Cellulosic Ethanol Finds A Friend In Hot Water

The U.S. Environmental Protection Agency (EPA) was originally counting on U.S. ethanol producers to mix 500 million gallons of cellulosic ethanol into the country’s gasoline supply in 2012. Ain’t happening—by a long shot. After ethanol producers indicated that they would fail to meet the 2011 renewable fuel standard, the EPA reduced its 2012 mandate to a mere 8.65 million gallons.

Alas, even this modest target will be difficult for producers to meet without significant cost reductions. (The Obama administration has tried to prop up the fledgling industry with loan guarantees for cellulosic ethanol plants in projects in Kansas, Iowa and Oregon.)

Criticisms aside, part of the problem is that the current method of producing ethanol from cellulosic feedstocks like switchgrass is expensive. The two-phase process requires the use of expensive enzymes that break down plant materials to yield sugars. The sugars are then fermented into ethanol in a separate process.

However, a recent study by scientists at the U.S. Department of Energy’s BioEnergy Science Center at Oak Ridge National Laboratory (ORNL) could help ethanol producers streamline this production process into a “one-pot method.” The breakthrough comes from a surprising source: a bacterium first found in the hot springs of Yellowstone National Park.

According to ORNL scientist Richard Giannone, the research is focused on “consolidated bioprocessing”—a method that will enable ethanol producers to “throw plant material into a pot with the microorganism and allow it to degrade the material and produce ethanol at the same time.”

The microorganism in question, Caldicellulosiruptor obsidiansis, breaks down organic material such as sticks and leaves in its natural environment. But it can also thrive at extremely high temperatures, leading ORNL scientists to believe it may be the key to the one-pot method of ethanol production.

The BESC team conducted a comparative analysis of the proteomics (a study of the structures and functions of the proteins) of C. obsidiansis grown on four different carbon sources ranging from a simple sugar to switchgrass. They found that, unlike simple sugar and cellulose, the switchgrass prompted the organism to express proteins that work together to break down the plant material and import the resulting sugars into the cell. Once inside the cell, the organism activates other enzymes that are involved in further breaking down these sugars into usable energy.

“By comparing how C. obsidiansis reacted to switchgrass, relative to pure cellulose, we were able to pinpoint the specific proteins and enzymes that are important to plant cell wall deconstruction—a major roadblock to the production of advanced biofuels,” Giannone said.

“One of the goals is to identify new proteins that we haven’t seen before. If an unknown protein doesn’t show up on the simple sugars or cellulose, but it shows up on the switchgrass, then we can say something about that gene or protein—that it responds to something the switchgrass is providing.”

The team’s research can now be combined with other sciences such as genomics, transcriptomics and metabolomics to help provide future researchers with insight into the functions of the microorganism, and how it might be relevant to bioenergy processes like ethanol production. The team documented its findings in a paper featured on the cover of the Journal of Proteome Research.

source: earthtechling