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Subject: search.filters.subject.Anabaena siamensis

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    Increasing Hydrogen Production Efficiency of N2-Fixing Cyanobacterium Anabaena siamensis TISTR 8012 by Cell Immobilization
    (2017-01-01)
    Taikhao, Samart
    ;
    Phunpruch, Saranya
    H<inf>2</inf> produced by cyanobacteria is one of the interesting alternative energy carriers for the future. The filamentous N<inf>2</inf>-fixing cyanobacterium Anabaena siamensis TISTR 8012 is a potential microorganism for H<inf>2</inf> production. It can produce H<inf>2</inf> via both photosynthesis and nitrogen fixation processes. This study aimed to increase the efficiency of H<inf>2</inf> production by immobilization of A. siamensis cells. The result showed that H<inf>2</inf> production rate by A. siamensis grown in BG11<inf>0</inf> medium was higher than that in BG11 and Allen-Arnon media due to an increase of the heterocyst cells. The sulfur deprivation during adaptation period for 24 hours increased its H<inf>2</inf> production rate. The optimal conditions for H<inf>2</inf> production by immobilized cells were immobilization with alginate and using 150 gel beads in 20 mL glass vial. In immobilized cells, an addition of 0.5% fructose resulted in a 2-fold increase of H<inf>2</inf> production rate. Finally, the reducing agents β-mercaptoethanol and methylviologen enhanced H<inf>2</inf> production rate with 3.092 and 2.426 μmolH<inf>2</inf> mg chl a<sup>-1</sup> h<sup>-1</sup>, respectively, in A. siamensis immobilized cells whereas NADH, dithiothreitol and sodium dithionite were not capable of increasing H<inf>2</inf> production rate.
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    Effect of Metal Cofactors of Key Enzymes on Biohydrogen Production by Nitrogen Fixing Cyanobacterium Anabaena siamensis TISIR 8012
    (2017-01-01)
    Taikhao, Samart
    ;
    Phunpruch, Saranya
    In N<inf>2</inf>-fixing cyanobacteria, three enzymes are involved in the H<inf>2</inf> metabolism. Nitrogenase catalyzes the N<inf>2</inf> fixation which produces H<inf>2</inf> as a by-product. The produced H<inf>2</inf> is taken up to protons and electrons by an activity of uptake hydrogenase. Reversible enzyme catalyzes both reactions of the H<inf>2</inf> evolution and the H<inf>2</inf> uptake. These enzymes are all metalloenzyme. The cyanobacterial nitrogenase normally requires molybdenum and iron as cofactors; however nitrogenase of few cyanobacterial species is dependent on vanadium. The cyanobacterial uptake and reversible hydrogenase requires nickel and iron as cofactors. This research aimed to investigate the effect of these metal cofactors on H<inf>2</inf> production and hydrogenase activity by N<inf>2</inf>-fixing cyanobacterium Anabaena siamensis TISTR 8012 isolated from rice paddle field in Thailand. The result showed that A. siamensis cells incubated in N-deprived BG11 medium (BG11<inf>0</inf>) gave clearly higher H<inf>2</inf> production rate and hydrogenase activity than those in normal BG11 medium. Under nitrogen deprivation, an increase of iron, nickel, and molybdenum concentrations obviously enhanced H<inf>2</inf> production rate. But only higher iron concentrations increased hydrogenase activity, indicating that the iron metal assisted in the function of reversible hydrogenase activity. In addition, vanadium seemed not to be a metal cofactor of key enzymes involving in H<inf>2</inf> production in A. siamensis. The optimal concentrations of iron, nickel and molybdenum ions for H<inf>2</inf> production rate by A. siamensis were 60 μM, 4 μM and 4 μM, respectively. The highest H<inf>2</inf> production rate of 0.057 μmolH<inf>2</inf> mg chl a<sup>-1</sup> h<sup>-1</sup> was observed in cells incubated in BG11<inf>0</inf> medium supplemented with 4 μM nickel ion.
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    Nucleotide sequencing and transcriptional analysis of uptake hydrogenase genes in the filamentous N2-fixing cyanobacterium Anabaena siamensis
    (2006-12-01)
    Phunpruch, Saranya
    ;
    Baebprasert, Wipawee
    ;
    Thongpeng, Chamaporn
    ;
    Incharoensakdi, Aran
    The hupSL encoding uptake hydrogenase of the N<inf>2</inf>-fixing cyanobacterium Anabaena siamensis was cloned and sequenced. Anabaena siamensis hupS and hupL contained 963 and 1,596 bp, respectively. The predicted gene products for hupS and hupL consisted of 320 amino acids with a molecular mass of 35,436 Da and 531 amino acids with a molecular mass of 60,704 Da, respectively. Their deduced amino acid sequences showed higher than 90% and 88% similarity for HupS and HupL respectively, compared to those of other cyanobacteria including non N<inf>2</inf>-fixing cyanobacteria. The intergenic 195-bp sequence between hupS and hupL showed no homology to others among cyanobacteria but it still contained the repetitive sequence, which could form a hairpin structure commonly found in other N<inf>2</inf>-fixing cyanobacteria. RT-PCR analysis showed higher transcription level of hupS and hupL in Anabaena siamensis grown in BG11<inf>0</inf> under anaerobic conditions. Nickel exogenously added to the culture was also found to increase hupL transcript. © 2006 Springer Science+Business Media, Inc.