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Behold the THETA Cycle: A new way to turn E.coli into tiny factories that grab CO2 from air


Behold the THETA Cycle: A new way to turn E.coli into tiny factories that grab CO2 from thin air

Using synthetic biology, scientists have designed a pathway to convert CO2 into valuable industrial chemicals. . . and it is far faster than the ways plants fix carbon
January 11, 2024

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Researchers have developed a biosynthetic pathway that efficiently captures carbon dioxide from air and converts it into an industrially useful chemical. The team at Max Planck Institute could implement the pathway in living E. coli bacteria, they report in the journal Nature Catalysis.

Climate experts agree that to meet the Paris climate agreement’s goal of keeping global temperature rise within 1.5°C, it will be necessary to not only reduce carbon dioxide emissions, but also remove them from the atmosphere.

Efforts are underway around the world to capture carbon dioxide from power plants and directly from air. The idea is to either store the gas underground or convert it to valuable chemicals and fuels. Most carbon capture technologies are expensive, though.

So scientists are looking at natural carbon-capture processes that could have a lower price tag. Plants, algae and other organisms that convert carbon dioxide from air into energy, are an obvious source of inspiration. There are seven known carbon-fixation pathways found in nature. But researchers are now trying to develop new ways to fix carbon dioxide that are faster and more efficient.

In the new work, the Max Planck team developed a new pathway that relies on carbon-fixing catalysts found in bacteria. The pathway, termed the THETA cycle, uses 17 such biocatalysts. This includes two of the fastest carbon-fixing enzymes found to date, which capture carbon dioxide 10 times faster that enzymes found in plant cells, but are not found together in natural photosynthesis.


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So the researchers paired them up. The resulting THETA cycle converts two carbon dioxide molecules into one acetyl-CoA molecule. Acetyl-CoA is an important building block for a range of biofuels and pharmaceuticals. After optimizing the process using machine learning and many rounds of experiments, the team could boost the yield of the process by 100 times.

Finally, the authors incorporated the THETA cycle into living bacterial cells. The whole 17-step process was too complicated for one bacterial cell. So they split it up into three stages, and implemented each stage in a different cells. Each stage worked as they planned, and in concert resulted in the final chemical pathway of turning carbon dioxide into the useful acetyl-CoA.

The work paves the way towards harnessing bacterial cells to produce biofuels in a sustainable way from carbon dioxide.

Source: Shanshan Luo et al. Construction and modular implementation of the THETA cycle for synthetic CO2 fixation. Nature Catalysis, 2024.

Image: ©Anthropocene Magazine



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