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Author: search.filters.author.Junyapoon, SuwanneeSubject: search.filters.subject.Aphanothece halophytica

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    Factors affecting biohydrogen production by unicellular halotolerant cyanobacterium Aphanothece halophytica
    (2013-04-01)
    Taikhao, Samart
    ;
    Junyapoon, Suwannee
    ;
    Incharoensakdi, Aran
    ;
    Phunpruch, Saranya
    The effects of several physiological parameters on H<inf>2</inf> production rate in the unicellular halotolerant cyanobacterium Aphanothece halophytica were investigated. Under nitrogen deprivation, the growth of cells was inhibited, but H<inf>2</inf> production rate was enhanced approximately fourfold. Interestingly, cells grown under sulfur deprivation exhibited a decrease in cell growth, H<inf>2</inf> production rate, and bidirectional hydrogenase activity. Glucose was the preferred sugar source for H<inf>2</inf> production by A. halophytica, but H<inf>2</inf> production decreased at high glucose concentrations. H<inf>2</inf> production rate was optimum when cells were grown in the presence of 0. 75 M NaCl, or 0. 4 μM Fe<sup>3+</sup>, or 1 μM Ni<sup>2+</sup>. The optimum light intensity and temperature for H<inf>2</inf> production were 30 μmol photons m<sup>-2</sup> s<sup>-1</sup> and 35 °C, respectively. A two-stage culture of A. halophytica was performed in order to overcome the reduction of cell growth in N-free medium. In the first stage, cells were grown in normal medium to accumulate biomass, and in the second stage, H<inf>2</inf> production by the obtained biomass was induced by growing cells in N-free medium supplemented with various chemicals for 24 h. A. halophytica grown in N-free medium containing various MgSO<inf>4</inf> concentrations had a high H<inf>2</inf> production rate between 11. 432 and 12. 767 μmol H<inf>2</inf> mg chlorophyll a (chl a)<sup>-1</sup> h<sup>-1</sup>, a 30-fold increase compared to cells grown in normal medium. The highest rate of 13. 804 μmol H<inf>2</inf> mg chl a<sup>-1</sup> h<sup>-1</sup> was obtained when the N-free growth medium contained 0. 4 μM Fe<sup>3+</sup>. These results suggested the possibility of using A. halophytica and some other halotolerant cyanobacteria thriving under extreme environmental conditions in the sea as potential sources for H<inf>2</inf> production in the future. © 2012 Springer Science+Business Media B.V.