Genetic Researchers Identify Enzymes for Biofuels

(Agricultural Research Service)

Researchers have used large-scale DNA sequencing to characterize the genes and genomes of plant-digesting microbes isolated from the rumen — pre-stomach — of a cow, and identify the most promising enzymes for breaking down cellulose in the biofuel switchgrass. The team from the Department of Energy’s Joint Genome Institute, several universities and national labs, and the company Illumina Inc. in Hayward, California, published their findings in this week’s issue of the journal Science (paid subscription required).

Developers of alternative fuels from plants has been stymied to some extent by the high cost and energy needed to process plant biomass so that it can be more easily converted into sugars and from there into biofuels. The process in a cow’s rumen of degrading plant cell wall materials in pasture grass can help meet that challenge faced by biofuel producers.

Since the domestication of cows, microbes in the rumen have evolved to produce enzymes that can efficiently break down otherwise inedible plant cell wall materials such as cellulose and hemicellulose into small sugar molecules.  As those sugar molecules are digested, they provide energy for the cow.

In this study, the researchers have developed — at a much larger scale than before — a picture of the enzyme capabilities encoded in the genomes of these cow-rumen microbes. This more detailed picture of nearly 30,000 genes generating enzymes can enable biofuel producers to better understand what it takes to efficiently degrade biomass into simple sugars, the essential first step in cellulosic biofuel production.

The research involved a massive data analysis task, filtering through 2 million predicted genes to result in some 28,000 candidate genes. These candidates encoded a specific type of enzymes called carbohydrate-active enzymes (CAZymes) that can break down plant cellulose into small sugars. A subset of these candidates had cellulose-degrading activity, with almost 20 percent able to break down switchgrass, an important biofuel feedstock.

Read more: Researchers Getting Genetic Help for Biofuel Production

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