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Ecology and application of haloalkaliphilic anaerobic microbial communities.

Sousa JA, Sorokin DY, Bijmans MF, Plugge CM, Stams AJ - Appl. Microbiol. Biotechnol. (2015)

Bottom Line: These globally spread lakes harbour interesting anaerobic microorganisms that have the potential of being applied in existing technologies or create new opportunities.Also, the general advantages of operation at haloalkaline conditions, such as low volatile fatty acid and sulfide toxicity, are addressed.Finally, an outlook into the main challenges like ammonia toxicity and lack of aggregation is provided.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, The Netherlands. joao.sousa@wetsus.nl.

ABSTRACT
Haloalkaliphilic microorganisms that grow optimally at high-pH and high-salinity conditions can be found in natural environments such as soda lakes. These globally spread lakes harbour interesting anaerobic microorganisms that have the potential of being applied in existing technologies or create new opportunities. In this review, we discuss the potential application of haloalkaliphilic anaerobic microbial communities in the fermentation of lignocellulosic feedstocks material subjected to an alkaline pre-treatment, methane production and sulfur removal technology. Also, the general advantages of operation at haloalkaline conditions, such as low volatile fatty acid and sulfide toxicity, are addressed. Finally, an outlook into the main challenges like ammonia toxicity and lack of aggregation is provided.

No MeSH data available.


Related in: MedlinePlus

Effect of ammonia, sulfide and acetate (representing VFAs in general) on microorganisms living at alkaline pH and chemical equilibrium of ammonia sulfide and acetate at different pH values. 1—at alkaline pH, ammonia tends to the un-ionized species (NH3) which can cross cell membranes in contrast with the ionized species (NH4+); 2—due to the close to neutral pH inside the cell, the chemical equilibrium shifts towards the NH4+ species, consuming one proton (H+) and disrupting the proton balance; 3—to compensate the lost H+, the primary source of H+ is from the catabolic reactions; 4—also, antiporters in the cell membrane may pump H+ in and simultaneously pump sodium (Na+) or potassium (K+) out, generating an osmotic difference that needs to be compensated; 5—at alkaline pH, sulfide and acetate exist in the ionized form, HS− and CH3COO−, which cannot easily pass the cell membrane
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Fig1: Effect of ammonia, sulfide and acetate (representing VFAs in general) on microorganisms living at alkaline pH and chemical equilibrium of ammonia sulfide and acetate at different pH values. 1—at alkaline pH, ammonia tends to the un-ionized species (NH3) which can cross cell membranes in contrast with the ionized species (NH4+); 2—due to the close to neutral pH inside the cell, the chemical equilibrium shifts towards the NH4+ species, consuming one proton (H+) and disrupting the proton balance; 3—to compensate the lost H+, the primary source of H+ is from the catabolic reactions; 4—also, antiporters in the cell membrane may pump H+ in and simultaneously pump sodium (Na+) or potassium (K+) out, generating an osmotic difference that needs to be compensated; 5—at alkaline pH, sulfide and acetate exist in the ionized form, HS− and CH3COO−, which cannot easily pass the cell membrane

Mentions: Methanogenic fermentation of wastes at haloalkaline conditions can be an interesting option for renewable biogas production. At high pH, VFA toxicity is reduced because VFA are mostly present in the dissociated form which cannot easily cross cell membranes and disrupt the proton balance (Fig. 1). This would allow the operation of such bioreactors at higher organic loadings. At high pH, the CO2 is more retained as carbonates which could lead to a lower CO2 content in the biogas. Also, sulfide at high pH is mainly in the ionized form (HS−) which is less volatile and toxic, resulting in a gas with very low concentrations of sulfide. A recent study on the digestion of the microalgae Spirulina at haloalkaline conditions resulted in a biogas with a methane content of 96 % and without traces of sulfide (Nolla-Ardèvol et al 2015). This might reduce the need for biogas post-treatment to remove CO2 and H2S, allowing the use of the biogas directly in natural gas supply grid.Fig. 1


Ecology and application of haloalkaliphilic anaerobic microbial communities.

Sousa JA, Sorokin DY, Bijmans MF, Plugge CM, Stams AJ - Appl. Microbiol. Biotechnol. (2015)

Effect of ammonia, sulfide and acetate (representing VFAs in general) on microorganisms living at alkaline pH and chemical equilibrium of ammonia sulfide and acetate at different pH values. 1—at alkaline pH, ammonia tends to the un-ionized species (NH3) which can cross cell membranes in contrast with the ionized species (NH4+); 2—due to the close to neutral pH inside the cell, the chemical equilibrium shifts towards the NH4+ species, consuming one proton (H+) and disrupting the proton balance; 3—to compensate the lost H+, the primary source of H+ is from the catabolic reactions; 4—also, antiporters in the cell membrane may pump H+ in and simultaneously pump sodium (Na+) or potassium (K+) out, generating an osmotic difference that needs to be compensated; 5—at alkaline pH, sulfide and acetate exist in the ionized form, HS− and CH3COO−, which cannot easily pass the cell membrane
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4628080&req=5

Fig1: Effect of ammonia, sulfide and acetate (representing VFAs in general) on microorganisms living at alkaline pH and chemical equilibrium of ammonia sulfide and acetate at different pH values. 1—at alkaline pH, ammonia tends to the un-ionized species (NH3) which can cross cell membranes in contrast with the ionized species (NH4+); 2—due to the close to neutral pH inside the cell, the chemical equilibrium shifts towards the NH4+ species, consuming one proton (H+) and disrupting the proton balance; 3—to compensate the lost H+, the primary source of H+ is from the catabolic reactions; 4—also, antiporters in the cell membrane may pump H+ in and simultaneously pump sodium (Na+) or potassium (K+) out, generating an osmotic difference that needs to be compensated; 5—at alkaline pH, sulfide and acetate exist in the ionized form, HS− and CH3COO−, which cannot easily pass the cell membrane
Mentions: Methanogenic fermentation of wastes at haloalkaline conditions can be an interesting option for renewable biogas production. At high pH, VFA toxicity is reduced because VFA are mostly present in the dissociated form which cannot easily cross cell membranes and disrupt the proton balance (Fig. 1). This would allow the operation of such bioreactors at higher organic loadings. At high pH, the CO2 is more retained as carbonates which could lead to a lower CO2 content in the biogas. Also, sulfide at high pH is mainly in the ionized form (HS−) which is less volatile and toxic, resulting in a gas with very low concentrations of sulfide. A recent study on the digestion of the microalgae Spirulina at haloalkaline conditions resulted in a biogas with a methane content of 96 % and without traces of sulfide (Nolla-Ardèvol et al 2015). This might reduce the need for biogas post-treatment to remove CO2 and H2S, allowing the use of the biogas directly in natural gas supply grid.Fig. 1

Bottom Line: These globally spread lakes harbour interesting anaerobic microorganisms that have the potential of being applied in existing technologies or create new opportunities.Also, the general advantages of operation at haloalkaline conditions, such as low volatile fatty acid and sulfide toxicity, are addressed.Finally, an outlook into the main challenges like ammonia toxicity and lack of aggregation is provided.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, The Netherlands. joao.sousa@wetsus.nl.

ABSTRACT
Haloalkaliphilic microorganisms that grow optimally at high-pH and high-salinity conditions can be found in natural environments such as soda lakes. These globally spread lakes harbour interesting anaerobic microorganisms that have the potential of being applied in existing technologies or create new opportunities. In this review, we discuss the potential application of haloalkaliphilic anaerobic microbial communities in the fermentation of lignocellulosic feedstocks material subjected to an alkaline pre-treatment, methane production and sulfur removal technology. Also, the general advantages of operation at haloalkaline conditions, such as low volatile fatty acid and sulfide toxicity, are addressed. Finally, an outlook into the main challenges like ammonia toxicity and lack of aggregation is provided.

No MeSH data available.


Related in: MedlinePlus