Research on photobiological H-2 production processes is pointing towards the use of low cost substrates as sources of reduced carbon for H-2 generation. Those substrates (either wastewaters or effluents derived from other fermentation processes) are often rich not only in carbon, but also in fixed nitrogen. NH4+ is an inhibitor of nitrogenase-mediated H-2 production in purple non sulfur bacteria. A Rhodopseudomonas palustris mutant strain (NifA*), which constitutively expresses nitrogenase genes, was utilized in order to test the use of NH4+, containing fermentation products for photobiological production of H-2. The strain was grown on both synthetic and waste-derived NH4+ containing media. The nifA* mutant produced H-2 in the presence of high concentrations of NH4+ both in a synthetic medium and in a real vegetable waste-derived medium resulting in higher H-2 levels than the wild-type strain. Thus, this study demonstrates that the NifA* strain is well suited to overcome the effects of inhibitory naturally occurring NH4+ as it converts agricultural waste into biofuel. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.