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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
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Taikhao, Samart
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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−1 h−1 and achieved a maximum cumulative H<inf>2</inf> production of 1153.78 ± 52.65 μmol H<inf>2</inf> mg Chl−1 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.
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Physiological and Environmental Factors Influencing Hydrogen Production by Unicellular Green Alga Monoraphidium sp. KMITL-1
(2025-10-01)
Krutpan, Varanya
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Supakriangkrai, Thaninthorn
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Lohasupthawee, Pana
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Phunpruch, Saranya
With the growing global energy demand and the urgent need to reduce carbon emissions, hydrogen (H<inf>2</inf>) has emerged as a promising clean energy carrier. Among various biological H<inf>2</inf> production, green algae present a sustainable and eco-friendly alternative due to their ability to produce H<inf>2</inf> via photobiological pathways. This study aimed to investigate H<inf>2</inf> production by unicellular green alga Monoraphidium sp. KMITL-1, isolated from hydroponic water at the Plant Tissue Culture Laboratory, King Mongkut’s Institute of Technology Ladkrabang. The taxonomic identity of the strain, belonging to the genus Monoraphidium within the Selenastraceae family, was confirmed through morphological observation and molecular characterization using 23S plastid rRNA gene sequencing. Various physiological and environmental parameters influencing H<inf>2</inf> production were evaluated, including cell age, cell density, nutrient deprivation, carbon source, pH, temperature, and light intensity. A 24-hour-old culture with an OD<inf>750</inf> of 0.8 exhibited a significant increase in H<inf>2</inf> production. The optimal medium was potassium-deprived Tris-acetate-phosphate (TAP-K) supplemented with glucose at a concentration of 350 mmol C-atom L-1. The ideal environmental conditions for H<inf>₂</inf> production were pH 7.2, a temperature of 30 °C, and a light intensity of 60 μmol photons m-2 s-1. Under these optimized conditions, Monoraphidium sp. KMITL-1 achieved a maximum H<inf>2</inf> production rate of 67.976 ± 1.096 μmol H<inf>2</inf> mg Chl-1 h-1 and a cumulative H<inf>2</inf> yield of 3,190.436 ± 2.219 μmol H<inf>2</inf> mg Chl-1 after 72 h of incubation. These results highlight the potential of Monoraphidium sp. KMITL-1 for large-scale biohydrogen production and its applicability in the development of sustainable energy technologies.
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Effect of cell density and nutrient deprivation on hydrogen production by unicellular green alga Scenedesmus sp. KMITL-OVG1
(2019-01-01)
Warichanan, Kittiphat
;
Phunpruch, Saranya
Hydrogen is considered as one of the energy carriers for the near future. H2 production by green algae is catalyzed by hydrogenase activity using electrons from photosynthetic process under the light and from accumulated carbohydrate catabolism in the dark. This research aimed to investigate the effect of cell density and nutrient deprivation on H<inf>2</inf> production by Scenedesmus sp. KMITL-OVG1 isolated in Thailand. The result showed that cell culture with the optical density at 750 nm of 0.8 gave the highest H2 production rate. Interestingly, the highest H2 production rate of 1.957 ± 0.100 mL L-1 h-1 and hydrogenase activity of 0.031 ± 0.001 ml L-1 min-1 were found in cells incubated under potassium deprivation. H<inf>2</inf> production rate was approximately 3 folds higher than that of cells incubated in normal TAP medium. The increased H2 production rate and hydrogenase activity might be involved in the reduction of starch accumulation. Moreover, the deprivation of potassium combined with other nutrients did not enhance H<inf>2</inf> production rate by Scenedesmus sp. KMITL-OVG1.
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Enhanced hydrogen production by optimization of immobilized cells of the green alga Tetraspora sp. CU2551 grown under anaerobic condition
(2018-04-01)
Maswanna, Thanaporn
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Phunpruch, Saranya
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Lindblad, Peter
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Maneeruttanarungroj, Cherdsak
The green alga Tetraspora sp. CU2551 has previously been identified and characterized as a photosynthetic microorganism with high potential for H<inf>2</inf> production. In the present study, cells of Tetraspora CU2551 were entrapped and immobilized in an alginate matrix with the aim to analyze the effect of cell stacking and a reduced exposure of O<inf>2</inf> to the cells. The results showed that the most favorable immobilization conditions were 4% (w/v) of final alginate concentration and a cell concentration of 0.125 mg cell dry wt/mL alginate with a bead diameter of 2.80–3.35 mm. The H<inf>2</inf> production yields increased when the immobilized cells were incubated in S-deprived medium and this could be repeated at least for 3 production times. Maximal total H<inf>2</inf> production reached 7.68 ± 0.88 mL H<inf>2</inf>/25 mL medium, corresponding to a rate of 1182.45 ± 24.40 nmol H<inf>2</inf>/h/mg DW. This production is about 6 times higher compared to by cells in suspension, 2–10 times higher when compared to by other green algae, and 10–50 times higher when comparing with cyanobacteria. Based on our observations, immobilized cells of Tetraspora CU2551 is considered a very promising biological system for significant photobiological H<inf>2</inf> production by a photosynthetic microorganism.

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