Optimization of the Feeding Condition for Mixed Culture Photo Fermentative Hydrogen and Polyhydroxyalcanohates Production from Dark Fermentation Effluents

The work analyses the differences, in terms of process efficiency, existing among batch, semi-continuous, and continuous photo fermentation of dark fermentation effluents. Obtained results indicate that the highest hydrogen production is obtained in semi-continuous operation mode. Indeed, in this condition a hydrogen productivity of 99.57 mL L−1 was achieved, representing 86.31% of the total produced biogas. In addition, 76.3% of the initial chemical oxygen demand was removed. Finally, from a detailed characterization of the polyhydroxyalkanoates stored by the microbial community the study reveals, for the first time, that via mixed culture photo fermentation, it is possible to obtain the copolymer polyhydroxybutyrate-co-hydroxyvalerate.