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1.
J Environ Manage ; 301: 113914, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34628280

RESUMO

Humic acid (HA) is an important active compound formed during anaerobic digestion process, with a complex structure and dynamic electron transfer capacity (ETC). However, the mechanisms by which these macromolecular organic compounds dynamically interact with the microbial anaerobic digestion process at different operating temperatures are still unclear. In this study, the link between the evolution of the ETC of HAs and the microbial community under mesophilic and thermophilic conditions was investigated. The results showed an increasing trend in the ETC of HAs in both mesophilic (671-1479 µmol gHA-1) and thermophilic (774-1506 µmol gHA-1) anaerobic digestion (AD) until day 25. The ETC was positively correlated with the bacterial community of hydrolytic and acidogenic phases, but negatively correlated with the archaeal community of the methanogenic phase. Furthermore, the relationship between ETC and key enzyme activity was explored using a co-occurrence network analysis. HAs revealed a high potential to promote key enzyme activities during hydrolysis (amylase and protease) and acidification (acetate kinase, butyrate kinase, and phosphotransacetylase) while inhibiting the key enzyme activity in the methanogenic phase during the anaerobic digestion process. Moreover, HAs formed under thermophilic conditions had a greater influence on key enzyme activities than those formed under mesophilic conditions. This study advances our understanding of the mechanisms underlying the influence of HAs on anaerobic digestion performance.


Assuntos
Euryarchaeota , Substâncias Húmicas , Anaerobiose , Reatores Biológicos , Elétrons , Metano , Esgotos , Temperatura
2.
Sci Total Environ ; 804: 150073, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34517312

RESUMO

The Power-to-Gas concept corresponds to the use of the electric energy surplus to produce H2 by water electrolysis, that can be further converted to methane by biomethanation. However, the fluctuant production of renewable energy sources can lead to discontinuous H2 injections into the reactors, that may interfere with the adaptation of the microbial community to high H2 partial pressures. In this study, the response of the microbial community to H2 and organic feed starvation was evaluated in in-situ and ex-situ biomethanation. The fed-batch reactors were fed with acetate or glucose and H2, and one or four weeks of starvation periods were investigated. Methane productivity was mostly affected by the four-week starvation period. However, both in-situ and ex-situ biomethanation reactors recovered their methane production rate after starvation within approximately one-week of normal operation, while the anaerobic digestion (AD) reactors did not recover their performances even after 3 weeks of normal operation. The recovery failure of the AD reactors was probably related to a slow growth of the syntrophic and methanogen microorganisms, that led to a VFA accumulation. On the contrary, the faster recovery of both biomethanation reactors was related to the replacement of Methanoculleus sp. by Methanobacterium sp., restoring the methane production in the in-situ and ex-situ biomethanation reactors. This study has shown that biomethanation processes can respond favourably to the intermittent H2 addition without compromising their CH4 production performance.


Assuntos
Euryarchaeota , Microbiota , Anaerobiose , Biocombustíveis , Reatores Biológicos , Hidrogênio , Metano
3.
Appl Microbiol Biotechnol ; 105(23): 8937-8949, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34694448

RESUMO

Methanogenesis is central to anaerobic digestion processes. The conversion of propionate as a key intermediate for methanogenesis requires syntrophic interactions between bacterial and archaeal partners. In this study, a series of methanogenic enrichments with propionate as the sole substrate were developed to identify microbial populations specifically involved in syntrophic propionate conversion. These rigorously controlled propionate enrichments exhibited functional stability with consistent propionate conversion and methane production; yet, the methanogenic microbial communities experienced substantial temporal dynamics, which has important implications on the understanding of mechanisms involved in microbial community assembly in anaerobic digestion. Syntrophobacter was identified as the most abundant and consistent bacterial partner in syntrophic propionate conversion regardless of the origin of the source culture, the concentration of propionate, or the temporal dynamics of the culture. In contrast, the methanogen partners involved in syntrophic propionate conversion lacked consistency, as the dominant methanogens varied as a function of process condition and temporal dynamics. Methanoculleus populations were specifically enriched as the syntrophic partner at inhibitory levels of propionate, likely due to the ability to function under unfavorable environmental conditions. Syntrophic propionate conversion was carried out exclusively via transformation of propionate into acetate and hydrogen in enrichments established in this study. Microbial populations highly tolerant of elevated propionate, represented by Syntrophobacter and Methanoculleus, are of great significance in understanding methanogenic activities during process perturbations when propionate accumulation is frequently encountered. Key points • Syntrophobacter was the most consistent bacterial partner in propionate metabolism. • Diverse hydrogenotrophic methanogen populations could serve as syntrophic partners. • Methanoculleus emerged as a methanogen partner tolerant of elevated propionate.


Assuntos
Euryarchaeota , Propionatos , Archaea , Metano , Methanomicrobiaceae
4.
Environ Sci Technol ; 55(21): 14817-14827, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34657430

RESUMO

During anaerobic digestion, the active microbiome synthesizes enzymes by transcription and translation, and then enzymes catalyze multistep bioconversions of substrates before methane being produced. However, little information is available on how ammonia affects truly active microbes containing the expressed enzymes, enzyme synthesis, and key enzymes. In this study, an integrated metagenomic and metaproteomic investigation showed that ammonia suppressed not only the obligate acetotrophic methanogens but also the syntrophic propionate and butyrate oxidation taxa and their assistant bacteria (genus Desulfovibrio), which declined the biotransformations of propionate and butyrate → acetate → methane. Although the total population of the hydrolyzing and acidifying bacteria was not affected by ammonia, the bacteria with ammonia resistance increased. Our study also revealed that ammonia restrained the enzyme synthesis process by inhibiting the RNA polymerase (subunits A' and D) during transcription and the ribosome (large (L3, L12, L13, L22, and L25) and small (S3, S3Ae, and S7) ribosomal subunits) and aminoacyl-tRNA synthesis (aspartate-tRNA synthetase) in translation. Further investigation suggested that methylmalonyl-CoA mutase, acetyl-CoA C-acetyltransferase, and CH3-CoM reductase, which regulate propionate and butyrate oxidation and acetoclastic methanation, were significantly downregulated by ammonia. This study provides intrinsic insights into the fundamental mechanisms of how ammonia inhibits anaerobic digestion.


Assuntos
Amônia , Euryarchaeota , Anaerobiose , Bactérias/genética , Reatores Biológicos , Metano
5.
J Biol Chem ; 297(4): 101219, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34560100

RESUMO

Polyamines are fundamental molecules of life, and their deep evolutionary history is reflected in extensive biosynthetic diversification. The polyamines putrescine, agmatine, and cadaverine are produced by pyridoxal 5'-phosphate-dependent L-ornithine, L-arginine, and L-lysine decarboxylases (ODC, ADC, LDC), respectively, from both the alanine racemase (AR) and aspartate aminotransferase (AAT) folds. Two homologous forms of AAT-fold decarboxylase are present in bacteria: an ancestral form and a derived, acid-inducible extended form containing an N-terminal fusion to the receiver-like domain of a bacterial response regulator. Only ADC was known from the ancestral form and limited to the Firmicutes phylum, whereas extended forms of ADC, ODC, and LDC are present in Proteobacteria and Firmicutes. Here, we report the discovery of ancestral form ODC, LDC, and bifunctional O/LDC and extend the phylogenetic diversity of functionally characterized ancestral ADC, ODC, and LDC to include phyla Fusobacteria, Caldiserica, Nitrospirae, and Euryarchaeota. Using purified recombinant enzymes, we show that these ancestral forms have a nascent ability to decarboxylate kinetically less preferred amino acid substrates with low efficiency, and that product inhibition primarily affects preferred substrates. We also note a correlation between the presence of ancestral ODC and ornithine/arginine auxotrophy and link this with a known symbiotic dependence on exogenous ornithine produced by species using the arginine deiminase system. Finally, we show that ADC, ODC, and LDC activities emerged independently, in parallel, in the homologous AAT-fold ancestral and extended forms. The emergence of the same ODC, ADC, and LDC activities in the nonhomologous AR-fold suggests that polyamine biosynthesis may be inevitable.


Assuntos
Proteínas Arqueais , Bactérias , Proteínas de Bactérias , Poliaminas Biogênicas , Carboxiliases , Euryarchaeota , Evolução Molecular , Ornitina Descarboxilase , Proteínas Arqueais/química , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Bactérias/enzimologia , Bactérias/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Poliaminas Biogênicas/biossíntese , Poliaminas Biogênicas/química , Carboxiliases/química , Carboxiliases/genética , Carboxiliases/metabolismo , Euryarchaeota/enzimologia , Euryarchaeota/genética , Ornitina Descarboxilase/química , Ornitina Descarboxilase/genética , Ornitina Descarboxilase/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
6.
Bioresour Technol ; 341: 125756, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34419881

RESUMO

Undigested and dewatered sludge at 10% total solids was pretreated at 60 °C for 3 h and fed to a lab-scale horizontal anaerobic bioreactor for 130 days with solids retention time (SRTs) from 25 to 16 d. The low-thermal pretreatment enabled higher net energy production, improved sludge treatment efficiency, and enhanced digestion stability. The highest average biomethane yield and production rate were 138.5 mL/g VS and 0.43 L/L.d, respectively, and the economic benefit was expected to be the maximum at SRT 16 d. Pretreatment did not increase the specific methanogenic activity per unit methanogen, but resulted in higher abundance of methanogenic archaea and hydrolytic bacteria. Methanogenic population shifted from hydrogenotrophic to acetoclastic, consistent with predicted gene expression at SRT equal or below 20 d. Anaerobic digestion along with low-thermal could be a feasible management strategy for undigested dewatered sludge from small WWTPs.


Assuntos
Euryarchaeota , Microbiota , Anaerobiose , Reatores Biológicos , Metano , Esgotos
7.
Bioresour Technol ; 340: 125694, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34352646

RESUMO

Four different types of ceramic gas distributors (Al2O3 of 1.2 µm and SiC of 0.5, 7 and 14 µm) were evaluated to increase biomethane formation during ex-situ biogas upgrading process. Each type of gas diffuser was tested independently at three different gas retention times of 10, 5 and 2.5 h, at thermophilic conditions. CH4 production rate increased by increasing input gas flow rate for all type of distributors, whereas CH4 concentration declined. Reactors equipped with SiC gas distributors effectively improved biomethane content fulfilling natural gas standards. Microbial analysis showed high abundance of hydrogenotrophic methanogens and proliferated syntrophic bacteria, i.e. syntrophic acetate oxidizers and homoacetogens, confirming the effect of H2 to alternate anaerobic digestion microbiome and enhance hydrogenotrophic methanogenesis. A detailed anaerobic bioconversion model was adapted to simulate the operation of the R1-R4 reactors. The model was shown to be effective for the simulation of biogas upgrading process in up-flow reactors.


Assuntos
Biocombustíveis , Euryarchaeota , Reatores Biológicos , Hidrogênio , Metano
8.
Water Res ; 203: 117494, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34412021

RESUMO

Compared with anaerobic pressure sewers, gravity sewers have much more complex operational conditions, such as anaerobic/aerobic spatial variations along variable structures of the pipe network. This greatly complicates the prediction of sulfide generation from spatially heterogeneous sewer sediments. This study proposes a novel quantitative approach for rapidly estimating the sulfide generation flux by understanding the sulfidogenic conversion under complex sewer conditions. Significant anaerobic/aerobic spatial variations were the most critical factor affecting the sulfide production in residential gravity sewers. The dynamic aeration-related process stimulated the growth of sulfide-oxidizing bacteria (SOB) in the surface zone, while the sulfidogenic and methanogenic zone moved into deeper layers. A detailed mechanism model incorporating dynamic alternative anaerobic/aerobic transformation was developed to predict apparent sulfide production, as well as the microscale spatial profiles of chemicals and microbial communities in sediments. The model was evaluated to establish a rapid quantitative approach that only depended on a few key parameters (e.g., flow velocity, pipe diameter, slope, mean hydraulic depth and sulfate concentration), which can provide an important basis for estimating different sulfide generation fluxes under various sewer factors. The identification of sulfide generation hotspots will greatly help determine how to economically control sulfide generation by chemical dosing or pipe structural modification.


Assuntos
Euryarchaeota , Sulfeto de Hidrogênio , Metano , Esgotos , Sulfatos , Sulfetos
9.
Huan Jing Ke Xue ; 42(7): 3472-3481, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212674

RESUMO

It is known that methanogens play a critical role in the carbon cycle in soil, while methanogen community characteristics and their environmental influencing factors in the soil planted with salt-tolerant rice remain unclear. In this study, methanogen abundance, community composition, and relationships with environmental factors in soils planted with the salt-tolerant rice (YC1703) and ordinary rice (Lindao 10) were evaluated in the rice improvement demonstration base of Qingdao Wisdom Agricultural Industry using real-time fluorescence quantitative PCR and Illumina high-throughput sequencing. The results indicated that the abundance and community richness of methanogens in Lindao 10 soil were significantly higher than those in YC1703 soil, and methanogens in YC1703 soil exhibited higher diversity. The combined effects of rice varieties, rice growth period, and environmental factors had impacts on the methanogen community. The hydrogenotrophic methanogens were dominant in the YC1703 and Lindao 10 soils; thus, we speculated that the dominant pathway of methane production in these soils was hydrogenotrophic methanogenesis.


Assuntos
Euryarchaeota , Oryza , Metano , RNA Ribossômico 16S , Solo , Microbiologia do Solo
10.
Water Res ; 200: 117268, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34098269

RESUMO

Methanogenic bioelectrochemical systems (BESs) can convert carbon dioxide (CO2) to methane (CH4) and may be used for anaerobic digester biogas upgrading. However, the effect of hydrogen sulfide (H2S), a common biogas component, on BES performance is unknown. Thus, the objective of this study was to assess the effect of H2S addition to the cathode headspace on BES performance at a range of initial gas-phase H2S concentrations (0-6% v/v), as well as its effect on the anode and cathode microbial communities. As the initial cathode headspace H2S increased from 0 to 2% (v/v), biocathodic CH4 production increased by two-fold to 3.56 ± 0.36 mmol/L-d, due to dissolved H2S transport from the cathode to the anode where H2S was oxidized. Elemental sulfur and sulfate were H2S oxidation products detected in the anode. Above 3% initial cathode headspace H2S, biocathodic CH4 production declined due to inhibition. A phylotype most closely related to Methanobrevibacter arboriphilus dominated the cathode archaeal communities. In the sulfide-amended BES, a phylotype similar to the exoelectrogen Ochrobactrum anthropi was enriched in both the anode and cathode, whereas phylotypes related to sulfate-reducing and sulfur oxidizing Bacteria were detected in the bioanode. Thus, sulfide transport and oxidation in the anode play an important role in methanogenic BESs treating sulfide-bearing biogas.


Assuntos
Euryarchaeota , Sulfeto de Hidrogênio , Biocombustíveis , Reatores Biológicos , Dióxido de Carbono/análise , Metano
11.
J Environ Qual ; 50(4): 817-835, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34021608

RESUMO

National inventories of methane (CH4 ) emission from manure management are based on guidelines from the Intergovernmental Panel on Climate Change using country-specific emission factors. These calculations must be simple and, consequently, the effects of management practices and environmental conditions are only crudely represented in the calculations. The intention of this review is to develop a detailed understanding necessary for developing accurate models for calculating CH4 emission from liquid manure, with particular focus on the microbiological conversion of organic matter to CH4 . Themes discussed are (a) the liquid manure environment; (b) methane production processes from a modeling perspective; (c) development and adaptation of methanogenic communities; (d) mass and electron conservation; (e) steps limiting CH4 production; (f) inhibition of methanogens; (g) temperature effects on CH4 production; and (h) limits of existing estimation approaches. We conclude that a model must include calculation of microbial response to variations in manure temperature, substrate availability and age, and management system, because these variables substantially affect CH4 production. Methane production can be reduced by manipulating key variables through management procedures, and the effects may be taken into account by including a microbial component in the model. When developing new calculation procedures, it is important to include reasonably accurate algorithms of microbial adaptation. This review presents concepts for these calculations and ideas for how these may be carried out. A need for better quantification of hydrolysis kinetics is identified, and the importance of short- and long-term microbial adaptation is highlighted.


Assuntos
Euryarchaeota , Esterco , Animais , Metano , Temperatura
12.
Water Sci Technol ; 83(9): 2087-2099, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33989178

RESUMO

Interspecific competition for substrate and space gives rise to considerable variation in biomass distribution within the microbial community. To study microbial community in depth, we used several research methods as sampling and analytical measurements, and developed a cellular automata (CA) model that would facilitate a description of the microbial growth process based on Anaerobic Digestion Model No. 1 (ADM1) of the International Water Association (IWA). Using the CA model, we aimed to determine whether interspecific competition occurs among acidogens, acetogens and methanogens, and to examine the influence of interspecific competition on the spatial structure of microbial communities. We found that acetogens and methanogens competed for core space, resulting in a multi-layer structure. Butyrate-degrading acetogens increased in number, resulting in inhibition of propionate-degrading acetogens. Hydrogenotrophic methanogens showed stronger competitive advantage than acetotrophic methanogens. The simulation showed that the multi-layer structure of the microbial community was formed by interspecific competition.


Assuntos
Euryarchaeota , Microbiota , Anaerobiose , Reatores Biológicos , Simulação por Computador , Ecologia , Metano
13.
PLoS One ; 16(4): e0249023, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33793629

RESUMO

Understanding the microbial communities in anaerobic digesters, especially bacteria and archaea, is key to its better operation and regulation. Microbial communities in the anaerobic digesters of the Gulf region where climatic conditions and other factors may impact the incoming feed are not documented. Therefore, Archaeal and Bacterial communities of three full-scale anaerobic digesters, namely AD1, AD3, and AD5 of the Jebel Ali Sewage water Treatment Plant (JASTP) were analyzed by Illumina sequencing of 16S rRNA genes. Among bacteria, the most abundant genus was fermentative bacteria Acetobacteroides (Blvii28). Other predominant bacterial genera in the digesters included thermophilic bacteria (Fervidobacterium and Coprothermobacter) and halophilic bacteria like Haloterrigena and Sediminibacter. This can be correlated with the climatic condition in Dubai, where the bacteria in the incoming feed may be thermophilic or halophilic as much of the water used in the country is desalinated seawater. The predominant Archaea include mainly the members of the phyla Euryarchaeota and Crenarchaeota belonging to the genus Methanocorpusculum, Metallosphaera, Methanocella, and Methanococcus. The highest population of Methanocorpusculum (more than 50% of total Archaea), and other hydrogenotrophic archaea, is in agreement with the high population of bacterial genera Acetobacteroides (Blvii28) and Fervidobacterium, capable of fermenting organic substrates into acetate and H2. Coprothermobacter, which is known to improve protein degradation by establishing syntrophy with hydrogenotrophic archaea, is also one of the digesters' dominant genera. The results suggest that the microbial community in three full-scale anaerobic digesters is different. To best of our knowledge this is the first detailed report from the UAE.


Assuntos
Bactérias Anaeróbias/genética , Microbiota/genética , Filogenia , Esgotos/microbiologia , Anaerobiose/genética , Archaea/genética , Archaea/isolamento & purificação , Bactérias Anaeróbias/classificação , Bactérias Anaeróbias/isolamento & purificação , Bacteroidetes/genética , Bacteroidetes/isolamento & purificação , Euryarchaeota/genética , Euryarchaeota/isolamento & purificação , Sequenciamento de Nucleotídeos em Larga Escala , RNA Ribossômico 16S/genética
14.
Mol Ecol ; 30(11): 2560-2572, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33817881

RESUMO

The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydrological and biogeochemical cycles and function as a significant CH4 source contributing to the global carbon balance. Unique geochemical factors may drive the microbial community composition and, consequently, affect CH4 emissions across floodplain areas. Here, we report the in situ composition of CH4 cycling microbial communities in Amazonian floodplain sediments. We considered how abiotic factors may affect the microbial community composition and, more specifically, CH4 cycling groups. We collected sediment samples during wet and dry seasons from three different types of floodplain forests, along with upland forest soil samples, from the Eastern Amazon, Brazil. We used high-resolution sequencing of archaeal and bacterial 16S rRNA genes combined with real-time PCR to quantify Archaea and Bacteria, as well as key functional genes indicative of the presence of methanogenic (mcrA) and methanotrophic (pmoA) microorganisms. Methanogens were found to be present in high abundance in floodplain sediments, and they seem to resist the dramatic environmental changes between flooded and nonflooded conditions. Methanotrophs known to use different pathways to oxidise CH4 were detected, including anaerobic archaeal and bacterial taxa, indicating that a wide metabolic diversity may be harboured in this highly variable environment. The floodplain environmental variability, which is affected by the river origin, drives not only the sediment chemistry but also the composition of the microbial communities. These environmental changes seem also to affect the pools of methanotrophs occupying distinct niches. Understanding these shifts in the methanotrophic communities could improve our comprehension of the CH4 emissions in the region.


Assuntos
Euryarchaeota , Metano , Archaea/genética , Brasil , RNA Ribossômico 16S/genética , Microbiologia do Solo
15.
Environ Sci Pollut Res Int ; 28(30): 40288-40307, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33844144

RESUMO

Microbial activities within oil reservoirs have adversely impacted the world's majority of oil by lowering its quality, thereby increasing its recovery and refining cost. Moreover, conventional method of extraction leaves behind nearly two-thirds of the fossil fuels in the oil fields. This huge potential can be extracted if engineered methanogenic consortium is adapted to convert the hydrocarbons into natural gas. This process involves conversion of crude oil hydrocarbons into methanogenic substrates by syntrophic and fermentative bacteria, which are subsequently utilized by methanogens to produce methane. Microbial diversity of such environments supports the viability of this process. This review illuminates the potentials of abundant microbial groups such as Syntrophaceae, Anaerolineaceae, Clostridiales and Euryarchaeota in petroleum hydrocarbon-related environment, their genetic markers, biochemical process and omics-based bioengineering methods involved in methane generation. Increase in the copy numbers of catabolic genes during methanogenesis highlights the prospect of developing engineered biofuel recovery technology. Several lab-based methanogenic consortia from depleted petroleum reservoirs and microcosm studies so far would not be enough for field application without the advent of multi-omics-based technologies to trawl out the bottleneck parameters of the enhanced fuel recovery process. The adaptability of efficient consortium of versatile hydrocarbonoclastic and methanogenic microorganisms under environmental stress conditions is further needed to be investigated. The improved process might hold the potential of methane extraction from petroleum waste like oil tank and refinery sludge, oil field deposits, etc. What sounds as biodegradation could be a beginning of converting waste into wealth by recovery of stranded energy assets.


Assuntos
Euryarchaeota , Petróleo , Biodegradação Ambiental , Biocombustíveis , Marcadores Genéticos , Hidrocarbonetos , Metano
16.
Water Res ; 197: 117120, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33862393

RESUMO

As a clean and renewable energy, biogas is an important alternative to fossil fuels. However, the high carbon dioxide (CO2) content in biogas limits its value as a fuel. 'Biogas upgrading' is an advanced process which removes CO2 from biogas, thereby converting biogas to biomethane, which has a higher commercial value. Microbial technologies offer a sustainable and cost-effective way to upgrade biogas, removing CO2 using hydrogen (H2) as electron donor, generated by surplus electricity from renewable wind or solar energy. Hydrogenotrophic methanogens can be applied to convert CO2 with H2 to methane (CH4), or alternatively, homoacetogens can convert both CO2 and H2 into value-added chemicals. Here, we comprehensively review the current state of biogas generation and utilization, and describe the advances in biological, H2-dependent biogas upgrading technologies, with particular attention to key challenges associated with the processes, e.g., metabolic limitations, low H2 transfer rate, and finite CO2 conversion rate. We also highlight several new strategies for overcoming technical barriers to achieve efficient CO2 conversion, including process optimization to eliminate metabolic limitation, novel reactor designs to improve H2 transfer rate and utilization efficiency, and employing advanced genetic engineering tools to generate more efficient microorganisms. The insights offered in this review will promote further exploration into microbial, H2-driven biogas upgrading, towards addressing the global energy crisis and climate change associated with use of fossil fuels.


Assuntos
Biocombustíveis , Euryarchaeota , Reatores Biológicos , Dióxido de Carbono , Hidrogênio , Metano
17.
Environ Sci Technol ; 55(9): 5917-5928, 2021 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-33856788

RESUMO

Previous studies often attribute microbial reductive dechlorination to organohalide-respiring bacteria (OHRB) or cometabolic dechlorination bacteria (CORB). Even though methanogenesis frequently occurs during dechlorination of organic chlorinated pollutants (OCPs) in situ, the underestimated effect of methanogens and their interactions with dechlorinators remains unknown. We investigated the association between dechlorination and methanogenesis, as well as the performance of methanogens involved in reductive dechlorination, through the use of meta-analysis, incubation experiment, untargeted metabolomic analysis, and thermodynamic modeling approaches. The meta-analysis indicated that methanogenesis is largely synchronously associated with OCP dechlorination, that OHRB are not the sole degradation engineers that maintain OCP bioremediation, and that methanogens are fundamentally needed to sustain microenvironment functional balance. Laboratory results further confirmed that Methanosarcina barkeri (M. barkeri) promotes the dechlorination of γ-hexachlorocyclohexane (γ-HCH). Untargeted metabolomic analysis revealed that the application of γ-HCH upregulated the metabolic functioning of chlorocyclohexane and chlorobenzene degradation in M. barkeri, further confirming that M. barkeri potentially possesses an auxiliary dechlorination function. Finally, quantum analysis based on density functional theory (DFT) indicated that the methanogenic coenzyme F430 significantly reduces the activation barrier to dechlorination. Collectively, this work suggests that methanogens are highly involved in microbial reductive dechlorination at OCP-contaminated sites and may even directly favor OCP degradation.


Assuntos
Poluentes Ambientais , Euryarchaeota , Bactérias , Biodegradação Ambiental , Hexaclorocicloexano
18.
Bioresour Technol ; 333: 125135, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33892429

RESUMO

In this study, a fully automated process converting hydrogen and carbon dioxide to methane in a high temperature trickle-bed reactor was developed from lab scale to field test level. The reactor design and system performance was optimized to yield high methane content in the product gas for direct feed-in to the gas grid. The reaction was catalyzed by a pure culture of Methanothermobacter thermoautotrophicus IM5, which formed a biofilm on ceramic packing elements. During 600 h in continuous and semi-continuous operation in countercurrent flow, the 0.05 m3 reactor produced up to95.3 % of methane at a methane production rate of 0.35 [Formula: see text] . Adding nitrogen as carrier gas during startup, foam control and dosing of ammonium and sodium sulfide as nitrogen and sulfur source were important factors for process automation.


Assuntos
Dióxido de Carbono , Euryarchaeota , Reatores Biológicos , Hidrogênio , Metano
19.
Archaea ; 2021: 8865133, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33746613

RESUMO

Electromethanogenesis refers to the bioelectrochemical synthesis of methane from CO2 by biocathodes. In an electromethanogenic system using thermophilic microorganisms, metagenomic analysis along with quantitative real-time polymerase chain reaction and fluorescence in situ hybridization revealed that the biocathode microbiota was dominated by the methanogen Methanothermobacter sp. strain EMTCatA1 and the actinobacterium Coriobacteriaceae sp. strain EMTCatB1. RNA sequencing was used to compare the transcriptome profiles of each strain at the methane-producing biocathodes with those in an open circuit and with the methanogenesis inhibitor 2-bromoethanesulfonate (BrES). For the methanogen, genes related to hydrogenotrophic methanogenesis were highly expressed in a manner similar to those observed under H2-limited conditions. For the actinobacterium, the expression profiles of genes encoding multiheme c-type cytochromes and membrane-bound oxidoreductases suggested that the actinobacterium directly takes up electrons from the electrode. In both strains, various stress-related genes were commonly induced in the open-circuit biocathodes and biocathodes with BrES. This study provides a molecular inventory of the dominant species of an electromethanogenic biocathode with functional insights and therefore represents the first multiomics characterization of an electromethanogenic biocathode.


Assuntos
Euryarchaeota , Microbiota , Hibridização in Situ Fluorescente , Metano , Methanobacteriaceae
20.
J Environ Manage ; 288: 112363, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33756388

RESUMO

This study evaluated the effects of thermal pretreatment of brewery spent grain (BSG) (by autoclave 121 °C, 1.45 atm for 30 min) on methane production (CH4). Operation temperature (31-59 °C) and substrate concentration (8.3-19.7 g BSG.L-1) factors were investigated by Response Surface Methodology (RSM) and Central Composite Design (CCD). Values ranging from 81.1 ± 2.0 to 290.1 ± 3.5 mL CH4.g-1 TVS were obtained according to operation temperature and substrate concentration variation. The most adverse condition for methanogenesis (81.1 ± 2.0 mL CH4.g-1 TVS) was at 59 °C and 14 g BSG.L-1, in which there was increase in the organic matter concentration from 173.6 ± 4.94 to 3036 ± 7.78 mg.L-1) result of a higher final concentration of volatile fatty acids (VFA, 2662.7 mg.L-1). On the other hand, the optimum condition predicted by the statistical model was at 35 °C and 18 g BSG.L-1 (289.1 mL CH4.g-1 TVS), which showed decrease in the organic matter concentration of 78.6% and a lower final concentration of VFA (533.2 mg.L-1). Hydrogenospora and Methanosaeta were identified in this optimum CH4 production condition, where acetoclastic methanogenic pathway prevailed. The CH4 production enhancement was concomitant to acetic acid concentration decrease (from 578.9 to 135.7 mg.L-1).


Assuntos
Euryarchaeota , Metano , Anaerobiose , Reatores Biológicos , Grão Comestível , Ácidos Graxos Voláteis , Metano/análise , Temperatura
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