Manifestation of behavioural and physiological functions of Synechococcus sp. Miami BG 043511 in a photobioreactor

Abstract.

Synechococcus sp. Miami BG 043511, a unicellular marine cyanobacterium, offers possibilities for biotechnological purposes. It was tested for the first time in the present work as a component of specially designed biosolar system. The testing was carried out using a 4.35-l helical tubular photobioreactor. The cell culture of this cyanobacterium was found to exhibit persistent cyclic oscillations in O₂ evolution and CO₂ consumption during the growth in the photobioreactor under N₂-fixing autotrophic conditions and continuous illumination. The cycles of these two activities during bubbling of the culture with air + 2% CO₂ lasted for 23.5 h and were of the same pattern and phase. The cycles consisted of two phases: a short (8.3 h) and a long (15.2 h) phase, with a minor and a major peak of gas exchange, respectively. Additionally, the culture exhibited transient increase in optical density at each major peak of O₂ evolution. The growth rate of the continuous culture (4 µg chl a ml^–1) of the cyanobacterium, sparged with CO₂-enriched air under light of 150 µE m^–2 s^–1, was 0.024 h^–1. The culture in the photobioreactor produced an appreciable amount of H₂ under argon + 2% CO₂. However, it produced no H₂ under air + 2% CO₂. The activation of H₂ production in the cyanobacterium by CO₂-enriched argon was accompanied by frequent oscillations in the optical density, essential elongation of the cycle of O₂ evolution and inhibition of the growth rate of the culture. H₂ and O₂ evolution changed with time in very similar oscillatory patterns, but inversely to each other. The results showed that Synechococcus sp. Miami BG 043511 could be successfully cultivated in the helical tubular type of biosolar system. It is also clear that further efforts should be made to extend our knowledge of this cyanobacterium.