This work aimed at investigating concomitant production of biohydrogen and poly-beta-hydroxybutyrate (PHB) by photofermentation (PF) using dark fermentation effluents (DFE). An adapted culture of Rhodobacter sphaeroides AV1b (pH 6.5, 24 +/- 2 degrees C) achieved H-2 and PHB yields of 256 (+/- 2) N mL H-2/g Chemical Oxygen Demand (COD) and 273.8 mg PHB/g COD (32.5 +/- 3% of the dry cells weight (DCW)), respectively. When a diluted (1:2) DFE medium was applied to the adapted pure and mixed photofermentative culture, the respective H-2 yields were 164.0 (+/- 12) and 71.3 (+/- 6) N mL H-2/g COD and the PHB yields were 212.1 (+/- 105.2) and 50.7 (+/- 2.7) mg PHB/g COD added, corresponding to 24 (+/- 0.7) and 6.3 (+/- 0) % DCW, respectively. The concomitant H-2 and PHB production from the PF process gave a good DFE post treatment achieving up to 80% COD removal from the initial DFE. (C) 2016 Elsevier Ltd. All rights reserved.