Flasks of glucose Buffalo

Sweet-toothed microbes could power future cars

Image credit: Douglas Levere / University at Buffalo

Researchers from the University of Buffalo and the University of California-Berkeley have harnessed genetically engineered E. coli to glucose and turned it into petrol molecules. The technique has the potential to help power the cars of the future.

The E. coli turned glucose into olefins: a type of hydrocarbon and a constituent molecule of petrol. At it is currently produced, olefins make up a small fraction of the molecules in petrol.

However, the researchers suggest that in future, an adapted version of the technique could be used to generate other types of hydrocarbon, including other constituents of petrol. The researchers also note that olefins have non-fuel applications, as they are also used in industrial lubricants and as precursors for making plastics.

The researchers began by feeding glucose to strains of harmless strains of E. coli. Professor Zhen Wang, a Buffalo biochemist, joked: “These microbes are sugar junkies, even worse than our kids.”

The E. coli were genetically engineered to produce a suite of four enzymes that convert glucose into compounds (3-hydroxy fatty acids). When the bacteria consume the glucose, they start producing the fatty acids.

Next, the researchers used a catalyst (niobium pentoxide or Nb2O5) to slice away unwanted parts of the fatty acids in a chemical process. This generated the olefins. The scientists identified the enzymes and catalysts through trial and error, testing different molecules with properties that were relevant to the tasks at hand.

“We combined what biology can do with what chemistry can do the best, and we put them together to create this two-step process,” said Wang. “Using this method, we were able to make olefins directly from glucose.”

“Making biofuels from renewable resources like glucose has great potential to advance green energy technology. Glucose is produced by plants through photosynthesis, which turns carbon dioxide and water into oxygen and sugar. So, the carbon in the glucose – and later the olefins – is actually from carbon dioxide that has been pulled out of the atmosphere.”

The researchers acknowledge that more research is required to understand the benefits of this method, and whether it can be scaled up efficiently for making biofuels that could play a part in the effort to decarbonise transport, industry, heating, and other sectors. Among other questions that must be answered is how much energy the process of producing the olefins consumes; if the energy cost is too high, the technology would need to be optimised to become practical on an industrial scale.

Scientists are also interested in increasing yield. Currently, it takes 100 glucose molecules to produce about eight olefin molecules, Wang explained. She would like to improve that ratio, with a focus on coaxing the E. coli to produce more of the 3-hydroxy fatty acids for every gram of glucose consumed.

The study has been published in Nature Chemistry.

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