Genetically engineered intestinal bacteria produce sustainable biofuel

Olefins from Sugar

Robert Klatt

Genetically modified Escherichia coli cultures produce biofuel from vegetable sugar. Because photosynthesis removes CO2 from the air, the method is considered sustainable.

Buffalo (U.S.A.). Many bacteria can use enzymes to break down plant material. In the ideal case, this results in low energy consumption, from which climate-friendly and sustainable fuels can be generated. Like Zhen Wang from the University of California in Berkeley explains, “Many synthetic compounds, including primarily unsubstituted hydrocarbons, are still difficult to produce with the help of cells alone.”

Together with scientists from University at Buffalo The scientists therefore looked for a method that enables the intestinal bacterium Escherichia coli to synthesize molecules that can be converted into olefins. The collective term olefins includes all hydrocarbons that contain at least one double bond. They are found in gasoline, among other things, but also serve as raw materials for plastic production and other chemical processes.

Genetically engineered bacteria produce olefins from sugar

According to their publication in the specialist magazine Nature Chemistry normal Escherichia coli cultures were used as the starting point for the study. “These microbes are real sugar junkies,” explains Wang. The aim of the researchers was for these bacteria to produce hydroxy fatty acids as efficiently as possible, regardless of their cell growth. These are medium-length hydrocarbon chains that can then be converted into olefins. To do this, the team smuggled genes for four additional enzymes into the Escherichia coli bacteria.

In this way, they were able to create a bacterial strain which, in a four-step process, forms hydroxy fatty acids from sugar with high efficiency. The yield per liter of microbe solution was between 780 and 1,600 milligrams, i.e. with an efficiency of around 86 percent.

Conversion into alkenes

The hydroxy fatty acids were then converted into alkenes with a length of six to nine carbon atoms using chemical catalysts. “We have combined what biology does best with what is chemically feasible and thus developed this two-step process. In principle, we can use it to produce olefins directly from glucose, ”explains Wang.

Climate-friendly fuels

The fuels produced from biomass are considered to be climate-friendly because the processed vegetable sugar is produced during photosynthesis. During the production of the raw material, CO2 is removed from the atmosphere.

“Producing biofuels from renewable raw materials such as vegetable sugars therefore has the potential to advance green technologies,” said Wang. This is particularly sustainable if plant waste is used in production. However, microbial olefin synthesis is still in its infancy and the alkene yield of around eight percent is still relatively low. It is therefore unclear whether and how the process can be used on an industrial scale.

Nature Chemistry, doi: 10.1038/s41557-021-00820-0

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