Photosynthetic bacterial hydrogen production with fermentation products of cyanobacterium Spirulina platensis

The cyanobacterium Spirulina platensis accumulates glycogen photo autotrophically in a nitrogen-deficient medium. Under anaerobic conditions in the dark, the glycogen degrades into organic compounds. As molecular hydrogen also evolves in this process, hydrogenase participation is suggested in this metabolism. We investigated the several conditions necessary for the evolution of hydrogen and production of organic compounds. The effects of cell concentration, initial pH, and concentration of the buffer were determined. These fermentation products were then converted into molecular hydrogen by using the photosynthetic bacterium Rhodobacter sphaeroides RV with light energy. The composition of the evolved gas was mainly hydrogen and carbon dioxide. This photosynthetic bacterial production of hydrogen was caused by a nitrogenase-dependent mechanism. Combining this system with photosynthesis of cyanobacteria resulted in the production of hydrogen by splitting water.