Improved hydrogen production of the downstream bioreactor by coupling single chamber microbial fuel cells between series-connected photosynthetic biohydrogen reactors

To obtain additional hydrogen recovery from the downstream photosynthetic biohydrogen reactor (PBR), a system (PBR1–MFCs–PBR2) that combined PBRs with three single chamber microbial fuel cells (MFCs) was proposed in this study. The results revealed that the PBR2 in PBR1–MFCs–PBR2 showed a hydrogen production rate of 0.44 ± 0.22 mmol L h−1, which was 15 and 4 times higher than those obtained by direct connecting the two PBRs (PBR1–PBR2) and pH regulated system (PBR1–pH regulation–PBR2), respectively. In addition, the PBR1–MFCs–PBR2 exhibited the highest glucose utilization (ηg) of 97.6 ± 2.1 %, while lower ηg values of 75.6 ± 2.2% and 70.1 ± 1.2% was obtained for PBR1–PBR2 and PBR1–pH regulation–PBR2, respectively. These improvements were due to the removal of inhibitory byproduct and H+ from the PBR1 effluent by the MFCs. •A combined system of PBRs and MFCs was proposed for additional biohydrogen recovery.•Inhibitory VFAs and H+ generated in PBR1 were removed by the MFCs.•Byproduct removal in MFCs resulted in a notably improved hydrogen production in PBR2.•A glucose utilization efficiency of 97.6% was achieved in the combined system.