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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.


Effect of OLR on performance of Rarab (a) hydrogen production rate and HRT, (b) soluble fermentation products and residual arabinose.
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Figure 2: Effect of OLR on performance of Rarab (a) hydrogen production rate and HRT, (b) soluble fermentation products and residual arabinose.

Mentions: Hydrogen production rates in arabinose- and glucose-fed reactors (Rarab and Rgluc) are shown in Figures 2 and 3, respectively. Only H2 and CO2 were detected in the gas phase; methane was not produced during all operation time. During start-up (period I), hydrogen production rates of approximately 0.3 L H2 L-1d-1 were observed in both reactors. This corresponds to hydrogen yields of roughly 0.2 and 0.3 mol H2 per mol of substrate consumed, for Rarab and Rgluc respectively (Table 1). In period II, the increase in arabinose and glucose inlet concentration to 16.6 mM and 13.8 mM, respectively, resulted in hydrogen yields of about 0.80 mol H2 per mole of substrate in both Rarab and Rgluc (Table 1). Maximum hydrogen production rates in period II were of 1.36 ± 0.04 and 1.12 ± 0.07 LH2 L-1 d-1 in Rarab and Rgluc, respectively. Substrate was completely consumed in both reactors and the main by-products formed were butyrate, acetate and lactate (Figures 2 and 3). In operation period III, substrate concentrations fed to Rarab and Rgluc were increased to 33.3 mM of arabinose and 27.7 mM of glucose, respectively. As a result of this increase, there was a temporary raise in arabinose/glucose concentration in the effluent but, after 13 days of acclimation to the higher substrate loads, virtually all glucose and an average of 79% arabinose were used in the reactors (Table 1) Steady state hydrogen production rates of 3.26 ± 0.16 and 2.06 ± 0.06 L H2 L-1 d-1 were observed in Rarab and Rgluc, respectively (Figures 2 and 3). During period III, Rgluc showed a stable hydrogen yield of about 0.75 mol H2 per mole of substrate consumed. Hydrogen yield in Rarab was significantly higher, that is. 1.10 mol H2 per mole of substrate consumed. Lactate concentration in Rgluc increased sharply during period III of operation reaching values of approximately 20 mM (Figure 3). An increase in lactate concentration was also observed in Rarab, but did not exceed 11 mM (Figure 2). Estimation of the theoretical reduced form of nicotinamide adenine dinucleotide (NADH) {AU Query: Please replace NADH in full.} production from glucose and arabinose, considering the main catabolic pathways (that is, Embden-Meyerhof for glucose and a combination of pentose phosphate and Embden-Meyerhof pathways for arabinose (Figure 1)), demonstrates that a higher reducing power was potentially formed in Rgluc than in Rarab. Estimated NADH concentration in Rgluc was 42 mM after three days of operation, while in Rarab was 37 mM after five days of operation.


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)

Effect of OLR on performance of Rarab (a) hydrogen production rate and HRT, (b) soluble fermentation products and residual arabinose.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Effect of OLR on performance of Rarab (a) hydrogen production rate and HRT, (b) soluble fermentation products and residual arabinose.
Mentions: Hydrogen production rates in arabinose- and glucose-fed reactors (Rarab and Rgluc) are shown in Figures 2 and 3, respectively. Only H2 and CO2 were detected in the gas phase; methane was not produced during all operation time. During start-up (period I), hydrogen production rates of approximately 0.3 L H2 L-1d-1 were observed in both reactors. This corresponds to hydrogen yields of roughly 0.2 and 0.3 mol H2 per mol of substrate consumed, for Rarab and Rgluc respectively (Table 1). In period II, the increase in arabinose and glucose inlet concentration to 16.6 mM and 13.8 mM, respectively, resulted in hydrogen yields of about 0.80 mol H2 per mole of substrate in both Rarab and Rgluc (Table 1). Maximum hydrogen production rates in period II were of 1.36 ± 0.04 and 1.12 ± 0.07 LH2 L-1 d-1 in Rarab and Rgluc, respectively. Substrate was completely consumed in both reactors and the main by-products formed were butyrate, acetate and lactate (Figures 2 and 3). In operation period III, substrate concentrations fed to Rarab and Rgluc were increased to 33.3 mM of arabinose and 27.7 mM of glucose, respectively. As a result of this increase, there was a temporary raise in arabinose/glucose concentration in the effluent but, after 13 days of acclimation to the higher substrate loads, virtually all glucose and an average of 79% arabinose were used in the reactors (Table 1) Steady state hydrogen production rates of 3.26 ± 0.16 and 2.06 ± 0.06 L H2 L-1 d-1 were observed in Rarab and Rgluc, respectively (Figures 2 and 3). During period III, Rgluc showed a stable hydrogen yield of about 0.75 mol H2 per mole of substrate consumed. Hydrogen yield in Rarab was significantly higher, that is. 1.10 mol H2 per mole of substrate consumed. Lactate concentration in Rgluc increased sharply during period III of operation reaching values of approximately 20 mM (Figure 3). An increase in lactate concentration was also observed in Rarab, but did not exceed 11 mM (Figure 2). Estimation of the theoretical reduced form of nicotinamide adenine dinucleotide (NADH) {AU Query: Please replace NADH in full.} production from glucose and arabinose, considering the main catabolic pathways (that is, Embden-Meyerhof for glucose and a combination of pentose phosphate and Embden-Meyerhof pathways for arabinose (Figure 1)), demonstrates that a higher reducing power was potentially formed in Rgluc than in Rarab. Estimated NADH concentration in Rgluc was 42 mM after three days of operation, while in Rarab was 37 mM after five days of operation.

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.