Enhanced bio-hydrogenesis by co-culturing photosynthetic bacteria with acidogenic process: Augmented dark-photo fermentative hybrid system to regulate volatile fatty acid inhibition

•Hybrid dark-photo fermentation process is effective towards H2 production.•Effective reduction in VFA and COD concentrations after augmentation.•Significant role of bacteriochlorophyll and bacteriopheophytin on H2 production.

To overcome induced fatty acid inhibition during dark-fermentative hydrogen (H2) production process, a hybrid strategy was designed and evaluated by co-culturing photosynthetic bacteria with acidogenic microflora. Augmented dark-photo fermentation system (ADPFS) illustrated 40% increment in cumulative H2 production (CHP, 250 ml) compared to dark-fermentation system (DFS) along with 10% enhancement in COD removal efficiency. Co-culturing helped to reduce VFA accumulation by 40% which supports the functional role of photosynthetic organisms in reducing the fatty acid concentration in association to additional H2 production. Relatively higher reduction in individual fatty acids viz., acetic acid (43%), butyric acid (57%) and propionic acid (65%) was observed with AD-PFS operation. Increment in bacteriochlorophyll (Bchl) after augmentation corroborated well with results. At lower pH, pheophytinization was observed which hindered H2 production. Voltammograms illustrated dominant oxidation behavior during hybrid AD-PFS operation and provides viable option for enhancing performance by regulating system buffering microenvironment.

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