Phototrophic hydrogen production by agar-immobilized Rhodobacter capsulatus

Elkahlout, Kamal E. M.
photosynthetic bacteria is attractive field as production is fueled by solar energy. Hydrogen production potential of two photosynthetic bacteria R.capsulatus (DSM1710 wild type and R.capsulatus YO3 Hup- uptake hydrogenase deleted mutant strain) were examined in agar immobilized systems. In the present work agar and glutamate concentrations were optimized for immobilization of bacteria while feeding bacteria with 40/2-4 mM acetate/ glutamate. Immobilized bacteria produced hydrogen for 420-1428 hours covering 5-7 rounds. Optimizing of acetate concentration indicated that 60 mM produced the highest observed yield around 90-95%. Results shown that 2.5 mg dry cell weight/mL is the optimum cell concentration for wild type strain while 5 mg dry cell weight/mL was optimum for YO3 strain. Using either glycerol or sodium dithionite caused decrease in hydrogen production capacity of immobilized bacteria. It was observed that agar provided protection against inhibition effect of ammonium. Co- v immobilization of bacteria with packed cells of H. salinarium increased total hydrogen production capacity by about 1.14-1.41 folds. Hydrogen production by immobilized bacteria in panel photobioreactor was achieved by a novel system which allowed long term hydrogen production. Immobilized R. capsulatus DSM 1710 in panel reactor worked for about 67-82 days covering 4-5 rounds while immobilized R. capsulatus YO3 worked for 69-72 days covering seven rounds.