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

为了一个可持续发展的未来，科学家面临的一个挑战是想出创新和鼓舞人心的新想法来解决废物和鼓励回收利用。从农业废弃物到食品垃圾和包装，再到大规模的工业污染，来自各个专业领域的科学家都可以在寻找可持续解决方案方面发挥作用。能源工业、运输部门和其他重工业（如钢铁、混凝土）产生的气态二氧化碳是一种众所周知的、对环境重要的废气。减少二氧化碳排放需要一篮子不同的解决方案，而生物学提供了一些令人兴奋的选择。微小的单细胞细菌习惯于生活在极端环境中，并经常进行植物和动物无法进行的生化反应。例如，通常无害的肠道细菌大肠杆菌可以在完全缺氧的情况下生长。当它这样做时，它消化糖并产生二氧化碳和氢气作为气态产物。我们灵机一动，或许可以让这个反应倒着进行。果然，当大肠杆菌被置于二氧化碳和H2的环境中，并施加一定压力时，细菌就会吸收二氧化碳并将其转化为其他物质。另一种物质是甲酸，这一发现可能是生物技术的重要突破。我们现在可以在生长的活细胞中更详细地研究二氧化碳转化为甲酸的过程，并优化它，使其主要在一个方向上发挥作用，成为一种“氢依赖的二氧化碳还原酶”。我们还可以考虑甲酸的用途——例如，也许可以利用进一步适应的细菌来制造甲醇或乳酸，我们可以解决一些关键的障碍，使这项新发现对广泛的工业有用。最终，基础科学和由此产生的应用生物技术有可能帮助减少各种来源的二氧化碳排放，并将二氧化碳废物转化为更有用的产品。这种新的生物技术有一天将有助于实现真正的循环生物经济，使废物流降到最低。

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.