The optimal conditions for ZX-5, a newly isolated PNS bacterial strain, to produce hydrogen and the potential for it to treat wastewater were investigated. The strain could grow and produce hydrogen at pH 5.5-9.5, and it was able to adjust the pH value to about 7 during photo-fermentation by itself. ZX-5 could use 22 tested carbon sources for growth, and 15 of these carbon sources to produce hydrogen. The hydrogen conversion efficiencies of ZX-5 from succinate, lactate, butyrate, malate, acetate, pyruvic acid, propionate, D-mannitol and glucose were 89.7, 81.5, 71.5, 78.8, 69.0, 72.6, 61.9, 64.5, and 52.6%, respectively The highest hydrogen-producing rate of 118ml/lh was observed when butyrate was used as a carbon source. Relatively high efficiencies for reducing chemical oxygen demand (>80%) and hydrogen production were achieved when ZX-5 was used for photo-fermentation of succinate wastewater, or effluents from dark fermentation of wastewater from a fuel ethanol manufacturer or kitchen waste. The concentration of total fatty acids was <0.001% after photo-fermentation by ZX-5. The above results suggest that ZX-5 would possess the potential for hydrogen production while treating wastewater. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.