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1.
Microbes Environ ; 35(1)2020.
Artigo em Inglês | MEDLINE | ID: mdl-31932538

RESUMO

Accretionary prisms are thick masses of sedimentary material scraped from the oceanic crust and piled up at convergent plate boundaries found across large regions of the world. Large amounts of anoxic groundwater and natural gas, mainly methane (CH4), are contained in deep aquifers associated with these accretionary prisms. To identify the subsurface environments and potential for CH4 production by the microbial communities in deep aquifers, we performed chemical and microbiological assays on groundwater and natural gas derived from deep aquifers associated with an accretionary prism and its overlying sedimentary layers. Physicochemical analyses of groundwater and natural gas suggested wide variations in the features of the six deep aquifers tested. On the other hand, a stable carbon isotope analysis of dissolved inorganic carbon in the groundwater and CH4 in the natural gas showed that the deep aquifers contained CH4 of biogenic or mixed biogenic and thermogenic origins. Live/dead staining of microbial cells contained in the groundwater revealed that the cell density of live microbial cells was in the order of 104 to 106| |cells| |mL-1, and cell viability ranged between 7.5 and 38.9%. A DNA analysis and anoxic culture of microorganisms in the groundwater suggested a high potential for CH4 production by a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogenic archaea. These results suggest that the biodegradation of organic matter in ancient sediments contributes to CH4 production in the deep aquifers associated with this accretionary prism as well as its overlying sedimentary layers.


Assuntos
Sedimentos Geológicos/microbiologia , Água Subterrânea/microbiologia , Metano/biossíntese , Consórcios Microbianos , Anaerobiose , Archaea/classificação , Archaea/genética , Archaea/isolamento & purificação , Archaea/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Carbono/análise , Sedimentos Geológicos/química , Água Subterrânea/química , Hidrogênio/metabolismo , Japão , Metano/análise , Gás Natural/análise , RNA Ribossômico 16S/genética
2.
Chemphyschem ; 21(5): 385-396, 2020 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-31926045

RESUMO

A new methane formation pathway, which uses methylphosphonate (MPn) as the methane precursor, has been discovered in the upper ocean. Methylphosphonate synthase (MPnS) is a key piece in this pathway to produce MPn from 2-hydroxyethylphosphonate (2-HEP), using an untypical 2-His-1-Gln non-heme iron architecture. Herein, the MPnS reaction mechanism was demonstrated by the density functional calculations to mainly include the substrate hydroxyl deprotonation, the formation of a MPn radical and a formate, and the hydrogen abstraction of formate by MPn radical. The second-shell Lys28' may serve as a proton reservoir activating 2-HEP and regenerating the Fe site. The Fe-bound superoxide radical is a bifunctional species to deprotonate the substrate hydroxyl and abstract the substrate methylene hydrogen. Several alternative mechanisms have been ruled out. Furthermore, the catalytic activity of MPnS was found to be inactivated/reduced by the mutation of Gln152E/Gln152H/Gln152D, rendering a significant evolutionary advantage with an uncommon 2-His-1-Gln triad introduced to the ferrous coordination sphere.


Assuntos
Metano/biossíntese , Ferroproteínas não Heme/metabolismo , Compostos Organofosforados/metabolismo , Oxigenases/metabolismo , Metano/química , Ferroproteínas não Heme/química , Compostos Organofosforados/química , Oxigenases/química
3.
Appl Biochem Biotechnol ; 190(1): 30-43, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31297754

RESUMO

Rapid development of the industrial and domestic sectors has led to the rise of several energy and environmental issues. In accordance with sustainable development and waste minimization issues, biohydrogen production along with biomethane production via two-stage fermentation process using microorganisms from renewable sources has received considerable attention. In the present study, biohythane production with simultaneous wastewater treatment was studied in a two-stage (Biohydrogen and Biomethane) fermentation process under anaerobic conditions. Optimization of high organic content (COD) distillery spent wash effluent (DSPW) with dilution using sewage wastewater was carried out. Addition of leachate as a nutrient source was also studied for effective biohythane production. The experimental results showed that the maximum biohythane production at optimized concentration (substrate concentration of 60 g/L with 30% of leachate as a nutrient source) was 67 mmol/L bio-H2 and with bio-CH4 production of 42 mmol/L. Graphical Abstract.


Assuntos
Biocombustíveis , Fermentação , Esgotos , Águas Residuárias , Poluentes Químicos da Água , Anaerobiose , Reatores Biológicos , Hidrogênio , Metano/biossíntese
4.
J Dairy Sci ; 102(11): 10616-10631, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31477298

RESUMO

There is a need to quantify methane (CH4) emissions with alternative methods. For the past decade, milk fatty acids (MFA) could be used as proxies to predict CH4 emissions from dairy cows because of potential common rumen biochemical pathways. However, equations have been developed based on a narrow range of diets and with limited data. The objectives of this study were to (1) construct a set of empirical models based on individual data of CH4 emissions and MFA from a large number of lactating dairy cows fed a wide range of diets; (2) further increase the models' level of complexity (from farm to research level) with additional independent variables such as dietary chemical composition (organic matter, neutral detergent fiber, crude protein, starch, and ether extract), dairy performance (milk yield and composition), and animal characteristics (days in milk or body weight); and (3) evaluate the performance of the developed models on independent data sets including measurements from individual animals or average measurements of groups of animals. Prediction equations based only on MFA [C10:0, iso C17:0 + trans-9 C16:1,cis-11 C18:1, and trans-11,cis-15 C18:2 for CH4 production (g/d); iso C16:0, cis-11 C18:1, trans-10 C18:1, and cis-9,cis-12 C18:2 for CH4 yield (g/kg of dry matter intake, DMI); and iso C16:0, cis-15 C18:1, and trans-10 + trans-11 C18:1 for CH4 intensity (g/kg of milk)] had a root mean squared error of 65.1 g/d, 2.8 g/kg of DMI, and 2.9 g/kg of milk, respectively, whereas complex equations that additionally used DMI, dietary neutral detergent fiber, ether extract, days in milk, and body weight had a lower root mean squared error of 46.6 g/d, 2.6 g/kg of DMI, and 2.7 g/kg of milk, respectively). External evaluation with individual or mean data not used for equation development led to variable results. When evaluations were performed using individual cow data from an external data set, accurate predictions of CH4 production (g/d) were obtained using simple equations based on MFA. Better performance was observed on external evaluation with individual data for the simple equation of CH4 production (g/d, based on MFA), whereas better performance was observed on external evaluation mean data for the simple equation of CH4 yield (g/kg of DMI). The performance of evaluation of the models is dependent on the domain of validity of the evaluation data sets used (individual or mean).


Assuntos
Bovinos/metabolismo , Dieta/veterinária , Ácidos Graxos/fisiologia , Metano/biossíntese , Leite/química , Animais , Ácidos Graxos/análise , Feminino , Intestino Delgado/metabolismo , Lactação , Rúmen/metabolismo
5.
Int J Mol Sci ; 20(18)2019 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-31500341

RESUMO

Methanogenesis occurs in many natural environments and is used in biotechnology for biogas production. The efficiency of methane production depends on the microbiome structure that determines interspecies electron transfer. In this research, the microbial community retrieved from mining subsidence reservoir sediment was used to establish enrichment cultures on media containing different carbon sources (tryptone, yeast extract, acetate, CO2/H2). The microbiome composition and methane production rate of the cultures were screened as a function of the substrate and transition stage. The relationships between the microorganisms involved in methane formation were the major focus of this study. Methanogenic consortia were identified by next generation sequencing (NGS) and functional genes connected with organic matter transformation were predicted using the PICRUSt approach and annotated in the KEGG. The methane production rate (exceeding 12.8 mg CH4 L-1 d-1) was highest in the culture grown with tryptone, yeast extract, and CO2/H2. The analysis of communities that developed on various carbon sources casts new light on the ecophysiology of the recently described bacterial phylum Caldiserica and methanogenic Archaea representing the genera Methanomassiliicoccus and Methanothrix. Furthermore, it is hypothesized that representatives of Caldiserica may support hydrogenotrophic methanogenesis.


Assuntos
Sedimentos Geológicos/microbiologia , Metano/biossíntese , Microbiota , Biodiversidade , Biocombustíveis , Carbono/metabolismo , Hidrogênio/metabolismo , Temperatura Ambiente
6.
J Dairy Sci ; 102(12): 10887-10902, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31548054

RESUMO

The European livestock sector has a significant deficit of high-quality protein feed ingredients. Consequently there is interest in using locally grown protein grain crops to partially or completely replace imported protein feeds in dairy cow rations. Field bean (FB; Vicia faba) has been identified as a locally grown crop with significant potential. The current study was designed to examine the effects of FB on cow performance and nutrient utilization in the diet of early-lactation dairy cows, including high levels of FB (up to 8.4 kg/cow per day). The experiment used 72 dairy cows in a 3-treatment continuous design (from calving until wk 20 of lactation). All cows were given ad libitum access to a mixed ration comprising grass silage and concentrates [45:55 on a dry matter (DM) basis]. Concentrates offered contained either 0, 349, or 698 g of FB/kg of concentrate (treatments FB0, FB-Low, and FB-High, respectively), with FB completely replacing soybean meal, rapeseed meal, maize gluten, and wheat in the concentrate for the FB-High treatment. Following completion of the 20-wk experiment, ration digestibility, nutrient utilization, and methane (CH4) production were measured using 4 cows from each treatment. Neither silage DM intake, total DM intake, nor milk yield were affected by treatment. Cows on FB0 had a higher milk fat content than those on FB-High, and cows on FB0 and FB-Low had higher milk protein contents than did those on FB-High. Field bean inclusion increased the degree of saturation of milk fat produced. Milk fat yield, milk protein yield, and milk fat plus protein yield were higher with FB0 than with either FB-Low or FB-High. Treatment had no effect on the digestibility of DM, organic matter, nitrogen (N), gross energy, or neutral detergent fiber, whereas digestibility of acid detergent fiber was higher with FB0 than with FB-High. Neither the efficiency of gross energy or N utilization, nor any of the CH4 production parameters examined, were affected by treatment. Similarly, none of the fertility or health parameters examined were affected by treatment. The reduction in milk fat observed may have been due to the higher starch content of the FB-High diet, and the reduction in milk protein may have been due to a deficit of methionine in the diet. It is likely that these issues could be overcome by changes in ration formulation, thus allowing FB to be included at the higher range without loss in performance.


Assuntos
Ração Animal , Bovinos , Vicia faba , Animais , Brassica rapa , Dieta/veterinária , Digestão , Feminino , Lactação , Metano/biossíntese , Leite/química , Proteínas do Leite , Poaceae , Silagem/análise , Soja , Zea mays
7.
Bioresour Technol ; 291: 121881, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31394488

RESUMO

To understand the effect of inoculum concentration on direct interspecies electron transfer (DIET) for methanogenesis, batch-type anaerobic bioreactors with different inoculum concentrations were operated with and without supplemented granular activated carbon (GAC). With decrease in inoculum concentration, GAC-supplemented bioreactors showed faster methane production rates and reduced lag times. Geobacter species were specifically enriched on the GAC surfaces under lower inoculum concentration conditions. Together, the relative abundance of aceticlastic methanogens (competitors of Geobacter species for acetate) gradually decreased when the inoculum concentration increased. These results suggested that the specific enrichment of Geobacter species by outcompeting with aceticlastic methanogens through low inoculum concentrations on GAC surfaces accelerated methanogenesis by DIET via GAC in anaerobic bioreactors. Taken together, the results of this study suggested that inoculum concentration is an important factor in stimulating DIET for methane production.


Assuntos
Transporte de Elétrons , Metano/biossíntese , Microbiota , Reatores Biológicos , Euryarchaeota/metabolismo , Geobacter/metabolismo
8.
Bioresour Technol ; 291: 121849, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31387051

RESUMO

Anaerobic digestion (AD) has been widely applied as an economic option for food waste (FW) treatment. In this study, the group treated with ethanol pre-fermentation (EP) for 12 h (EP12) exhibited the highest cumulative biogas yield (206 mL/g-volatile solid) during AD process and therefore it was used to illuminate the underlying metabolic processes of AD with EP. Carbon isotope labeled glucose was supplemented to FW substrate, and the EP process was found to alleviate the acidification inhibition with conducting extremely high carbon flux towards ethanol formation (43.7%). Then an efficient acetogenesis phase was also observed in EP12 group, because of high carbon conversion rate from ethanol to acetate. Overall, higher carbon conversion rate to methane (90.1%) during methanogenesis was found in the AD system with EP than in the control experiment (80.3%). Thus, we quantitatively confirmed that EP affects the AD metabolism of FW in terms of carbon flow distribution.


Assuntos
Alimentos , Metano/biossíntese , Anaerobiose , Biocombustíveis , Isótopos de Carbono , Etanol/metabolismo , Fermentação , Marcação por Isótopo
9.
Bioresour Technol ; 291: 121851, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31374416

RESUMO

Thermotolerant cellulolytic consortium for improvement biogas production from oil palm empty fruit bunches (EFB) by prehydrolysis and bioaugmentation strategies was investigated via solid-state anaerobic digestion (SS-AD). The prehydrolysis EFB with Clostridiaceae and Lachnospiraceae rich consortium have maximum methane yield of 252 and 349 ml CH4 g-1 VS with total EFB degradation efficiency of 62% and 86%, respectively. Clostridiaceae and Lachnospiraceae rich consortium augmentation in biogas reactor have maximum methane yield of 217 and 85.2 ml CH4 g-1 VS with degradation efficiency of 42% and 16%, respectively. The best improvement of biogas production was achieved by prehydrolysis EFB with Lachnospiraceae rich consortium with maximum methane production of 113 m3 CH4 tonne-1 EFB. While, Clostridiaceae rich consortium was suitable for augmentation in biogas reactor with maximum methane production of 70.6 m3 CH4 tonne-1 EFB. Application of thermotolerant cellulolytic consortium into the SS-AD systems could enhance biogas production of 3-11 times.


Assuntos
Clostridiaceae/metabolismo , Clostridiales/metabolismo , Anaerobiose , Biocombustíveis , Celulose/metabolismo , Frutas/metabolismo , Metano/biossíntese , Óleo de Palmeira/metabolismo
10.
Anim Sci J ; 90(10): 1350-1361, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31393669

RESUMO

The objective of this study was to evaluate the effects of using encapsulated nitrate product (ENP) replacing soybean meal in diets differing in concentrate to forage ratio on ruminal fermentation and methane production in vitro using a semi-automatic gas production technique. Eight treatments were used in a randomized complete design with a 2 × 4 factorial arrangement: two diet (20C:80F and 80C:20F concentrate to forage ratio) and four levels of ENP addition (0%, 1.5%, 3.0%, and 4.5% of DM) replacing soybean meal. There was a diet × ENP interaction (p = 0.02) for methane production. According to ENP addition, diets with 80C:20F showed more intense reduction on methane production that 20C:80F. A negative linear effect was observed for propionate production with ENP addition in diet with 80C:20F and to the relative abundance of methanogens Archaea, in both diet. The replacement of soybean meal by ENP in levels up to 3% of DM inhibited methane production due to a reduction in the methanogens community without affecting the organic matter degradability. However, ENP at 4.5% of DM level affected fiber degradability, abundance of cellulolytic bacteria, and propionic acid production, indicating that this level of inclusion is not recommended for ruminant production.


Assuntos
Archaea/metabolismo , Dieta/veterinária , Fermentação/efeitos dos fármacos , Metano/biossíntese , Nitratos/uso terapêutico , Rúmen/microbiologia , Ração Animal/análise , Animais , Fermentação/fisiologia , Microbioma Gastrointestinal , Técnicas In Vitro , Metano/metabolismo , Nitratos/metabolismo , Rúmen/metabolismo , Ruminantes , Soja
11.
Bioresour Technol ; 289: 121712, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31272803

RESUMO

In this study, effect of hardwood biochar on solid state anaerobic digestion of wheat straw has been investigated. The concentration of biochar was 5, 10, 15, 20, 25 and 30 g/L and added in inoculum along with wheat straw for anaerobic action. Results showed that 10 g/L of hardwood biochar led to 2-fold increment in methane yield (223 L/kg VS) compared to the control (110 L/kg VS). However, increasing the concentration of hardwood biochar did not help in significant increase in methane yield and raised pH and alkalinity up to 8.3 and 24.3 g/L respectively. Principal component analysis showed that methane yield is positively correlated with volatile solid reduction while biochar loading is directly correlated with pH as well as alkalinity and inversely correlated with total volatile fatty acid. This study revealed that biochar may help to maintain syntrophy in the anaerobic reactor and enhance methane yield significantly.


Assuntos
Carvão Vegetal/metabolismo , Metano/biossíntese , Anaerobiose , Ácidos Graxos Voláteis/biossíntese , Triticum/metabolismo
12.
PLoS One ; 14(7): e0218856, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31291286

RESUMO

There are large amounts of waste activated sludge (WAS) and kitchen waste (KW) produced every year in China. It has been confirmed that anaerobic co-digestion is an effective method to solve this problem. The targets of the present study were optimizing the digestive performances and clearing of the mechanism of bentonite addition by adding bentonite into digestive system. Group M (WAS: KW = 1:2, based on VS) presented higher cumulative methane yield (CMY), where the CMY increased from 19.8 to 36.3 mL/g VS with the bentonite dosage from 0 to 2 g/g VS. After bentonite addition, the lag phase of every digester presented an obvious decrease from 15.1 to 1.4 d. Furthermore, and the moderating effects on microbial community by bentonite. The addition of bentonite improved methane production, and it can also reduce the lag phase of methane production in co-digestion. What's more, bentonite addition increased the speed of pH recovery from 4.2-4.8 to normal level (7.0-8.0) and thus enhanced the system stability. The conclusion of this study can be used to guide practical engineering.


Assuntos
Bentonita/farmacologia , Metano/biossíntese , Microbiota/efeitos dos fármacos , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Anaerobiose/fisiologia , Biodegradação Ambiental , Reatores Biológicos , Humanos , Concentração de Íons de Hidrogênio , Microbiota/fisiologia
13.
Molecules ; 24(13)2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31277372

RESUMO

This paper deals with the development of a citrus peel waste (CPW) biorefinery that employs low environmental impact technologies for production of ethanol and methane. Three major yeasts were compared for ethanol production in batch fermentations using CPW pretreated through acid hydrolysis and a combination of acid and enzyme hydrolysis. The most efficient conditions for production of CPW-based hydrolyzates included processing at 116 °C for 10 min. Pichia kudriavzevii KVMP10 achieved the highest ethanol production that reached 30.7 g L-1 in fermentations conducted at elevated temperatures (42 °C). A zero-waste biorefinery was introduced by using solid biorefinery residues in repeated batch anaerobic digestion fermentations achieving methane formation of 342 mL gVS-1 (volatile solids). Methane production applying untreated and dried CPW reached a similar level (339-356 mL gVS-1) to the use of the side stream, demonstrating that the developed bioprocess constitutes an advanced alternative to energy intensive methods for biofuel production.


Assuntos
Biotecnologia/métodos , Citrus/química , Etanol/metabolismo , Metano/biossíntese , Resíduos , Anaerobiose , Ácidos Graxos/metabolismo , Fermentação , Açúcares/análise , Volatilização , Leveduras/metabolismo
14.
J Dairy Sci ; 102(9): 7927-7935, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31255278

RESUMO

To lower the effect of climate change from cattle production, we should aim at decreasing their enteric methane emissions per kilogram of milk or meat. Glycerol may be absorbed through the rumen epithelium and would consequently be less available to microbes in the rumen. Glycerol could thus supply dairy cows with energy for milk production without contributing much to methane production. This study evaluated the effect of replacing wheat starch with glycerol on milk production, feed intake, and methane emissions. Twenty-two Swedish Red cows in mid lactation were used in a switch-back, change-over experiment with 3 periods of 21 d. The 2 dietary treatments consisted of a total mixed ration based on (g/kg of dry matter) grass silage (605), rapeseed meal (120), and barley (70) and either wheat starch or refined glycerol (200) fed ad libitum. The glycerol diet resulted in higher dry matter intake (21.6 vs. 20.1 kg/d) and methane emissions (482 vs. 423 g/d) compared with the diet containing wheat starch, whereas no difference was found in energy-corrected milk yield (28.4 vs. 29.7 kg/d). These results indicate that when glycerol is mixed with the feed, it is available to rumen microbes to a larger extent than initially assumed. Compared with wheat starch, adding refined glycerol (200 g/kg of dry matter) to the feed of dairy cows does not seem to have the potential to decrease enteric methane emissions.


Assuntos
Bovinos/fisiologia , Glicerol/farmacologia , Metano/biossíntese , Leite/metabolismo , Silagem/análise , Animais , Dieta/veterinária , Digestão/efeitos dos fármacos , Feminino , Lactação/efeitos dos fármacos , Leite/química , Rúmen , Amido , Triticum
15.
Bioresour Technol ; 289: 121698, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31260933

RESUMO

This work proposes a new treatment approach involving both food waste disposal and sewerage treatment called MOWFAST i.e. Municipal Organic Waste management by combined Food waste disposal and Sewerage Treatment. MOWFAST involves mixing of food waste directly with raw sewage instead of separate addition to sludge and their combined anaerobic digestion (AD). Compared to conventional sludge digestion, MOWFAST exhibited better digestion capability and allowed a greater degradation of organic material along with higher production of methanogenic-favourable products from the beginning of digestion. This resulted in producing higher specific methane yields (7.86 LCH4/kg VSadded versus 0.95 LCH4/kg VSadded) and 1.4-fold higher cumulative methane yield over sludge AD. Furthermore, compared with conventional food waste-sludge co-digestion, MOWFAST gave higher solubilization of organic material (0.82 g sCOD/g VSadded versus 0.23 g sCOD/g VSadded) and specific methane yields (7.86 LCH4/kg VSadded versus 3.2 LCH4/kg VSadded). This proves its feasibility for digestion and methane generation potential.


Assuntos
Alimentos , Eliminação de Resíduos/métodos , Esgotos , Anaerobiose , Reatores Biológicos , Metano/biossíntese
16.
Bioresour Technol ; 289: 121716, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323721

RESUMO

This study integrated the sugar and carboxylate platforms to enhance duckweed processing in biorefineries. Two or three bioprocesses (ethanol fermentation, acidogenic digestion, and methanogenic digestion) were sequentially integrated to maximize the carbon-to-carbon conversion of wastewater-derived duckweed into bioproducts, through a series of laboratory-scale experiments. Reactors were fed either raw (dried), liquid-hot-water-pretreated, or enzymatically-saccharified duckweed. Subsequently, the target bioproduct was separated from the reactor liquor and the residues further processed. The total bioproduct carbon yield of 0.69 ±â€¯0.07 g per gram of duckweed-C was obtained by sequential acidogenic and methanogenic digestion. Three sequential bioprocesses revealed nearly as high yields (0.66 ±â€¯0.08 g of bioproduct-C per duckweed-C), but caused more gaseous carbon (dioxide) loss. For this three-stage value cascade, yields of each process in conventional units were: 0.186 ±â€¯0.001 g ethanol/g duckweed; 611 ±â€¯64 mg volatile fatty acids as acetic acid/g VS; and 434 ±â€¯0.2 ml methane/g VS.


Assuntos
Araceae/metabolismo , Águas Residuárias/química , Ácido Acético/metabolismo , Anaerobiose , Araceae/química , Etanol/metabolismo , Euryarchaeota/metabolismo , Fermentação , Metano/biossíntese
17.
Environ Int ; 131: 105006, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31330362

RESUMO

Electron allocation through the suppression or the stimulation of methanogenesis is critical for microbial electrolysis cells (MECs) to produce the desired target product (e.g., CH4 or H2). In this study, selective methanogenesis control using the coenzyme M (CoM) and 2-bromoethanesulfonate (2-BES) was investigated in a two-chambered MEC to evaluate the effect of CoM and 2-BES on the production of different electrobiofuels, net energy conversion efficiency and microbial community structure. Because the CoM is a crucial methyl-group carrier in the final process of methanogenesis, it was postulated that CoM would stimulate methanogenic activity at the anode, while a structural analog of the CoM (i.e., 2-BES) was expected to improve cathodic H2 yield using electrons conserved because of methanogen inhibition (electron equivalence: 8 mol e- = 1 mol CH4 = 4 mol H2). CoM injection in MECs significantly enhanced their CH4 production rate, purity, and yield by 4.5-fold, 14.5%, and 76.1%, respectively, compared to the control. Moreover, microbial community analysis indicated that Methanosaeta, the major acetoclastic methanogen, continued to dominate the microbial community but steadily decreased in relative abundance after the CoM injection. On the other hand, drastic increases in hydrogenotrophic methanogens, such as Methanoculleus and Methanolinea, were observed along with potential syntrophic acetate-oxidizing bacteria. In contrast, CH4 production in the 2-BES injected trials was significantly inhibited by 79.5%, resulting in a corresponding increase of H2 production by 145.5% compared to the control. Unlike the CoM, the microbial community did not noticeably change when 2-BES was injected, although the population size gradually decreased over time. Also, a single injection of CoM and 2-BES, even at low concentrations (500 µM), enabled the desired allocation of electrons as characterized by a high sensitivity, fast response, and negligible interference. In terms of energy conversion efficiency, methanogenesis stimulation approach resulted in higher net energy production than inhibition approach, whereas the remained electrons were not fully converted to hydrogen in case of the inhibition trial, thus producing less energy.


Assuntos
Ácidos Alcanossulfônicos/metabolismo , Biocombustíveis , Mesna/metabolismo , Metano/biossíntese , Acetatos/metabolismo , Bactérias/metabolismo , Eletrólise
18.
Bioresour Technol ; 289: 121706, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279320

RESUMO

Microbial electrosynthesis (MES) is a promising technology to convert CO2 and electricity into the biofuel methane using methanogens. Until now, most investigations on electro-methanogenesis are "proof-of-principle" studies. In this paper, different strains were quantitatively compared in regard to final methane concentration, yields based on CO2-conversion, productivities as well as Coulombic efficiencies in order to identify suitable organisms for MES. Methanococcus vannielii, Methanococcus maripaludis, Methanolacinia petrolearia, Methanobacterium congolense, and Methanoculleus submarinus were able to produce methane via MES at -700 mV vs. standard hydrogen electrode (SHE). Beside methane also biological H2 production was detected during MES, which might be due to the involvement of hydrogenases. A direct electron transfer pathway is most likely. Obviously, M. maripaludis is the most resource efficient methane producer in microbial electrosynthesis regarding the methane productivity (8.81 ±â€¯0.51 mmol m-2 d-1) and the Coulombic efficiency (58.9 ±â€¯0.8%).


Assuntos
Dióxido de Carbono/metabolismo , Metano/biossíntese , Mathanococcus/metabolismo , Methanomicrobiaceae/metabolismo , Eletrodos , Hidrogenase/metabolismo , Methanobacterium/metabolismo
19.
PLoS One ; 14(7): e0220247, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31348816

RESUMO

Crossbreeding has been used to improve performance in beef cattle, however the effects of breed composition on methane (CH4) production, yield and intensity from cattle raised in tropical intensive and integrated systems remain unknown. To assess the impact of breed composition on performance and methane emissions, Nellore (NEL; yr 1: BW = 171.5 ± 19.4 kg; n = 10; yr 2: BW = 215.8 ± 32.3 kg, n = 25) and Angus x Nellore crossbred (AN; yr 1: BW = 214.2 ± 26.4 kg, n = 10; yr 2: BW = 242.5 ± 32.2 kg, n = 25) were compared. The animals grazed on integrated crop-livestock system in the growing phase (stocking rate 2452 kg BW/ha, herbage mass 4,884 kg dry matter (DM)/ha, forage allowance 5.9 kg DM/100kg BW) and then were finished in a feedlot. Steers (n = 8) from each breed composition were randomly selected in each phase to measure CH4 production using a sulfur hexafluoride (SF6) tracer technique and DM intake (DMI) using titanium dioxide. Compared with NEL, AN had both superior total gain and average daily gain (ADG) in the grazing period. The AN presented greater ADG in the feedlot with a shorter finishing period and resulted in greater carcass yield and carcass ADG. Methane production (kg/period) was lower in NEL (19% less) than AN in grazing (P<0.01), and no difference was observed in feedlot. The NEL had less CH4 intensity (CH4/BW) in grazing but greater CH4 per unit of ADG in the feedlot compared to AN. Breed composition did not influence the CH4 yield (CH4/DMI) in either phase, despite the difference in feedlot DMI (kg/day). In conclusion, crossbreeding may be an option to improve performance and reduce the CH4 per ADG in tropical climate conditions, resulting in lower methane emission per kg of meat produced.


Assuntos
Bovinos/fisiologia , Hibridização Genética , Metano/análise , Ração Animal/análise , Animais , Brasil , Bovinos/classificação , Dieta/veterinária , Herbivoria , Metano/biossíntese , Titânio/análise , Clima Tropical
20.
Bioresour Technol ; 291: 121847, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31357044

RESUMO

Effects of magnetite on methane production and fate of antibiotic resistance genes (ARGs) during anaerobic digestion (AD) of swine manure were investigated. Results showed that methane production was increased by maximum 16.1%, and magnetite could enhance the acetoclastic methanogenesis not hydrogenotrophic methanogenesis reflected by the functional gene quantification and microbial community analysis. The propionate degradation rate was improved, and it was syntrophic oxidized into H+/e-/CO2 for direct interspecies electron transfer (DIET) and acetate, where DIET was further enhanced by magnetite and the acetate was transformed into methane through syntrophic acetate oxidation (SAO) pathway. Magnetite mainly influenced the ARGs at the interim period of AD, where ARGs especially ermF were significantly enriched. Magnetite did not influence the total ARGs abundance at the end, although the tetM was enriched and mefA was reduced finally. Statistical analysis indicated that magnetite influenced the ARGs fate mainly through the changes of microbial community.


Assuntos
Óxido Ferroso-Férrico/farmacologia , Esterco , Metano/biossíntese , Anaerobiose/efeitos dos fármacos , Animais , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Transporte de Elétrons , Microbiota/efeitos dos fármacos , Oxirredução , Suínos
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