Hydrogen production by means of an Artificial Bacterial Algal Symbiosis (Project ArBAS)

Bakterienkulturen Purple bacteria: Of Ardley (a small island in the antarctica) up to Zagora (a desert at the edge of the sahara) they will be found. About 500 water samples were collected at the Institut for Bionics and Evolutiontechnique during the last 15 years. Purple bacteria carry out a biological HABER-BOSCH process. But if nitrogen for the ammonia-synthesis is not available, hydrogen will be released.
The technical remodeling of results of the biological evolution is the field of Bionics. Results of the evolution please, because they are optimized and per se ecologically gentle. For the Bionics-Scientist the model to split the water is the two-stage way, which takes the hydrogen in nature from H2O to NH3. This is usually done in nature by a division of labor: Nodule bacteria obtain carbohydrates from the Leguminosa and they return the favour with synthetized nitrogen products. Marine algae excrete carbohydrates, which will be assimilated by nitrogen-fixing bacteria. At the end the algae get back their effort in the form of nitrogen fertilizer. For several blue algae the evolution has combined this exchange process in one organism. The vegetative cells and the heterocysts of Nostoc muscorum work together as possibly the marine algae and the purple bacteria.
The idea to model the technique of Nostoc muscorum to split the water is simply formulated: A flask containing green algae corresponds with the vegetative cell. The flask containing purple bacteria is the counterpart to the heterocyst. Carbon dioxide works as a carrier molecule, circulating in the process. It will be loaded with hydrogen and unloaded from it. Is nitrogen not available to synthesize NH3, then the hydrogen will be released. For the ideal process it is necessary that the green algae excrete carbohydrates. Strains of algae are known, which excrete 50% of the total photosynthetic production into the surroundings.

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Sahara-Experiment
Sahara-Bioreaktor
Hydrogen: The fuel of the future

Every year an extraordinary experiment takes place in the dunes of the Sahara. Purple bacteria and green algae are growing in a photo-bioreactor and produce solar hydrogen. The photolysis of water is based on the integrated metabolism between vegetative cells and heterocysts in the blue alga Nostoc muscorum. The pilot experiments are part of the Berlin project "Artificial Bacterial Algal Symbiosis" (ArBAS).

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Ingo Rechenberg: Proceedings of the 11th World Hydrogen Energy Conference. Stuttgart, Germany 23-28 June 1996, pp 2427-2435.

Ingo Rechenberg: Photobiologische Wasserstoffproduktion in der Sahara. Frommann-Holzboog, Stuttgart 1994.

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