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Factors affecting hydrogen production by unicellular green alga chlamydomonas reinhardtii cc-125
(2021-01-01)
Sereetrakul, Kodchaporn
;
Phunpruch, Saranya
In this study, factors affecting H<inf>2</inf> production by the unicellular green alga Chlamydomonas reinhardtii CC-125 were investigated. It was found that the cell density, O<inf>2</inf> concentration and nutrient deprivation in media play important roles in H<inf>2</inf> production by C. reinhardtii CC-125. C. reinhardtii CC-125 at a cell age of 36 hours with an optical density at 750 nm of 0.8 shows the highest H<inf>2</inf> production rate. Similar to other microorganisms, higher O<inf>2</inf> concentrations decrease H<inf>2</inf> production. However, hydrogenase activity in C. reinhardtii CC-125 seems to show high O<inf>2</inf> tolerance, with an O<inf>2</inf>I<inf>50</inf> of 16.87 ± 0.81%. Under atmospheric air, maximum H<inf>2</inf> production of 100.90 ± 7.92 and 107.47 ± 3.72 mL L-1 was found in cells incubated in sulfur-deprived and sulfur-nitrogen-deprived media, respectively, after 7 days of incubation. The deprivation of both sulfur and nitrogen prolongs H<inf>2</inf> production in this algal strain.
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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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Effect of light intensity and light pattern on hydrogen production by unicellular green alga chlorella sp. LSD-W2
(2019-01-01)
Puangplub, Amornrat
;
Phunpruch, Saranya
Green microalgae can use solar energy and water to produce H2 via hydrogenase enzyme activity. The unicellular green alga Chlorella sp. LSD-W2 has been previously shown to produce high H2 under nitrogen deprivation. This research aimed to examine the effects of light intensity and light pattern on H2 production by Chlorella sp. LSD-W2 under nitrogen deprivation. The result showed that H<inf>2</inf> production rate was significantly enhanced when light intensities were increased. The cells could hardly produce H2 in the dark. The highest H2 production rate with 0.956 ± 0.015 mL L-1 h-1 was obtained in cells incubated in TAP-N medium in a 120-mL glass bottle under light intensity of 60 μmol photons m-2 s-1. H<inf>2</inf> production by cells incubated under light/dark or dark/light cycles was lower than that under continuous light illumination. In order to reduce O2 which is an inhibitor of hydrogenase enzyme, the PSII inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was added to the Chlorella sp. LSD-W2 cell cultures. It was found that O<inf>2</inf> was obviously decreased in cells treated with 10 μM DCMU. Unexpectedly, DCMU caused the reduction of H<inf>2</inf> production by Chlorella sp. LSD-W2.
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Dark fermentative hydrogen production by the unicellular halotolerant cyanobacterium Aphanothece halophytica grown in seawater
(2015-02-01)
Taikhao, Samart
;
Incharoensakdi, Aran
;
Phunpruch, Saranya
Biohydrogen is an environmentally friendly alternative energy carrier that can be produced by a number of different microorganisms. The unicellular halotolerant cyanobacterium Aphanothece halophytica is one of the high potential H<inf>2</inf> producers. Under dark fermentation, it is capable of producing H<inf>2</inf> by the bidirectional hydrogenase activity via the catabolism of glycogen stored during photosynthesis. This work aimed to cultivate A. halophytica in natural seawater containing high salinity and minerals, with an addition of some essential nutrients, and to investigate effects of various nutritional and physical factors on its dark fermentative H<inf>2</inf> production. A. halophytica was able to grow in natural seawater added with NaNO<inf>3</inf>. Cells grown in seawater supplemented with as little as 1.76 mM NaNO<inf>3</inf> showed similar growth to those cultivated in normal BG11 supplemented with Turk Island salt solution. H<inf>2</inf> production was the highest when incubating the cells in seawater without any supplementation of NaNO<inf>3</inf>. Under this condition, the highest rate of dark fermentative H<inf>2</inf> production of 82.79 ± 3.47 nmol H<inf>2</inf> mg-1 dry weight h−1 was found in cells incubated at 35 °C, pH 6 with the supplementation of 378 mmolC L−1 glucose, 0.25 M NaCl, and 0.4 μM Fe3+. Long-term H<inf>2</inf> accumulation of 1,864 ± 81 nmol H<inf>2</inf> mg−1 dry weight was observed after 8 days of dark incubation under anoxic condition, and the high yield of H<inf>2</inf> was sustained at least up to 14 days, suggesting the possibility of utilizing natural seawater to grow A. halophytica for long-term production of H<inf>2</inf>.
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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 Fe3+, or 1 μM Ni2+. The optimum light intensity and temperature for H<inf>2</inf> production were 30 μmol photons m-2 s-1 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)-1 h-1, 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-1 h-1 was obtained when the N-free growth medium contained 0. 4 μM Fe3+. 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.

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