Biofuels new enzyme for low cost biofuel

Published on January 8th, 2014 | by Tina Casey


This Little Bug Could Be The Graphene Of Low Cost Biofuel

January 8th, 2014 by  

From the exotic Valley of Geysers in far eastern Russia comes a bacteria that could propel the biofuel market far past its petroleum rivals. We’re comparing it to graphene, that atom-thin “wonder material,” because like graphene this little bug possesses uniquely powerful properties, enabling it to function faster and more efficiently than its conventional counterparts.

And for that pathway to low cost biofuel, we US taxpayer can thank ourselves: The latest research on this bug was supported by the Department of Energy’s Office of Science, through the Bioenergy Research Center anchored by Oak Ridge National Laboratory and the University of Georgia.

A Superbug For Biofuel

The bacteria in the spotlight is Caldicellulosiruptor bescii, which thrives in hot water, as in 75 to 90 degrees Centigrade (up to 194 degrees Fahrenheit).

new enzyme for low cost biofuel

Caldicellulosiruptor bescii (cropped) courtesy of ORNL.

It was discovered back in 1990 but if that name doesn’t ring a bell you’re not alone. Until 2010 it went under the moniker Anaerocellum thermophilum but was reclassified in 2010 with its current and slightly less pronounce-able name.

Back home in Mother Russia the bacteria’s diet consisted of whatever it could find in a really hot environment with no oxygen: crystalline cellulose, hemicellulose, pectin, starch, and gum Arabic.

If you’re looking at the cellulose in that list, you’re seeing what biofuel researchers saw, which is the potential to use the bacteria for munching through the tough cell walls of woody plants (that’s the cellulose) and converting the biomass to sugars, at a far lower cost than current technology allows.

The money part of the process is the bacteria’s cellulase, CelA, which is the enzyme that converts cellulose into sugars.

Researchers have found that the bacteria loves to digest napier grass, Bermuda grass, and switchgrass as well as poplar, which is significant because the poplar tree is becoming the It Girl of the biofuel world. It touches all the bases: a non-food, low-maintenance perennial plant requiring little or no extra water, which can be raised on marginal lands and double as a natural remediation for contaminated sites.

How Fast Is That Bug?

This whole Caldicellulosiruptor bescii thing has been flying under our radar for a while, although last year we did take note of its heat-loving cousin, Caldicellulosiruptor obsidiansis, which is found right here in hot springs at Yellowstone Park.

In terms of biofuel costs, the heat tolerant angle is important because it enables the enzymes to keep chugging away with greater efficiency in the harsh environment of a biofuel processing operation.

The latest news comes from the National Renewable Energy Laboratory (NREL), which has just completed a thorough analysis of the enzyme CelA, published in the journal Science.

In this round of tests, the researchers confirmed that CelA can digest cellulose almost twice as fast as its conventional counterpart, a widely used enzyme called Cel7A (I know, confusing, right? Couldn’t they use a different name or something?).

How’d They Figure That Out?

To get to that conclusion, NREL researchers fed the enzyme a commercially available crystalline form of cellulose called Avicel, which you food people out there may recognize as a form of dietary fiber. It is also used in the biofuel industry as a standard test platform for cellulose degradation.

Here’s the meat  of NREL’s findings:

…CelA not only can digest cellulose in the more common surface removal, but that it also creates cavities in the material, which leads to greater synergy with more conventional cellulases, resulting in higher sugar release.

As for the graphene comparison, the researchers sound just as excited over their results as the graphene news we’ve been covering. This is what NREL scientist Yannick Bomble has to say:

CelA is the most efficient single cellulase we’ve ever studied – by a large margin. It is an amazingly complex enzyme, combining two catalytic domains with three binding modules. The fact that it has two complementary catalytic domains working in concert most likely makes it such a good cellulose degrader.

Another Step For Low Cost Biofuel

If CelA ends up in commercial biofuel production, it won’t be working all on its own. Currently, most biofuel production is based on a “cocktail” of 15 to 20 different enzymes including Cel7A. However, according to NREL Cel7A is the one doing most of the work.

So, if CelA can sub in for Cel7A, that will have a significant impact on the efficiency of the digestion process, leading to significantly lower biofuel production costs.

Also helping things along is NREL’s discovery that CelA loves xylose, so it could also replace other xylose-specializing enzymes in the biofuel cocktail (xylose is a sugar widely occurring in woody plants), which will also help to reduce costs.

Let’s note for the record that high efficiency heat-loving bacteria are just one pathway toward biofuel’s inevitable march toward parity with petroleum products.

For woody biomass you also have the fungus path and the E. coli path, among others.

And then there’s algae biofuel, which is turning into a superhighway all its own.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • TCFlood

    The paper on which this story is based is very interesting science that appears to be high quality work. However, I found this story itself a little disappointing. First, graphene has absolutely nothing to do with anything related to the story. I would call it “grasping for readership by appeal to trendy buzzword”.

    The center of the discussion is a cellulase catalyst, designated CelA, which is an assembly of several proteins, called a cellulosome, comprising two catalytic sites and three carbohydrate binding modules plus a protein scaffolding holding it all together. Thus, it is about 4 times the molecular mass of Cel7A which is currently the main component of the enzyme mixtures most commonly used for converting cellulosic feedstocks to monosaccharides. Since catalyst efficiency is most commonly assessed on a gram of feedstock / mg of enzyme basis, this means any mole-for-mole enzyme activity comparison is diminished by a factor of 4 in reality.

    CelA is more active than Cel7A in hydrolyzing crystalline purified cellulose (Avicel), but it is actually slower in hydrolyzing plant feedstocks independent of how they are pre-treated (acid wash, ammonia wash, alkaline wash, etc.). This is thought to be a result of the large size of the cellulosome causing non-productive binding and trapping of the catalyst in the substrate matrix.

    The point of all this is that this is fascinating science, but it is no breakthrough toward the practical production of cellulosic ethanol fuel.

  • Jim Nelson

    Appreciate the article, but…

    “a bacteria”?

    “we US taxpayer”?

    A bacteriUM probably doesn’t get much gum Arabic to eat in Russia. It’s the product of an acacia tree that grows in the Sudan.

  • JamesWimberley

    Tina: “…heat-loving bacteria are just one pathway toward biofuel’s inevitable march toward parity with petroleum products.” The first part is right – this is one promising pathway among others. The second part is absurd. Fossil petroleum will die, from exhaustion or carbon policy or technological supercession. But it’s simply guessing to say that biofuels in particular will wield the knife, rather than P2G or dirt cheap solar.or super-batteries, among other possibilities

    • TinaCasey

      Errr…yep. Your point about the reasons why fossil fuels will be edged out of the picture is spot on but I think liquid fuels will have a role to play in the foreseeable future. So, biofuel.

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