A new hydrogen-producing photosynthetic bacterium, designated as Rhodovulum sulfidophilum P5, was enriched and isolated from the sludge of a marine shrimp cultivation farm. During fermentation, hydrogen was mainly produced in the late exponential and stationary phases. The optimum culture conditions of strain P5 for hydrogen production were NaCl concentration of 20 g/L, initial pH of 8, temperature of 30 degrees C, and light intensity of 100 mu mol photons/m(2) s. The maximum hydrogen yield and rate were 2.56 +/- 0.18 mol/mol acetate and 19.4 +/- + 1.6 mL/L h, respectively. Under optimum culture conditions, the hydrogen conversion efficiencies of P5 from acetate, propionate, and butyrate were (64.62 +/- 5.05)%, (17.95 +/- 0.72)%, and (41.83 +/- 2.68)%, respectively. Taken together, these results suggest that this strain has a high salt tolerance and the potential to be used for biohydrogen production and biological treatment of marine organic wastewater. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.