Effects of hydrogen partial pressure on fermentative biohydrogen production by a chemotropic Clostridium bacterium in a new horizontal rotating cylinder reactor

The fermentative production of hydrogen using chemotrophic anaerobic bacteria offers a new way to produce “green” energy from a large variety of renewable resources and organic wastes. In order to produce hydrogen at high yields and production rates, efficient bioreactors must be designed. A new reactor called “horizontal rotating cylinder bioreactor” allows the production of biohydrogen from glucose with the selected Clostridium sp. strain at high yields (1,9molH2·molglucose-1) and production rates (48,6mmolH2·lmilieu-1.molhexose-1·h-1). The rotative cylinder where the bacteria are fixed enables efficient gas transfer (mainly hydrogen) from the liquid phase where it is produced by the bacteria. This is an important way to allow the bacteria metabolism to shift in a fermentation pathway that produces more hydrogen. This was confirmed by varying the total pressure in the bioreactor. An increase of the total pressure 0,18bar lowered the yields of 19,5% while a decrease of 0,11bar increased the yields of 7%. Our work concludes the importance of providing good liquid to gas transfers in the biohydrogen-producing reactors in order to reach higher yields and production rates.