Bacteria from human intestines could improve fuel production — study

Source: Amanda Peterka, E&E reporter • Posted: Friday, September 26, 2014

Bacteria found in the human gut can one day be a source of the microbes needed to break down plants into biofuels, according to a new study from the University of Illinois.

Scientists created an enzyme mix from two types of bacteria commonly found in the human intestinal tract that efficiently broke down xylan, a complex rigid fibrous material found in foods, into its component sugars. The same process could be used to break down tough plant material into sugars that are fed into the biofuels production process, the researchers said.

Previous research has looked at the capacity of microbes found in the guts of cows and termites for breaking down those rigid parts of plants into the sugars needed for biofuels production (Greenwire, June 20, 2013). This is the first study to use biochemical approaches to find that microbes living in the human gut can be just as useful in producing biofuels.

The findings were published this week in the Proceedings of the National Academy of Sciences.

The two bacteria studied, Bacteroides intestinalis and Bacteroides ovatus, are found in the lower human intestinal tract, a part of the body that contains trillions of bacteria that perform vital functions such as helping to capture energy from food. While there have been efforts to sequence the genes of the bacteria found in the human gut, research on the functions of those genes has lagged behind the sequencing.

The researchers said they were led to the bacteria through the prior studies that pointed to cow rumen as a possible source of the microbes needed in biofuels production.

“In looking for biofuels microbes in the cow rumen, we found that Prevotella bryantii, a bacterium that is known to efficiently break down [the plant fiber] hemicellulose, gears up production of one gene more than others when it is digesting plant matter,” said Isaac Cann, a professor of animal sciences and genomic biology at the University of Illinois.

The researchers found similar genes in the genetic databases for the microbes that live in the human gut. The study found that the two human bacteria possess “a remarkable repertoire of genes” that are aimed at using sugars in foods, as well as extensive enzyme systems capable of breaking down xylan.

In some cases, the human microbes were actually more efficient in breaking down hard plant matter than the cow gut organisms previously studied. The bacteria contain an enzyme that effectively shreds plant fiber so that other enzymes can come in and break it down into its component sugars.

“In addition to finding microbes in the cow rumen and termite gut, it looks like we 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.”

The study was funded by the Energy Biosciences Institute, a public research institution supported by BP PLC, and a competitive grant from the Department of Agriculture.