Anaerobic Digesters

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Seokhwan Hwang - One of the best experts on this subject based on the ideXlab platform.

  • Temporal variation in bacterial and methanogenic communities of three full-scale Anaerobic Digesters treating swine wastewater
    Environmental Science and Pollution Research, 2019
    Co-Authors: Seung Gu Shin, Seokhwan Hwang
    Abstract:

    To investigate the effects of temporal variations of process parameters on microbial community structures in the two types of full-scale Anaerobic digester treating swine wastewater, three full-scale Anaerobic Digesters were monitored. An Anaerobic filter (AF)-type digester located in Gong-Ju (GJ) showed the highest COD removal among three Digesters and maintained stable efficiency. A digester in Hong-Seong (HS) was of the same type as it GJ and showed improved efficiency over the sampling period. A continuously stirred tank reactor (CSTR)-type digester in Soon-Cheon (SC) showed decreasing efficiency due to a high residual concentration of VFAs and NH_4^+. These process efficiencies were closely correlated to the Simpson indices of the methanogenic communities. Genera Bacillus , Methanosaeta , and Methanospirillum that have filamentous morphology were dominant in both AF-type Digesters, but genera Acholeplasma , Methanosarcina , and Methanoculleus that have spherical or coccoid morphology were dominantly abundant in the CSTR-type digester. Correlation between populations suggests a possible syntrophic relationship between genera Desulfobulbus and Methanosaeta in Digesters GJ and HS.

  • bacteria and archaea communities in full scale thermophilic and mesophilic Anaerobic Digesters treating food wastewater key process parameters and microbial indicators of process instability
    Bioresource Technology, 2017
    Co-Authors: Seung Gu Shin, Seokhwan Hwang
    Abstract:

    Abstract In this study, four different mesophilic and thermophilic full-scale Anaerobic Digesters treating food wastewater (FWW) were monitored for 1–2 years in order to investigate: 1) microbial communities underpinning Anaerobic digestion of FWW, 2) significant factors shaping microbial community structures, and 3) potential microbial indicators of process instability. Twenty-seven bacterial genera were identified as abundant bacteria underpinning the Anaerobic digestion of FWW. Methanosaeta harundinacea, M. concilii, Methanoculleus bourgensis, M. thermophilus, and Methanobacterium beijingense were revealed as dominant methanogens. Bacterial community structures were clearly differentiated by Digesters; archaeal community structures of each digester were dominated by one or two methanogen species. Temperature, ammonia, propionate, Na+, and acetate in the digester were significant factors shaping microbial community structures. The total microbial populations, microbial diversity, and specific bacteria genera showed potential as indicators of process instability in the Anaerobic digestion of FWW.

  • correlations between bacterial populations and process parameters in four full scale Anaerobic Digesters treating sewage sludge
    Bioresource Technology, 2016
    Co-Authors: Seung Gu Shin, Taewoan Koo, Joonyeob Lee, Gyuseong Han, Kyungjin Cho, Woong Kim, Seokhwan Hwang
    Abstract:

    Process parameters and bacterial populations were investigated in four full-scale Anaerobic Digesters treating sewage sludge. Although the four Digesters were operated under similar conditions, Digesters A and B had higher pH (7.2-7.4) and lipid removal efficiencies (>50%) than C and D (pH 6.1-6.4; average lipid removal <16%). Bacterial richness, diversity, and evenness were higher in Digesters C and D. Among the top-populated genera, ten (group I) were more abundant in Digesters A and/or B; they were putative syntrophic fatty acid or protein/amino acid-utilizers. In contrast, fifteen others (group II) were less abundant in A and/or B and included potentially dormant/dead cells originated from activated sludge. Despite the overall richness trend, the presence of the 25 genera in groups I/II was greater in Digesters A and B (24) than in C and D (17); this observation suggests that group I bacteria might be essential in AD of sewage sludge.

  • Temporal variation in methanogen communities of four different full-scale Anaerobic Digesters treating food waste-recycling wastewater.
    Bioresource Technology, 2014
    Co-Authors: Byungchul Hwang, Seung Gu Shin, Seokhwan Hwang
    Abstract:

    Methanogen communities were investigated using 454 pyrosequencing in four different full-scale Anaerobic Digesters treating food waste-recycling wastewater. Seasonal samples were collected for 2 years, and 24 samples were available for microbial analysis from a plug flow thermophilic (PT) digester, a continuously-stirred tank thermophilic (CT) digester, an upflow anerobic sludge blanket mesophilic (UM) digester, and a continuously-stirred tank mesophilic (CM) digester. Methanoculleus, Methanobacterium, Methanothermobacter, and Methanosaeta were revealed to be key methanogens in full-scale Anaerobic digestion process treating food waste-recycling wastewater. In the PT digester, Methanoculleus was dominant (96.8%). In the CT digester, Methanoculleus was dominant (95.4%) during the first year of operation, but the dominant genus was shifted to Methanothermobacter (98.5%) due to pH increase. In the UM digester, Methanosaeta was dominant (87.2%). In the CM digester, Methanoculleus was constantly dominant (74.8%) except during CM5 when Methanosaeta was dominant (62.6%) due to the low residual acetate concentration (0.1 g/L).

Sarina J Ergas - One of the best experts on this subject based on the ideXlab platform.

  • review of small scale tubular Anaerobic Digesters treating livestock waste in the developing world
    Renewable & Sustainable Energy Reviews, 2016
    Co-Authors: Maureen N Kinyua, Laurel E Rowse, Sarina J Ergas
    Abstract:

    Small-scale tubular Anaerobic Digesters are an attractive technology for treatment of livestock waste in the developing world. These systems produce biogas (a mixture of CH4 and CO2) that is mainly used for cooking. Digester effluent is rich in nutrients (nitrogen and phosphorus) and can be used as a soil amendment. These systems also assist in mitigating deforestation by providing an alternative fuel source, reducing water pollution due to runoff of untreated livestock waste, decreasing air pollution from biomass combustion and promoting gender equality. However, for these benefits to be significant, the effects of design, substrate characteristics and operating parameters on system performance must be understood. This review provides a detailed summary of the research that has been conducted on tubular Anaerobic Digesters treating livestock waste in developing countries. Links between successful digester performance and energy, environmental, public health and social benefits are also provided. In addition, this review discusses governmental policies that have successfully increased adoption of livestock waste Anaerobic digestion systems in Africa, Asia and Latin America.

  • use of physical and biological process models to understand the performance of tubular Anaerobic Digesters
    Biochemical Engineering Journal, 2016
    Co-Authors: Jie Zhang, Maureen N Kinyua, Fabricio Camachocespedes, Andres E Tejadamartinez, Sarina J Ergas
    Abstract:

    Abstract Tubular Anaerobic Digesters are used in developing countries to produce biogas from livestock waste. In this research, field measurements and physical and biological process modeling studies were used to investigate transport and transformation mechanisms for particulate and soluble organic matter in household-scale tubular Digesters in the Monteverde region of Costa Rica. Greater than 75% removal of volatile solids and biochemical oxygen demand (BOD5) were observed. The high effluent quality was attributed to the formation of a biologically active floccular sludge layer, which allowed for separation of hydraulic and mean cell residence times (HRT and MCRT). A reduced order transport model was developed and validated using field tracer study data. Key assumptions of the reduced order model were verified via computational fluid dynamics (CFD) analysis. The mean HRT predicted by the reduced order model was 23 days and was in good agreement with the tracer experiment. A simplified floccular sludge biological process model was developed and used to estimate an average MCRT of 115 days. The results showed that household-scale tubular Anaerobic Digesters can provide enough biogas to meet households’ cooking energy needs, which was consistent with field results. This is the first study to combine mathematical modeling with field studies of tubular Anaerobic digester performance.

  • semi continuous mesophilic Anaerobic digester performance under variations in solids retention time and feeding frequency
    Bioresource Technology, 2015
    Co-Authors: Nathan D Manser, James R Mihelcic, Sarina J Ergas
    Abstract:

    The goal of this research was to understand the effect of solids retention time (SRT) and feeding frequency on the performance of Anaerobic Digesters used to recover bioenergy from swine waste. Semi-continuous mesophilic Anaerobic Digesters were operated at varying SRTs and feeding frequencies. Performance metrics included biogas and methane production rates, biomass robustness and functionality and removals of volatile solids, soluble chemical oxygen demand, the fecal-indicator bacteria Escherichia coli, and the human pathogen Salmonella. Biochemical methane formation potential and specific methanogenic activity assays were used to demonstrate biomass robustness and functionality. Results indicated that Anaerobic Digesters fed weekly had higher average methane yields (0.20 vs. 0.18m(3)CH4/kg-VSadded), specific methanogenic activities (40 vs. 35ml/day), and fecal indicator bacteria destruction (99.9% vs. 99.4%) than those fed every-other day. Salmonella, soluble COD, and VS destruction did not change with varied feeding frequency; however, higher removals were observed with longer SRT.

Seung Gu Shin - One of the best experts on this subject based on the ideXlab platform.

  • Temporal variation in bacterial and methanogenic communities of three full-scale Anaerobic Digesters treating swine wastewater
    Environmental Science and Pollution Research, 2019
    Co-Authors: Seung Gu Shin, Seokhwan Hwang
    Abstract:

    To investigate the effects of temporal variations of process parameters on microbial community structures in the two types of full-scale Anaerobic digester treating swine wastewater, three full-scale Anaerobic Digesters were monitored. An Anaerobic filter (AF)-type digester located in Gong-Ju (GJ) showed the highest COD removal among three Digesters and maintained stable efficiency. A digester in Hong-Seong (HS) was of the same type as it GJ and showed improved efficiency over the sampling period. A continuously stirred tank reactor (CSTR)-type digester in Soon-Cheon (SC) showed decreasing efficiency due to a high residual concentration of VFAs and NH_4^+. These process efficiencies were closely correlated to the Simpson indices of the methanogenic communities. Genera Bacillus , Methanosaeta , and Methanospirillum that have filamentous morphology were dominant in both AF-type Digesters, but genera Acholeplasma , Methanosarcina , and Methanoculleus that have spherical or coccoid morphology were dominantly abundant in the CSTR-type digester. Correlation between populations suggests a possible syntrophic relationship between genera Desulfobulbus and Methanosaeta in Digesters GJ and HS.

  • bacteria and archaea communities in full scale thermophilic and mesophilic Anaerobic Digesters treating food wastewater key process parameters and microbial indicators of process instability
    Bioresource Technology, 2017
    Co-Authors: Seung Gu Shin, Seokhwan Hwang
    Abstract:

    Abstract In this study, four different mesophilic and thermophilic full-scale Anaerobic Digesters treating food wastewater (FWW) were monitored for 1–2 years in order to investigate: 1) microbial communities underpinning Anaerobic digestion of FWW, 2) significant factors shaping microbial community structures, and 3) potential microbial indicators of process instability. Twenty-seven bacterial genera were identified as abundant bacteria underpinning the Anaerobic digestion of FWW. Methanosaeta harundinacea, M. concilii, Methanoculleus bourgensis, M. thermophilus, and Methanobacterium beijingense were revealed as dominant methanogens. Bacterial community structures were clearly differentiated by Digesters; archaeal community structures of each digester were dominated by one or two methanogen species. Temperature, ammonia, propionate, Na+, and acetate in the digester were significant factors shaping microbial community structures. The total microbial populations, microbial diversity, and specific bacteria genera showed potential as indicators of process instability in the Anaerobic digestion of FWW.

  • correlations between bacterial populations and process parameters in four full scale Anaerobic Digesters treating sewage sludge
    Bioresource Technology, 2016
    Co-Authors: Seung Gu Shin, Taewoan Koo, Joonyeob Lee, Gyuseong Han, Kyungjin Cho, Woong Kim, Seokhwan Hwang
    Abstract:

    Process parameters and bacterial populations were investigated in four full-scale Anaerobic Digesters treating sewage sludge. Although the four Digesters were operated under similar conditions, Digesters A and B had higher pH (7.2-7.4) and lipid removal efficiencies (>50%) than C and D (pH 6.1-6.4; average lipid removal <16%). Bacterial richness, diversity, and evenness were higher in Digesters C and D. Among the top-populated genera, ten (group I) were more abundant in Digesters A and/or B; they were putative syntrophic fatty acid or protein/amino acid-utilizers. In contrast, fifteen others (group II) were less abundant in A and/or B and included potentially dormant/dead cells originated from activated sludge. Despite the overall richness trend, the presence of the 25 genera in groups I/II was greater in Digesters A and B (24) than in C and D (17); this observation suggests that group I bacteria might be essential in AD of sewage sludge.

  • Temporal variation in methanogen communities of four different full-scale Anaerobic Digesters treating food waste-recycling wastewater.
    Bioresource Technology, 2014
    Co-Authors: Byungchul Hwang, Seung Gu Shin, Seokhwan Hwang
    Abstract:

    Methanogen communities were investigated using 454 pyrosequencing in four different full-scale Anaerobic Digesters treating food waste-recycling wastewater. Seasonal samples were collected for 2 years, and 24 samples were available for microbial analysis from a plug flow thermophilic (PT) digester, a continuously-stirred tank thermophilic (CT) digester, an upflow anerobic sludge blanket mesophilic (UM) digester, and a continuously-stirred tank mesophilic (CM) digester. Methanoculleus, Methanobacterium, Methanothermobacter, and Methanosaeta were revealed to be key methanogens in full-scale Anaerobic digestion process treating food waste-recycling wastewater. In the PT digester, Methanoculleus was dominant (96.8%). In the CT digester, Methanoculleus was dominant (95.4%) during the first year of operation, but the dominant genus was shifted to Methanothermobacter (98.5%) due to pH increase. In the UM digester, Methanosaeta was dominant (87.2%). In the CM digester, Methanoculleus was constantly dominant (74.8%) except during CM5 when Methanosaeta was dominant (62.6%) due to the low residual acetate concentration (0.1 g/L).

Maureen N Kinyua - One of the best experts on this subject based on the ideXlab platform.

  • review of small scale tubular Anaerobic Digesters treating livestock waste in the developing world
    Renewable & Sustainable Energy Reviews, 2016
    Co-Authors: Maureen N Kinyua, Laurel E Rowse, Sarina J Ergas
    Abstract:

    Small-scale tubular Anaerobic Digesters are an attractive technology for treatment of livestock waste in the developing world. These systems produce biogas (a mixture of CH4 and CO2) that is mainly used for cooking. Digester effluent is rich in nutrients (nitrogen and phosphorus) and can be used as a soil amendment. These systems also assist in mitigating deforestation by providing an alternative fuel source, reducing water pollution due to runoff of untreated livestock waste, decreasing air pollution from biomass combustion and promoting gender equality. However, for these benefits to be significant, the effects of design, substrate characteristics and operating parameters on system performance must be understood. This review provides a detailed summary of the research that has been conducted on tubular Anaerobic Digesters treating livestock waste in developing countries. Links between successful digester performance and energy, environmental, public health and social benefits are also provided. In addition, this review discusses governmental policies that have successfully increased adoption of livestock waste Anaerobic digestion systems in Africa, Asia and Latin America.

  • use of physical and biological process models to understand the performance of tubular Anaerobic Digesters
    Biochemical Engineering Journal, 2016
    Co-Authors: Jie Zhang, Maureen N Kinyua, Fabricio Camachocespedes, Andres E Tejadamartinez, Sarina J Ergas
    Abstract:

    Abstract Tubular Anaerobic Digesters are used in developing countries to produce biogas from livestock waste. In this research, field measurements and physical and biological process modeling studies were used to investigate transport and transformation mechanisms for particulate and soluble organic matter in household-scale tubular Digesters in the Monteverde region of Costa Rica. Greater than 75% removal of volatile solids and biochemical oxygen demand (BOD5) were observed. The high effluent quality was attributed to the formation of a biologically active floccular sludge layer, which allowed for separation of hydraulic and mean cell residence times (HRT and MCRT). A reduced order transport model was developed and validated using field tracer study data. Key assumptions of the reduced order model were verified via computational fluid dynamics (CFD) analysis. The mean HRT predicted by the reduced order model was 23 days and was in good agreement with the tracer experiment. A simplified floccular sludge biological process model was developed and used to estimate an average MCRT of 115 days. The results showed that household-scale tubular Anaerobic Digesters can provide enough biogas to meet households’ cooking energy needs, which was consistent with field results. This is the first study to combine mathematical modeling with field studies of tubular Anaerobic digester performance.

Ryan M Ziels - One of the best experts on this subject based on the ideXlab platform.

  • elucidating syntrophic butyrate degrading populations in Anaerobic Digesters using stable isotope informed genome resolved metagenomics
    mSystems, 2019
    Co-Authors: Ryan M Ziels, Masaru K Nobu, D Z Sousa
    Abstract:

    Linking the genomic content of uncultivated microbes to their metabolic functions remains a critical challenge in microbial ecology. Resolving this challenge has implications for improving our management of key microbial interactions in biotechnologies such as Anaerobic digestion, which relies on slow-growing syntrophic and methanogenic communities to produce renewable methane from organic waste. In this study, we combined DNA stable-isotope probing (SIP) with genome-centric metagenomics to recover the genomes of populations enriched in 13C after growing on [13C]butyrate. Differential abundance analysis of recovered genomic bins across the SIP metagenomes identified two metagenome-assembled genomes (MAGs) that were significantly enriched in heavy [13C]DNA. Phylogenomic analysis assigned one MAG to the genus Syntrophomonas and the other MAG to the genus Methanothrix. Metabolic reconstruction of the annotated genomes showed that the Syntrophomonas genome encoded all the enzymes for beta-oxidizing butyrate, as well as several mechanisms for interspecies electron transfer via electron transfer flavoproteins, hydrogenases, and formate dehydrogenases. The Syntrophomonas genome shared low average nucleotide identity (<95%) with any cultured representative species, indicating that it is a novel species that plays a significant role in syntrophic butyrate degradation within Anaerobic Digesters. The Methanothrix genome contained the complete pathway for acetoclastic methanogenesis, indicating that it was enriched in 13C from syntrophic acetate transfer. This study demonstrates the potential of stable-isotope-informed genome-resolved metagenomics to identify in situ interspecies metabolic cooperation within syntrophic consortia important to Anaerobic waste treatment as well as global carbon cycling.IMPORTANCE Predicting the metabolic potential and ecophysiology of mixed microbial communities remains a major challenge, especially for slow-growing anaerobes that are difficult to isolate. Unraveling the in situ metabolic activities of uncultured species may enable a more descriptive framework to model substrate transformations by microbiomes, which has broad implications for advancing the fields of biotechnology, global biogeochemistry, and human health. Here, we investigated the in situ function of mixed microbiomes by combining stable-isotope probing with metagenomics to identify the genomes of active syntrophic populations converting butyrate, a C4 fatty acid, into methane within Anaerobic Digesters. This approach thus moves beyond the mere presence of metabolic genes to resolve "who is doing what" by obtaining confirmatory assimilation of the labeled substrate into the DNA signature. Our findings provide a framework to further link the genomic identities of uncultured microbes with their ecological function within microbiomes driving many important biotechnological and global processes.

  • elucidating syntrophic butyrate degrading populations in Anaerobic Digesters using stable isotope informed genome resolved metagenomics
    bioRxiv, 2019
    Co-Authors: Ryan M Ziels, Masaru K Nobu, D Z Sousa
    Abstract:

    Linking the genomic content of uncultivated microbes to their metabolic functions remains a critical challenge in microbial ecology. Resolving this challenge has implications for improving our management of key microbial interactions in biotechnologies such as Anaerobic digestion, which relies on slow-growing syntrophic and methanogenic communities to produce renewable methane from organic waste. In this study, we combined DNA stable isotope probing (SIP) with genome-centric metagenomics to recover the genomes of populations enriched in 13C after feeding 13C-labeled butyrate. Differential abundance analysis on recovered genomic bins across the SIP metagenomes identified two metagenome-assembled genomes (MAGs) that were significantly enriched in the heavy 13C DNA. Phylogenomic analysis assigned one MAG to the genus Syntrophomonas, and the other MAG to the genus Methanothrix. Metabolic reconstruction of the annotated genomes showed that the Syntrophomonas genome encoded all the enzymes for beta-oxidizing butyrate, as well as several mechanisms for interspecies electron transfer via electron transfer flavoproteins, hydrogenases, and formate dehydrogenases. The Syntrophomonas genome shared low average nucleotide identity (< 95%) with any cultured representative species, indicating it is a novel species that plays a significant role in syntrophic butyrate degradation within Anaerobic Digesters. The Methanothrix genome contained the complete pathway for aceticlastic methanogenesis, indicating that it was enriched in 13C from syntrophic acetate transfer. This study demonstrates the potential of stable-isotope-informed genome-resolved metagenomics to elucidate the nature of metabolic cooperation in slow-growing uncultured microbial populations, such as syntrophic bacteria and methanogens, that are important to waste treatment as well as global carbon cycling. Importance: Predicting the metabolic potential and ecophysiology of mixed microbial communities remains a major challenge, especially for slow-growing anaerobes that are difficult to isolate. Unraveling the in-situ metabolic activities of uncultured species could enable a more descriptive framework to model substrate transformations by microbiomes, which has broad implications for advancing the fields of biotechnology, global biogeochemistry, and human health. Here, we investigated the in-situ function of mixed microbiomes by combining DNA-stable isotope probing with metagenomics to identify the genomes of active syntrophic populations converting butyrate, a C4 fatty acid, into methane within Anaerobic Digesters. This approach thus moves beyond the mere presence of metabolic genes to resolve "who is doing what" by obtaining confirmatory assimilation of labeled substrate into the DNA signature. Our findings provide a framework to further link the genomic identities of uncultured microbes with their ecological function within microbiomes driving many important biotechnological and global processes.

  • microbial rrna gene expression and co occurrence profiles associate with biokinetics and elemental composition in full scale Anaerobic Digesters
    Microbial Biotechnology, 2018
    Co-Authors: Ryan M Ziels, Bo H Svensson, Carina Sundberg, Madeleine Larsson, Anna Karlsson, Sepehr Shakeri Yekta
    Abstract:

    This study examined whether the abundance and expression of microbial 16S rRNA genes were associated with elemental concentrations and substrate conversion biokinetics in 20 full-scale Anaerobic Digesters, including seven municipal sewage sludge (SS) Digesters and 13 industrial coDigesters. SS digester contents had higher methane production rates from acetate, propionate and phenyl acetate compared to industrial coDigesters. SS Digesters and industrial coDigesters were distinctly clustered based on their elemental concentrations, with higher concentrations of NH3 -N, Cl, K and Na observed in coDigesters. Amplicon sequencing of 16S rRNA genes and reverse-transcribed 16S rRNA revealed divergent grouping of microbial communities between mesophilic SS Digesters, mesophilic coDigesters and thermophilic Digesters. Higher intradigester distances between Archaea 16S rRNA and rRNA gene profiles were observed in mesophilic coDigesters, which also had the lowest acetate utilization biokinetics. Constrained ordination showed that microbial rRNA and rRNA gene profiles were significantly associated with maximum methane production rates from acetate, propionate, oleate and phenyl acetate, as well as concentrations of NH3 -N, Fe, S, Mo and Ni. A co-occurrence network of rRNA gene expression confirmed the three main clusters of Anaerobic digester communities based on active populations. Syntrophic and methanogenic taxa were highly represented within the subnetworks, indicating that obligate energy-sharing partnerships play critical roles in stabilizing the digester microbiome. Overall, these results provide new evidence showing that different feed substrates associate with different micronutrient compositions in Anaerobic Digesters, which in turn may influence microbial abundance, activity and function.

  • dna sip based genome centric metagenomics identifies key long chain fatty acid degrading populations in Anaerobic Digesters with different feeding frequencies
    The ISME Journal, 2018
    Co-Authors: Ryan M Ziels, D Z Sousa, David H Stensel, David A C Beck
    Abstract:

    Fats, oils and greases (FOG) are energy-dense wastes that can be added to Anaerobic Digesters to substantially increase biomethane recovery via their conversion through long-chain fatty acids (LCFAs). However, a better understanding of the ecophysiology of syntrophic LCFA-degrading microbial communities in Anaerobic Digesters is needed to develop operating strategies that mitigate inhibitory LCFA accumulation from FOG. In this research, DNA stable isotope probing (SIP) was coupled with metagenomic sequencing for a genome-centric comparison of oleate (C18:1)-degrading populations in two Anaerobic coDigesters operated with either a pulse feeding or continuous-feeding strategy. The pulse-fed codigester microcosms converted oleate into methane at over 20% higher rates than the continuous-fed codigester microcosms. Differential coverage binning was demonstrated for the first time to recover population genome bins (GBs) from DNA-SIP metagenomes. About 70% of the 13C-enriched GBs were taxonomically assigned to the Syntrophomonas genus, thus substantiating the importance of Syntrophomonas species to LCFA degradation in Anaerobic Digesters. Phylogenetic comparisons of 13C-enriched GBs showed that phylogenetically distinct Syntrophomonas GBs were unique to each codigester. Overall, these results suggest that syntrophic populations in Anaerobic Digesters can have different adaptive capacities, and that selection for divergent populations may be achieved by adjusting reactor operating conditions to maximize biomethane recovery.