Investigating the factors for fermentative biohydrogen improvement: original bioreactors design and hydrogen partial pressure effect

The anaerobic production of hydrogen from biomass offers the potential production of usable biogas from a variety of renewable resources. However, in order to produce hydrogen at high yields and production rates the biotechnological process needs to be further optimized and efficient bioreactors must be designed [1]. At the CWBI, a continuous horizontal rotating cylinder bioreactor has been designed and investigated to produce biohydrogen from glucose by the strain Clostridium butyricum [2] at good yields (1,9molH2•molglucose-1) and production rates (48,6mmolH2•Lmilieu-1.molhexose-1•h-1). This reactor has an internal volume of 2.3L and a small working volume (300ml) (fig.1).
It enhances the hydrogen production rates (by about three times more than a completely stirred bioreactor) by partially immobilizing the bacteria on the porous support. Moreover, the rotating cylinder design enables efficient H2 gas transfer from the liquid phase increasing hydrogen yields by about 25% compared to a completely stirred bioreactor [3-4]. Other original bioreactors, such as a trickle bed, have been built with the same aim of lowering the hydrogen partial pressure and led to similar results. Our work shows the importance of a good liquid to gas transfers in the biohydrogen-producing reactors to reach higher performances.