Enhanced coproduction and trade-off of the hydrogen and butanol in the coupled system of pervaporation and repeated-cycle fixed-bed fermentation

[Display omitted] •Repeated cycle fermentation with immobilized cells was coupled with pervaporation.•Long-term fermentation was efficiently conducted in the coupled system.•Hydrogen and butanol production per unit cell weight were increased by two times.•Trade-off between hydrogen versus butanol tilted to butanol production.•Respiration heat provided 35 % of the energy requirement by pervaporation. In the study, a coupled system of pervaporation and repeated-cycle fixed bed fermentation with the bagasse as the carrier material was developed. Three repeated cycles of fermentation lasting for 540 h was efficiently carried out to coproduce hydrogen and butanol with the strain Clostridium acetobutylicum. From 1st cycle to 3rd cycle, the average hydrogen productivity and butanol productivity were around 130 mLL−1 h−1 and 0.15 gL−1 h−1, respectively. Average hydrogen yield and butanol yield were around 0.17 Lg−1 and 0.19 gg−1. The hydrogen and butanol production per unit cell weight were 27 Lg−1 and 31 gg−1, which were more than two times of those in a conventional repeated-cycle fermentation. The trade-off and competition between the hydrogen and butanol production was studied and analyzed. Compared with the pervaporation-free fermentation, the hydrogen yield was decreased by 14 % and butanol yield was increased by 27 % in the coupled system. Instantaneous solvent removal from the broth by pervaporation changed probably the metabolic pathway to more butanol production over hydrogen. From 1st cycle to 3rd cycle, the respiration heat generated during each fermentation cycle could cover 45 %, 24 % and 37 % of the total energy requirement of the pervaporation achieving the best use of the energy.