupy an immensely important role as decomposers of plant litter and debris.
In a UW-Madison press release, study researcher John Ralph said, "The speed and efficiency with which the termite is breaking down the lignin polymer is totally unexpected. The tantalizing implication is that this gut system holds keys to breaking down lignin using processes that are completely unknown."
For termites, the science does not stop with the deconstruction of lignin. Tropical termites that farm fungus for food then deposit their poop on a comb in the interior of the colony, usually underground. Most of us have heard of honeycomb made by bees — well, termites add their excrement to a fungal comb.
Subterranean fungus-farming termites enjoy a symbiotic relationship with a fungus by the name of Termitomyce. Once the termites deposit their poop, fungi colonize the comb, working to deconstruct the material further. Within about 45 days, the fungus has decomposed the comb to make simple sugars that are eaten by older worker termites. Now that's slow food.
"This system is unique because the fungus and the termite can't live without each other,"Daniel Yelle, co-author and a research forest products technologist with the USDA, said in the press release. "They're symbiotic, and they work together very efficiently to do things fungi can't do in nature. Together they do everything more rapidly."
Historically, researchers assumed young termites played little part in the processing of lignin because of how quickly they digest it. Co-first author, Hongjie Li, a post-doctoral student in the Department of Bacteriology, said that "for decades, everybody just thought that the young worker wasn't doing anything, because of how rapidly the wood passes through its gut."
Through analysis of termite output, and the comb, scientists are excited to discover the secret sauce for rapid breakdown of lignin resides within the gut of the young termites. On examination, the dominant bacterial species in the gut of these termites are from the family Lachnospiraceae. Researchers find this family of bacteria commonly in the gut microbiota of humans and mammals, where they break down fiber and other food.
The specialized digestive processes of these termites have developed to feed the fungi that then occupy termite comb as their food and home. The output of the fungi then feeds the termite colony.
The wood's energy, taken in as food by young termites, eventually becomes nourishment for the whole termite colony. In future studies, researchers hope to identify and isolate enzymatic or bacterial processes responsible for the rapid deconstruction of lignin and determine if that can be engineered to work outside the termite gut.
Cameron Currie, professor of Bacteriology, said:
This is a great example of the value of basic science research. Studying how termites process plant biomass in nature not only helps us understand our natural world, but it could contribute to our own efforts to break down biomass.
This tight relationship between termite and fungus could help the energy industry to develop methods of producing biofuels that are more efficient and cost-effective, proving that solutions to big problems can come in very small packages.