Concomitant biohydrogen and poly-β-hydroxybutyrate production from dark fermentation effluents by adapted Rhodobacter sphaeroides and mixed photofermentative cultures

Highlight•Dark fermentation effluent was valorized via photofermentative H2 and PHB production.•R. sphaeroides and mixed PNSB cultures were applied.•H2 (256 mL H2/g COD) and PHB (32.5% DCW) production was achieved from R. sphaeroides.•More than 70% COD removal from DFE was achieved by mixed PNSB cultures.

This work aimed at investigating concomitant production of biohydrogen and poly-β-hydroxybutyrate (PHB) by photofermentation (PF) using dark fermentation effluents (DFE). An adapted culture of Rhodobacter sphaeroides AV1b (pH 6.5, 24 ± 2 °C) achieved H2 and PHB yields of 256 (±2) N mL H2/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 H2 yields were 164.0 (±12) and 71.3 (±6) N mL H2/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 H2 and PHB production from the PF process gave a good DFE post treatment achieving up to 80% COD removal from the initial DFE.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide