Process turns E. coli into efficient biofuel ‘factories’

Laboratory-adapted E. coli that lack the features that make humans sick still grow fast enough to transform into the tiniest of factories.

When scientists harness its chemical production properties, E. coli has the potential to create biofuels, pharmaceuticals, and other useful products.

Now, researchers have discovered a new method that cuts out a major stumbling block to the production process. That means they can produce certain biofuels in E. coli much more efficiently. “It’s a critical step that we’ve figured out how to solve this problem,” says Fuzhong Zhang, assistant professor of energy, environmental & chemical engineering.

Fatty acids for biofuels

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.

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“From the process aspect, common bacteria produce mostly SCFA,” Zhang says. “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.”

Fixing a bottleneck

Zhang’s lab has previously researched methods to reduce SCFA concentrations in E. coli. The new paper, published in the journal Metabolic Engineering, improves upon that work. By developing two different protein pathways that chemically affect the bacteria, Zhang’s team fixed what it called a bottleneck in the BCFA production line. The protein pathways enabled the E. coli to boost its BCFA manufacture to 80 percent of all fuel products.

“It’s a higher quality,” says lead author Gayle Bentley, a doctoral student in Zhang’s lab. “A lot of people have been making these SCFA fuels, and while that’s important work, they don’t have the improved qualities like we’re generating. The difference is quite significant.”

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Now that the chemical workaround has been discovered, the researchers say the applications for their work have potential to expand to other products derived from fatty acid compounds.

“The compounds we’ve made as fatty-acid forms are beneficial as a nutraceutical, effective as an anti-tumor compound,” Bentley says. “It’s also been shown to be effective to prevent and treat neonatal necrotizing enterocolitis. These compounds are really expensive to derive from their original source but using this platform may actually make it more economically feasible.”

“We really think this is an important step toward a platform that can offer a variety of different products for different applications,” Zhang says.

Zhang is working with the Washington University Office of Technology Management (OTM) on patent filing and licensing efforts for the new technology. The Defense Advanced Research Projects Agency funded the work.

Source: Washington University in St. Louis

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Source: Futurity