Photosynthesis driven continuous hydrogen production by diazotrophic cyanobacteria in high cell density capillary photobiofilm reactors.

Hydrogen (H) is a promising fuel in the context of climate neutral energy carriers and photosynthesis-driven H-production is an interesting option relying mainly on sunlight and water as resources. However, this approach depends on suitable biocatalysts and innovative photobioreactor designs to maximize cell performance and H titers. Cyanobacteria were used as biocatalysts in capillary biofilm photobioreactors (CBRs). We show that biofilm formation/stability depend on light and CO availabilityH production rates correlate with these parameters but differ between Anabaena and Nostoc. We demonstrate that high light and corresponding O levels influence biofilm stability in CBR. By adjusting these parameters, biofilm formation/stability could be enhanced, and H formation was stable for weeks. Final biocatalyst titers reached up to 100 g l for N. punctiforme atcc 29133 NHM5 and Anabaena sp. pcc 7120 AMC 414. H production rates were up to 300 µmol H lh and 3 µmol H gh in biofilms.