Biofuel Enzyme in Hot Water

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The future of biofuel production may be in hot water, or at least in a microbe that lives in hot water.

Researchers from the Universities of California and Maryland found an enzyme in a recently discovered microbe that could streamline the process of breaking down cellulose, a strong material that helps give plants structure and support.

The newly discovered microbe eats cellulose at higher temperatures than any other known organism. It does this by using an enzyme, a chemical that facilitates other chemical reactions, to break down cellulose at temperatures above the boiling point of water.

The enzyme is most active at 228 degrees Fahrenheit (108 degrees Celsius). Other cellulose digesting enzymes, called cellulases, can't stand that kind of heat.

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Breaking down cellulose is exactly what engineers have to do to create biofuel from plant material like grass and tree trunks. Cellulose is made up of simpler sugars. The yeasts that create ethanol need the cellulose broken down into those sugars.

Normally, during the pre-treatment step of making cellulose biofuel, the temperatures used to free cellulose from lignin, another structural material, are too hot for most enzymes. So the breaking down of cellulose into simple sugars has to be done in a separate, cooler temperature step. But the heat tolerant enzyme could allow engineers to combine the two steps.

"Our hope is that this example, and examples from other organisms found in extreme environments – such as high-temperature, highly alkaline or acidic, or high salt environments – can provide cellulases that will show improved function under conditions typically found in industrial applications, including the production of biofuels," said coauthor Douglas S. Clark, UC Berkeley professor of chemical and biomolecular engineering in a press release.

The microbe is from and ancient group of organisms called Archaea. The microbes are thermophilic, from the Greek root words meaning “heat-loving.”

"These are the most thermophilic Archaea discovered that will grow on cellulose and the most thermophilic cellulase in any organism," Clark said. "We were surprised to find this bug in our first sample."

"This discovery is interesting because it helps define the range of natural conditions under which cellulolytic [cellulose devouring] organisms exist and how prevalent these bugs are in the natural world," Clark said. "It indicates that there are a lot of potentially useful cellulases in places we haven't looked yet."

To find this cellulose cracking creature, the researchers dredged sediment from the scalding waters of the Boiling Hot Springs near Gerlach, Nevada. The microbes were grown on pulverized Miscanthus, a grass used in creating biofuels, to weed out the microbes that couldn’t eat plants.

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Three species of cellulose eating Archaea were found but only the most abundant contained the high-temp enzyme, called EBI-244.

The results of the research were published in the journal Nature Communications.

Researchers hope that by finding more heat loving microbes they may find even more enzymes for use in industrial processes.

"We might even find a cellulase that could be used as-is," Clark said, "but at least they will give us information to engineer new cellulases, and a better understanding of the diversity of nature."

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