Sustained outdoor H2 production with Rhodopseudomonas palustris cultures in a 50 L tubular photobioreactor

Sunlight represents an important choice for low cost photosynthetic cultures irradiation, especially in up-scaled processes. The aim of this study was the assessment of the hydrogen production performances of Rhodopseudomonas palustris strain 42OL cultivated outdoors, under sunlight, in a 50 L tubular photobioreactor. Moreover, bacteriochlorophyll a fluorescence was used for the first time as a tool for monitoring the physiological status of Rp. palustris mass cultures.The maximum H2 production rate of 27.2 ml L−1 h−1, and the mean rate per illuminated surface of 3.54 ± 1.53 L m−2 d−1 obtained resulted the highest so far reported for outdoor experiments carried out with purple bacteria in tubular photobioreactors of comparable dimensions. The in-situ measurement of bacteriochlorophyll a fluorescence (Fv/Fm) showed that the photosystem was unaffected by changing light irradiance during the day and remained fully active over the whole period of hydrogen production.

► Rp. palustris 42OL produced H2 at a max hour rate of 27.2 mL L−1 h−1. ► Rp. palustris 42OL produced H2 at a mean rate of 3.54 ± 1.53 L m−2 d−1. ► Dissolved H2 was lost during dark periods lowering the total amount of H2 obtained. ► Bchl a fluorescence effectively monitors fitness of PNSB in outdoor cultures. ► No alteration in PS performances (Fv/Fm) detected over the H2 production period.