Hydrogen production by Rhodobacter sphaeroides DSM 158 under intense irradiation

To identify optimal hydrogen production conditions using growing cultures of Rhodobacter sphaeroides DSM 158 the effects of varying the reactor’s volumetric power input (0.01–1.4 kW m−3) and irradiation intensity (5–2500 W m−2) were investigated in batch and continuous production modes. Irradiation intensity had a greater effect on hydrogen production than volumetric power input. Hydrogen production and photofermentative biomass formation were maximized by irradiation at 2250 W m−2 with a volumetric power input of 0.55 kW m−3. The bacterial dry weight (2.64 g L−1) and rate of hydrogen production (195 mL L−1 h−1) achieved under these conditions were greater than any that have previously been reported for batch-mode hydrogen production by R. sphaeroides. Continuous mode experiments (D = 0.1 h−1) yielded a bacterial dry weight, hydrogen production rate, productivity and hydrogen yield of 2.35 ± 0.18 g L−1, 165 ± 6.2 mL L−1 h−1, 3.96 L L−1 d−1 and 36.6%, respectively.