共查询到20条相似文献,搜索用时 31 毫秒
1.
Magnetite accelerates syntrophic acetate oxidation in methanogenic systems with high ammonia concentrations 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Microbial biotechnology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ammonia accumulation is a major inhibitory substance causing anaerobic digestion upset and failure in CH4 production. At high ammonia levels, CH4 production through syntrophic acetate oxidization (SAO) pathways is more tolerant to ammonia toxicity than the acetoclastic methanogenesis pathway, but the low CH4 production rate through SAO constitutes the main reason for the low efficiency of energy recovery in anaerobic digesters treating ammonia‐rich substrates. In this study, we showed that acetate fermentation to CH4 and CO2 occurred through SAO pathway in the anaerobic reactors containing a high ammonia concentration (5.0 g l?1 NH4+–N), and the magnetite nanoparticles supplementation increased the CH4 production rates from acetate by 36–58%, compared with the anaerobic reactors without magnetite under the same ammonia level. The mechanism of facilitated methanogenesis was proposed to be the establishment of direct interspecies electron transfer (DIET) for SAO, in which magnetite facilitated DIET between syntrophic acetate oxidizing bacteria and methanogens. High‐throughput 16S rRNA gene sequencing analysis revealed that the bacterial Geobacteraceae and the archaeal Methanosarcinaceae and Methanobacteriaceae might be involved in magnetite‐mediated DIET for SAO and CH4 production. This study demonstrated that magnetite supplementation might provide an effective approach to accelerate CH4 production rates in the anaerobic reactors treating wastewater containing high ammonia. 相似文献
2.
Methanogenesis in thermophilic biogas reactors 总被引:2,自引:0,他引:2
Birgitte Kiær Ahring 《Antonie van Leeuwenhoek》1995,67(1):91-102
Methanogenesis in thermophilic biogas reactors fed with different wastes is examined. The specific methanogenic activity with acetate or hydrogen as substrate reflected the organic loading of the specific reactor examined. Increasing the loading of thermophilic reactors stabilized the process as indicated by a lower concentration of volatile fatty acids in the effluent from the reactors. The specific methanogenic activity in a thermophilic pilot-plant biogas reactor fed with a mixture of cow and pig manure reflected the stability of the reactor. The numbers of methanogens counted by the most probable number (MPN) technique with acetate or hydrogen as substrate were further found to vary depending on the loading rate and the stability of the reactor. The numbers of methanogens counted with antibody probes in one of the reactor samples was 10 times lower for the hydrogen-utilizing methanogens compared to the counts using the MPN technique, indicating that other non-reacting methanogens were present. Methanogens that reacted with the probe againstMethanobacterium thermoautotrophicum were the most numerous in this reactor. For the acetate-utilizing methanogens, the numbers counted with the antibody probes were more than a factor of 10 higher than the numbers found by MPN. The majority of acetate utilizing methanogens in the reactor wereMethanosarcina spp. single cells, which is a difficult form of the organism to cultivatein vitro. No reactions were observed with antibody probes raised againstMethanothrix soehngenii orMethanothrix CALS-1 in any of the thermophilic biogas reactors examined. Studies using 2-14C-labeled acetate showed that at high concentrations (more than approx. 1 mM) acetate was metabolized via the aceticlastic pathway, transforming the methyl-group of acetate into methane. When the concentration of acetate was less than approx. 1 mM, most of the acetate was oxidized via a two-step mechanism (syntrophic acetate oxidation) involving one organism oxidizing acetate into hydrogen and carbon dioxide and a hydrogen-utilizing methanogen forming the products of the first microorganism into methane. In thermophilic biogas reactors, acetate oxidizing cultures occupied the niche ofMethanothrix species, aceticlastic methanogens which dominate at low acetate concentrations in mesophilic systems. Normally, thermophilic biogas reactors are operated at temperatures from 52 to 56° C. Experiments using biogas reactors fed with cow manure showed that the same biogas yield found at 55° C could be obtained at 61° C after a long adaptation period. However, propionate degradation was inhibited by increasing the temperature. 相似文献
3.
The influence of ammonia on the anaerobic degradation of peptone by mesophilic and thermophilic populations of biowaste was
investigated. For peptone concentrations from 5 g l−1 to 20 g l−1 the mesophilic population revealed a higher rate of deamination than the thermophilic population, e.g. 552 mg l−1 day−1 compared to 320 mg l−1 day−1 at 10 g l−1 peptone. The final degree of deamination of the thermophilic population was, however, higher: 102 compared to 87 mg NH3/g peptone in the mesophilic cultures. If 0.5–6.5 g l−1 ammonia was added to the mesophilic biowaste cultures, deamination of peptone, degradation of its chemical oxygen demand
(COD) and formation of biogas were increasingly inhibited, but no hydrogen was formed. The thermophilic biowaste cultures
were most active if around 1 g ammonia l−1 was present. Deamination, COD degradation and biogas production decreased at lower and higher ammonia concentrations and
hydrogen was formed in addition to methane. Studies of the inhibition by ammonia of peptone deamination, COD degradation and
methane formation revealed a K
i (50%) for NH3 of 92, 95 and 88 mg l−1 at 37 °C and 251, 274 and 297 mg l−1 at 55 °C respectively. This indicated that the thermophilic flora tolerated significantly more NH3 than the mesophilic flora. In the mesophilic reactor effluent 4.6 × 108 peptone-degrading colony-forming units (cfu)/ml were culturable, whereas in the thermophilic reactor effluent growth of only
5.6 × 107 cfu/ml was observed.
Received: 24 April 1998 / Received revision: 26 June 1998 / Accepted: 27 June 1998 相似文献
4.
Maria Westerholm Lotta Levén Anna Schnürer 《Applied and environmental microbiology》2012,78(21):7619-7625
The importance of syntrophic acetate oxidation for process stability in methanogenic systems operating at high ammonia concentrations has previously been emphasized. In this study we investigated bioaugmentation of syntrophic acetate-oxidizing (SAO) cultures as a possible method for decreasing the adaptation period of biogas reactors operating at gradually increased ammonia concentrations (1.5 to 11 g NH4+-N/liter). Whole stillage and cattle manure were codigested semicontinuously for about 460 days in four mesophilic anaerobic laboratory-scale reactors, and a fixed volume of SAO culture was added daily to two of the reactors. Reactor performance was evaluated in terms of biogas productivity, methane content, pH, alkalinity, and volatile fatty acid (VFA) content. The decomposition pathway of acetate was analyzed by isotopic tracer experiments, and population dynamics were monitored by quantitative PCR analyses. A shift in dominance from aceticlastic methanogenesis to SAO occurred simultaneously in all reactors, indicating no influence by bioaugmentation on the prevailing pathway. Higher abundances of Clostridium ultunense and Tepidanaerobacter acetatoxydans were associated with bioaugmentation, but no influence on Syntrophaceticus schinkii or the methanogenic population was distinguished. Overloading or accumulation of VFA did not cause notable dynamic effects on the population. Instead, the ammonia concentration had a substantial impact on the abundance level of the microorganisms surveyed. The addition of SAO culture did not affect process performance or stability against ammonia inhibition, and all four reactors deteriorated at high ammonia concentrations. Consequently, these findings further demonstrate the strong influence of ammonia on the methane-producing consortia and on the representative methanization pathway in mesophilic biogas reactors. 相似文献
5.
Mesophilic and thermophilic anaerobic digestion of source-sorted organic wastes: effect of ammonia on glucose degradation and methane production 总被引:5,自引:0,他引:5
The wet organic fraction of household wastes was digested anaerobically at 37 °C and 55 °C. At both temperatures the volatile
solids loading was increased from 1 g l−1 day−1 to 9.65 g l−1 day−1, by reducing the nominal hydraulic retention time from 93 days to 19 days. The volatile solids removal in the reactors at
both temperatures for the same loading rates was in a similar range and was still 65% at 19 days hydraulic retention time.
Although more biogas was produced in the thermophilic reactor, the energy conservation in methane was slightly lower, because
of a lower methane content, compared to the biogas of the mesophilic reactor. The slightly lower amount of energy conserved
in the methane of the thermophilic digester was presumably balanced by the hydrogen that escaped into the gas phase and thus
was no longer available for methanogenesis. In the thermophilic process, 1.4 g/l ammonia was released, whereas in the mesophilic
process only 1 g/l ammonia was generated, presumably from protein degradation. Inhibition studies of methane production and
glucose fermentation revealed a K
i (50%) of 3 g/l and 3.7 g/l ammonia (equivalent to 0.22 g/l and 0.28 g/l free NH3) at 37 °C and a K
i (50%) of 3.5 g/l and 3.4 g/l ammonia (equivalent to 0.69 g/l and 0.68 g/l free NH3) at 55 °C. This indicated that the thermophilic flora tolerated at least twice as much of free NH3 than the mesophilic flora and, furthermore, that the thermophilic flora was able to degrade more protein. The apparent ammonia
concentrations in the mesophilic and in the thermophilic biowaste reactor were low enough not to inhibit glucose fermentation
and methane production of either process significantly, but may have been high enough to inhibit protein degradation. The
data indicated either that the mesophilic and thermophilic protein degraders revealed a different sensitivity towards free
ammonia or that the mesophilic population contained less versatile protein degraders, leaving more protein undegraded.
Received: 26 March 1997 / Received revision: 13 May 1997 / Accepted: 19 May 1997 相似文献
6.
Prathap Parameswaran César I. Torres Hyung‐Sool Lee Rosa Krajmalnik‐Brown Bruce E. Rittmann 《Biotechnology and bioengineering》2009,103(3):513-523
We demonstrate that the coulombic efficiency (CE) of a microbial electrolytic cell (MEC) fueled with a fermentable substrate, ethanol, depended on the interactions among anode respiring bacteria (ARB) and other groups of micro‐organisms, particularly fermenters and methanogens. When we allowed methanogenesis, we obtained a CE of 60%, and 26% of the electrons were lost as methane. The only methanogenic genus detected by quantitative real‐time PCR was the hydrogenotrophic genus, Methanobacteriales, which presumably consumed all the hydrogen produced during ethanol fermentation (~30% of total electrons). We did not detect acetoclastic methanogenic genera, indicating that acetate‐oxidizing ARB out‐competed acetoclastic methanogens. Current production and methane formation increased in parallel, suggesting a syntrophic interaction between methanogens and acetate‐consuming ARB. When we inhibited methanogenesis with 50 mM 2‐bromoethane sulfonic acid (BES), the CE increased to 84%, and methane was not produced. With no methanogenesis, the electrons from hydrogen were converted to electrical current, either directly by the ARB or channeled to acetate through homo‐acetogenesis. This illustrates the key role of competition among the various H2 scavengers and that, when the hydrogen‐consuming methanogens were present, they out‐competed the other groups. These findings also demonstrate the importance of a three‐way syntrophic relationship among fermenters, acetate‐consuming ARB, and a H2 consumer during the utilization of a fermentable substrate. To obtain high coulombic efficiencies with fermentable substrates in a mixed population, methanogens must be suppressed to promote new interactions at the anode that ultimately channel the electrons from hydrogen to current. Biotechnol. Bioeng. 2009;103: 513–523. © 2009 Wiley Periodicals, Inc. 相似文献
7.
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
8.
Carbon nanotubes accelerate methane production in pure cultures of methanogens and in a syntrophic coculture
下载免费PDF全文
![点击此处可从《Environmental microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Andreia F. Salvador Gilberto Martins Manuel Melle‐Franco Ricardo Serpa Alfons J.M. Stams Ana J. Cavaleiro M. Alcina Pereira M. Madalena Alves 《Environmental microbiology》2017,19(7):2727-2739
Carbon materials have been reported to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens improving methane production in anaerobic processes. In this work, the effect of increasing concentrations of carbon nanotubes (CNT) on the activity of pure cultures of methanogens and on typical fatty acid‐degrading syntrophic methanogenic coculture was evaluated. CNT affected methane production by methanogenic cultures, although acceleration was higher for hydrogenotrophic methanogens than for acetoclastic methanogens or syntrophic coculture. Interestingly, the initial methane production rate (IMPR) by Methanobacterium formicicum cultures increased 17 times with 5 g·L?1 CNT. Butyrate conversion to methane by Syntrophomonas wolfei and Methanospirillum hungatei was enhanced (~1.5 times) in the presence of CNT (5 g·L?1), but indications of DIET were not obtained. Increasing CNT concentrations resulted in more negative redox potentials in the anaerobic microcosms. Remarkably, without a reducing agent but in the presence of CNT, the IMPR was higher than in incubations with reducing agent. No growth was observed without reducing agent and without CNT. This finding is important to re‐frame discussions and re‐interpret data on the role of conductive materials as mediators of DIET in anaerobic communities. It also opens new challenges to improve methane production in engineered methanogenic processes. 相似文献
9.
Bocher BT Agler MT Garcia ML Beers AR Angenent LT 《Journal of industrial microbiology & biotechnology》2008,35(5):321-329
Many beer breweries use high-rate anaerobic digestion (AD) systems to treat their soluble high-strength wastewater. Biogas
from these AD systems is used to offset nonrenewable energy utilization in the brewery. With increasing nonrenewable energy
costs, interest has mounted to also digest secondary residuals from the high-rate digester effluent, which consists of yeast
cells, bacteria, methanogens, and small (hemi)cellulosic particles. Mesophilic (37 °C) and thermophilic (55 °C) lab-scale,
low-rate continuously-stirred anaerobic digestion (CSAD) bioreactors were operated for 258 days by feeding secondary residuals
at a volatile solids (VS) concentration of ∼40 g l−1. At a hydraulic retention time (HRT) of 15 days and a VS loading rate of 2.7 g VS l−1 day−1, the mesophilic bioreactor showed an average specific volumetric biogas production rate of 0.88 l CH4 l−1 day−1 and an effluent VS concentration of 22.2 g VS l−1 (43.0% VS removal efficiency) while the thermophilic bioreactor displayed similar performances. The overall methane yield
for both systems was 0.21 l CH4 g−1 VS fed and 0.47–0.48 l CH4 g−1 VS removed. A primary limitation of thermophilic digestion of this protein-rich waste is the inhibition of methanogens due
to higher nondissociated (free) ammonia (NH3) concentrations under similar total ammonium (NH4
+) concentrations at equilibrium. Since thermophilic AD did not result in advantageous methane production rates or yields,
mesophilic AD was, therefore, superior in treating secondary residuals from high-rate AD effluent. An additional digester
to convert secondary residuals to methane may increase the total biogas generation at the brewery by 8% compared to just conventional
high-rate digestion of brewery wastewater alone.
JIMB-2008: BioEnergy—Special issue. 相似文献
10.
Carla Pereira Magalhães Joaquim A. Ribeiro Ana P. Guedes Ana L. Arantes Diana Z. Sousa Alfons J. M. Stams Maria M. Alves Ana Júlia Cavaleiro 《Microbial biotechnology》2020,13(4):962-973
Glycerol-rich waste streams produced by the biodiesel, bioethanol and oleochemical industries can be treated and valorized by anaerobic microbial communities to produce methane. As current knowledge of the microorganisms involved in thermophilic glycerol conversion to methane is scarce, thermophilic glycerol-degrading methanogenic communities were enriched. A co-culture of Thermoanaerobacter and Methanothermobacter species was obtained, pointing to a non-obligately syntrophic glycerol degradation. This hypothesis was further studied by incubating Thermoanaerobacter brockii subsp. finnii and T. wiegelii with glycerol (10 mM) in pure culture and with different hydrogenotrophic methanogens. The presence of the methanogen accelerated glycerol fermentation by the two Thermoanaerobacter strains up to 3.3 mM day−1, corresponding to 12 times higher volumetric glycerol depletion rates in the methanogenic co-cultures than in the pure bacterial cultures. The catabolic pathways of glycerol conversion were identified by genome analysis of the two Thermoanaerobacter strains. NADH and reduced ferredoxin formed in the pathway are linked to proton reduction, which becomes thermodynamically favourable when the hydrogen partial pressure is kept low by the hydrogenotrophic methanogenic partner. 相似文献
11.
12.
13.
Nuria Fernandez-Gonzalez Chiara Pedizzi Juan M. Lema Marta Carballa 《Microbial biotechnology》2019,12(6):1403-1416
Air-side stripping without a prior solid–liquid phase separation step is a feasible and promising process to control ammonia concentration in thermophilic digesters. During the process, part of the anaerobic biomass is exposed to high temperature, high pH and aerobic conditions. However, there are no studies assessing the effects of those harsh conditions on the microbial communities of thermophilic digesters. To fill this knowledge gap, the microbiomes of two thermophilic digesters (55°C), fed with a mixture of pig manure and nitrogen-rich co-substrates, were investigated under different organic loading rates (OLR: 1.1–5.2 g COD l−1 day−1), ammonia concentrations (0.2–1.5 g free ammonia nitrogen l−1) and stripping frequencies (3–5 times per week). The bacterial communities were dominated by Firmicutes and Bacteroidetes phyla, while the predominant methanogens were Methanosarcina sp archaea. Increasing co-substrate fraction, OLR and free ammonia nitrogen (FAN) favoured the presence of genera Ruminiclostridium, Clostridium and Tepidimicrobium and of hydrogenotrophic methanogens, mainly Methanoculleus archaea. The data indicated that the use of air-side stripping did not adversely affect thermophilic microbial communities, but indirectly modulated them by controlling FAN concentrations in the digester. These results demonstrate the viability at microbial community level of air side-stream stripping process as an adequate technology for the ammonia control during anaerobic co-digestion of nitrogen-rich substrates. 相似文献
14.
Ana L. Arantes Joana I. Alves Alfons J. M. Stams M. Madalena Alves Diana Z. Sousa 《Microbial biotechnology》2018,11(4):639-646
The substitution of natural gas by renewable biomethane is an interesting option to reduce global carbon footprint. Syngas fermentation has potential in this context, as a diverse range of low‐biodegradable materials that can be used. In this study, anaerobic sludge acclimatized to syngas in a multi‐orifice baffled bioreactor (MOBB) was used to start enrichments with CO. The main goals were to identify the key players in CO conversion and evaluate potential interspecies metabolic interactions conferring robustness to the process. Anaerobic sludge incubated with 0.7 × 105 Pa CO produced methane and acetate. When the antibiotics vancomycin and/or erythromycin were added, no methane was produced, indicating that direct methanogenesis from CO did not occur. Acetobacterium and Sporomusa were the predominant bacterial species in CO‐converting enrichments, together with methanogens from the genera Methanobacterium and Methanospirillum. Subsequently, a highly enriched culture mainly composed of a Sporomusa sp. was obtained that could convert up to 1.7 × 105 Pa CO to hydrogen and acetate. These results attest the role of Sporomusa species in the enrichment as primary CO utilizers and show their importance for methane production as conveyers of hydrogen to methanogens present in the culture. 相似文献
15.
Fan Lü Tianshui Li Tianfeng Wang Liming Shao Pinjing He 《Applied microbiology and biotechnology》2014,98(2):969-977
The sludge digestate stabilized by mesophilic anaerobic digestion was further degraded through thermophilic anaerobic digestion using 0–10 % (v/v) of thermophilic, proteolytic Coprothermobacter proteolyticus, and/or methanogenic granular sludge. The results demonstrated that the temperature shift to thermophilic condition promoted abiotic solubilization of proteins and reactivated the fermentative bacteria and methanogens indigenous in the sludge digestate, resulting in a final methane yield of 6.25 mmol-CH4/g-volatile suspended solid (VSS) digestate. The addition of C. proteolyticus accelerated the hydrolysis and fermentation of proteins and polysaccharides in the digestate during the early stage of thermophilic anaerobic digestion and stimulated methane production by syntrophic cooperation with methanogenic granular sludge. In the treatment with granular sludge and inoculated with 10 % (v/v) of C. proteolyticus, a final methane yield of 7 mmol-CH4/g-VSS digestate was obtained, and 48.4 % proteins and 27.0 % polysaccharides were degraded. The dissolved proteins were contributed by abiotic factor, C. proteolyticus, and indigenous digestate bacteria, respectively, by around 16, 28, and 56 %. 相似文献
16.
Nutrient and acetate amendment leads to acetoclastic methane production and microbial community change in a non‐producing Australian coal well
下载免费PDF全文
![点击此处可从《Microbial biotechnology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michiel H. in 't Zandt Sabrina Beckmann Ruud Rijkers Mike S.M. Jetten Mike Manefield Cornelia U. Welte 《Microbial biotechnology》2018,11(4):626-638
Coal mining is responsible for 11% of total anthropogenic methane emission thereby contributing considerably to climate change. Attempts to harvest coalbed methane for energy production are challenged by relatively low methane concentrations. In this study, we investigated whether nutrient and acetate amendment of a non‐producing sub‐bituminous coal well could transform the system to a methane source. We tracked cell counts, methane production, acetate concentration and geochemical parameters for 25 months in one amended and one unamended coal well in Australia. Additionally, the microbial community was analysed with 16S rRNA gene amplicon sequencing at 17 and 25 months after amendment and complemented by metagenome sequencing at 25 months. We found that cell numbers increased rapidly from 3.0 × 104 cells ml?1 to 9.9 × 107 in the first 7 months after amendment. However, acetate depletion with concomitant methane production started only after 12–19 months. The microbial community was dominated by complex organic compound degraders (Anaerolineaceae, Rhodocyclaceae and Geobacter spp.), acetoclastic methanogens (Methanothrix spp.) and fungi (Agaricomycetes). Even though the microbial community had the functional potential to convert coal to methane, we observed no indication that coal was actually converted within the time frame of the study. Our results suggest that even though nutrient and acetate amendment stimulated relevant microbial species, it is not a sustainable way to transform non‐producing coal wells into bioenergy factories. 相似文献
17.
Lisa M. Gieg Irene A. Davidova Kathleen E. Duncan Joseph M. Suflita 《Environmental microbiology》2010,12(11):3074-3086
Petrochemical and geological evidence suggest that petroleum in most reservoirs is anaerobically biodegraded to some extent. However, the conditions for this metabolism and the cultivation of the requisite microorganisms are rarely established. Here, we report on microbial hydrocarbon metabolism in two distinct oilfields on the North Slope of Alaska (designated Fields A and B). Signature anaerobic hydrocarbon metabolites were detected in produced water from the two oilfields offering evidence of in situ biodegradation activity. Rate measurements revealed that sulfate reduction was an important electron accepting process in Field A (6–807 µmol S l?1 day?1), but of lesser consequence in Field B (0.1–10 µmol S l?1 day?1). Correspondingly, enrichments established at 55°C with a variety of hydrocarbon mixtures showed relatively high sulfate consumption but low methane production in Field A incubations, whereas the opposite was true of the Field B enrichments. Repeated transfer of a Field B enrichment showed ongoing methane production in the presence of crude oil that correlated with ≥ 50% depletion of several component hydrocarbons. Molecular‐based microbial community analysis of the methanogenic oil‐utilizing consortium revealed five bacterial taxa affiliating with the orders Thermotogales, Synergistales, Deferribacterales (two taxa) and Thermoanaerobacterales that have known fermentative or syntrophic capability and one methanogen that is most closely affiliated with uncultured clones in the H2‐using family Methanobacteriaceae. The findings demonstrate that oilfield‐associated microbial assemblages can metabolize crude oil under the thermophilic and anaerobic conditions prevalent in many petroleum reservoirs. 相似文献
18.
Sasaki K Morita M Hirano S Ohmura N Igarashi Y 《Applied microbiology and biotechnology》2011,90(4):1555-1561
Ammonia accumulation is one of the main causes of the loss of methane production observed during fermentation. We investigated
the effect of addition of carbon fiber textiles (CFT) to thermophilic methanogenic bioreactors with respect to ammonia tolerance
during the process of degradation of artificial garbage slurry, by comparing the performance of the reactors containing CFT
with the performance of reactors without CFT. Under total ammonia-N concentrations of 3,000 mg L−1, the reactors containing CFT were found to mediate stable removal of organic compounds and methane production. Under these
conditions, high levels of methanogenic archaea were retained at the CFT, as determined by 16S rRNA gene analysis for methanogenic
archaea. In addition, Methanobacterium sp. was found to be dominant in the suspended fraction, and Methanosarcina sp. was dominant in the retained fraction of the reactors with CFT. However, the reactors without CFT had lower rates of
removal of organic compounds and production of methane under total ammonia-N concentrations of 1,500 mg L−1. Under this ammonia concentration, a significant accumulation of acetate was observed in the reactors without CFT (130.0 mM),
relative to the reactors with CFT (4.2 mM). Only Methanobacterium sp. was identified in the reactors without CFT. These results suggest that CFT enables stable proliferation of aceticlastic
methanogens by preventing ammonia inhibition. This improves the process of stable garbage degradation and production of methane
in thermophilic bioreactors that include high levels of ammonia. 相似文献
19.
The degradation potential of trichloroethene by the aerobic methane- and ammonia-oxidizing microorganisms naturally associated
with wetland plant (Carex comosa) roots was examined in this study. In bench-scale microcosm experiments with washed (soil free) Carex comosa roots, the activity of root-associated methane- and ammonia-oxidizing microorganisms, which were naturally present on the
root surface and/or embedded within the roots, was investigated. Significant methane and ammonia oxidation were observed reproducibly
in batch reactors with washed roots incubated in growth media, where methane oxidation developed faster (2 weeks) compared
to ammonia oxidation (4 weeks) in live microcosms. After enrichment, the methane oxidizers demonstrated their ability to degrade
150 μg l−1 TCE effectively at 1.9 mg l−1 of aqueous CH4. In contrast, ammonia oxidizers showed a rapid and complete inhibition of ammonia oxidation with 150 μg l−1 TCE at 20 mg l−1 of NH4
+-N, which may be attributed to greater sensitivity of ammonia oxidizers to TCE or its degradation product. No such inhibitory
effect of TCE degradation was detected on methane oxidation at the above experimental conditions. The results presented here
suggest that microorganisms associated with wetland plant roots can assist in the natural attenuation of TCE in contaminated
aquatic environments. 相似文献
20.
M. Salomé Duarte Andreia F. Salvador Ana J. Cavaleiro Alfons J. M. Stams M. Alcina Pereira M. Madalena Alves 《Environmental microbiology》2020,22(9):3650-3659
Anaerobic degradation of long-chain fatty acids (LCFA) involves syntrophic bacteria and methanogens, but facultative anaerobic bacteria (FAB) might have a relevant role as well. Here we investigated oleate degradation by a syntrophic synthetic co-culture of Syntrophomonas zehnderi (Sz) and Methanobacterium formicicum (Mf) and FAB (two oleate-degrading Pseudomonas spp. I1 + I2). Sz + Mf were first cultivated in a continuous bioreactor under strict anaerobic conditions. Thereafter, I1 + I2 were inoculated and microaerophilic conditions were provided. Methane and acetate were the main degradation products by Sz + Mf in anaerobiosis and by Sz + Mf + I1 + I2 in microaerophilic conditions. However, acetate production from oleate was higher in microaerophilic conditions (5% O2) with the four microorganisms together (0.41 ± 0.07 mmol day−1) than in anaerobiosis with Sz + Mf (0.23 ± 0.05 mmol day−1). Oleate degradation in batch assays was faster by Sz + Mf + I1 + I2 (under microaerophilic conditions) than by Sz + Mf alone (under strict anaerobic conditions). I1 + I2 were able to grow with oleate and with intermediates of oleate degradation (hydrogen, acetate and formate). This work highlights the importance of FAB, particularly Pseudomonas sp., in anaerobic reactors treating oleate-based wastewater, because they accelerate oleate conversion to methane, by protecting strict anaerobes from oxygen toxicity and also by acting as alternative hydrogen/formate and acetate scavengers for LCFA-degrading anaerobes. 相似文献