Using microbes to make carbon neutral fuel

Researchers at Washington University in St. Louis have discovered a new way to train microbes to make a readily usable biofuel.

A team of biologists and engineers modified a microbe called Rhodopseudomonas palustris TIE-1 to produce a biofuel using only three renewable and naturally abundant source ingredients: carbon dioxide, solar panel-generated electricity and light.

The resulting biofuel, n-butanol, is a carbon neutral fuel alternative that can be used in blends with diesel or gasoline. The U.S. National Science Foundation-funded results are reported in the journal Communications Biology.

The study was led by biologist Arpita Bose and co-authored by engineers at Washington University's McKelvey School of Engineering.

"Microorganisms have evolved a bewildering array of techniques to obtain nutrients from their surrounding environments," Bose said. "Perhaps one of the most fascinating of these feeding techniques uses microbial electrosynthesis (MES). Here we have harnessed the power of microbes to convert carbon dioxide into value-added multi-carbon compounds in a usable biofuel."

The first author of the study is engineer Wei Bai. Bai is now a scientist at Amyris, a manufacturer of sustainable ingredients made with synthetic biology. "The fuel we made, n-butanol, has a high energy content and low tendency to vaporize or dissolve in water without combustion," Bai said. "This is especially true when compared with ethanol, which is a commonly used biofuel."

Microbes that feed via microbial electrosynthesis attach directly to a negatively charged cathode inside the MES reactor so they can "eat" electricity.

As scientists learn more about these microbes, their potential uses are becoming more promising, Bose said, although she acknowledged that improvements are needed before the techniques can be rolled out on an industrial scale.