With more than 70 countries across the world setting net zero greenhouse gas emissions targets,[1] there is an increasing global effort to mitigate the impact of these gases, released by human industry, into the environment. A key aspect of this goal is to identify methods of reducing levels of greenhouse gases, such as CO2, that are already present in the atmosphere.
Over the years, many groups have investigated the potential for harnessing the natural metabolic pathways of different bacteria to absorb and convert greenhouse gases. One such bacterium of interest is Cupriavidus necator. Researchers have previously shown that this species can produce the higher alcohols isobutanol and 3-methyl-1-butanol when provided with CO2 and electricity in a bioreactor,[2] suggesting that environmental CO2 could be used to produce commercially desirable chemicals in future.
Now, researchers from the Korea Advanced Institute of Science and Technology have demonstrated that using the same versatile microorganism in a “biohybrid” reactor can present a two-for-one in terms of environmental gains by reducing greenhouse gases and producing biodegradable plastics.
A biohybrid system is one in which an artificial component is combined with a biological component. In this case, the team found that CO2 electrolysis (the catalysts facilitating this being the artificial component) can be used to produce formate, which can then be converted by microbial fermentation using C. necator (the metabolic pathways of which form the biological component) to make the biodegradable polyester poly-3-hydroxybutyrate (PHB).[3]
Not only did the researchers find that circulation of a solution containing the formate throughout the system allowed for an efficient build-up of PHB in the microbial cells, but they also found that removing accumulated PHB and adding fresh C. necator cells allowed them to operate the system continuously.
Although one can imagine that the need for an electricity source will still pose limitations on using even such an efficient system on a large scale, this research suggests that the exciting prospect of microorganisms being used to reduce levels of greenhouse gases in the atmosphere could one day become an industrially practical reality.
[1] https://www.un.org/en/climatechange/net-zero-coalition
[2] Li H, Opgenorth PH, Wernick DG, Rogers S, Wu T-Y, Higashide W et al. (2012) “Integrated electromicrobial conversion of CO2 to higher alcohols”. Science, 335(6076), 1596.
[3] Lim J, Choi SY, Kee JW and Lee H (2023) “Biohybrid CO2 electrolysis for the direct synthesis of polyesters from CO2”, Applied Biological Sciences, 120(14), e2221438120.
Stuart represents clients in the chemical field, with particular experience in pharmaceuticals, transdermal patches, medical devices, industrial chemistry, chemical engineering, vaccines, coatings…
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