Role of L-cysteine and iron oxide nanoparticle in affecting hydrogen yield potential and electronic distribution in biohydrogen production from dark fermentation effluents by photo-fermentation

Dark fermentation effluent is a potential substrate for hydrogen production by photosynthetic bacteria(PSB). Influences of adding L-cysteine and Fe3O4 nanoparticles (NPs) on hydrogen production performance and electronic distribution from dark fermentation effluents (DFEs) during photo fermentation hydrogen production(PFHP) process were experimentally studied, as well as the critical kinetic analysis. L-cysteine addition can promote flocculability and cell growth rates of PSB HAU-M1 while addition of 300 mg/L L-cysteine and 100 mg/L Fe(3)O4 NPs can peak H-2 yield from the DFEs, resulting in 29.94% and 29.23% substrate electrons were diverted to H-2, respectively. Controlling the adding time interval of L-cysteine and Fe3O4 NPs can improve the activity of nitrogenase without weakening flocculation and increase the hydrogen production, the maximum hydrogen yield of 234.55 +/- 7.5 mL was obtained at 12 h interval time, 35.94% substrate electrons diverted towards bio-hydrogen generation, and the corresponding nitrogenase activity increased by 2.12 times as comparing to the control. The modified Gompertz and Han-Levenspiel models were employed to model the effect of the L-cysteine and Fe3O4 NPs on hydrogen production, the predicted critical L-cysteine and Fe3O4 NPs concentrations were 4630.87 and 1969.18 mg/L, respectively. (C) 2020 Elsevier Ltd. All rights reserved.