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. --------------------------------------------------------------------------------