Want to build a better biofuel? Talk to the cow

Enzymes locked away in the stomachs of cows might help us manufacture biofuels more quickly and cheaply. That’s according to a new paper in Science, published online today.

I spoke to Dr. Eddy Rubin, one of the authors of the study and director of the U.S. Department of Energy’s Joint Genome Institute. He explained that burning biofuel – fuel made from plant material – can be, gallon per gallon, up to 10 times less polluting than fossil fuel.

But, he said, biofuels can be difficult and expensive to produce: scientists haven’t perfected the process of breaking down plant material – cellulose – into simple sugars. Simple sugars are the building blocks of petroleum-like fuel.

Enter: the cow. If cows are good at anything, it’s digesting plant material until it turns into sugar; Dr. Rubin noted that cows have been eating grass for a few million years. That’s why Rubin’s team decided to do major genetic analysis of microbes inside the stomachs of cows. He explained that he was interested in their gut microbes, and also the enyzmes those microbes build. Rubin said:

We saw the machinery that [cows use] to break down that grass material. That machinery is really enzymes, which are able to take the long molecules that are used in making up grass and convert them to sugars.

Inside the stomachs of cows, Dr. Rubin discovered 30,000 novel enzymes, many of which break down plant material (e.g., grass) quite powerfully.

Dr. Rubin’s work is cutting-edge because, as his press release notes, it would have been hard to get at all these enzymes without looking hard at microbes. Only about one percent of the planet’s microbial species can easily be grown in the laboratory. New techniques of genetic analysis allowed Rubin to look at millions of microbes at once. And, voila, he was also able to spot tens of thousands of enzymes, buried in that genetic data.

Rubin expects that much of the genetic information he collected and catalogued will be used by the biofuel industry in the future. Genes from microbes that build specific enzymes can be inserted into yeast, which will enable that yeast to build enzymes, like a tiny enzyme factory. The enzymes will chomp away on grass, breaking it down into sugars, the precursor to fuel. They’ll do this speedily, and at low cost, said Dr. Rubin.

The disadvantage of biofuels is that we’re not good [today] at converting plant material into sugar that’s needed eventually in the creation of the biofuel. This research is helping us in the breakdown of plant material to increase the feasibility of next-gen biofuels.

Dr. Rubin noted that we already have a well-known biofuel called ethanol that’s corn-based. But we eat corn. Rubin said we need to move towards grass-based biofuels, warning against pitting our food needs against our fuel needs – especially with 9 billion mouths to feed by the year 2050.

Grass doesn’t compete with food crops. It grows on different land. It frequently grows on marginal land.

In other words, grass doesn’t need a lot of time or attention from either humans or nature.

The promise and peril of energy from cellulose

Dr. Rubin did note that biofuel isn’t the most sustainable fuel on Earth. It’s not as clean as renewables like wind or solar. But, he said, it’s a good transition fuel while the world switches to those things. Plus, he said, it’s hard to imagine powering airplanes (in the near future, at least) with sunlight.

So the enzymes locked away in cows’ stomachs might be useful indeed – during the transitional period from fossil fuels to renewables like wind and solar – in the effort to manufacture biofuel faster and with less expense.

Mike Goosey looks ahead to next generation of biofuels