Enhanced biohydrogen generation from organic wastewater containing NH 4 + by phototrophic bacteria Rhodobacter sphaeroides AR-3

NH 4 + is typically an inhibitor to hydrogen production from organic wastewater by photo-bacteria. In this experiment, biohydrogen generation with wild-type anoxygenic phototrophic bacterium Rhodobacter sphaeroides was found to be sensitive to NH 4 + due to the significant inhibition of NH 4 + to its nitrogenase. In order to avoid the inhibition of NH 4 + to biohydrogen generation by R. sphaeroides , a glutamine auxotrophic mutant R. sphaeroides AR-3 was obtained by mutagenizing with ethyl methane sulfonate. The AR-3 mutant could generate biohydrogen efficiently in the hydrogen production medium with a higher NH 4 + concentration, because the inhibition of NH 4 + to nitrogenase of AR-3 was released. Under suitable conditions, AR-3 effectively produced biohydrogen from tofu wastewater, which normally contains 50–60 mg/L NH 4 + , with an average generation rate of 14.2 mL/L·h. This generation rate was increased by more than 100% compared with that from wild-type R. sphaeroides .