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Renewable hydrogen fuel has for many years loomed on the horizon, promising the ultimate clean energy carrier. Using electricity to split hydrogen from water would allow us to capture the energy produced intermittently by renewables such as solar and wind, allowing it to be stored and easily transported. This would diminish the world’s dependence on coal, oil and gas, while tackling the challenge of global warming.
How do we achieve large-scale hydrogen production in a way that is both environmentally friendly and economically viable? Answering this question is essential to achieving the EU’s goal of a sustainable and climate-neutral economy.
At Uppsala University in Sweden, CaBiS project coordinator Gustav Berggren is working on an innovative solution: replacing the rare metals required for the catalysts used in electrolysis, such as platinum and iridium, with an alternative method that blends natural biological processes with synthetic chemistry.
At the heart of the approach are semi-synthetic metalloenzymes, which replicate the action by which hydrogen is produced in living cells. This field was recently boosted by the 2018 Nobel Prize in Chemistry awarded to Frances Arnold, for her work using directed evolution to engineer enzymes.
“We employ synthetic chemistry tools to simplify preparation of the enzyme, but also to generate modified versions of this enzyme, which we call ‘organometallic mutants’,” Berggren explains. This methodology contrasts with other attempts that often involve creating hydrogen-processing enzymes from scratch.
Berggren’s team were able to incorporate functional artificial metalloenzymes in the cytoplasm of bacteria – a rare example of artificial enzymes functioning inside living cells. These advancements have accelerated the pace of research and open new avenues for the exploration of photobiological hydrogen production systems. Berggren notes, “We can do this at a greatly accelerated pace compared to classical biological methods.” This capability has not only enhanced their understanding of hydrogen metabolism, but also contributed to the discovery of novel hydrogenases in various organisms.
Pioneering applications and future directions
The results open the door for photobiological hydrogen production, the use of photosynthetic bacteria to optimise the production of hydrogen from sunlight. “We are using this powerful tool to optimise hydrogen production efficiencies from cells containing hydrogenases, with a focus on optimising the enzyme catalyst itself as well as its integration in the cellular electron flow,” Berggren says.
Yet the implications of the work extend beyond renewable fuel. The team’s breakthroughs in hydrogenase technology have potential applications in various fields, including medical sciences.
The methodologies developed in CaBiS are now being applied to study hydrogen metabolism in the human gut. Berggren highlights the potential impact: “An improved understanding of gas metabolism in this context is expected to have a significant impact on life sciences, and potentially enable the design of new drugs and medical treatments.”
Despite these promising developments, Berggren acknowledges that translating these breakthroughs into practical applications will require further research and optimisation. “For these technologies to take off, we also need to optimise bioreactor design for high safety and efficient light capture, as well as efficient downstream harvesting and processing of the hydrogen gas being produced,” he adds.
The CaBiS project, which was funded by the European Research Council, undoubtedly represents a significant step forward in the quest for sustainable hydrogen production. By combining cutting-edge synthetic chemistry with naturally occurring biological systems, Berggren and his team have created a powerful platform for future innovations, which they continue to refine to this day.