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. sphacroides, 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(-1)h(-1), it was increased by more than 100 % compared with that from wild-type R. sphaeroides.