Seventeen purple non sulfur bacterial strains isolated from the trophic lake Averno Naples Italy, were phylogenetically classified and their H(2) producing performances were tested utilizing various synthetic substrates and the fermentation broth derived from the spontaneous fermentation of vegetable residues All the strains showed the capability to produce hydrogen on at least one of the four carbon substrates tested (malic lactic acetic and succinic acid) On lactate, Rhodopseudomonas palustris strain AV33 showed the best maximum production rate (50 7 +/- 2 6 mL (H(2)) L(-1) h(-1)) with a mean rate calculated on the whole period of production of 17 9 mL +/- 0 7 (H(2)) L(-1) h(-1) In the presence of acetate AV33 produced only few mL of H(2) but intracellularly accumulated poly beta hydroxybutyrate up to a concentration of 214 +/- 34% (w/w) of cell dry weight Rp palustris AV33 also produced H(2) on the fermentation broth supplemented with Fe with a maximum production rate of 16 4 +/- 2 3 mL (H(2)) L(-1) h(-1) and a conversion yield of 44 2% (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved