Cows’ guts yield clues for new biofuels

WASHINGTON - A new study has found dozens of previously unknown microbial enzymes in the bovine rumen-the cow’s primary grass-digestion chamber-that contribute to the breakdown of switchgrass, a renewable biofuel energy source.

The study tackles a major barrier to the development of more affordable and environmentally sustainable biofuels.n previous studies beginning in 2008, Roderick Mackie of the University of Illinois and Washington State University Matthias used a decades-old technique for studying ruminant nutrition.

They placed small, mesh bags containing either milled alfalfa or switchgrass through a cannula (a permanent, surgically installed portal) into the cow rumen and examined the microbes that adhered to each plant type after two or three days.

Visual and chemical analyses showed that microbes in the rumen were efficiently breaking down both types of plant matter, with a different community of microbes attacking each plant type.

This and later experiments proved that the technique could help scientists find the microbes in the cow rumen that were most efficient at degrading a particular type of plant matter, said Mackie.

In the new study, the researchers focused on switchgrass, a promising biofuels crop. After incubating the switchgrass in the rumen for 72 hours, researchers conducted a genomic analysis of all of the microbes that adhered to switchgrass.

This ‘metagenomic’ approach, led by Edward Rubin, of the DOE Joint Genome Institute and the Lawrence Berkeley National Laboratory, analyzed all the genes in all the microbes present in a sample, rather than one at a time.

Using a variety of techniques, the researchers sequenced and analyzed the total DNA in the sample, a huge undertaking that allowed them to identify 27,755 potential “carbohydrate-active” genes. They cloned some of these genes into bacteria, and successfully produced 90 proteins of interest. They found that 57 percent of these proteins demonstrated enzymatic activity against cellulosic plant material.

The researchers also were able to assemble the genomes of 15 previously “uncultured” (never before grown in a lab) microbes, said Hess, who is first author on the new study. Several techniques, including sequencing the genomes of individual cells and comparing those to the assembled genomes, validated this approach, he said.

These results suggest that the bovine rumen is one of the best microbial habitats to explore for sources of plant-degrading enzymes, reported the researchers.

The findings have been published in the journal Science. (ANI)