Biohydrogen production by Rhodobacter capsulatus Hup− mutant in pilot solar tubular photobioreactor

In this study, a pilot solar tubular photobioreactor was successfully implemented for fed batch operation in outdoor conditions for photofermentative hydrogen production with Rhodobacter capsulatus (Hup−) mutant. The bacteria had a rapid growth with a specific growth rate of 0.052 h−1 in the batch exponential phase and cell dry weight remained in the range of 1–1.5 g/L throughout the fed batch operation. The feeding strategy was to keep acetic acid concentration in the photobioreactor at the range of 20 mM by adjusting feed acetate concentration. The maximum molar productivity obtained was 0.40 mol H2/(m3 h) and the yield obtained was 0.35 mol H2 per mole of acetic acid fed. Evolved gas contained 95–99% hydrogen and the rest was carbon dioxide by volume.

► Biohydrogen production was realized at pilot scale tubular photobioreactor.
► Circulation for effective gas separation is important.
► A new feeding strategy for fed batch operation was developed.