Research creates living droplets that produce hydrogen, paving the way for a future alternative energy source

(Nanowerk News) Scientists have built tiny microbial factories based on droplets that produce hydrogen, instead of oxygen, when exposed to daylight in the air.

The findings of the international research group based at the University of Bristol and Harbin Institute of Technology in China, are published today in Nature Communications (“Production of photosynthetic hydrogen by microbial micro-reactors based on droplets under aerobic conditions”). Electron microscope image of a densely packed droplet of hydrogen-producing algal cells. Scale bar, 10 micrometers. (Image: Prof Xin Huang, Harbin Institute of Technology)

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

Hydrogen is potentially a climate-neutral fuel, offering many possible uses as a future source of energy. One major drawback is that hydrogen production involves the use of a lot of energy, so green alternatives are being sought and this discovery could provide an important step forward.

The team, made up of Professor Stephen Mann and Dr Mei Li of the Bristol School of Chemistry together with Professor Xin Huang and colleagues from the Harbin Institute of Technology in China, trapped around ten thousand algal cells in each droplet, which were then massed together by osmotic compression.

By burying the cells deep within the droplets, the oxygen levels dropped to a level that activated special enzymes called hydrogenases that hijacked the normal photosynthetic pathway to produce hydrogen.

In this way, about a quarter of a million microbial factories, typically only a tenth of a millimeter in size, could be prepared in one milliliter of water.

To increase the level of hydrogen evolution, the team coated the living micro-reactors with a thin shell of bacteria, which were able to clean up the oxygen and thus increase the number of algal cells predisposed for the activity of the ‘hydrogenase.

Although still in an early stage, the work represents 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 simple droplets as vectors for controlling algal cell organization and photosynthesis in synthetic micro-spaces offers a potentially environmentally friendly approach to hydrogen production which we hope to develop in future work “.

Professor Xin Huang of the Harbin Institute of Technology added: “Our methodology is easy and should be able to increase without compromising the viability of living cells. It also appears flexible; for example, we have recently captured a large number of human cells. yeast in the droplets and used the microbial reactors to produce ethanol. ”