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    Optimal conditions for maximized H2 yield from a new green algal strain Chlorella sp. KLSc61
    (2022-08-01)
    Laokua, Natwikar
    ;
    Rittiyan, Nutnicha
    ;
    Kornrawudaphikasama, Yosita
    ;
    Klinsalee, Rachaneekorn
    ;
    Tonawut, Yothawut
    Hydrogen produced from microalgae is attracting the attention of scientists as a potential new ‘Bio-Circular-Green’ energy source. We screened a selection of naturally occurring algal strains for H<inf>2</inf> yield as a basis for high yield development. The best strain was a new strain of biohydrogen-producing green algae from a fresh water source at King Mongkut's Institute of Technology Ladkrabang, Thailand. Using morphological and 18S rDNA sequencing analyses, this alga was identified and classified as Chlorella sp. KLSc61. When adapted cells in TAP-K medium (with starting pH at 9.0) containing 25 mM ethanol, with 54 μmol photons m<sup>−2</sup> s<sup>−1</sup> light, and incubated at 35 °C, Chlorella sp. KLSc61 showed a maximum H<inf>2</inf> yield of 9,804 ± 469.5 μmol H<inf>2</inf> mg<sup>−1</sup> Chl at day 7. Under these conditions, the cells produced ~ 12.2 times more H<inf>2</inf> gas than without optimization (753.0 μmol H<inf>2</inf> mg<sup>−1</sup>Chl). Our optimized system also produced H<inf>2</inf> at a rate 11–570 times greater than previously reported microalgae. Thus Chlorella sp. KLSc61 could be a viable strain for biohydrogen production as a clean future energy source.
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    Item type:Publication,
    Response of green alga Tetraspora sp. CU2551 under potassium deprivation: a new promising strategy for hydrogen production
    (2022-04-01)
    Pewnual, Totsapon
    ;
    Jampapetch, Narirat
    ;
    Saladtook, Sathonkorn
    ;
    Raksajit, Wuttinun
    ;
    Klinsalee, Rachaneekorn
    With increasing world energy consumption, renewable energy sources can fulfill the need and many have net zero carbon dioxide emissions. One of these is hydrogen, which is biologically produced molecular hydrogen from organisms. Although many studies have produced hydrogen from green algae and optimized conditions to obtain the highest yield, following our previous works on production optimization from Tetraspora sp. CU2551, we tested deprivation of Fe, Cu, Ca, S, Mg, or K, and surprisingly found that K deprivation showed another promising switch in increased H<inf>2</inf> yield, representing 9.2 ± 0.1 μmol mg<sup>−1</sup> DW within 32 h incubation anaerobically. Moreover, longer cell adaptation by aerobic incubation, before production phase, resulted in higher hydrogen yield. Cells adapted in potassium deprivation (TAP-K medium) promoted hydrogen production to a yield of 14.8 ± 0.03 μmol mg<sup>−1</sup> DW, or about 3.0 times higher than normal TAP (5.0 ± 0.82 μmol mg<sup>−1</sup> DW). The increased yield was caused by (1) lowering PSII activity (direct biophotolysis), resulted in less oxygen being produced, lowering hydrogenase inhibitor levels, and (2) increasing accumulated starch degradation (indirect biophotolysis) (12.2% starch remaining or 7.2 ± 0.9 μg mg<sup>−1</sup> DW), increased the flow of electrons to hydrogenase. Our finding makes potassium deprivation conditions as another the promising choice to enhance hydrogen production in biological systems.