Enzyme Could Create Biofuels 14 Times Faster than Current Methods

by Bill Scanlon (National Renewable Energy Laboratory/Renewable Energy World) Scientists at the Energy Department's National Renewable Energy Laboratory (NREL) have developed an enzyme that could change the economics of biofuel conversion by converting biomass to sugars up to 14 times faster and much cheaper than competing catalysts in enzyme cocktails today.

This enzyme is called CelA, a cellulase from the bacteriumCaldicellulosiruptor bescii, and the fact that it's from a bacterium, and not a fungus, is just one reason why it is such a potential game-changer. Here are some others:

Unlike most catalysts, CelA can digest not one, but two major components in biomass: both cellulose and xylan.
CelA works in two mechanical realms, not just one. It is an ablater, scraping the valuable material off the cell walls of the plants. But it is also a borer, digging deep into the wall to grab more of the digestible biomass. It is the only enzyme known to dig pits into biomass; others only ablate.
It can operate at much higher temperatures than other enzymes. That's important because high temperatures mean faster action. Also, because it can operate above the boiling point of alcohol, the alcohol is separated naturally, saving a costly step in the conversion process—and the high temperatures kill many of the microorganisms that would otherwise interfere with the process.

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In one scenario, the best commercially used enzyme converted sugars at a 30 percent extent in seven days. CelA converted to double that extent. And while it took the alternative enzyme seven days to achieve that conversion, CelA, with a small boost from an extra beta glucosidase, achieved double in just about two days.

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Just CelA alone is four to five times faster at breaking down sugars than the enzymes in today's cocktails. A more typical usage would be CelA combined with a beta glucosidase — the improvement that makes it 14 times faster. READ MORE and MORE (Biofuels Digest) and MORE (National Renewable Energy Laboratory Abstract (Science 2013)

Excerpt from Biofuels Digest: ... The good news is that, indeed, such an enzyme exists, though it doesn’t quite perform at the 14X level and isn’t out of the lab yet. The bad news is that the research that inspired the article actually was originally published in Science in 2013. Sorry folks, not a new breakthrough.

What is creating all the fuss is an enzyme, known as CelA, which has been isolated from the bacterium caldicelluoruptor bescii, which in the lab has outperformed that traditional workhorse of cellulase enzymes, Cel7A, by a wide margin. They get the “14X” figure from the fact that initial lab results (combining CelA with some beta glucosidase) revealed twice the total sugar conversion (around 60%), in two days, that Cel7A usually produced in seven.

I know, 3.5 times 2 is “7X” not “14X”, but you get the idea. It’s been big stuff in research circles.

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But let’s locate all of this where it is, which is in the lab. Which is about 10 years from appearing in an at-scale process somewhere, if you average out the timelines for bringing processes based on other microbes to full commercial scale.

Which is to say, no one has shown that these results can be achieved in a 500 liter fermenter, much less in a million liter monster as we see in commercial scale operations. There’s going to be, lime, zero knowledge at this stage about the behavior of these microbes in a fermenter under the incomplete mixing conditions that almost invariably are found at scale.

So, let’s keep the risks in mind, and the timelines too — even as we hail a genuinely promising and fascinating scientific advance.

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For some time, researchers have been unlocking the secrets of the entire Caldicellulosiruptor species — they’ve shown remarkable abilities to breakdown biomass in weird conditions that could have significant cost-busting application in advanced biofuels. There are a number of strains under intense investigation — C. obsidiansis, C. kronotskiensis, C. saccharolyticus, C. lactoaceticus, C. acetigenus in addition to C. bescii. READ MORE