Scientists are building tiny microbial factories that photosynthesize hydrogen

Scientists have built tiny microbial factories out of droplets that produce hydrogen, instead of oxygen, when exposed to daylight in the air.

The findings of the international research team based in University of Bristol and Harbin Institute of Technology in China, are published today (November 25, 2020) in Nature communications.

Normally, algal cells fix carbon dioxide and produce oxygen through photosynthesis. The study used sweet droplets filled with living algal cells to generate hydrogen, rather than oxygen, through photosynthesis.

Hydrogen is potentially a climate neutral fuel, offering many possible uses as a future energy source. A major drawback is that the manufacture of hydrogen involves the use of a lot of energy, therefore green alternatives are sought and this discovery could be an important step forward.

The team, consisting of Professor Stephen Mann and Dr Mei Li from the Bristol School of Chemistry, along with Professor Xin Huang and colleagues from the Harbin Institute of Technology in China, trapped tens of thousands of algae cells in each droplet, which were then crowded together by osmotics. compression. By burying cells deep inside the droplets, oxygen levels dropped to a level that activated special enzymes called hydrogenases that hijack the normal photosynthetic pathway to produce hydrogen. In this way, about a quarter of a million microbial plants, typically only a tenth of a millimeter, could be prepared in a milliliter of water.

To increase the level of hydrogen release, the team covered the living micro-reactors with a thin shell of bacteria, which were able to trap oxygen and therefore increase the number of algae cells adapted to the activity. hydrogenase.

Although still at an early stage, the work is a step towards the development of photobiological green energy under natural aerobic conditions.

Professor Stephen Mann, Co-Director of the Max Planck Bristol Center for Minimal Biology in Bristol, said: “The use of single droplets as vectors to control algal cell organization and photosynthesis in synthetic micro-spaces offers a potentially environmentally friendly from the production of hydrogen. hopes to develop in future work.

Professor Xin Huang from Harbin Institute of Technology added, “Our methodology is easy and should be able to be extended without harming the viability of living cells. It also seems flexible; for example, we recently captured a large number of yeast cells in the droplets and used the microbial reactors for the production of ethanol. “

Reference: “Production of Photosynthetic Hydrogen by Microbial Droplet-Based Micro-Reactors Under Aerobic Conditions” by Xu Z, Wang S, Li S, Liu X, Wang L, Li M, Huang X and Mann S, November 25 2020, Nature communications.
DOI: 10.1038 / s41467-020-19823-5