Engineering a better biofuel

While the bacteria E. coli is often considered a bad bug, researchers commonly use laboratory-adapted E. coli that lacks the features that can make humans sick, but can grow just as fast. That same quality allows it to transform into the tiniest of factories: when its chemical production properties are harnessed, E. coli has the potential to crank out biofuels, pharmaceuticals and other useful products. 

Now, a team from the School of Engineering & Applied Science at Washington University in St. Louis has developed a way to make the production of certain biofuels in E. coli much more efficient. Fuzhong Zhang, assistant professor in the Department of Energy, Environmental & Chemical Engineering, along with researchers in his lab, have discovered a new method to cut out a major stumbling block to production process.

"It's a critical step that we've figured out how to solve this problem," Zhang said.

Branched-chain fatty acids (BCFA) are important precursors to the production of freeze-resistant or improved cold-flow biofuels. However, making it in bacterial hosts is difficult. It's co-produced with different compounds called straight-chain fatty acids (SCFA), which have inferior fuel properties. Past attempts to engineer E. coli that churned out BCFA also made a large amount of SCFA, and made it difficult to isolate the BCFA for future use.

"From the process aspect, common bacteria produce mostly SCFA," Zhang said. "That is really not the best fuel to use. Previously, the best you could do was a 20 percent BCFA concentration. Then you needed to use some additional chemical processes to separate the BCFA from the SCFA and enrich it. It consumes so much energy that it's not cost-effective.

"Instead, our approach engineers this organism so it can produce something as close to 100 percent BCFA as possible," he said.