Enzyme With Big Appetite Could Boost Biofuel

Lignocellulosic fuels – those made from plant fiber, instead of food feedstocks like corn or soybeans – are one of the great hopes for greening the transportation sector. They’ve been slow to come to market, but government researchers think they might have found a bacterium that could allow for a cheaper, more efficient “enzyme cocktail,” the collection of chemicals used to turn the gnarly biomass into sugars.

The new enzyme goes by the name CelA, researchers from the National Renewable Energy Laboratory said, and it comes from a microorganism discovered 15 years ago in the Valley of Geysers on the Kamchatka Peninsula in Russia.

Arundo donax, also known as giant reed. (image via Wikimedia Commons)

Arundo donax is one possible feedstock for cellulosic biofuels. (image via Wikimedia Commons)

The scientists said that in tests against Cel7A, “the most abundant cellulose in the leading commercial mixtures,” CelA kicked butt.

“When researchers compared CelA to Cel7A, they discovered that at its optimal temperature of 50 degrees Celsius (122 degrees F), Cel7A achieves only 50% of the performance of CelA,” the NREL said.

One way that CelA appears to do better, the researchers said, was by acting on xylose, in addition to cellulose. “That could mean that levels of enzymes that specialize in removing xylose in commercial cocktails could be lowered, translating to lower costs,” the NREL said. “If an enzyme can produce sugars more efficiently, it means lower cost for the enzyme cocktail, which is a major cost driver in the process of converting biomass into fuel.”

Of course, decomposing the biomass is just one step in the long process of making cellulosic biofuels – there’s growing the material, harvesting it, transporting it, storing it before decomposition, and fermentation and then separation of the fuel afterward.

In the face of those challenges, there has been slow progress. What’s been called “the world’s first commercial scale cellulosic ethanol plant” and “the world’s largest advanced biofuels facility” opened in Italy last year, and in the U.S., the Indian River BioEnergy Center in Florida said in August that it had just begun producing at a commercial scale. There’s also a KiOR plant down in Mississippi that’s begun making cellulosic diesel.

Still, without costs coming down, few think the U.S. industry is about to come anywhere near the quantities needed to meet the demands of the renewable fuel standard.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.