Understanding and harnessing the hydrogen-dependent carbon dioxide reductase activity of E. coli.

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For a sustainable future one challenge to scientists is to think of innovative and inspiring new ideas to tackle waste and encourage recycling. From agricultural waste, to food waste and packaging, and all the way to large-scale industrial pollution, scientists from all areas of expertise have a part to play in finding sustainable solutions.Gaseous carbon dioxide produced by the energy industry, transport sector and other heavy industries (e.g. steel, concrete) is a well-known and environmentally important waste gas. Reducing carbon dioxide emissions will require a basket of different solutions and biology offers some exciting options. Microscopic, single-celled bacteria are used to living in extreme environments and often perform biochemical reactions that plants and animals cannot do. The usually harmless gut bacterium Escherichia coli, for example, can grow in the complete absence of oxygen. When it does this it digests sugars and produces carbon dioxide and hydrogen as gaseous products. We had a brainwave that we might be able to get this reaction to run backwards instead. Sure enough, when E. coli is placed under a CO2 and H2 atmosphere, and some pressure is applied, then the bacterium takes up the CO2 and converts it into something else. That something else is formic acid and this finding is potentially an important breakthrough for biotechnology. We can now examine the conversion of CO2 to formic acid in more detail in growing, living cells, and optimise it to work mainly in one direction as a 'hydrogen-dependent CO2 reductase'. We can also think about what the formic acid could be used for - maybe to make methanol or lactate using further adapted bacteria, for example, and we can address some of the key obstacles to making this new discovery useful to a wide range of industries.Ultimately, the underpinning science, and the applied biotechnology that results, has the potential to help reduce carbon dioxide emissions from a whole range of sources, and to convert that CO2 waste into more useful products. This new biotechnology will one day contribute to a truly circular bioeconomy where waste streams are minimal.