Photofermentative Hydrogen Production by Agar Immobilized Co-Cultures of Purple Non-Sulfur Bacteria

Purple non-sulfur (PNS) bacteria have the ability to produce biohydrogen via photofermentation. This study focuseson hydrogen production using co-cultures of immobilized PNS bacteria, investigates the possible synergistic effectof their co-cultures, and the advantages of immobilization. Growth, hydrogen production and substrate utilization ofsingle-cultures and, double and triple co-cultures of R. capsulatus hup- (YO3), Rp. palustris (DSM 127) and R.sphaeroides O.U.001 (DSM 5864) were compared using an artificial hydrogen production medium in 150 mL indoorsand outdoors photobioreactors on 40/2 Acetate/Glutamate medium under continuous illumination and anaerobicconditions. Hydrogen yields were found to be within 1.71-3.21 mol H2/mol acetate and hydrogen productivities werefound to be within 0.0447-0.406 mol H2/(L.h). Additional studies with different temperature, illumination, andsubstrate concentration parameters need to be carried out for deeper understanding of the mechanism of hydrogenproduction in immobilized co-cultures in order to further improve and standardize hydrogen yields and productivities