Biohydrogen Production from Tofu Wastewater with Glutamine Auxotrophic Mutant of Rhodobacter sphaeroides

Hydrogen production from organic wastewater by photo‐bacteria has been attracted more attention, not only because hydrogen is a clean energy, but also because it can be a process for organic wastewater pre‐treatment. However NH4+, which normally is the integrant in organic wastewater, is the inhibitor to hydrogen production with photo‐bacteria. In this study, the NH4+ effect on biohydrogen generation and nitrogenase activity of anoxygenic phototrophic bacteria‐Rhodobacter sphaeroides was studied. Biohydrogen generation with wild‐type R. sphaeroides was found to be more sensitive to NH4+ due to the obvious inhibition of NH4+ to its nitrogenase. For avoiding inhibition of NH4+ to biohydrogen generation of R. sphaeroides, a glutamine auxotrophic mutant R. sphaeroides AR‐3 was obtained by EMS treatment. The mutant could generate biohydrogen efficiently in the medium with higher NH4+ concentration. Under suitable conditions, AR‐3 produced biohydrogen from tofu wastewater with an average generation rate of 14.2 ml L−1h−1, it was increased by more than 100% compared with that from wild‐type R. sphaeroides.