Increasing biological hydrogen production

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Hydrogen is widely considered as a potential fuel of the future with a large amount of research and development world-wide, including the production of demonstration cars and bus transportation systems. However, a practical renewable means of hydrogen production is lacking. Biological hydrogen production holds promise as a sustainable process for hydrogen production since various waste products or lignocellulosic substrates could be converted to hydrogen, thus potentially producing energy and carrying out waste treatment at the same time. The photosynthetic bacteria have long been studied for their photofermentative hydrogen evolution capacity and have served as model organisms for research on photosynthesis, nitrogen fixation, and biotechnological conversions.***     Using the purple non-sulfur photosynthetic bacterium Rhodobacter capsulatus we have recently demonstrated a number of improvements in biolgocial hydrogen production. In the present work, rates and yields of hydrogen will be improved using two approaches; development of bioreactor technology using a redox stat to control the oxygen levels for achieving maximum substrate conversion, and metabolic engineering to increase metabolic flux in the desired direction. Metabolic engineering, changing how the metabolism of the cell is used by introducing genetic changes, will be used to increase the flow of energy to hydrogen production and to increase photosynthetic efficiency. In order to make these changes, genetic tools for the creation of multiple markerless mutations will be established for this organism which could also be useful for other researchers interested in the production of other useful compounds. This same system will be used to extend the limits of hydrogen production by the newly described microaerobic pathway. Mutants will be created in pathways that divert metabolic flux away from hydrogen production, such as acetate formation, and tested in a redox stat where the respiratory rate and hence redox level are regulated by the controlled addition of oxygen.***     Increasing hydrogen production through both physiological manipulation and metabolic engineering will not only potentially provide a practical means of sustainable hydrogen generation from various waste materials, but could also pave the way for the sustainable production of a variety of other useful chemicals and chemical products.**