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Biohydrogen production from arabinose and glucose using extreme thermophilic anaerobic mixed cultures.

Abreu AA, Karakashev D, Angelidaki I, Sousa DZ, Alves MM - Biotechnol Biofuels (2012)

Bottom Line: Denaturing gradient gel electrophoresis (DGGE) results revealed no significant difference on the bacterial community composition between operational periods and between the reactors.Continuous hydrogen production rate from arabinose was significantly higher than from glucose, when higher organic loading rate was used.The effect of hydrogen partial pressure on hydrogen production from glucose in batch mode was related to the extent of sugar utilization and not to the efficiency of substrate conversion to hydrogen.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal. madalena.alves@deb.uminho.pt.

ABSTRACT

Background: Second generation hydrogen fermentation technologies using organic agricultural and forestry wastes are emerging. The efficient microbial fermentation of hexoses and pentoses resulting from the pretreatment of lingocellulosic materials is essential for the success of these processes.

Results: Conversion of arabinose and glucose to hydrogen, by extreme thermophilic, anaerobic, mixed cultures was studied in continuous (70°C, pH 5.5) and batch (70°C, pH 5.5 and pH 7) assays. Two expanded granular sludge bed (EGSB) reactors, Rarab and Rgluc, were continuously fed with arabinose and glucose, respectively. No significant differences in reactor performance were observed for arabinose and glucose organic loading rates (OLR) ranging from 4.3 to 7.1 kgCOD m-3 d-1. However, for an OLR of 14.2 kgCOD m-3 d-1, hydrogen production rate and hydrogen yield were higher in Rarab than in Rgluc (average hydrogen production rate of 3.2 and 2.0 LH2 L-1 d-1 and hydrogen yield of 1.10 and 0.75 molH2 mol-1substrate for Rarab and Rgluc, respectively). Lower hydrogen production in Rgluc was associated with higher lactate production. Denaturing gradient gel electrophoresis (DGGE) results revealed no significant difference on the bacterial community composition between operational periods and between the reactors. Increased hydrogen production was observed in batch experiments when hydrogen partial pressure was kept low, both with arabinose and glucose as substrate. Sugars were completely consumed and hydrogen production stimulated (62% higher) when pH 7 was used instead of pH 5.5.

Conclusions: Continuous hydrogen production rate from arabinose was significantly higher than from glucose, when higher organic loading rate was used. The effect of hydrogen partial pressure on hydrogen production from glucose in batch mode was related to the extent of sugar utilization and not to the efficiency of substrate conversion to hydrogen. Furthermore, at pH 7.0, sugars uptake, hydrogen production and yield were higher than at pH 5.5, with both arabinose and glucose as substrates.

No MeSH data available.


Time course of hydrogen production and substrate consumption, O PiH2 ; ■ arabinose; x glucose. a, b) pH 5.5 without headspace flushing. c, d) pH 5.5 with headspace flushing. e, f) pH 7 with headspace flushing.
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Figure 5: Time course of hydrogen production and substrate consumption, O PiH2 ; ■ arabinose; x glucose. a, b) pH 5.5 without headspace flushing. c, d) pH 5.5 with headspace flushing. e, f) pH 7 with headspace flushing.

Mentions: In the NHF (pH 5.5), maximum hydrogen concentration in the gas was achieved 44 and 20 h after the second addition of arabinose or glucose addition, respectively (Figure 5a, b). At this point, hydrogen partial pressure in both arabinose and glucose assays was roughly 1.2 × 104 Pa (at 70°C), which corresponds to a dissolved hydrogen concentration of 105 μM. From this point on, hydrogen production was not significant, even though only 35% of arabinose and 13% of glucose were present at the end of the experiment. Identical hydrogen yield, that is, 0.7 mol H2 per mole of substrate, was obtained for NHF arabinose and glucose experiments (Table 2).


Biohydrogen production from arabinose and glucose using extreme thermophilic anaerobic mixed cultures.

Abreu AA, Karakashev D, Angelidaki I, Sousa DZ, Alves MM - Biotechnol Biofuels (2012)

Time course of hydrogen production and substrate consumption, O PiH2 ; ■ arabinose; x glucose. a, b) pH 5.5 without headspace flushing. c, d) pH 5.5 with headspace flushing. e, f) pH 7 with headspace flushing.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3298801&req=5

Figure 5: Time course of hydrogen production and substrate consumption, O PiH2 ; ■ arabinose; x glucose. a, b) pH 5.5 without headspace flushing. c, d) pH 5.5 with headspace flushing. e, f) pH 7 with headspace flushing.
Mentions: In the NHF (pH 5.5), maximum hydrogen concentration in the gas was achieved 44 and 20 h after the second addition of arabinose or glucose addition, respectively (Figure 5a, b). At this point, hydrogen partial pressure in both arabinose and glucose assays was roughly 1.2 × 104 Pa (at 70°C), which corresponds to a dissolved hydrogen concentration of 105 μM. From this point on, hydrogen production was not significant, even though only 35% of arabinose and 13% of glucose were present at the end of the experiment. Identical hydrogen yield, that is, 0.7 mol H2 per mole of substrate, was obtained for NHF arabinose and glucose experiments (Table 2).

Bottom Line: Denaturing gradient gel electrophoresis (DGGE) results revealed no significant difference on the bacterial community composition between operational periods and between the reactors.Continuous hydrogen production rate from arabinose was significantly higher than from glucose, when higher organic loading rate was used.The effect of hydrogen partial pressure on hydrogen production from glucose in batch mode was related to the extent of sugar utilization and not to the efficiency of substrate conversion to hydrogen.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal. madalena.alves@deb.uminho.pt.

ABSTRACT

Background: Second generation hydrogen fermentation technologies using organic agricultural and forestry wastes are emerging. The efficient microbial fermentation of hexoses and pentoses resulting from the pretreatment of lingocellulosic materials is essential for the success of these processes.

Results: Conversion of arabinose and glucose to hydrogen, by extreme thermophilic, anaerobic, mixed cultures was studied in continuous (70°C, pH 5.5) and batch (70°C, pH 5.5 and pH 7) assays. Two expanded granular sludge bed (EGSB) reactors, Rarab and Rgluc, were continuously fed with arabinose and glucose, respectively. No significant differences in reactor performance were observed for arabinose and glucose organic loading rates (OLR) ranging from 4.3 to 7.1 kgCOD m-3 d-1. However, for an OLR of 14.2 kgCOD m-3 d-1, hydrogen production rate and hydrogen yield were higher in Rarab than in Rgluc (average hydrogen production rate of 3.2 and 2.0 LH2 L-1 d-1 and hydrogen yield of 1.10 and 0.75 molH2 mol-1substrate for Rarab and Rgluc, respectively). Lower hydrogen production in Rgluc was associated with higher lactate production. Denaturing gradient gel electrophoresis (DGGE) results revealed no significant difference on the bacterial community composition between operational periods and between the reactors. Increased hydrogen production was observed in batch experiments when hydrogen partial pressure was kept low, both with arabinose and glucose as substrate. Sugars were completely consumed and hydrogen production stimulated (62% higher) when pH 7 was used instead of pH 5.5.

Conclusions: Continuous hydrogen production rate from arabinose was significantly higher than from glucose, when higher organic loading rate was used. The effect of hydrogen partial pressure on hydrogen production from glucose in batch mode was related to the extent of sugar utilization and not to the efficiency of substrate conversion to hydrogen. Furthermore, at pH 7.0, sugars uptake, hydrogen production and yield were higher than at pH 5.5, with both arabinose and glucose as substrates.

No MeSH data available.