An inorganic culture medium contaminated with ammonium was used to generate molecular hydrogen by cyanobacteria. First, ammonium ion uptake by immobilized on hollow fibers cells of cyanobacterium Anabaena variabilis was studied in flasks and in a photo-bioreactor. Next, after the ammonium was removed from water, H-2 production by hollow fibers-immobilized cyanobacterial cells was investigated in flasks and in a photobioreactor. The photobioreactor was designed so that the growth medium with ammonium from a medium reservoir (where ammonium ion concentration was measured) was cycled through a photobioreactor column with hollow fiber-attached cells. The ammonium ion uptake efficiency by attached cells in the photobioreactor was found to be 90% after 25 days. The depletion of the ammonium in water inside a photobioreactor stimulated H2 production by cyanobacteria which was observed at an average rate of 18 mL.g dw(-1).h(-1) for three months. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.