Photobiological hydrogen production of Platymonas subcordiformis in four culture media by direct transferring from spent growth media

Significant cost-saving can be achieved in photobiological hydrogen production by green microalgae if the algae in the growth medium could be directly used for hydrogen production without the concentration and separation of algal biomass. The growth kinetics of a marine green algae Platymonas subcordiformis in four different culture media (Walne medium, marine No3 medium, TAP medium, an optimized medium) were investigated. The algal cells in the spent growth media were subjected to 24 h dark anaerobic induction and directly used for photobiological hydrogen production with an uncoupler 15 μmol/L carbonylcyanide-m-chlorophenylhydrazone (CCCP). Results showed that the best growth was obtained in the optimized medium from our laboratory, with a specific growth rate 0.192 d^-1. The highest photobiological hydrogen production was obtained for the cells grown in walne medium. About 4.2 mL hydrogen was produced at 3 × 10⁶ cells/mL for 24 h in a 500 mL photo-bioreactor. The medium micronutrients have a significant impact on achieving high density cell culture and the yield of photobiological hydrogen gas production in the spent growth media.