Who knew that a possible solution to our growing energy needs could be found in a cow’s gut? Chemical engineering professor Michelle O’Malley suspected it could, and now the anaerobic gut fungi that have evolved over millennia to
break down the tough lignins in plants are being eyed for their biofuel potentials.
“Compared to microbes that thrive in the presence of oxygen, anaerobes are woefully understudied,” O’Malley said.
Research into these primitive and little-understood anaerobic gut fungi — found primarily in the digestive systems of large herbivores — has given O’Malley and her group an insider’s look at how they work to access the cellulose trapped behind the tough lignin walls of the “non-food” parts of plants, such as stems and roots. The fungi can also secrete enzymes that convert cellulose and hemicellulose into sugars, and ferment them. In a large herbivore, the enzymes act to release much needed energy for the animal, but they can also be used to generate biochemicals and biofuels.
Thanks to a collaboration with partners including the federal Joint Genome Institute and the Pacific Northwest National Laboratory, and colleagues at Harvard, MIT, and Harper Adams University in the U.K., the researchers have been able to genetically sequence representative fungal strains — which are difficult to isolate and grow — and molecularly sequence their large repertoire of novel enzymes. That knowledge could allow researchers to fine-tune the specific compounds they produce from plant cellulose.
This breakthrough represents a significant step in the effort to generate fuels from alternative sources. While food crops provide the most accessible sources of cellulose, using food crops for fuel has several down sides, including the potential to drive food prices higher and divert food from human consumption just as a growing world population needs more.
There is still much to learn, according to O’Malley, who has received early-career awards from both the U.S. Department of Energy and the National Science Foundation to investigate the energy potential of anaerobic gut fungi. New knowledge about gut microbes and the enzymes they secrete may also find application in bioprocessing techniques that could result in efficient production of advanced pharmaceuticals derived from sugars.