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1
Chen, Jing, Matthew J. Wade, Jan Dolfing, and Orkun S. Soyer. "Increasing sulfate levels show a differential impact on synthetic communities comprising different methanogens and a sulfate reducer." Journal of The Royal Society Interface 16, no. 154 (May 2019): 20190129. http://dx.doi.org/10.1098/rsif.2019.0129.
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Methane-producing microbial communities are of ecological and biotechnological interest. Syntrophic interactions among sulfate reducers and aceto/hydrogenotrophic and obligate hydrogenotrophic methanogens form a key component of these communities, yet, the impact of these different syntrophic routes on methane production and their stability against sulfate availability are not well understood. Here, we construct model synthetic communities using a sulfate reducer and two types of methanogens representing different methanogenesis routes. We find that tri-cultures with both routes increase methane production by almost twofold compared to co-cultures and are stable in the absence of sulfate. With increasing sulfate, system stability and productivity decreases and does so faster in communities with aceto/hydrogenotrophic methanogens despite the continued presence of acetate. We show that this is due to a shift in the metabolism of these methanogens towards co-utilization of hydrogen with acetate. These findings indicate the important role of hydrogen dynamics in the stability and productivity of syntrophic communities.
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Zhang, Guishan, Na Jiang, Xiaoli Liu, and Xiuzhu Dong. "Methanogenesis from Methanol at Low Temperatures by a Novel Psychrophilic Methanogen, “Methanolobus psychrophilus” sp. nov., Prevalent in Zoige Wetland of the Tibetan Plateau." Applied and Environmental Microbiology 74, no. 19 (August 1, 2008): 6114–20. http://dx.doi.org/10.1128/aem.01146-08.
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ABSTRACT The Zoige wetland of the Tibetan plateau is at permanent low temperatures and is a methane emission heartland of the plateau; however, cold-adaptive methanogens in the soil are poorly understood. In this study, a variety of methanogenic enrichments at 15�C and 30�C were obtained from the wetland soil. It was demonstrated that hydrogenotrophic methanogenesis was the most efficient type at 30�C, while methanol supported the highest methanogenesis rate at 15�C. Moreover, methanol was the only substrate to produce methane more efficiently at 15�C than at 30�C. A novel psychrophilic methanogen, strain R15, was isolated from the methanol enrichment at 15�C. Phylogenetic analysis placed strain R15 within the genus Methanolobus, loosely clustered with Methanolobus taylorii (96.7% 16S rRNA similarity). R15 produced methane from methanol, trimethylamine, and methyl sulfide and differed from other Methanolobus species by growing and producing methane optimally at 18�C (specific growth rate of 0.063 � 0.001 h−1) and even at 0�C. Based on these characteristics, R15 was proposed to be a new species and named “Methanolobus psychrophilus” sp. nov. The Km and V max of R15 for methanol conversion were determined to be 87.5 � 0.4 μM and 0.39 � 0.04 mM h−1 at 18�C, respectively, indicating a high affinity and conversion efficiency for methanol. The proportion of R15 in the soil was determined by quantitative PCR, and it accounted for 17.2% � 2.1% of the total archaea, enumerated as 107 per gram of soil; the proportion was increased to 42.4% � 2.3% in the methanol enrichment at 15�C. This study suggests that the psychrophilic methanogens in the Zoige wetland are likely to be methylotrophic and to play a role in methane emission of the wetland.
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Japperi, Nur Shuhadah, Zharif Zainulazfar Mohd Asri, Wan Zairani Wan Bakar, 'Aqilah Dollah, Mohd Fazril Irfan Ahmad Fuad, and Siti Nurliyana Che Mohamed Hussein. "Review on landfill gas formation from leachate biodegradation." Malaysian Journal of Chemical Engineering and Technology (MJCET) 4, no. 1 (May 21, 2021): 39. http://dx.doi.org/10.24191/mjcet.v4i1.12719.
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Landfill waste management is a very crucial procedure in handling Municipal Solid Waste (MSW) because it may create significant environmental issues if it is not managed properly. Landfill leachate and landfill gas (LFG) is part of the landfill waste management which triggered lot of researchers especially in terms of the environmental implications associated with the movement of the gasses during the waste constituents’ processes. Hence, this paper review is aiming to understand the behaviour of leachate itself as a decomposition agent in producing landfill gas (biogas). Biogas is naturally produced by anaerobic bacteria through anaerobic digestion which is affected by operating parameters and substrate characteristic. The results indicate that temperature, pH, and C/N ratio of leachate are the important factors that could increase the production of biogas with high content of methane. Furthermore, in terms of microbial activity during anaerobic digestion process, hydrogenotrophic and acetoclastic methanogen are the dominant substrate that contribute in producing methane gas as the final product. Firmicutes and Bacteroidetes are the common fermentative bacteria that had been found during fermentation process in hydrolysis and acidogenic phases. While, methanobacterial, methanococcal, methanomicrobial, methanosarcinal, and methanopyral are being classified as orders among 65 types of methanogenic archaea during methanogenesis stage. Overall, the relationships between operating parameters and microbial structure are important aspects that need to be considered in order to optimize the production of methane gas.
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Chaucheyras-Durand, Frédérique, Sébastien Masséglia, Gérard Fonty, and Evelyne Forano. "Influence of the Composition of the Cellulolytic Flora on the Development of Hydrogenotrophic Microorganisms, Hydrogen Utilization, and Methane Production in the Rumens of Gnotobiotically Reared Lambs." Applied and Environmental Microbiology 76, no. 24 (October 22, 2010): 7931–37. http://dx.doi.org/10.1128/aem.01784-10.
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ABSTRACT We investigated the influence of the composition of the fibrolytic microbial community on the development and activities of hydrogen-utilizing microorganisms in the rumens of gnotobiotically reared lambs. Two groups of lambs were reared. The first group was inoculated with Fibrobacter succinogenes, a non-H2-producing species, as the main cellulolytic organism, and the second group was inoculated with Ruminococcus albus, Ruminococcus flavefaciens, and anaerobic fungi that produce hydrogen. The development of hydrogenotrophic bacterial communities, i.e., acetogens, fumarate and sulfate reducers, was monitored in the absence of methanogens and after inoculation of methanogens. Hydrogen production and utilization and methane production were measured in rumen content samples incubated in vitro in the presence of exogenous hydrogen (supplemented with fumarate or not supplemented with fumarate) or in the presence of ground alfalfa hay as a degradable substrate. Our results show that methane production was clearly reduced when the dominant fibrolytic species was a non-H2-producing species, such as Fibrobacter succinogenes, without significantly impairing fiber degradation and fermentations in the rumen. The addition of fumarate to the rumen contents stimulated H2 utilization only by the ruminal microbiota inoculated with F. succinogenes, suggesting that these communities could play an important role in fumarate reduction in vivo.
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Kobayashi, Hajime, Ryohei Toyoda, Hiroyuki Miyamoto, Yasuhito Nakasugi, Yuki Momoi, Kohei Nakamura, Qian Fu, Haruo Maeda, Takashi Goda, and Kozo Sato. "Analysis of a Methanogen and an Actinobacterium Dominating the Thermophilic Microbial Community of an Electromethanogenic Biocathode." Archaea 2021 (March 1, 2021): 1–13. http://dx.doi.org/10.1155/2021/8865133.
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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.
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Gieg, Lisa M., Kathleen E. Duncan, and Joseph M. Suflita. "Bioenergy Production via Microbial Conversion of Residual Oil to Natural Gas." Applied and Environmental Microbiology 74, no. 10 (March 31, 2008): 3022–29. http://dx.doi.org/10.1128/aem.00119-08.
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ABSTRACT World requirements for fossil energy are expected to grow by more than 50% within the next 25 years, despite advances in alternative technologies. Since conventional production methods retrieve only about one-third of the oil in place, either large new fields or innovative strategies for recovering energy resources from existing fields are needed to meet the burgeoning demand. The anaerobic biodegradation of n-alkanes to methane gas has now been documented in a few studies, and it was speculated that this process might be useful for recovering energy from existing petroleum reservoirs. We found that residual oil entrained in a marginal sandstone reservoir core could be converted to methane, a key component of natural gas, by an oil-degrading methanogenic consortium. Methane production required inoculation, and rates ranged from 0.15 to 0.40 μmol/day/g core (or 11 to 31 μmol/day/g oil), with yields of up to 3 mmol CH4/g residual oil. Concomitant alterations in the hydrocarbon profile of the oil-bearing core revealed that alkanes were preferentially metabolized. The consortium was found to produce comparable amounts of methane in the absence or presence of sulfate as an alternate electron acceptor. Cloning and sequencing exercises revealed that the inoculum comprised sulfate-reducing, syntrophic, and fermentative bacteria acting in concert with aceticlastic and hydrogenotrophic methanogens. Collectively, the cells generated methane from a variety of petroliferous rocks. Such microbe-based methane production holds promise for producing a clean-burning and efficient form of energy from underutilized hydrocarbon-bearing resources.
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Iino, Takao, Koji Mori, and Ken-ichiro Suzuki. "Methanospirillum lacunae sp. nov., a methane-producing archaeon isolated from a puddly soil, and emended descriptions of the genus Methanospirillum and Methanospirillum hungatei." International Journal of Systematic and Evolutionary Microbiology 60, no. 11 (November 1, 2010): 2563–66. http://dx.doi.org/10.1099/ijs.0.020131-0.
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A mesophilic, hydrogenotrophic methanogen, designated strain Ki8-1T, was isolated from soil. Cells were strictly anaerobic, Gram-stain-negative, non-sporulating, motile by means of a single flagellum or tufted flagella, and curved or wavy rod-shaped (11–25 μm long). The temperature and pH for optimum growth were 30 °C and 7.5. The strain grew best in basal medium without the addition of NaCl. Methane was produced from H2 and formate. Acetate or yeast extract was required for growth. The G+C content of the genomic DNA of strain Ki8-1T was 45.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Ki8-1T was a member of the genus Methanospirillum and showed 95.1 % sequence similarity to Methanospirillum hungatei NBRC 100397T. On the basis of its phenotypic characteristics and phylogenetic position, strain Ki8-1T is considered to represent a novel species of the genus Methanospirillum, for which the name Methanospirillum lacunae sp. nov. is proposed. The type strain is Ki8-1T (NBRC 104920T =JCM 16384T =DSM 22751T). Emended descriptions of the genus Methanospirillum and of Methanospirillum hungatei are also provided.
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Jianrong, Zhu, Hu Jicui, and Gu Xiasheng. "The bacterial numeration and an observation of a new syntrophic association for granular sludge." Water Science and Technology 36, no. 6-7 (September 1, 1997): 133–40. http://dx.doi.org/10.2166/wst.1997.0584.
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The bacterial numeration and microbial observation were made on granular sludge from laboratory single and two-phase UASB reactors. It was shown that the fermentative bacteria (group I), H2-producing acetogenic bacteria (group II) and methanogenic bacteria (group III) of granular sludge in single UASB reactor were 9.3 × 108−4.3 × 109, 4.3 × 107−4.3 × 108, 2.0−4.3 × 108, respectively, during the granulation process. The sludge of methanogenic reactor exhibited the similar results. That indicates there is no big difference between suspended and granular sludge, and bacterial population for three groups of anaerobic bacteria are similar. The formation of granular sludge depends mainly on the organization and arrangement of bacteria. An observation of granular sludge using electron microscope revealed that the fermentative bacteria and hydrogenotrophic methanogens existed on outer surface of granules, and aceticlastic methanogens and H2-producing acetogenic bacteria occupied the inner layer. A new syntrophic association between Methanosaeta sp. and Syntrophomonas sp. (even plus Methanobrevibacter sp.) was observed. Because Methanosaeta can effectively convert the acetate (the end product of propionate and butyrate) to methane, such a new syntrophic association is supposed to support the degradation of short fatty acids and high methanogenic activity of granular sludge. Based on structural pattern, a hypothesis on mechanism of granulation called “crystallized nuclei formation” is proposed.
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Welander, Paula V., and William W. Metcalf. "Mutagenesis of the C1 Oxidation Pathway in Methanosarcina barkeri: New Insights into the Mtr/Mer Bypass Pathway." Journal of Bacteriology 190, no. 6 (January 4, 2008): 1928–36. http://dx.doi.org/10.1128/jb.01424-07.
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ABSTRACT A series of Methanosarcina barkeri mutants lacking the genes encoding the enzymes involved in the C1 oxidation/reduction pathway were constructed. Mutants lacking the methyl-tetrahydromethanopterin (H4MPT):coenzyme M (CoM) methyltransferase-encoding operon (Δmtr), the methylene-H4MPT reductase-encoding gene (Δmer), the methylene-H4MPT dehydrogenase-encoding gene (Δmtd), and the formyl-methanofuran:H4MPT formyl-transferase-encoding gene (Δftr) all failed to grow using either methanol or H2/CO2 as a growth substrate, indicating that there is an absolute requirement for the C1 oxidation/reduction pathway for hydrogenotrophic and methylotrophic methanogenesis. The mutants also failed to grow on acetate, and we suggest that this was due to an inability to generate the reducing equivalents needed for biosynthetic reactions. Despite their lack of growth on methanol, the Δmtr and Δmer mutants were capable of producing methane from this substrate, whereas the Δmtd and Δftr mutants were not. Thus, there is an Mtr/Mer bypass pathway that allows oxidation of methanol to the level of methylene-H4MPT in M. barkeri. The data further suggested that formaldehyde may be an intermediate in this bypass; however, no methanol dehydrogenase activity was found in Δmtr cell extracts, nor was there an obligate role for the formaldehyde-activating enzyme (Fae), which has been shown to catalyze the condensation of formaldehyde and H4MPT in vitro. Both the Δmer and Δmtr mutants were able to grow on a combination of methanol plus acetate, but they did so by metabolic pathways that are clearly distinct from each other and from previously characterized methanogenic pathways.
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Wilkins, David, Xiao-Ying Lu, Zhiyong Shen, Jiapeng Chen, and Patrick K. H. Lee. "Pyrosequencing ofmcrAand Archaeal 16S rRNA Genes Reveals Diversity and Substrate Preferences of Methanogen Communities in Anaerobic Digesters." Applied and Environmental Microbiology 81, no. 2 (November 7, 2014): 604–13. http://dx.doi.org/10.1128/aem.02566-14.
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ABSTRACTMethanogenic archaea play a key role in biogas-producing anaerobic digestion and yet remain poorly taxonomically characterized. This is in part due to the limitations of low-throughput Sanger sequencing of a single (16S rRNA) gene, which in the past may have undersampled methanogen diversity. In this study, archaeal communities from three sludge digesters in Hong Kong and one wastewater digester in China were examined using high-throughput pyrosequencing of the methyl coenzyme M reductase (mcrA) and 16S rRNA genes.Methanobacteriales,Methanomicrobiales, andMethanosarcinaleswere detected in each digester, indicating that both hydrogenotrophic and acetoclastic methanogenesis was occurring. Two sludge digesters had similar community structures, likely due to their similar design and feedstock. Taxonomic classification of themcrAgenes suggested that these digesters were dominated by acetoclastic methanogens, particularlyMethanosarcinales, while the other digesters were dominated by hydrogenotrophicMethanomicrobiales. The proposed euryarchaeotal orderMethanomassiliicoccalesand the uncultured WSA2 group were detected with the 16S rRNA gene, and potentialmcrAgenes for these groups were identified. 16S rRNA gene sequencing also recovered several crenarchaeotal groups potentially involved in the initial anaerobic digestion processes. Overall, the two genes produced different taxonomic profiles for the digesters, while greater methanogen richness was detected using themcrAgene, supporting the use of this functional gene as a complement to the 16S rRNA gene to better assess methanogen diversity. A significant positive correlation was detected between methane production and the abundance ofmcrAtranscripts in digesters treating sludge and wastewater samples, supporting themcrAgene as a biomarker for methane yield.
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Jia, Yangyang, David Wilkins, Hongyuan Lu, Mingwei Cai, and Patrick K. H. Lee. "Long-Term Enrichment on Cellulose or Xylan Causes Functional and Taxonomic Convergence of Microbial Communities from Anaerobic Digesters." Applied and Environmental Microbiology 82, no. 5 (December 28, 2015): 1519–29. http://dx.doi.org/10.1128/aem.03360-15.
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ABSTRACTCellulose and xylan are two major components of lignocellulosic biomass, which represents a potentially important energy source, as it is abundant and can be converted to methane by microbial action. However, it is recalcitrant to hydrolysis, and the establishment of a complete anaerobic digestion system requires a specific repertoire of microbial functions. In this study, we maintained 2-year enrichment cultures of anaerobic digestion sludge amended with cellulose or xylan to investigate whether a cellulose- or xylan-digesting microbial system could be assembled from sludge previously used to treat neither of them. While efficient methane-producing communities developed under mesophilic (35°C) incubation, they did not under thermophilic (55°C) conditions. Illumina amplicon sequencing results of the archaeal and bacterial 16S rRNA genes revealed that the mature cultures were much lower in richness than the inocula and were dominated by single archaeal (genusMethanobacterium) and bacterial (orderClostridiales) groups, although at finer taxonomic levels the bacteria were differentiated by substrates. Methanogenesis was primarily via the hydrogenotrophic pathway under all conditions, although the identity and growth requirements of syntrophic acetate-oxidizing bacteria were unclear. Incubation conditions (substrate and temperature) had a much greater effect than inoculum source in shaping the mature microbial community, although analysis based on unweighted UniFrac distance found that the inoculum still determined the pool from which microbes could be enriched. Overall, this study confirmed that anaerobic digestion sludge treating nonlignocellulosic material is a potential source of microbial cellulose- and xylan-digesting functions given appropriate enrichment conditions.
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Syutsubo, K., N. Sinthurat, A. Ohashi, and H. Harada. "Population dynamics of anaerobic microbial consortia in thermophilic granular sludge in response to feed composition change." Water Science and Technology 43, no. 1 (January 1, 2001): 59–66. http://dx.doi.org/10.2166/wst.2001.0015.
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A thermophilic UASB reactor was operated at 55°C for greater than 470 days in order to investigate the effects of feed composition on the changes in microbial community structure where thermophilic granular sludge was used as the inoculum source. The feed compositions were changed with cultivation days; phase 1 (1–70 days), alcohol distillery wastewater; phase 2 (71–281 days), artificial acetate wastewater; phase 3 (282–474 days), artificial sucrose wastewater. During the first one month of each phase, the methanogenic activity and cell density of methanogens quantified by fluorescence in situ hybridization (FISH) drastically changed as a result of shift in feed composition. When artificial acetate wastewater was used as feed, retained granular sludge was partially disintegrated due to a decrease in the number of symbiotic bacterial community members: acetogens (acidogens) and hydrogenotrophic methanogens. In contrast, when the feed was shifted to sucrose (phase 3), granulation of biomass was promoted by a remarkable proliferation of the symbiotic community. The presence of hydrogen-utilizing methanogens and acetogens (acidogens) are shown to be effective for the enhancement of thermophilic granulation. The cell density of methanogens determined by FISH was strongly correlated with the methane-producing potential of the retained thermophilic granular sludge.
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Colleran, S., and S. Pender. "Mesophilic and thermophilic anaerobic digestion of sulphate-containing wastewaters." Water Science and Technology 45, no. 10 (May 1, 2002): 231–35. http://dx.doi.org/10.2166/wst.2002.0339.
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The effect of sulphate at an influent chemical oxygen demand (COD):sulphate ratio of 4 on the operational performance of anaerobic hybrid reactors treating molasses wastewater was investigated under mesophilic and thermophilic conditions in a long-term laboratory-scale study over a 1,081 day period. The presence of sulphate reduced the COD removal efficiency under both mesophilic and thermophilic conditions. At 55°C, effluent acetate levels were consistently greater than 4000 mg L−1, indicating that thermophilic acetate-utilising methane-producing bacteria (MPB) or sulphate-reducing bacteria (SRB) had not developed in the reactor under the conditions applied. At 37°C, acetate was exclusively utilised by acetoclastic methanogens, whereas H2-utilising SRB predominated over H2-utilising MPB in the competition for hydrogen. By contrast, hydrogenotrophic MPB were shown to outcompete H2-utilising SRB during long-term thermophilic operation. 16SrDNA analysis of the seed sludge and reactor biomass on conclusion of the 37°C and 55°C trials illustrated that the dominant methanogen present on conclusion of the thermophilic trial in the absence of influent sulphate was related to Methanocorpusculum parvuum, and was capable of growth on both acetate and hydrogen. By contrast, an organism closely related to Methanobacterium thermoautotrophicum was the dominant methanogen present in the sulphate-fed reactor on completion of the thermophilic trial.
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Waldron, Patricia J., Steven T. Petsch, Anna M. Martini, and Klaus Nüsslein. "Salinity Constraints on Subsurface Archaeal Diversity and Methanogenesis in Sedimentary Rock Rich in Organic Matter." Applied and Environmental Microbiology 73, no. 13 (April 27, 2007): 4171–79. http://dx.doi.org/10.1128/aem.02810-06.
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ABSTRACT The diversity of microorganisms active within sedimentary rocks provides important controls on the geochemistry of many subsurface environments. In particular, biodegradation of organic matter in sedimentary rocks contributes to the biogeochemical cycling of carbon and other elements and strongly impacts the recovery and quality of fossil fuel resources. In this study, archaeal diversity was investigated along a salinity gradient spanning 8 to 3,490 mM Cl− in a subsurface shale rich in CH4 derived from biodegradation of sedimentary hydrocarbons. Shale pore waters collected from wells in the main CH4-producing zone lacked electron acceptors such as O2, NO3 −, Fe3+, or SO4 2−. Acetate was detected only in high-salinity waters, suggesting that acetoclastic methanogenesis is inhibited at Cl− concentrations above ∼1,000 mM. Most-probable-number series revealed differences in methanogen substrate utilization (acetate, trimethylamine, or H2/CO2) associated with chlorinity. The greatest methane production in enrichment cultures was observed for incubations with salinity at or close to the native pore water salinity of the inoculum. Restriction fragment length polymorphism analyses of archaeal 16S rRNA genes from seven wells indicated that there were links between archaeal communities and pore water salinity. Archaeal clone libraries constructed from sequences from 16S rRNA genes isolated from two wells revealed phylotypes similar to a halophilic methylotrophic Methanohalophilus species and a hydrogenotrophic Methanoplanus species at high salinity and a single phylotype closely related to Methanocorpusculum bavaricum at low salinity. These results show that several distinct communities of methanogens persist in this subsurface, CH4-producing environment and that each community is adapted to particular conditions of salinity and preferential substrate use and each community induces distinct geochemical signatures in shale formation waters.
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Mota, V. T., and M. Zaiat. "Two- vs. single-stage anaerobic reactors: evaluation of effluent quality and energy production potential using sucrose-based wastewater." Water Science and Technology 78, no. 9 (November 12, 2018): 1966–79. http://dx.doi.org/10.2166/wst.2018.470.
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Abstract Two- and single-stage anaerobic treatment systems were assessed for treatment performance and for bioenergy production from sucrose-based wastewater. In the two-stage system, a hydrogen-producing upflow anaerobic sludge blanket reactor (HU reactor) was used in the acidogenic phase. The methanogenic reactor of the two-stage system (MF reactor) and the single-stage reactor (SSF reactor) were structured fixed-bed reactors. The two-stage system showed superior performance, evidenced by lower organic acids, chemical oxygen demand (COD) and suspended solids concentrations in the effluent, and higher biogas methane content and yield. Continuous and stable H2 production was obtained in the acidogenic reactor. At the end of operation, the organic loading rates applied to the two- and single-stage systems were 6.4 and 5.2 gCOD L−1 d−1, respectively. Under these conditions, the effluent soluble COD and volatile suspended solids (VSS) concentrations were 165 and 92 mg L−1 in the two-stage system, and 256 and 244 mg L−1 in the single-stage system, respectively. The energy yield of the two-stage system was 20.69 kJ g−1CODadded, which was 34% higher than the yield of the single-stage system. The sequencing analyses showed that the archaeal distribution changed little between the inoculum and sludge from the MF reactor, in which acetoclastic Methanosaeta was predominant. However, hydrogenotrophic Methanospirillum was found most, followed by Methanosaeta, in the sludge from the SSF reactor.
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Detman, Anna, Michał Bucha, Laura Treu, Aleksandra Chojnacka, Łukasz Pleśniak, Agnieszka Salamon, Ewa Łupikasza, et al. "Evaluation of acidogenesis products’ effect on biogas production performed with metagenomics and isotopic approaches." Biotechnology for Biofuels 14, no. 1 (May 29, 2021). http://dx.doi.org/10.1186/s13068-021-01968-0.
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Abstract Background During the acetogenic step of anaerobic digestion, the products of acidogenesis are oxidized to substrates for methanogenesis: hydrogen, carbon dioxide and acetate. Acetogenesis and methanogenesis are highly interconnected processes due to the syntrophic associations between acetogenic bacteria and hydrogenotrophic methanogens, allowing the whole process to become thermodynamically favorable. The aim of this study is to determine the influence of the dominant acidic products on the metabolic pathways of methane formation and to find a core microbiome and substrate-specific species in a mixed biogas-producing system. Results Four methane-producing microbial communities were fed with artificial media having one dominant component, respectively, lactate, butyrate, propionate and acetate, for 896 days in 3.5-L Up-flow Anaerobic Sludge Blanket (UASB) bioreactors. All the microbial communities showed moderately different methane production and utilization of the substrates. Analyses of stable carbon isotope composition of the fermentation gas and the substrates showed differences in average values of δ13C(CH4) and δ13C(CO2) revealing that acetate and lactate strongly favored the acetotrophic pathway, while butyrate and propionate favored the hydrogenotrophic pathway of methane formation. Genome-centric metagenomic analysis recovered 234 Metagenome Assembled Genomes (MAGs), including 31 archaeal and 203 bacterial species, mostly unknown and uncultivable. MAGs accounted for 54%–67% of the entire microbial community (depending on the bioreactor) and evidenced that the microbiome is extremely complex in terms of the number of species. The core microbiome was composed of Methanothrix soehngenii (the most abundant), Methanoculleus sp., unknown Bacteroidales and Spirochaetaceae. Relative abundance analysis of all the samples revealed microbes having substrate preferences. Substrate-specific species were mostly unknown and not predominant in the microbial communities. Conclusions In this experimental system, the dominant fermentation products subjected to methanogenesis moderately modified the final effect of bioreactor performance. At the molecular level, a different contribution of acetotrophic and hydrogenotrophic pathways for methane production, a very high level of new species recovered, and a moderate variability in microbial composition depending on substrate availability were evidenced. Propionate was not a factor ceasing methane production. All these findings are relevant because lactate, acetate, propionate and butyrate are the universal products of acidogenesis, regardless of feedstock.
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Luxem, Katja E., William D. Leavitt, and Xinning Zhang. "Large Hydrogen Isotope Fractionation Distinguishes Nitrogenase-Derived Methane from Other Methane Sources." Applied and Environmental Microbiology 86, no. 19 (July 24, 2020). http://dx.doi.org/10.1128/aem.00849-20.
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ABSTRACT Biological nitrogen fixation is catalyzed by the enzyme nitrogenase. Two forms of this metalloenzyme, the vanadium (V)- and iron (Fe)-only nitrogenases, were recently found to reduce small amounts of carbon dioxide (CO2) into the potent greenhouse gas methane (CH4). Here, we report carbon (13C/12C) and hydrogen (2H/1H) stable isotopic compositions and fractionations of methane generated by V- and Fe-only nitrogenases in the metabolically versatile nitrogen fixer Rhodopseudomonas palustris. The stable carbon isotope fractionation imparted by both forms of alternative nitrogenase are within the range observed for hydrogenotrophic methanogenesis (13αCO2/CH4 = 1.051 ± 0.002 for V-nitrogenase and 1.055 ± 0.001 for Fe-only nitrogenase; values are means ± standard errors). In contrast, the hydrogen isotope fractionations (2αH2O/CH4 = 2.071 ± 0.014 for V-nitrogenase and 2.078 ± 0.018 for Fe-only nitrogenase) are the largest of any known biogenic or geogenic pathway. The large 2αH2O/CH4 shows that the reaction pathway nitrogenases use to form methane strongly discriminates against 2H, and that 2αH2O/CH4 distinguishes nitrogenase-derived methane from all other known biotic and abiotic sources. These findings on nitrogenase-derived methane will help constrain carbon and nitrogen flows in microbial communities and the role of the alternative nitrogenases in global biogeochemical cycles. IMPORTANCE All forms of life require nitrogen for growth. Many different kinds of microbes living in diverse environments make inert nitrogen gas from the atmosphere bioavailable using a special enzyme, nitrogenase. Nitrogenase has a wide substrate range, and, in addition to producing bioavailable nitrogen, some forms of nitrogenase also produce small amounts of the greenhouse gas methane. This is different from other microbes that produce methane to generate energy. Until now, there was no good way to determine when microbes with nitrogenases are making methane in nature. Here, we present an isotopic fingerprint that allows scientists to distinguish methane from microbes making it for energy versus those making it as a by-product of nitrogen acquisition. With this new fingerprint, it will be possible to improve our understanding of the relationship between methane production and nitrogen acquisition in nature.
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Deng, Yuying, Weihua Li, Wenquan Ruan, and Zhenxing Huang. "Applying EEM- PARAFAC Analysis With Quantitative Real-Time PCR to Monitor Methanogenic Activity of High-Solid Anaerobic Digestion of Rice Straw." Frontiers in Microbiology 12 (February 11, 2021). http://dx.doi.org/10.3389/fmicb.2021.600126.
Full textAbstract:
The methanogenic activity is an important indicator to assess the efficiency of high-solid anaerobic digestion. However, it is not yet elucidated clearly how to detect the parameter rapidly and reliably in the rice straw feeding reactor. Co-inoculated with ruminal digesta and anaerobic sludge, the digestion performance was studied at three different organic loading rates (OLRs). The excitation emission matrix–parallel factor analysis (EEM–PARAFAC) was used to detect dynamic changes in the characteristic of fluorescence components. Our results revealed that CH4 productivity reached 280.90 mL/g volatile solid (VS) with a 54.39% CH4 content under the OLR of 2.26 g/(L⋅d), which amount to 80.29% of its theoretical value. At the OLR of 2.47 g/(L⋅d), the average accumulated NH4+ concentration was 1082.63 mg/L, which resulted in the hydrogenotrophic Methanobacteriales decreasing from 1.70 × 109 to 1.04 × 106 copies/g in the solid residues, whereas the acetotrophic Methanosarcinales increased from 7.89 × 106 to 9.44 × 106 copies/g. The dynamics of the methanogenic community consequently influenced the bioconversion efficiency of rice straw, and CH4 productivity was reduced to 256.54 mL/g VS. The three fluorescent components, at the excitation/emission wavelength of 420 nm/470 nm, 340 nm/430 nm, and 280 nm/340 nm, were decomposed by PARAFAC model in the digestate. Fluorescence intensities of coenzyme F420 and NADH reflected the dynamic changes of CH4-producing activity and anaerobic digestion efficiency, respectively. The coenzyme F420, unique to hydrogenotrophic methanogens, was correlated with methane yield, suggesting they played a dominant role in the anaerobic reactor. This study demonstrates that the EEM–PARAFAC combined with Q-PCR can be used to characterize methanogenic activity variation during the high-solid anaerobic digestion of rice straw with 15% total solid (TS).