共查询到20条相似文献,搜索用时 609 毫秒
1.
2.
3.
Methanogenesis in an Upflow Anaerobic Sludge Blanket Reactor at pH 6 on an Acetate-Propionate Mixture 总被引:8,自引:4,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Erik ten Brummeler Look W. Hulshoff Pol Jan Dolfing Gatze Lettinga Alexander J. B. Zehnder 《Applied microbiology》1985,49(6):1472-1477
High-rate anaerobic digestion can be applied in upflow anaerobic sludge blanket reactors for the treatment of various wastewaters. In upflow anaerobic sludge blanket reactors, sludge retention time is increased by a natural immobilization mechanism (viz. the formation of a granular type of sludge). When this sludge is cultivated on acid-containing wastewater, the granules mainly consist of an acetoclastic methanogen resembling Methanothrix soehngenii. This organism grows either in rods or in long filaments. Attempts to cultivate a stable sludge consisting predominantly of Methanosarcina sp. on an acetate-propionate mixture as substrate by lowering the pH from 7.5 during the start-up to approximately 6 failed. After 140 days of continuous operation of the reactor a filamentous organism resembling Methanothrix soehngenii prevailed in the sludge. The specific methanogenic activity of this sludge on acetate-propionate was optimal at pH 6.6 to 6.8 and 7.0 to 7.2, respectively. 相似文献
4.
《Journal of Fermentation and Bioengineering》1992,73(3):213-218
A highly simplified anaerobic consortium which was able to degrade benzoate under mesophilic conditions was obtained from digested sludge acclimatized with benzoate. It converted 5 mM benzoate to methane quantitatively within 3 weeks in the absence of any organic nutrients under an N2/CO2 atmosphere. Degradation of benzoate was strictly inhibited by hydrogen. The consortium consisted of at least three microorganisms including an autofluorescent irregular coccus which was identified as Methanogenium sp., a short rod which did not autofluoresce and was considered to be a benzoate degrader, and a filamentous bacterium apparently classified as Methanothrix (= “Methanosaeta”. When sulfate was added to the medium, the methanogens were readily replaced by a sulfate-reducing bacterium, probably belonging to the genus Desulfovibrio, which had still remained in very low number in the consortium in the absence of sulfate, and benzoate was stoichiometrically converted to acetate without methanogenesis. Of various compounds which were expected to be intermediates in the benzoate degradation, only crotonate was degraded by concentrated cells of the consortium. 相似文献
5.
Andrew R. St. James Joseph B. Yavitt Stephen H. Zinder Ruth E. Richardson 《The ISME journal》2021,15(1):293
Ombrotrophic bogs accumulate large stores of soil carbon that eventually decompose to carbon dioxide and methane. Carbon accumulates because Sphagnum mosses slow microbial carbon decomposition processes, leading to the production of labile intermediate compounds. Acetate is a major product of Sphagnum degradation, yet rates of hydrogenotrophic methanogenesis far exceed rates of aceticlastic methanogenesis, suggesting that alternative acetate mineralization processes exist. Two possible explanations are aerobic respiration and anaerobic respiration via humic acids as electron acceptors. While these processes have been widely observed, microbial community interactions linking Sphagnum degradation and acetate mineralization remain cryptic. In this work, we use ordination and network analysis of functional genes from 110 globally distributed peatland metagenomes to identify conserved metabolic pathways in Sphagnum bogs. We then use metagenome-assembled genomes (MAGs) from McLean Bog, a Sphagnum bog in New York State, as a local case study to reconstruct pathways of Sphagnum degradation and acetate mineralization. We describe metabolically flexible Acidobacteriota MAGs that contain all genes to completely degrade Sphagnum cell wall sugars under both aerobic and anaerobic conditions. Finally, we propose a hypothetical model of acetate oxidation driven by changes in peat redox potential that explain how bogs may circumvent aceticlastic methanogenesis through aerobic and humics-driven respiration.Subject terms: Microbial ecology, Metagenomics, Soil microbiology, Biogeochemistry, Microbial ecology 相似文献
6.
7.
8.
The short-term effects of temperature on methanogenesis from acetate or CO2 in a thermophilic (58°C) anaerobic digestor were studied by incubating digestor sludge at different temperatures with 14C-labeled methane precursors (14CH3COO− or 14CO2). During a period when Methanosarcina sp. was numerous in the sludge, methanogenesis from acetate was optimal at 55 to 60°C and was completely inhibited at 65°C. A Methanosarcina culture isolated from the digestor grew optimally on acetate at 55 to 58°C and did not grow or produce methane at 65°C. An accidental shift of digestor temperature from 58 to 64°C during this period caused a sharp decrease in gas production and a large increase in acetate concentration within 24 h, indicating that the aceticlastic methanogens in the digestor were the population most susceptible to this temperature increase. During a later period when Methanothrix sp. was numerous in the digestor, methanogenesis from 14CH3COO− was optimal at 65°C and completely inhibited at 75°C. A partially purified Methanothrix enrichment culture derived from the digestor had a maximum growth temperature near 70°C. Methanogenesis from 14CO2 in the sludge was optimal at 65°C and still proceeded at 75°C. A CO2-reducing Methanobacterium sp. isolated from the digestor was capable of methanogenesis at 75°C. During the period when Methanothix sp. was apparently dominant, sludge incubated for 24 h at 65°C produced more methane than sludge incubated at 60°C, and no acetate accumulated at 65°C. Methanogenesis was severely inhibited in sludge incubated at 70°C, but since neither acetate nor H2 accumulated, production of these methanogenic substrates by fermentative bacteria was probably the most temperature-sensitive process. Thus, there was a correlation between digestor performance at different temperatures and responses to temperature by cultures of methanogens believed to play important roles in the digestor. 相似文献
9.
Selective Inhibition by 2-Bromoethanesulfonate of Methanogenesis from Acetate in a Thermophilic Anaerobic Digestor 总被引:8,自引:5,他引:3
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The effects of 2-bromoethanesulfonate, an inhibitor of methanogenesis, on metabolism in sludge from a thermophilic (58°C) anaerobic digestor were studied. It was found from short-term experiments that 1 μmol of 2-bromoethanesulfonate per ml completely inhibited methanogenesis from 14CH3COO−, whereas 50 μmol/ml was required for complete inhibition of 14CO2 reduction. When 1 μmol of 2-bromoethanesulfonate per ml was added to actively metabolizing sludge which was then incubated for 24 h. it caused a 60% reduction in methanogenesis and a corresponding increase in acetate accumulation; at 50 μmol/ml it caused complete inhibition of methanogenesis and accumulation of acetate. H2, and ethanol. 相似文献
10.
Methanosarcina sp. strain TM-1, an acetotrophic, thermophilic methanogen isolated from an anaerobic sludge digestor, was originally reported to require an anaerobic sludge supernatant for growth. It was found that the sludge supernatant could be replaced with yeast extract (1 g/liter), 6 mM bicarbonate-30% CO2, and trace metals, with a doubling time on methanol of 14 h. For growth on either methanol or acetate, yeast extract could be replaced with CaCl2 · 2H2O (13.6 μM minimum) and the vitamin p-aminobenzoic acid (PABA, ca. 3 nM minimum), with a doubling time on methanol of 8 to 9 h. Filter-sterilized folic acid at 0.3 μM could not replace PABA. The antimetabolite sulfanilamide (20 mM) inhibited growth of and methanogenesis by Methanosarcina sp. strain TM-1, and this inhibition was reversed by the addition of 0.3 μM PABA. When a defined medium buffered with 20 mM N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid was used, it was shown that Methanosarcina sp. strain TM-1 required 6 mM bicarbonate-30% CO2 for optimal growth and methanogenesis from methanol. Cells growing on acetate were less dependent on bicarbonate-CO2. When we used a defined medium in which the only organic compounds present were methanol or acetate, nitrilotriacetic acid (0.2 mM), and PABA, it was possible to limit batch cultures of Methanosarcina sp. strain TM-1 for nitrogen at NH4+ concentrations at or below 2.0 mM, in marked contrast with Methanosarcina barkeri 227, which fixes dinitrogen when grown under NH4+ limitation. 相似文献
11.
The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review 总被引:7,自引:0,他引:7
Among different conversion processes for biomass, biological anaerobic digestion is one of the most economic ways to produce
biogas from various biomass substrates. In addition to hydrolysis of polymeric substances, the activity and performance of
the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the
recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of
particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing
bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports
about their roles during this phase of the process are very limited. Despite, some conclusions can still be drawn. At low
concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently,
high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species
consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic
methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental
factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a biomass reactor. However, no general
rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens. Presumably,
it depends only on the hydrogen concentration, which is generally not mentioned in the literature. 相似文献
12.
《Journal of Fermentation and Bioengineering》1993,75(5):368-374
The effect of trace elements on the methanogenesis from methanol and acetate was studied utilizing granular sludge obtained from an anaerobic wastewater treatment plant. The methanogenic activity from methanol was dramatically stimulated by the addition of a cocktail of trace elements in the basal medium. When trace elements were supplied individually, cobalt greatly stimulated methanogenesis which equalled the stimulation observed with the complete trace element mixture. No remarkable influence of any trace element was observed when acetate was used as the substrate. Two Upflow Anaerobic Sludge Blanket (UASB) reactors were operated with and without supplementation of cobalt. Cobalt greatly stimulated both acetogenesis in the initial operational phase and later methanogenesis. The cobalt sufficient column provided almost 3 times the methane productivity compared to the cobalt deprived column. At an organic loading rate of 8 g COD/l·d, 87% of the COD was converted to methane in the cobalt sufficient column. Under low cobalt concentration, methanogens compete better for cobalt than acetogens. 相似文献
13.
14.
Sarah Refai Kati Wassmann Uwe Deppenmeier 《Applied microbiology and biotechnology》2014,98(16):7271-7280
Biochemical processes in biogas plants are still not fully understood. Especially, the identification of possible bottlenecks in the complex fermentation processes during biogas production might provide potential to increase the performance of biogas plants. To shed light on the question which group of organism constitutes the limiting factor in the anaerobic breakdown of organic material, biogas sludge from different mesophilic biogas plants was examined under various conditions. Therefore, biogas sludge was incubated and analyzed in anaerobic serum flasks under an atmosphere of N2/CO2. The batch reactors mirrored the conditions and the performance of the full-scale biogas plants and were suitable test systems for a period of 24 h. Methane production rates were compared after supplementation with substrates for syntrophic bacteria, such as butyrate, propionate, or ethanol, as well as with acetate and H2+CO2 as substrates for methanogenic archaea. Methane formation rates increased significantly by 35 to 126 % when sludge from different biogas plants was supplemented with acetate or ethanol. The stability of important process parameters such as concentration of volatile fatty acids and pH indicate that ethanol and acetate increase biogas formation without affecting normally occurring fermentation processes. In contrast to ethanol or acetate, other fermentation products such as propionate, butyrate, or H2 did not result in increased methane formation rates. These results provide evidence that aceticlastic methanogenesis and ethanol-oxidizing syntrophic bacteria are not the limiting factor during biogas formation, respectively, and that biogas plant optimization is possible with special focus on methanogenesis from acetate. 相似文献
15.
Combined removal of nitrate and carbon in granular sludge: Substrate competition and activities 总被引:6,自引:0,他引:6
Granular sludge from an upflow anaerobic sludge blanket reactor treating synthetic waste water containing a mixture of volatile fatty acids and nitrate showed a removal efficiency of nearly 100% for both nitrogen and carbon. This activity was achieved by a combined process of denitrification and methanogenesis under conditions of surplus carbon. Under batch conditions the two processes proceeded clearly separated in time with first denitrification dominating and excluding methanogenesis. However, as soon as nitrate was depleted, methane production was initiated, showing that the inhibition of methanogenesis by nitrate was reversible. Of the volatile fatty acids supplied to the reactor, i.e. acetate, propionate, and butyrate, the denitrifying population clearly preferred butyrate and propionate even though acetate could also be metabolized. Consequently, growth of syntrophic volatile fatty acid degraders was suppressed by the denitrifiers in cases of low C:N ratios in the medium, leaving acetate as the major substrate for methanogenesis.Abbreviations UASB
upflow anaerobic sludge blanket
- COD
chemical oxygen demand
- VFA
volatile fatty 相似文献
16.
Dang P. Ho Paul D. Jensen Damien J. Batstone 《Applied and environmental microbiology》2013,79(20):6491-6500
This study investigated the process of high-rate, high-temperature methanogenesis to enable very-high-volume loading during anaerobic digestion of waste-activated sludge. Reducing the hydraulic retention time (HRT) from 15 to 20 days in mesophilic digestion down to 3 days was achievable at a thermophilic temperature (55°C) with stable digester performance and methanogenic activity. A volatile solids (VS) destruction efficiency of 33 to 35% was achieved on waste-activated sludge, comparable to that obtained via mesophilic processes with low organic acid levels (<200 mg/liter chemical oxygen demand [COD]). Methane yield (VS basis) was 150 to 180 liters of CH4/kg of VSadded. According to 16S rRNA pyrotag sequencing and fluorescence in situ hybridization (FISH), the methanogenic community was dominated by members of the Methanosarcinaceae, which have a high level of metabolic capability, including acetoclastic and hydrogenotrophic methanogenesis. Loss of function at an HRT of 2 days was accompanied by a loss of the methanogens, according to pyrotag sequencing. The two acetate conversion pathways, namely, acetoclastic methanogenesis and syntrophic acetate oxidation, were quantified by stable carbon isotope ratio mass spectrometry. The results showed that the majority of methane was generated by nonacetoclastic pathways, both in the reactors and in off-line batch tests, confirming that syntrophic acetate oxidation is a key pathway at elevated temperatures. The proportion of methane due to acetate cleavage increased later in the batch, and it is likely that stable oxidation in the continuous reactor was maintained by application of the consistently low retention time. 相似文献
17.
Acetate production during anaerobic sludge treatment has significant economic and environmental benefits. In this study, trophic links between syntrophic acetogens and homoacetogens in the anaerobic acidogenic fermentation of sewage sludge were investigated using methanogenic inhibitor 2-bromoethanesulfonate (BES) to block the methanogenesis pathway and butyrate to enhance syntrophic acetogenesis. The Gibbs free energies (ΔG) of the butyrate-degrading and homoacetogenic processes were close to the thermodynamic threshold of the reaction activity (−15 kJ/mol). In addition, microbial quantification analysis revealed that the growth of syntrophic acetogenic bacteria and homoacetogens in the treatment incubations was higher than that of the control. The results indicated that hydrogen-producing butyrate degraders are stimulated with homoacetogens when methanogenesis was specifically inhibited. 相似文献
18.
The in situ physiology of the filamentous sulphur bacterium Thiothrix spp. was investigated in an industrial wastewater treatment plant with severe bulking problems as a result of overgrowth of Thiothrix. Identification and enumeration using fluorescence in situ hybridization (FISH) with species-specific 16S and 23S rRNA probes revealed that 5–10% of the bacteria in the activated sludge were Thiothrix spp. By using a combination of FISH and microautoradiography it was possible to study the in situ physiology of probe-defined Thiothrix filaments under different environmental conditions. The Thiothrix filaments were very versatile and showed incorporation of radiolabelled acetate and/or bicarbonate under heterotrophic, mixotrophic and chemolithoautotrophic conditions. The Thiothrix filaments were active under anaerobic conditions (with or without nitrate) in which intracellular sulphur globules were formed from thiosulphate and acetate was taken up. Thiothrix -specific substrate uptake rates and growth rates in activated sludge samples were determined under different conditions. Doubling times of 6–9 h under mixotrophic conditions and 15–30 h under autotrophic conditions were estimated. The key properties that Thiothrix might be employing to outcompete other microorganisms in activated sludge were probably related to the mixotrophic growth potential with strong stimulation of acetate uptake by thiosulphate, as well as stimulation of bicarbonate incorporation by acetate in the presence of thiosulphate. 相似文献
19.
20.
Cervantes FJ Gutiérrez CH López KY Estrada-Alvarado MI Meza-Escalante ER Texier AC Cuervo F Gómez J 《Biodegradation》2008,19(2):235-246
The capacity of two anaerobic consortia to oxidize different organic compounds, including acetate, propionate, lactate, phenol
and p-cresol, in the presence of nitrate, sulfate and the humic model compound, anthraquinone-2,6-disulfonate (AQDS) as terminal
electron acceptors, was evaluated. Denitrification showed the highest respiratory rates in both consortia studied and occurred
exclusively during the first hours of incubation for most organic substrates degraded. Reduction of AQDS and sulfate generally
started after complete denitrification, or even occurred at the same time during the biodegradation of p-cresol, in anaerobic sludge incubations; whereas methanogenesis did not significantly occur during the reduction of nitrate,
sulfate, and AQDS. AQDS reduction was the preferred respiratory pathway over sulfate reduction and methanogenesis during the
anaerobic oxidation of most organic substrates by the anaerobic sludge studied. In contrast, sulfate reduction out-competed
AQDS reduction during incubations performed with anaerobic wetland sediment, which did not achieve any methanogenic activity.
Propionate was a poor electron donor to achieve AQDS reduction; however, denitrifying and sulfate-reducing activities carried
out by both consortia promoted the reduction of AQDS via acetate accumulated from propionate oxidation. Our results suggest
that microbial reduction of humic substances (HS) may play an important role during the anaerobic oxidation of organic pollutants
in anaerobic environments despite the presence of alternative electron acceptors, such as sulfate and nitrate. Methane inhibition,
imposed by the inclusion of AQDS as terminal electron acceptor, suggests that microbial reduction of HS may also have important
implications on the global climate preservation, considering the green-house effects of methane. 相似文献