Could The Human Gut Provide The Next Biofuel Breakthrough?

Scientists searching the animal world for microbes that can help produce the next generation of biofuels need have looked no farther than their own bellies for some of the best specimens.

In their research, scientists at the University of Illinois had been examining the rumens, or first stomachs, of cows and the alimentary canals of termites, looking for microbes that can efficiently digest the cell walls of plants.

The cows deserve some credit for the research, according to Isaac Cann, a University of Illinois professor of animal sciences at the Institute for Genomic Biology, who led the study.

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“In looking for biofuels microbes in the cow rumen, we found that Prevotella bryantii, a bacterium that is known to efficiently break down [plant fiber] hemicellulose, gears up production of one gene more than others when it is digesting plant matter,” Cann told the University of Illinois News Bureau.

The researchers scoured a database for similar genes in organisms other than cows and found them, to their surprise, in the human gut. They examined two of these human microbes, Bacteroides intestinalis and Bacteroides ovatus, and discovered that they’re directly related to the Prevotella from the cow.
Even better, Cann said, the human microbes “actually were more active (in breaking down hemicellulose) than the enzymes from the cow.”

The findings are important for the production of biofuels because the same sugars can be fed to yeast to generate ethanol and other liquid fuels. The human microbes appear to be almost uniquely capable of breaking down a complex plant fiber component more efficiently than the most efficient microbes found in the cow rumen.

Closer inspection of the structure of the human enzymes revealed something unusual: Many protein chains, known as polypeptides, in fact contained two enzymes -- one embedded in the other. The embedded enzyme, a carbohydrate-binding module (CBM), turned out to be more important than the surrounding enzyme.

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The CBM’s job is to lock onto carbohydrates like the plant fiber hemicellulose, shredding it so that other enzymes can move in an break it down into its basic sugars.

“In addition to finding microbes in the cow rumen and the termite gut, it looks like we [humans] can actually make some contributions ourselves,” Cann said. “And our bugs seem to have some enzymes that are even better than those in the cow rumen.”

This means that microbes found in the human gut could potentially be a strong source for microbes that can help with biofuels production. Nevertheless, as with some other aspects of Cann’s research, more study is needed before his team can begin using the microbes.

The team’s research is published in the Proceedings of the National Academy of Sciences.

By Andy Tully of Oilprice.com

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