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Researchers engineer photosynthetic bacteria to produce hydrogen:

The price of photovoltaic power has plunged, making it competitive with fossil fuel-powered electrical generation. But there is still a range of applications, like ships and aircraft, where electrical power doesn't help much. And storing the electricity produced by solar power so that it can be used at night remains an unsolved problem. For those reasons, there's been continued interest in converting solar power to a fuel that can be stored, either through the use of electricity generated by photovoltaics or by using light to directly power fuel generation.

There's obviously a means of generating fuel through light that's been in use for roughly 3 billion years: photosynthesis. But photosynthesis requires a large and complex suite of proteins that's hard to maintain outside of cells. And inside of cells, the products of photosynthesis are quickly put to use to help the cells grow. So, engineering a version of photosynthesis that might be useful for fuel production has been challenging.

Earlier this week, however, researchers from the University of Kiel described how they've rearranged some photosynthetic proteins to make bacteria that emit hydrogen when exposed to light.

[...] The engineered cyanobacteria produced the highest levels of hydrogen yet seen in these organisms, and they could continue producing hydrogen for hours. Presumably, they'd eventually scavenge enough hydrogen ions from the solution they were growing in to change its pH, but this didn't seem to be a problem during several hours of illumination.

The researchers behind the work say there are a number of ways they can potentially improve the flow of electrons within their engineered complex. And, ultimately, it would be ideal to make the process less sensitive to oxygen in general.

But they argue that their approach provides a big benefit over previous efforts in this area. Many of these have focused on removing the photosynthesis components from a living cell in order to precisely control the pathways that are active in order to bias production toward hydrogen or other fuels. But, outside the cell, these components quickly pick up damage and can't be replaced. Alternatives that operate in an intact cell face the challenge of keeping the cell from diverting energy into the pathways it needs for rapid reproduction. This work, the researchers argue, confirms that you can have the benefits of working in living cells while at the same time engineering away some of those competing pathways.

Journal Reference
Jens Appel, Vanessa Hueren, Marko Boehm, et al. Cyanobacterial in vivo solar hydrogen production using a photosystem I–hydrogenase (PsaD-HoxYH) fusion complex, Nature Energy (DOI: 10.1038/s41560-020-0609-6)

Original Submission