Electron transfer in the alga C. reinhardtii

Electron transfer in the alga C. reinhardtii, that leads to the production of hydrogen or other substances. Hase = Hydrogenase © MPI CEC/RUB

Microalgae need only sunlight and water for the production of hydrogen. However, in order to make hydrogen production by microalgae economically feasible their efficiency has to be increased by 1-2 orders of magnitude. In the current issue of Energy and Environmental Science scientists from the AG Photobiotechnology of the Ruhr University Bochum and the Max Planck Institutes in Mülheim, Germany present how an improvement in efficiency can be achieved.

Microalgae use light energy to attract electrons from water during photosynthesis. Most of these electrons are transported by a small, iron-containing protein, the ferredoxin oxidoreductase (FNR), which feeds the electrons into the production chain of carbohydrates.

Using nuclear magnetic resonance spectroscopy the scientists investigated in great detail which amino acids of PetF with negatively-charged side chains are exclusively important for binding FNR. The directed genetic modification of exactly those two residues to amino acids with uncharged side chains led to an increased production of hydrogen. Together with further modifications of the FNR, this resulted in a five-fold increase in the rate of hydrogen production.

The change of electron transfer pathways has the potential to make further enhancements of hydrogen production possible. The efficiency necessary for an economic application of biological hydrogen production can probably be achieved by the combination of different modifications. Thus, the study results are important for the development of an environmentally friendly, regenerative energy supply that does not depend on expensive and rare noble metals.