Researchers at the U.S. Department of Energy’s BioEnergy Science Center (BESC) have developed a microbe which increases isobutanol yields 10-fold — overcoming another barrier to commercially viable production of biofuels from sources other than corn.

The new study, published in the journal Metabolic Engineering, builds on earlier work by BESC researchers to develop the first genetically engineered microbe to produce isobutanol directly from cellulose.

Isobutanol is attractive because it has similar energy density and octane values as gasoline. As well as directly replacing gasoline, it is used as a chemical feedstock for various products and can, for example, can be chemically upgraded into a hydrocarbon equivalent for jet fuel.

While the previous work by BESC researchers at DOE’s Oak Ridge National Laboratory and the University of California at Los Angeles was important from a proof-of-principle perspective, this new result represents a significant gain, the researchers said.

“When we reported our initial finding four years ago, we were using Clostridium celluloyticium, which is a less complex organism from a metabolic engineering perspective,” explained co-author James Liao of UCLA’s Henry Samueli School of Engineering and Applied Science.

“With this paper, we have successfully engineered similar traits in the much higher yielding Clostridium thermocellum, and that has taken us to new levels of consolidated bioprocessing efficiency.”

Consolidated bioprocessing refers to the bundling of several processes in a single microbe that can be used to extract sugar from a plant’s cellulose and convert those sugars into a biofuel. With this approach, processes such as pretreatment, enzyme treatment and fermentation are combined, producing biofuel at a lower cost.