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Author: search.filters.author.Chinchusak, NattanonSubject: search.filters.subject.Atmospheric air

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    Enhanced hydrogen production by green alga Scenedesmus obliquus TISTR 8546 under atmospheric air through potassium deprivation and cysteine supplementation
    (2026-03-01)
    Sereetrakul, Kodchaporn
    ;
    Taikhao, Samart
    ;
    Chinchusak, Nattanon
    ;
    Phunpruch, Saranya
    Hydrogen is a promising alternative energy carrier that can be produced by green microalgae. However, the key enzyme catalyzing this process, [FeFe]‑hydrogenase, is highly sensitive to O<inf>2</inf> generated during photosynthesis, which severely restricts its activity. This study aimed to screen the microalgal strain capable of producing high levels of H<inf>2</inf> in the presence of O<inf>2</inf> and to enhance H<inf>2</inf> production yields using O<inf>2</inf>-scavenging strategies to levels comparable to or exceeding those achieved under anaerobic conditions. Among the 24 strains tested, Scenedesmus obliquus TISTR 8546 demonstrated the highest H<inf>2</inf> production under both aerobic and anaerobic conditions. The O<inf>2</inf>I<inf>50</inf> of S. obliquus TISTR 8546 cells for H<inf>2</inf> evolution was 15.93 ± 0.24%. Potassium deprivation significantly enhanced H<inf>2</inf> production and hydrogenase activity by lowering O<inf>2</inf> levels through reduced photosynthetic O<inf>2</inf> evolution and increased dark respiration. Moreover, potassium deprivation promoted intracellular starch accumulation, providing reducing equivalents for H<inf>2</inf> generation. Cysteine supplementation further stimulated H<inf>2</inf> production by serving as a reducing agent. S. obliquus TISTR 8546 exhibited a maximum H<inf>2</inf> production rate of 22.92 ± 1.05 μmol H<inf>2</inf> mg Chl<sup>−1</sup> h<sup>−1</sup> and achieved a maximum cumulative H<inf>2</inf> production of 1153.78 ± 52.65 μmol H<inf>2</inf> mg Chl<sup>−1</sup> when incubated in potassium-deprived TAP medium supplemented with 0.1 mM cysteine under atmospheric air for 6 days. This rate was 23.6- and 2.7-fold higher than those obtained in TAP and TAP-K media, respectively. These findings demonstrate the potential of S. obliquus TISTR 8546 as a robust microalgal strain for sustainable H<inf>2</inf> production under atmospheric air, highlighting its promise for future industrial applications.