Light stimulation strategy for promoting bio-hydrogen production: Microbial community, metabolic pathway and long-term application

Abstract

Light stimulation strategy for promoting bio-H2 production was firstly investigated with incandescent light. The light condition controlled by photon number (NR, 0.63 × 104–6.25 × 104 μmol/(day∙L)) was applied to stimulate H2 fermentation process. The optimal NR of 3.75 × 104 μmol/(day∙L) contributed to 1.4 folds H2 yield of the dark reactor and promoted efficient H2 producing pathway (acetate and nicotinamide adenine dinucleotide pathway) with increased microbial activities.Furthermore, the effect of light stimulation on microbial community was identified. Fervidobacterium, Coprothermobacter and OPB95 were the dominant genera that could be activated by light stimulation for promoting acetate pathway and contribute to higher H2 production. Moreover, long-term operation showed more stable and higher H2 production of light stimulated bioreactor than the dark one, which resulted from the light stimulated metabolic pathway, increased sludge conductance and promoted microbial immobilization. This novel light stimulation strategy is promising for future application on promoting bio-H2 production.