Anaerobic cellulolytic microbial communities decomposing the biomass of <Emphasis Type="Italic">Anabaena variabilis</Emphasis>

Four previously isolated methanogenic anaerobic consortia, which were originally cultivated on a cellulose-containing substrate (filter paper), were used as inocula for the anaerobic conversion of the biomass of Anabaena variabilis into biogas at 55°C. The cumulative methane yield in the biogas produced by the most active consortia reached 64%. However, the biotransformation was only efficient in the course of the single inoculation and pretreatment of the cyanobacterial biomass by its concentration and freeze-thawing. The DGGE analysis of the structure of the selected microbial consortia, cultivated on the filter paper, revealed qualitative variations in the biodiversity of predominant Bacteria, showing differences in band number and intensity. The composition of methanogenic Archaea in these consortia was similar, with the presence of the genera Methanoculleus and Methanosarcina. The efficiency of the microbial consortia selection, and the role of the various microbial trophic groups in bioconversion of the substrates, such as cellulose and the biomass of phototrophic microorganisms are discussed.     

Assessment of active methanogenic archaea in a methanol-fed upflow anaerobic sludge blanket reactor

Methanogenic archaea enrichment of a granular sludge was undertaken in an upflow anaerobic sludge blanket (UASB) reactor fed with methanol in order to enrich methylotrophic and hydrogenotrophic methanogenic populations. A microbial community assessment, in terms of microbial composition and activity—throughout the different stages of the feeding process with methanol and acetate—was performed using specific methanogenic activity (SMA) assays, quantitative real-time polymerase chain reaction (qPCR), and high-throughput sequencing of 16S ribosomal RNA (rRNA) genes from DNA and complementary DNA (cDNA). Distinct methanogenic enrichment was revealed by qPCR of mcrA gene in the methanol-fed community, being two orders of magnitude higher with respect to the initial inoculum, achieving a final mcrA/16S rRNA ratio of 0.25. High-throughput sequencing analysis revealed that the resulting methanogenic population was mainly composed by methylotrophic archaea (Methanomethylovorans and Methanolobus genus), being also highly active according to the RNA-based assessment. SMA confirmed that the methylotrophic pathway, with a direct conversion of methanol to CH₄, was the main step of methanol degradation in the UASB. The biomass from the UASB, enriched in methanogenic archaea, may bear great potential as additional inoculum for bioreactors to carry out biogas production and other related processes.     

Total and active microbial communities and <Emphasis Type="Italic">phoD</Emphasis> as affected by phosphate depletion and pH in soil

Background and Aims

Soil microbial communities contribute to organic phosphorus cycling in a variety of ways, including secretion of the PhoD alkaline phosphatase. We sampled a long-term grassland fertilization trial in Switzerland characterized by a natural pH gradient. We examined the effects of phosphate depletion and pH on total and active microbial community structures and on the structure and composition of the total and active phoD-harboring community.

Methods

Archaeal, bacterial and fungal communities were investigated using T-RFLP and phoD-harboring members of these communities were identified by 454-sequencing.

Results

Phosphate depletion decreased total, resin-extractable and organic phosphorus and changed the structure of all active microbial communities, and of the total archaeal and phoD-harboring communities. Organic carbon, nitrogen and phosphorus increased with pH, and the structures of all total and active microbial communities except the total fungal community differed between the two pH levels. phoD-harboring members were affiliated to Actinomycetales, Bacilliales, Gloeobacterales, Planctomycetales and Rhizobiales.

Conclusions

Our results suggest that pH and associated soil factors are important determinants of microbial and phoD-harboring community structures. These associated factors include organic carbon and total nitrogen, and to a lesser degree phosphorus status, and active communities are more responsive than total communities. Key players in organic P mineralization are affiliated to phyla that are known to be important in organic matter decomposition.

     

Microorganisms of low-temperature heavy oil reservoirs (Russia) and their possible application for enhanced oil recovery

Physicochemical and microbiological characteristics of formation waters low-temperature heavy oil reservoirs (Russia) were investigated. The Chernoozerskoe, Yuzhno-Suncheleevskoe, and Severo-Bogemskoe oilfields, which were exploited without water-flooding, were shown to harbor scant microbial communities, while microbial numbers in the water-flooded strata of the Vostochno-Anzirskoe and Cheremukhovskoe oilfields was as high as 10⁶ cells/mL. The rates of sulfate reduction and methanogenesis were low, not exceeding 1982 ng S^2–/(L day) and 9045 nL СН₄/(L day), respectively, in the samples from water-flooded strata. High-throughput sequencing of microbial 16S rRNA gene fragments in the community of injection water revealed the sequences of the Proteobacteria (74.7%), including Betaproteobacteria (40.2%), Alphaproteobacteria (20.7%), Gammaproteobacteria (10.1%), Deltaproteobacteria (2.0%), and Epsilonproteobacteria (1.6%), as well as Firmicutes (7.9%), Bacteroidetes (4.1%), and Archaea (0.2%). DGGE analysis of microbial mcrA genes in the community of injection water revealed methanogens of the genera Methanothrix, Methanospirillum, Methanobacterium, Methanoregula, Methanosarcina, and Methanoculleus, as well as unidentified Thermoplasmata. Pure cultures of bacteria of the genera Rhodococcus, Pseudomonas, Gordonia, Cellulomonas, etc., capable of biosurfactant production when grown on heavy oil, were isolated. Enrichment cultures of fermentative bacteria producing significant amounts of volatile organic acids (acetic, propionic, and butyric) from sacchariferous substrates were obtained. These acids dissolve the carbonates of oil-bearing rock efficiently. Selection of the efficient microbial technology for enhanced recovery of heavy oil from terrigenous and carbonate strata requires model experiments with microbial isolates and the cores of oil-bearing rocks.     

Surface-attached and suspended bacterial community structure as affected by C/N ratios: relationship between bacteria and fish production

Bacteria play crucial roles in the combined system of substrate addition and C/N control, which has been demonstrated to improve aquaculture production. However, the complexity of surface-attached bacteria on substrates and suspended bacteria in the water column hamper further application of this system. This study firstly applied this combined system into the culture of grass carp, and then explored the relationship between microbial complexes from surface-attached and suspended bacteria in this system and the production of grass carp. In addition, this study investigated bacterial community structures as affected by four C/N ratios using Illumina sequencing technology. The results demonstrated that the weight gain rate and specific growth rate of grass carp in the CN20 group (C/N ratio 20:1) were the highest (P < 0.05), and dietary supplementation of the microbial complex had positive effects on the growth of grass carp (P < 0.05). Sequencing data revealed that, (1) the proportions of Verrucomicrobiae and Rhodobacter (surface-attached), sediminibacterium (suspended), and emticicia (surface-attached and suspended) were much higher in the CN20 group compared with those in the other groups (P < 0.05); (2) Rhodobacter, Flavobacterium, Acinetobacter, Pseudomonas, Planctomyces, and Cloacibacterium might be important for the microbial colonization on substrates; (3) as the C/N ratio increased, proportions of Hydrogenophaga (surface-attached and suspended), Zoogloea, and Flectobacillus (suspended) increased, but proportions of Bacillus, Clavibacter, and Cellvibro (surface-attached and suspended) decreased. In summary, a combined system of substrate addition and C/N control increased the production of grass carp, and Verrucomicrobiae and Rhodobacter in the surface-attached bacterial community were potential probiotic bacteria that contributed to the enhanced growth of grass carp.     

Vertical profiles of microbial communities in perfluoroalkyl substance-contaminated soils

Poly- and perfluoroalkyl compounds (PFASs) are ubiquitous in the environment, but their influences on microbial community remain poorly known. The present study investigated the depth-related changes of archaeal and bacterial communities in PFAS-contaminated soils. The abundance and structure of microbial community were characterized using quantitative PCR and high-throughput sequencing, respectively. Microbial abundance changed considerably with soil depth. The richness and diversity of both bacterial and archaeal communities increased with soil depth. At each depth, bacterial community was more abundant and had higher richness and diversity than archaeal community. The structure of either bacterial or archaeal community displayed distinct vertical variations. Moreover, a higher content of perfluorooctane sulfonate (PFOS) could have a negative impact on bacterial richness and diversity. The rise of soil organic carbon content could increase bacterial abundance but lower the richness and diversity of both bacterial and archaeal communities. In addition, Proteobacteria, Actinobacteria, Chloroflexi, Cyanobacteria, and Acidobacteria were the major bacterial groups, while Thaumarchaeota, Euryarchaeota, and unclassified Archaea dominated in soil archaeal communities. PFASs could influence soil microbial community.     

Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues

Several fungi and starch-rich industrial residues were screened for itaconic acid (IA) production. Out of 15 strains, only three fungal strains were found to produce IA, which was confirmed by HPLC and GC–MS analysis. These strains were identified as Aspergillus terreus strains C1 and C2, and Ustilago maydis strain C3 by sequencing of 18S rRNA gene and internal transcribed spacer regions. Cis-aconitate decarboxylase (cad) gene, which encodes a key enzyme in IA production in A. terreus, was characterized from strains C1 and C2. C1 and C2 cad gene sequences showed about 96% similarity to the only available GenBank sequence of A. terreus cad gene. 3-D structure and cis-aconitic acid binding pocket of Cad enzyme were predicted by structural modeling. Rice, corn and potato starch wastes were screened for IA production. These materials were enzymatically hydrolyzed under experimentally optimized conditions resulting in the highest glucose production of 230 mg/mL from 20% potato waste. On comparing the production potential of selected strains with different wastes, the best IA production was achieved with strain C1 (255.7 mg/L) using potato waste. Elemental composition as well as batch-to-batch variation in waste substrates were analyzed. The difference in IA production from two different batches of potato waste was found to inversely correlate with their phosphorus content, which indicated that A. terreus produced IA under phosphate limiting condition. The potato waste hydrolysate was deionized to remove inhibitory ions like phosphate, resulting in improved IA production of 4.1 g/L by C1 strain, which is commercially competitive.     

Phylogenetic Diversity of Microorganisms from the Sludge of a Biogas Reactor Processing Oil-Containing and Municipal Waste

High-throughput sequencing of the 16S rRNA gene fragments was used to determine the phylogenetic diversity of prokaryotes, including human pathogens, in the liquid phase of the sludge of a biogas reactor processing oil-containing and municipal waste. A unique microbial community was found to develop in the sludge, which comprised the microorganisms of municipal wastewater (bacteria of human feces) and specific groups of aerobic and anaerobic microorganisms, which possibly arrived with oil-containing water. In the 16S rRNA gene library, the sequences of representatives of Firmicutes prevailed (54.9%), which belonged to anaerobic bacteria of the genera Gelria (26.6%), Syntrophomonas (6.0%), Lutispora (2.0%), and uncultured Clostridia (group MBA03, 11.1%). The Proteobacteria sequences (20.7%) belonged mostly to the metabolically diverse members of the genus Pseudomonas (13.8%). The phylum Bacteroidetes (7%) was represented by uncultured bacteria (VadinBC27 wastewater-sludge group), while members of the phylum Cloacimonetes were mainly syntrophic bacteria Candidatus Cloacamonas (7.5%). The sequences of bacteria commonly occurring in oilfields (Clostridia, Anaerolinea, Bacteroidetes, sulfate-reducing Deltaproteobacteria, members of the family Syntrophaceae, and of the genera Thauera, Pseudomonas, Dechloromonas, and Petrimonas) were revealed. No sequences of bacteria known to be pathogenic to humans were found. The cultured microorganisms were aerobic organotrophic and anaerobic fermenting, denitrifying, and methanogenic prokaryotes. Fermenting and methanogenic enrichments grew on a broad range of organic substrates (sucrose, glycerol, starch), producing volatile fatty acids (acetate, n-butyrate, and propionate), gases (Н₂, СО₂, and CH₄), and decreasing pH of the medium from 7.0 to 4.5–5.0. The possible application of the biogas reactor sludge as a source of fermenting and methanogenic anaerobic prokaryotes, as well as of aerobic hydrocarbonoxidizing bacteria for oilfield introduction and for production of new preparations for enhanced oil recovery and for bioremediation of oil contamination is discussed.     

Antagonism betweenRhizoctonia solani Kühn and certain soil saprophytes: A laboratory study

U tňí saprofyt? byl sledován projev antagonismu proti pathogenuRhizoctonia solani v r?znýeh podm?nkách kultivace.Trichoderma viride aChaetomium cochlioides inhibovaly r?st R. solani ú?inněji p?i inkuba?ni teplotě25 a 30° C.T. viride bylo antagonisticky aktivněj?í v prost?edí kyselém,C. cochlioides v prost?edí alkalickém. Je vysloven p?edpoklad, ?e p?dni doplňky zvy?uj?c? aktivituC. cochlioides by být platným opat?en?m proti sledovanému pathogenu v alkalických p?dách. Na rozdíl od p?ede?lých zpráv byla kulturaR. solani celulolyticky zaktivněj?í ne?T. viride aC. cochlioides, a to i p?i pouzití chloridu amonného jako droje dusíku.     

Antibiotic activity of bacterial endobionts of basidiomycete fruit bodies

Bacterial strains (93 isolates) capable of growth on full-strength nutrient media were isolated from 86 fungal fruit bodies collected in the Moscow region. Antimicrobial activity of the endobiont isolates against 12 bacterial and fungal test strains (including drug-resistant ones) was studied in submerged cultures. Most of the strains (84.9%) were found to produce antibiotic compounds with different antimicrobial properties, including antifungal activity in 18.3% of the strains. Morphological characteristics and analysis of the 16S rRNA gene sequences were used to determine the taxonomic position of 16 bacterial strains of the following 10 species: Bacillus subtilis, Ewingella americana, Pseudomonas sp., Stenotrophomonas maltophilia, as well as Achromobacter spanius, B. licheniformis, Hafnia paralvei, Micrococcus terreus, Nocardia coeliaca, and St. rhizophila, which have not been previously known to be endobionts of basidiomycete fruit bodies. Antimicrobial activity of A. spanius, E. americana, H. paralvei, M. terreus, N. coeliaca, and St. rhizophila has not been reported previously. Complex mechanisms of symbiotic relations between fungi and bacteria, including those associated with antibiotic formation, probably developed in the course of co-evolution.     

Dynamics and diversity of a microbial community during the fermentation of industrialized <Emphasis Type="Italic">Qingcai</Emphasis> paocai,a traditional Chinese fermented vegetable food,as assessed by Illumina MiSeq sequencing,DGGE and qPCR assay

Paocai is a traditional Chinese fermented food and typically produced via spontaneous fermentation. We have investigated the microbial community utilized for the fermentation of industrialized Qingcai paocai using the combination of Illumina MiSeq sequencing, PCR-mediated denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) assay. Three main phyla, namely Firmicutes, Proteobacteria and Bacteroidetes, were identified by both MiSeq sequencing and PCR-DGGE. The dominant genera observed in the fermentation were Lactobacillus, Pseudomonas, Vibrio and Halomonas. Most genera affiliated with Proteobacteria or Bacteroidetes were detected more often during the earlier part of the fermentation, while Lactobacillus (affiliated with Firmicutes) was dominant during the later fermentation stages. Fungal community analysis revealed that Debaryomyces, Pichia and Kazachstania were the main fungal genera present in industrialized Qingcai paocai, with Debaryomyces being the most dominant during the fermentation process. The quantities of dominant genera Lactobacillus and Debaryomyces were monitored using qPCR and shown to be 10⁹–10¹² and 10⁶–10¹⁰ copies/mL, respectively. During the later fermentation process of industrialized Qingcai paocai, Lactobacillus and Debaryomyces were present at 10¹¹ and 10⁸ copies/mL, respectively. These results facilitate further understanding of the unique microbial ecosystem during the fermentation of industrialized Qingcai paocai and guide future improvement of the fermentation process.     

Reaction of microorganisms to the digestive fluid of earthworms

The reaction of soil bacteria and fungi to the digestive fluid of the earthworm Aporrectodea caliginosa was studied. The fluid was obtained by centrifugation of the native enzymes of the digestive tract. The inhibition of growth of certain bacteria, spores, and fungal hyphae under the effect of extracts from the anterior and middle sections of the digestive tract of A. caliginosa was discovered for the first time. In bacteria, microcolony formation was inhibited as early as 20–30 s after the application of the gut extracts, which may indicate the nonenzymatic nature of the effect. The digestive fluid exhibited the same microbicidal activity whether the earthworms were feeding on soil or sterile sand. This indicates that the microbicidal agents are formed within the earthworm’s body, rather than by soil microorganisms. The effect of the digestive fluid from the anterior and middle divisions is selective in relation to different microorganisms. Of 42 strains of soil bacteria, seven were susceptible to the microbicidal action of the fluid (Alcaligenes faecalis 345-1, Microbacterium sp. 423-1, Arthrobacter sp. 430-1, Bacillus megaterium 401-1, B. megaterium 413-1, Kluyvera ascorbata 301-1, Pseudomonas reactans 387-2). The remaining bacteria did not die in the digestive fluid. Of 13 micromycetes, the digestive fluid inhibited spore germination in Aspergillus terreus and Paecilomyces lilacinus and the growth of hyphae in Trichoderma harzianum and Penicillium decumbens. The digestive fluid stimulated spore germination in Alternaria alternata and the growth of hyphae in Penicillium chrysogenum. The reaction of the remaining micromycetes was neutral. The gut fluid from the posterior division of the abdominal tract did not possess microbicidal activity. No relation was found between the reaction of microorganisms to the effects of the digestive fluid and the taxonomic position of the microorganisms. The effects revealed are similar to those shown earlier for millipedes and wood lice in the following parameters: quick action of the digestive fluid on microorganisms, and the selectivity of the action on microorganisms revealed at the strain level. The selective effect of the digestive gut fluid of the earthworms on soil microorganisms is important for animal feeding, maintaining the homeostasis of the gut microbial community, and the formation of microbial communities in soils.     

Microbial community of freshwater sponges in Lake Baikal

The microbial community of Baikal sponges has been studied in five species belonging to the genera Swartschewskia, Baicalospongia, and Lubomirskia of the endemic family Lubomirskiidae. The results show that the total numbers of bacteria and bacterioplankton production have an effect on the growth of L. baicalensis body. Bacteria of the genera Pseudomonas, Bacillus, Micrococcus, Sarcina, Flavobacterium, Arthrobacter, and Acinetobacter living in the sponges are representatives of the Baikal bacterioplankton. Actinomycetes of the genera Streptomyces and Micromonospora are a permanent component of the cultivable sponge microbial community. The numbers and enzyme activities of heterotrophic, oligotrophic, and psychrophilic bacteria isolated from different sponge species and from the ambient water in autumn and in winter have been estimated.     

Dynamics of the composition of a microbial consortium during start-up of a single-stage constant flow laboratory nitritation/anammox setup

Dynamics of the composition of the microbial community was studied during start-up of a single-stage completely mixed constant flow laboratory setup for ammonium removal by the nitritation/anammox process from the filtrate of digested sludge of the Kuryanovo wastewater treatment plant (KWTP), Moscow. To decrease the period of the start-up, the setup was initially inoculated with two types of activated sludge (nitrifying sludge from a KWTP aeration tank and sludge from a sequencing batch reactor enriched with anammox bacteria). The start-up and adjustment stage was therefore decreased to 35–40 days, and nitrogen removal efficiency reached 80% after 120 days of the setup operation. Taxonomic analysis of the composition of the microbial community was carried out by pyrosequencing of the 16S rRNA fragments obtained using the universal and planctomycetes-specific primers. In the course of adaptation of activated sludge to increasing nitrogen load, microbial community of the setup became less diverse and more specialized. The contribution of anammox bacteria of the family Brocadiaceae, closely related to Candidatus “Brocadia caroliniensis,” increased gradually. Members of the order Nitrosomonadales were involved in ammonium oxidation to nitrite. While nitrite-oxidizing bacteria of the genus Nitrospira were also detected, their share decreased with accumulation of the activated sludge. The contribution of other bacteria varied as well: the shares of the phyla Ignavibacteria, Chloroflexi, and Acidobacteria increased significantly (up to 13, 12, and 10%, respectively of the total number of reads), while relative abundance of the Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Synergistetes, Aminicenantes, Thermotogae, and Cloacimonetes decreased. Thus, application of pyrosequencing made it possible to monitor succession of the bacterial community involved in nitrogen removal by nitritation/anammox process.     

Deep sequencing analysis of bacterial community structure of Soldhar hot spring,India

We investigated the bacterial community structure of Soldhar hot spring with extreme high temperature 95°C located in Uttarakhand, India using high throughput sequencing. Bacterial phyla Proteobacteria (88.8%), Deinococcus-Thermus (7.5%), Actinobacteria (2.3%), and Firmicutes (1.07%) were predominated in the sequencing survey, whereas Bacteroidetes, Verrucomicrobia, Aquificae and Acidobacteria were detected in relatively lower abundance in Soldhar hot spring. At the family level, Comamonadaceae (52.5%), Alteromonadaceae (15.9%), and Thermaceae (7.5%) were mostly dominated in the ecosystem followed by Chromatiaceae, Microbacteriaceae, and Cyclobacteriaceae. Besides, members of Rhodobacteraceae, Moraxellaceae, Xanthomonadaceae, Aquificaceae, Enterobacteriaceae, Bacillaceae, Methylophilaceae, etc. were detected as a relatively lower abundance. In the present study we discuss the overall microbial community structure and their relevance to the ecology of the Soldhar hot spring environment.     

Biodegradation optimization and metabolite elucidation of Reactive Red 120 by four different <Emphasis Type="Italic">Aspergillus</Emphasis> species isolated from soil contaminated with industrial effluent

Azo dyes are recalcitrant owing to their xenobiotic nature and exhibit high resistance to degradation processes. In the present study, different Aspergillus species (A. flavus, A. fumigatus, A. niger, and A. terreus) isolated from soil samples contaminated with industrial effluent, collected from Jeddah, Saudi Arabia, were analyzed for azo dye, Reactive Red 120 (RR120) biodegradation. The physicochemical parameters such as carbon (sucrose) and nitrogen (ammonium sulfate) sources, pH, and temperature affecting the biodegradation of RR120 were optimized using central composite design–response surface methodology (CCD-RSM). The maximum RR120 degradation was found to be 84% (predicted) at the optimum level of sucrose (11.73 g/L), ammonium sulfate (1.26 g/L), pH (5.71), and temperature (28.26 °C). Further, the validation results confirmed that the predicted values are in good agreement with the experimental results for RR120 degradation by A. flavus (86%), A. fumigatus (84%), A. niger (85%), and A. terreus (86%). The metabolic product of RR120 after biodegradation by different Aspergillus species was identified as sodium 2-aminobenzenesulfonate. The present study suggests that Aspergillus species are good candidates for azo dye-loaded effluent treatment.     

Differences in macrobenthic faunal communities in mangrove wetland habitats (Zhanjiang,China) invaded and non-invaded by exotic cordgrass <Emphasis Type="Italic">Spartina alterniflora</Emphasis>

Mangroves are essential for maintaining local biodiversity and human well-being, and mangrove structure and functioning depend on the macrobenthos. Although exotic cordgrass, Spartina alterniflora, is an increasing threat to the mangrove wetlands (including the associated unvegetated shoals) of China, its effects on the macrobenthic fauna in such wetlands is poorly understood. The macrobenthic faunal communities were compared in (1) an Avicennia marina monoculture vs. an S. alterniflora-invaded A. marina stand (a mixture of A. marina and S. alterniflora) and in (2) an unvegetated shoal vs. an S. alterniflora-invaded shoal that had rapidly become an S. alterniflora monoculture in Zhanjiang, China. S. alterniflora invasion significantly increased plant density regardless of invaded habitat but significantly increased the contents of total carbon, organic matter, and total sulfur in the sediment only in the unvegetated shoal. The presence of S. alterniflora had little influence on indices of the macrobenthic faunal community in the A. marina monoculture, but significantly decreased the density and biomass of macrobenthic faunal community in the unvegetated shoal. These results indicate that the effects of S. alterniflora on the macrobenthic faunal community depend on which type of mangrove habitat is invaded. The composition of the macrobenthic faunal community was more similar between the invaded and non-invaded A. marina stand than between the invaded and non-invaded unvegetated shoal. Overall, the differences in the macrobenthic faunal community between invaded and non-invaded habitats were associated with increases in the sediment organic matter content and plant density.     

Ammonium inhibition through the decoupling of acidification process and methanogenesis in anaerobic digester revealed by high throughput sequencing

Objective

To reveal the shifts of microbial communities along ammonium gradients, and the relationship between microbial community composition and the anaerobic digestion performance using a high throughput sequencing technique.

Results

Methane production declined with increasing ammonium concentration, and was inhibited above 4 g l^?1. The volatile fatty acids, especially acetate, accumulated with elevated ammonium. Prokaryotic populations showed different responses to the ammonium concentration: Clostridium, Tepidimicrobium, Sporanaerobacter, Peptostreptococcus, Sarcina and Peptoniphilus showed good tolerance to ammonium ions. However, Syntrophomonas with poor tolerance to ammonium may be inhibited during anaerobic digestion. During methanogenesis, Methanosarcina was the dominant methanogen.

Conclusion

Excessive ammonium inhibited methane production probably by decoupling the linkage between acidification process and methanogenesis, and finally resulted in different performance in anaerobic digestion.