Extreme biofuels and those heat-seeking X Bugs

February 16, 2012 |

As President’s Day weekend approaches and people flee from the north towards sunnier climates, biofuels researchers are exploring the potential of heat-loving bacteria and fungi found in and around volcano country.

It’s two days before February’s long weekend here in the US, and already the airport at the Digest’s home in Miami is swamped with beach-goers, cruise hounds and sun-worshippers.

But its a different class of heat seekers that have our attention today, based on new research coming out of Oak Ridge on a newly-discovered bacterium that may unlock new opportunities for low-cost conversion of cellulose to affordable, sustainable biofuels.

But first, some backstory on Yellowstone, where the bacteria in question have been living amidst the volcanoes and hot springs at Obsidian Pool.

Some of the first American visitors to Yellowstone, who began to record their journeys into the wilds of northwestern Wyoming during the early 1870s, noted the horrible taste of the water from the hot springs.

A visitor with the Hayden party compared the taste of the water at Soda Butte to a “a diabolic julep of lucifer matches, bad eggs, vinegar and magnesia.”

Halt there, right at the vinegar comment – that’s acetic acid, of course. And no one, noted the presence of a mashed-together muck of leaves, sticks and rotting vegetation.

X Bugs at Yellowstone

Which led researchers to consider that, amongst the volcanic stews of Yellowstone, there might be some crazy organism that can tolerate insane temperatures, and still find a way to break down and ferment cellulose into the organic acid known as acetic acid and, possibly, its cousin among the two-carbon alcohols, ethanol.

Turns out that researchers at the Department of Energy’s BioEnergy Science Center, located Caldicellulosiruptor obsidiansis, a naturally occurring bacterium, onsite at Yellowstone, Sure enough, it thrives at extremely high temperatures, breaks down organic material such as sticks and leaves in its natural environment, and scientists hope to transfer this capability to biofuel production tanks.

Now for the bad news. In its natural state, it makes a lot more acetic acid than ethanol.

But in a paper featured on the cover of the Journal of Proteome Research, the BESC team conducted a comparative analysis of proteins from C. obsidiansis grown on four different carbon sources, ranging from a simple sugar to more complex substrates such as pure cellulose and finally to switchgrass. The succession of carbon substrates allowed researchers to compare how the organism processes increasingly complex materials.

Understanding how bio-varmints attack and convert plant cells to usable energy

In the near term the discoveries are going to help unlock how bacteria attack the plant, with sub-systems work to break down the plant material and import the resulting sugars into the cell. Once inside the cell, the organism “switches on” certain enzymes involved in pentose metabolism in order to further process these hemicellulose-derived sugars into usable energy.

Like the Greek army before the gates of Troy, the little critter has developed a means to break through the walls, and wreak havoc on the other side. Of course, that’s to our benefit – since every breakthrough in making plant cell walls less defensible, is a step towards more affordable biofuels.

The appeal of heat-seeking organisms.

As researchers at the Clark Lab (at the Department of Chemical Engineering at Berkeley) write, “Extremely thermophilic microorganisms are ideal candidates for the development of more active, cost-effective enzymes for cellulose processing. In addition to lower risk of microbial contamination, a higher temperature would reduce cooling costs and facilitate ethanol (or, for example, butanol) removal and recovery.”

What does that, er, exactly mean?

Well, it means that the researchers are looking for organisms that can do their work at around 160 degrees fahrenheit (75 degree Celsius). There, you get process efficiency, low contamination, and its one heck of a lot cheaper to raise the temperature to the boiling point, which is generally how the fuel is separated from the water and other components in the broth that fermenting organisms make.

You see, a lot of the cost and hassle in biofuels is heating and cooling everything to make the process work.

Who else is working on the extremophiles, the X-Bugs?

Here are a few notable projects.

A team out of Lee Lynd’s lab at Dartmouth has been at work on Thermoanaerobacterium saccharolyticum, a thermophilic anaerobic bacterium that ferments xylan and biomass-derived sugars, to produce ethanol at high yield.

University of Texas researchers Alan Lambowitz and Georg Mohr have been working on Thermosynechococcus elongatus, a cyanobacterium discovered in Japan that can survive at temperatures of up to 150 degrees Fahrenheit.

A team of researchers from the DOE, Novozymes and Concordia University have been unlocking the genome of Thielavia terrestris and Myceliophthora thermophila, fungi that thrive in high-temperature environments above 45°C and whose enzymes remain active at temperatures ranging from 104°F to 160°F (40 °C to 75 °C),

We also recently looked at at work by biologists at Berkeley and the University of Maryland, who discovered a microbe in a Nevada hot spring that has an enzyme that processes cellulose and remains active at a record 109 degrees Celsius (228 degrees Fahrenheit), significantly above the 100℃ (212℉) boiling point of water.

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