Hydrogen-producing purple non-sulfur bacteria isolated from the trophic lake Averno (Naples, Italy)

Seventeen purple non sulfur bacterial strains, isolated from the trophic lake Averno, Naples, Italy, were phylogenetically classified and their H2-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, Rp. palustris strain AV33 showed the best maximum production rate (50.7 ± 2.6 mL (H2) L-1 h-1), with a mean rate, calculated on the whole period of production, of 17.9 mL ± 0.7 (H2) L-1h-1. In the presence of acetate, AV33 produced only few mL of H2, but intracellularly accumulated poly-β-hydroxybutyrate up to a concentration of 21.4 ± 3.4 % (w/w) of cell dry weight. Rp. palustris AV33 also produced H2 on the fermentation broth supplemented with Fe, with a maximum production rate of 16.4 ± 2.3 mL (H2) L-1 h-1 and a conversion yield of 44.2%.