Hydrogen gas has long been proposed as a promising energy carrier for future energy applications, but generating the gas from water has proved inefficient. Researchers at Uppsala University have now managed to activate a key enzyme called hydrogenase in E. coli bacteria, which opens the door to future applications in photosynthesising microorganisms.
The method involves inserting designed molecules into genetically modified E. coli bacteria to induce an otherwise inactive enzyme to start producing hydrogen gas. In other words, the method uses a combination of synthetic chemistry and biology.
Troublesome enzyme: the iron-iron-hydrogenase
Generating renewable hydrogen gas from water is feasible, but current systems for achieving this are limited. Nature’s enzymes that produce hydrogen gas in bacteria and algae are the ‘iron-iron-hydrogenases’. These enzymes have a very high capacity and have long interested scientists. However, they exist only in specific microorganisms that require special culture conditions, and to date have therefore only been used in small-scale laboratory experiments. Large-scale production of iron-iron-hydrogenases in bacteria relevant to biotechnological applications has yielded an inactive, unusable enzyme form.
It is this unusable enzyme that the scientists now have succeeded in activating, in genetically modified organisms, by combining it with designed synthetic molecules.
“We can modify selected organisms genetically and insert the gene encoding the enzyme into more easily manageable bacteria, and then activate it using our synthetic iron compounds. These artificially activated enzymes have proved fully functional, and transform E. coli bacteria into cellular hydrogen-gas factories,” says Professor Peter Lindblad.
He and his research colleague Gustav Berggren have jointly led the work at the Department of Chemistry – Ångström Laboratory.
Next: Hydrogen production in photosynthesising microorganisms
The scientists are now proceeding to apply the technique to photosynthetic microorganisms that get their energy from sunlight, instead of bacteria that need a constant nutrient supply. They want to further improve the artificial enzymes at genetic level and also enhance the process by modifying the synthetic catalysts.
“If we manage to refine the method as planned, it has the potential to make biological production of hydrogen gas from sunlight and water markedly easier,” says group leader Gustav Berggren.
The article In vivo activation of an [FeFe] hydrogenase using synthetic cofactors was published in Energy and Environmental Science on 11 April 2017.