Biological hydrogen production using co-cultures of PNS bacteria in an immobilized setting

Baysal, Görkem
Biological hydrogen production using purple nonsulfur bacteria is a promising field that would provide biofuel production from solar energy. This study focused on hydrogen production using co-cultures of different PNSB strains in an agar- immobilized setting and searched for both the synergistic effect of using co- cultures of PNSB and the potential advantages of utilizing an immobilized system. Different bioreactors having volumes of 1.4 L, 300 mL and 150 mL have been tested. The photobioreactors were operated anaerobically indoor (continuous illumination) with different light intensities, such as 2500 lux and 4000 lux, and outdoors for 15-25 days using a defined H2 production medium with different substrate concentrations, such as 40 mM Acetate + 2 mM Glutamate and 60 mM Acetate + 2 mM Glutamate. Best results were obtained by agar-immobilization of different PNSB strains, R. capsulatus hup- (YO3), R. palustris (DSMZ 127), and R. sphaeroides O.U.001 (DSMZ 5864) as single, double, and triple co-cultures on the inner surface of a glass 150 mL cylindrical bioreactor as biofilm formation. The growth, hydrogen production capacities, substrate utilization, and pH changes were recorded. The hydrogen yields were within 0.021-3.655 mol H 2 /mol Acetate and H2 productivities were within 0.005-0.737 mol H2 /L.h. It was concluded that co-cultivation of PNSB did not result in higher H2 yield and productivity compared to single cultures. However, the di-culture of R. capsulatus hup- (YO3) and R. palustris (DSMZ 127) seems as a promising co-culture couple, since together they perform optimal hydrogen production both in low and high substrate concentrations and light intensities, and also, H2 production by immobilized PNSB in a biofilm format cylindrical reactor seems promising for large-scale H2 output in outdoor photobioreactors since optimum illumination can be maintained despite the sun's varying incidence angles throughout the day and the year.
Citation Formats
G. Baysal, “Biological hydrogen production using co-cultures of PNS bacteria in an immobilized setting,” Ph.D. - Doctoral Program, Middle East Technical University, 2023.