Enhanced Hydrogen Production Through Two-Stage Fermentation Coupling Clostridium pasteurianum and Rhodobacter sphaeroides

ABSTRACT Biological H2 production via dark fermentation is constrained by low yields and inhibitory metabolite accumulation. Coupling dark and photo fermentation effectively overcomes these issues by enhancing substrate utilization and reducing wastewater pollution, yet scalable systems for industrial application remain rare. This study presents a 10-L two-stage fermentation system (5L dark/5L photo bioreactors) using Clostridium pasteurianum DSM 525 and Rhodobacter sphaeroides ZX-5. Dark fermentation generated 3372 mL H2 from glucose, yielding effluent with 1.29 g/L acetic and 3.11 g/L butyric acids. After centrifugation, pH adjustment, and clinoptilolite deamination (≥60% efficiency), ammonium was reduced to <100 mg/L. The pretreated effluent, supplemented with concentrated RCVBN medium, served as photo-fermentation substrate. A butyric acid feeding strategy extended the process by 120 h, boosting H2 yield by 16.4%. The coupled system produced 6480 mL H2 (80% increase), degrading 50% acetic acid and 42% butyric acid. This work demonstrates a scalable bioreactor configuration integrating efficient biohydrogen production with value-added wastewater treatment for industrial bioenergy applications. Competing Interest Statement The authors have declared no competing interest.