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To achieve non-carbon dioxide greenhouse gas emission reduction and control in municipal wastewater treatment plants （WWTPs）, this study conducted one-year long-term monitoring of nitrous oxide （N 2 O） in the anaerobic-anoxic-aerobic （A 2 O） process of a large-scale municipal wastewater treatment plant in Beijing. The experimental results showed that the anaerobic and anoxic zones of the A 2 O process could effectively remove dissolved N 2 O contained in the return sludge, while the aerobic zone was the main area for N 2 O generation and emission, and its generation pathway may have been dominated by ammonia oxidizing bacteria （AOB） denitrification. A significant difference was observed between winter and summer N 2 O production, and the difference in the average N 2 O release flux was up to 7.6 times, and the average monthly N 2 O emission in winter was 32.75 kg, which was significantly higher than that in summer （6.06 kg）. The accumulation of nitrite （NO 2 - -N） and the concentration of dissolved oxygen （DO） had a significant impact on N 2 O production. Therefore, to achieve N 2 O reduction in the A 2 O process, the concentration of NO 2 - -N in the aerobic zone should be controlled below 0.40 mg·L -1 in winter and 0.10 mg·L -1 in summer, while the DO concentration should be maintained above 1.2 mg·L -1 .

Achieving effective treatment and resource reuse of municipal sludge is a worthwhile research issue. Currently, anaerobic digestion treatment is an effective way to achieve the resource utilization of municipal sludge. However, due to the slow start-up, poor stability and low gas production efficiency of anaerobic digestion systems, sludge anaerobic digestion faces many challenges in practical engineering applications. Iron-based material has been proven to be a good conductive material for promoting anaerobic digestion of municipal sludge. On the basis of previous studies, this article summarized the effects of different iron-based materials on anaerobic digestion of municipal sludge. Simultaneously, from the perspectives of alleviating toxic substance inhibition, enhancing microbial metabolism, and promoting electron transfer between symbiotic microorganisms, the mechanism of iron-based materials enhancing anaerobic digestion of municipal sludge was summarized. The mechanism of direct interspecific electron transfer mediated by iron-based materials in enhancing anaerobic digestion of municipal sludge was described, and the research direction of iron-based materials enhancing anaerobic digestion of municipal sludge was prospected.

Food waste is one of the important reservoirs of antibiotic resistance genes （ARGs）, and its resource utilization has potential environmental risks. Anaerobic digestion （AD） technology can concurrently achieve resource recovery and ARGs removal, which is one of the popular resource technologies for food waste management. However, the removal efficiency of ARGs during the AD process is limited, and thus the safety of digestate for agricultural use is still questioned. Therefore, how to improve the performance of ARGs removal during the AD process is critical for efficient and environmentally friendly bioconversion of food waste. This study summarized the transmission pathways and mechanisms of ARGs in food waste； discussed the effects of different operation parameters on the transmission of ARGs in food waste during the AD process； described the research progress of exogenous addition of conductive materials, feedstock pretreatment, etc., strategies to enhance the removal of ARGs； and analyzed the migration regularity and removal mechanism of ARGs in food waste during the AD process, which mainly included microbial community structure evolution, mobile genetic element changes, and environmental factor changes. Finally, this study prospected the future improvement of methane yield and ARGs removal in the AD process of food waste based on the existing research.

The application of ANAMMOX technology is constrained by sluggish growth and difficulty in enriching ANAMMOX bacteria. Long-term starvation of functioning bacteria due to limited substrate supply makes the steady operation of ANAMMOX reactors more difficult. Re-examining the start-up and recovery performance of the ANAMMOX reactor and identifying its resistance mechanism are important from the standpoint of long-term starvation. By inoculating nitrifying and denitrifying sludge under various operating circumstances, the ANAMMOX reactors were successfully started. Under various start-up procedures, the tolerance mechanism and recovery performance were examined. The outcomes demonstrated that the denitrifying sludge-inoculated reactor operated steadily with a high substrate concentration and low flow rate. After 85 days of operation, the removal efficiencies of NH 4 + -N, NO 2 - -N, and total nitrogen reached 98.7%, 99.3%, and 89.3%, respectively. After 144 days of starvation and 30 days of recovery, the better nitrogen removal performance was achieved at a low substrate concentration and high flow rate, and the removal efficiencies were 99.8% （NH 4 + -N）, 99.8% （NO 2 - -N）, and 93.6% （total nitrogen）. During the starvation, extracellular polymeric substances wrapped the ANAMMOX bacteria and kept them intact to resist long-term starvation stress. The expression of nirS , hzsA , and hdh genes ensured the synthesis of nitrite/nitric oxide oxidoreductase, hydrazine synthase, and hydrazine dehydrogenase to maintain ANAMMOX activity. There was no significant difference in the relative abundance of ANAMMOX bacteria before and after starvation recovery. Candidatus Kuenenia had better anti-hunger ability, and the relative abundance increased by more than 86% after 30 days of recovery, confirming its tolerance to long-term starvation.

To evaluate the effect of thermal hydrolysis pretreatment time on the sludge anaerobic digestion system of wastewater treatment plants (WWTPs) in Daxing district, Beijing, the structure and diversity of microbial communities in primary sludge and an activated sludge anaerobic digestion system with different thermal hydrolysis pretreatment times (15 min, 30 min, and 45 min) were analyzed using Illumina MiSeq high-throughput sequencing. The results showed that the dominant groups of digested sludge were mainly distributed in Firmicutes, Cloacimonadota, Chloroflexi, and Synergistota, with W5 being the most common genus. The sum of relative abundance of the dominant phylum was greater than 60%, and W5 accounted for 20.8%-54.5%, showing a high abundance of a few dominant species. During the anaerobic digestion of thermo-hydrolyzed sludge, the relative abundance of acetogenic methanogens decreased due to high levels of volatile fatty acids (VFAs) and ammonia nitrogen (NH 4 + -N) concentrations, which suggested that the hydrogenophilic methanogenic pathway was more than that of the acetogenic methanogenic pathway. Correlation analysis showed that the soluble protein and pH of thermo-hydrolyzed sludge, NH 4 + -N of digested sludge, and thermal hydrolysis pretreatment time were the four main environmental factors affecting microbial community structure, and NH 4 + -N of digested sludge had the largest negative correlation with methanogens. The thermal hydrolysis pretreatment time was negatively correlated with both the Chao index and Shannon index, so longer thermal hydrolysis pretreatment time was not conducive to microbial flora during anaerobic digestion.

Objective: To explore the effect of intestinal nitrates on the growth of Klebsiella pneumoniae and its regulatory mechanisms., Methods: K. pneumoniae strains with nitrate reductase narG and narZ single or double gene knockout or with NarXL gene knockout were constructed and observed for both aerobic and anaerobic growth in the presence of KNO 3 using an automated bacterial growth analyzer and a spectrophotometer, respectively. The mRNA expressions of narG and narZ in K. pneumoniae in anaerobic cultures in the presence of KNO 3 and the effect of the binary regulatory system NarXL on their expresisons were detected using qRT-PCR. Electrophoretic mobility shift assays (EMSA) and MST analysis were performed to explore the specific regulatory mechanisms of NarXL in sensing and utilizing nitrates. Competitive experiments were conducted to examine anaerobic growth advantages of narG and narZ gene knockout strains of K. pneumoniae in the presence of KNO 3 ., Results: The presence of KNO 3 in anaerobic conditions, but not in aerobic conditions, promoted bacterial growth more effectively in the wild-type K. pneumoniae strain than in the narXL gene knockout strain. In anaerobic conditions, the narXL gene knockout strain showed significantly lowered mRNA expressions of narG and narZ ( P < 0.0001). EMSA and MST experiments demonstrated that the NarXL regulator could directly bind to narG and narZ promoter regions. The wild-type K. pneumoniae strain in anaerobic cultures showed significantly increased expressions of narG and narZ mRNAs in the presence of KNO 3 ( P < 0.01), and narG gene knockout resulted in significantly attenuated anaerobic growth and competitive growth abilities of K. pneumoniae in the presence of KNO 3 ( P < 0.01)., Conclusion: The binary regulatory system NarXL of K. pneumoniae can sense changes in intestinal nitrate concentration and directly regulate the expression of nitrate reductase genes narG and narZ to promote bacterial growth.

Objective: To construct a mutant strain of Klebsiella pneumoniae NTUH- K2044 with modA gene deletion and its complementary strain and explore the role of modA gene in modulating anaerobic nitrate respiratory growth and phenotypes of K. pneumoniae ., Methods: The modA deletion mutant K. pneumoniae strain was constructed by homologous recombination using the suicide vector pKO3-Km. To obtain the complementary strain C- modA , the whole sequence fragment containing the promoter, open reading frame and terminator regions of modA was cloned into pGEM-T-easy and electrically transformed into the modA deletion mutant. The NTUH-K2044 wild-type strain, modA gene deletion mutant and complementary strain were compared by measuring in vitro anaerobic nitrate respiration growth, competitiveness index, biofilm quantification, mucoviscosity assay and morphological measurement using Image J., Results: The modA deletion mutant strain Δ modA and the complementary strain C- modA were successfully constructed. The modA gene knockout strain showed inhibited anaerobic nitrate respiratory growth compared with the wild- type and C- modA strains with significantly weakened competitiveness, reduced capacity of biofilm synthesis during anaerobiosis, and lowered mucoviscosity under anaerobic conditions. The Δ modA strain showed a spherical morphology in anaerobic conditions as compared with the normal short rod-like morphology of K. pneumoniae , with also distinctly shorter length than the wild-type and C- modA strains., Conclusion: The molybdate transport system encoding gene modA is associated with the pathogenic capacity of K. pneumoniae by modulating its anaerobic nitrate respiration, competitiveness, biofilm formation, hypermucoviscous phenotype and morphology.

Tetrachloroethylene （PCE） and trichloroethylene （TCE） are typical volatile halogenated organic compounds in groundwater that pose serious threats to the ecological environment and human health. To obtain an anaerobic microbial consortium capable of efficiently dechlorinating PCE and TCE to a non-toxic end product and to explore its potential in treating contaminated groundwater， an anaerobic microbial consortium W-1 that completely dechlorinated PCE and TCE to ethylene was obtained by repeatedly feeding PCE or TCE into the contaminated groundwater collected from an industrial site. The dechlorination rates of PCE and TCE were （120.1 ±4.9） μmol·（L·d） -1 and （172.4 ±21.8） μmol·（L·d） -1 in W-1， respectively. 16S rRNA gene amplicon sequencing and quantitative PCR （qPCR） showed that the relative abundance of Dehalobacter increased from 1.9% to 57.1%， with the gene copy number increasing by 1.7×10 7 copies per 1 μmol Cl - released when 98.3 μmol of PCE was dechlorinated to cis -1，2-dichloroethylene （ cis -1，2-DCE）. The relative abundance of Dehalococcoides increased from 1.1% to 53.8% when cis -1，2-DCE was reductively dechlorinated to ethylene. The growth yield of Dehalococcoides gene copy number increased by 1.7×10 8 copies per 1 μmol Cl - released for the complete reductive dechlorination of PCE to ethylene. The results indicated that Dehalobacter and Dehalococcoides cooperated to completely detoxify PCE. When TCE was used as the only electron acceptor， the relative abundance of Dehalococcoides increased from （29.1 ±2.4）% to （7.7 ±0.2）%， and gene copy number increased by （1.9 ±0.4）×10 8 copies per 1 μmol Cl - released， after dechlorinating 222.8 μmol of TCE to ethylene. The 16S rRNA gene sequence of Dehalococcoides LWT1， the main functional dehalogenating bacterium in enrichment culture W-1， was obtained using PCR and Sanger sequencing， and it showed 100% similarity with the 16S rRNA gene sequence of D. mccartyi strain 195. The anaerobic microbial consortium W-1 was also bioaugmented into the groundwater contaminated by TCE at a concentration of 418.7 μmol·L -1 . The results showed that （69.2 ±9.8）% of TCE could be completely detoxified to ethylene within 28 days with a dechlorination rate of （10.3 ±1.5） μmol·（L·d） -1 . This study can provide the microbial resource and theoretical guidance for the anaerobic microbial remediation in PCE or TCE-contaminated groundwater.

In order to investigate the enzyme production mechanism of yak rumen-derived anaerobic fungus Orpinomyces sp. YF3 under the induction of different carbon sources, anaerobic culture tubes were used for in vitro fermentation. 8 g/L of glucose (Glu), filter paper (Flp) and avicel (Avi) were respectively added to 10 mL of basic culture medium as the sole carbon source. The activity of fiber-degrading enzyme and the concentration of volatile fatty acid in the fermentation liquid were detected, and the enzyme producing mechanism of Orpinomyces sp. YF3 was explored by transcriptomics. It was found that, in glucose-induced fermentation solution, the activities of carboxymethyl cellulase, microcrystalline cellulase, filter paper enzyme, xylanase and the proportion of acetate were significantly increased ( P < 0.05), the proportion of propionate, butyrate, isobutyrate were significantly decreased ( P < 0.05). The results of transcriptome analysis showed that there were 5 949 differentially expressed genes (DEGs) between the Glu group and the Flp group, 10 970 DEGs between the Glu group and the Avi group, and 6 057 DEGs between the Flp group and the Avi group. It was found that the DEGs associated with fiber degrading enzymes were significantly up-regulated in the Glu group. Gene ontology (GO) function enrichment analysis identified that DEGs were mainly associated with the xylan catabolic process, hemicellulose metabolic process, β-glucan metabolic process, cellulase activity, endo-1,4-β-xylanase activity, cell wall polysaccharide metabolic process, carbohydrate catabolic process, glucan catabolic process and carbohydrate metabolic process. Moreover, the differentially expressed pathways associated with fiber degrading enzymes enriched by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were mainly starch and sucrose metabolic pathways and other glycan degradation pathways. In conclusion, Orpinomyces sp. YF3 with glucose as carbon source substrate significantly increased the activity of cellulose degrading enzyme and the proportion of acetate, decreased the proportion of propionate, butyrate and isobutyrate. Furthermore, the degradation ability and energy utilization efficiency of fungus in the presence of glucose were improved by means of regulating the expression of cellulose degrading enzyme gene and participating in starch and sucrose metabolism pathway, and other glycan degradation pathways, which provides a theoretical basis for the application of Orpinomyces sp. YF3 in practical production and facilitates the application of Orpinomyces sp. YF3 in the future.

Anaerobic granular sludge (AnGS), a self-immobilized aggregate containing various functional microorganisms, is considered as a promising green process for wastewater treatment. AnGS has the advantages of high volume loading rate, simple process and low excess sludge generation, thus shows great technological and economical potentials. This review systematically summarizes the recent advances of the microbial community structure and function of anaerobic granular sludge, and discusses the factors affecting the formation and stability of anaerobic granular sludge from the perspective of microbiology. Moreover, future research directions of AnGS are prospected. This review is expected to facilitate the research and engineering application of AnGS.

In field conditions, a micro-aerobic layer with 1 cm thickness exists on the surface layer of paddy soil owing to the diffusion of dissolved oxygen via flooding water. However, the particularity of carbon and nitrogen transformation in this specific soil layer is not clear. A typical subtropical paddy soil was collected and incubated with 13 C-labelled rice straw for 100 days. The responses of exogenous fresh organic carbon( 13 C-rice straw) and original soil organic carbon mineralization to nitrogen fertilizer addition[(NH 4 ) 2 SO 4 ]in the micro-aerobic layer(0-1 cm) and anaerobic layer(1-5 cm) of paddy soil and their microbial processes were analyzed based on the analysis of 13 C incorporation into phospholipid fatty acid( 13 C-PLFAs). Nitrogen addition promoted the total CO 2 and 13 C-CO 2 emission from paddy soil by 11.4% and 12.3%, respectively. At the end of incubation, with the addition of nitrogen, the total soil organic carbon (SOC) and 13 C-recovery rate from rice straw in the anaerobic layer were 2.4% and 9.2% lower than those in the corresponding micro-aerobic layer, respectively. At the early stage(5 days), nitrogen addition increased the total microbial PLFAs in the anaerobic layer with a consistent response of bacterial and fungal PLFAs. However, there was no significant effect from nitrogen on microbial abundance in the micro-aerobic layer. Nitrogen addition had no significant impact on the abundance of total 13 C-PLFAs in the micro-aerobic and anaerobic layers, but the abundance of 13 C-PLFAs for bacteria and fungi in the micro-aerobic layer was decreased dramatically. At the late stage(100 days), the effect of nitrogen addition on microbial PLFAs was consistent with that at the early stage. The abundances of total, bacterial, and fungal 13 C-PLFAs were remarkably increased in the anaerobic layer. However, the abundance of 13 C-PLFAs in the micro-aerobic layer showed no significant response to nitrogen addition. During the incubation, the content of NH 4 + -N in the anaerobic soil layer was higher than that in the micro-aerobic soil layer. This indicates that nitrogen addition increased microbial activity in the anaerobic soil layer caused by the higher NH 4 + -N concentration, as majority of microorganisms preferred to use NH 4 + -N. Consequently, the microbial utilization and decomposition of organic carbon in the anaerobic soil layer were accelerated. By contrast, richer available N existed in the form of NO 3 - -N in the micro-aerobic soil layer owing to the ammoxidation process. Thus, the shortage of NO 3 - -N preference microorganisms in the paddy soil environment prohibited the microbial metabolism of organic carbon in the micro-aerobic layer. As a whole, nitrogen fertilization enhanced organic carbon loss via microbial mineralization in paddy soil with a weaker effect in the micro-aerobic layer than that in the anaerobic layer, indicating the limited microbial metabolic activity in the surface micro-aerobic layer could protect the organic carbon stabilization in paddy soil. This study emphasizes the heterogeneity of paddy soil and its significant particularity of carbon and nitrogen transformation in micro-aerobic layers. Consequently, this study has implications for optimizing the forms and method for the application of nitrogen fertilizer in paddy cropping systems.

Anaerobic digestion is another important anaerobic catabolism pathway besides lactic acid and ethanol fermentation, which is of great significance for recycling resources, maintaining the ecological balance, optimizing the energy structure, alleviating the energy crisis, and promoting the implementation of the "Carbon Peaking and Carbon Neutrality" strategy. However, such an important metabolic process has not been involved in the current textbooks and teaching of biochemistry courses, making the teaching system incomplete. The anaerobic digestion process involves many reactions and complex metabolic pathways. In order to improve the students' understanding to this process, we created a full chart of the whole anaerobic digestion process based on systemic literature review and integrated it into the classroom teaching through the BOPPPS teaching mode. It was found that the classroom teaching assisted by this metabolic chart could help students establish the structural framework of the anaerobic digestion process and enrich the knowledge system of metabolism, achieving a good teaching effect. This paper introduces the content of the metabolic pathways of anaerobic digestion and the design of the teaching process, which would facilitate the teaching reforms and perfection of textbooks for related courses, such as Biochemistry, Environmental Engineering Microbiology and New Energy Engineering.

Organic pollutant 2,4,6-trichlorophenol (2,4,6-TCP) is commonly found in anaerobic environments such as sediments and groundwater aquifers. To investigate the ability of the anaerobic consortium XH-1 to degrade 2,4,6-TCP, we established anaerobic incubations using 2,4,6-TCP as the substrate and inoculated the incubations with XH-1. Additional subcultures were established by amending with intermediate product 4-chlorophenol (4-CP) or phenol as the substrate. The transformation products of 2,4,6-TCP were analyzed and determined using high-performance liquid chromatography (HPLC). Microbial community structure and key microbial groups involved in the degradation of 2,4,6-TCP were analyzed based on 16S rRNA gene high-throughput sequencing. The results showed that the initial 122 μmol·L -1 2,4,6-TCP was completely transformed after a 80-day incubation at a rate of 0.15 μmol·d -1 . 2,4-dichlorophenol (2,4-DCP), 4-CP and phenol were identified as the intermediate products. All intermediate products generated from 2,4,6-TCP transformation were completely degraded after being incubated for 325 days. The main microbial groups responsible for the reductive dechlorination of 2,4,6-TCP might be the organohalide respiring Dehalobacter and Dehalococcoides . The subsequent reductive dechlorination of 4-CP to phenol was likely driven by Dehalococcoides . The cooperation between the organohalide respiring bacteria, Syntrophorhabdus and methanogens ( e.g. Methanosaeta and Methanofolis ) was responsible for the complete degradation of 2,4,6-TCP.

Traditionally, amino acids are produced mainly by chemical synthesis or aerobic fermentation. Compared to chemical synthesis, production of amino acids by microbial fermentation directly uses renewable resources as feedstock and this reduces the dependence on petroleum-based compounds and decreases pollutants generation and toxic substrates usage. Fermentation under aerobic conditions has been used widely for its fast growth and high titers. However, a large amount of carbon is used for cell growth and this results in high biomass but low yield of target chemicals. Unlike the long history of aerobic fermentation, the commercial production of amino acids by anaerobic fermentation is realized only in recent years. It has several advantages such as simpler operation, no need for oxygen supply, and high yield close to the theoretical maximum value. L-alanine is the first amino acid commercially produced by anaerobic fermentation. In this article, we summarize the key technology for anaerobic fermentative production of L-alanine and its commercialization. As it is shown to be low-cost, high-efficiency, and environmental-friendly, anaerobic fermentation is expected to be widely used in industrial process and brings greater economic values and social benefits in the future.

Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO 2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO 2 control platform with open top chambers and the 13 CH 4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens ( M. nitroreducens )-like archaea to the gradual increase of CO 2 concentration were investigated in paddy fields. We set up two CO 2 concentration treatments, including an ambient CO 2 and a gradual increase of CO 2 (increase of 40 μL·L -1 per year above ambient CO 2 concentration until 160 μL·L -1 ). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO 2 ·g -1 ·d -1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens -like archaeal mcrA genes of 2.2×10 6 -8.5×10 6 copies·g -1 . Compared to the ambient CO 2 treatment, the slow elevated CO 2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens -like archaea, particularly in 5-10 cm soil layer. The gradual increased CO 2 concentration treatment did not change the community composition of M. nitroreducens -like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO 2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.

The effects of two typical heavy metal ions[Cu(Ⅱ) and Ni(Ⅱ)] and humic acid on ANAMMOX nitrogen removal (SAA) were studied through batch experiments, and the kinetic model was analyzed. At the same time, the effects of humic acid-heavy metal on ANAMMOX nitrogen removal were discussed. The results showed that ANAMMOX was promoted when ρ [Cu(Ⅱ)] and ρ [Ni(Ⅱ)] were 3 mg·L -1 , and SAA was increased by 8.64% and 7.78%, respectively; ANAMMOX was inhibited when the ρ [Cu(Ⅱ)] and ρ [Ni(Ⅱ)] were 20 mg·L -1 and 5 mg·L -1 , respectively, and the inhibition effect was more significant with the increase in heavy metal ion concentration. The index fitting showed that the IC50 of Cu(Ⅱ) and Ni(Ⅱ) on ANAMMOX were 29.67 mg·L -1 and 28.75 mg·L -1 , respectively. SAA was increased by 7.37% when the ρ (humic acid) was 1 mg·L -1 , and the inhibition rate reached 36.80% when the humic acid concentration was 40 mg·L -1 . The linear fitting showed that the IC50 of humic acid on ANAMMOX was 58.36 mg·L -1 . The modified Michaelis-Menten model could better describe the inhibitory kinetic behavior of heavy metals and humic acid on ANAMMOX. The model fitting showed that the complete inhibition concentrations ( I * ) of Cu(Ⅱ), Ni(Ⅱ), and humic acid on ANAMMOX were 49.59, 74.46, and 84.27 mg·L -1 , respectively. An appropriate amount of humic acid was beneficial to improve the inhibition of heavy metals on ANAMMOX bacteria activity, and excessive humic acid would cause inhibition on ANAMMOX bacteria again.

The current study summarized the clinical characteristics of 8 patients with central nervous system anaerobic infections who visited the Second Hospital of Hebei Medical University from June 2019 to June 2021. Among the 8 patients, 7 cases had headache and fever as the first symptoms, and 1 case had left-sided limb weakness as the first symptom. Four patients had a previous history of diabetes (1 patient had a history of tooth extraction before the onset of the disease), 1 patient had a previous history of sinusitis, 1 patient had a history of tooth extraction before the onset of the disease, and 2 patients had chronic extensive periodontitis or periapical periodontitis. Five cases showed abnormal intracranial and/or meningeal enhancement on cranial magnetic resonance imaging (MRI), and 1 case showed swelling of the whole brain tissue on cranial computed tomography (CT). After treatment, symptoms of 4 cases were improved, symptoms of 1 case were aggravated, and 3 cases died. Anaerobic infections can occur in various parts of the body:the central nervous system, oral cavity, head and neck, chest, abdomen, pelvis, skin and soft tissues. It is generally believed that anaerobic bacteria rarely cause central nervous system infection, therefore, anaerobic culture of cerebrospinal fluid is usually not performed. Moreover, anaerobic culture is affected by many factors, and thus it is difficult to obtain positive results. Metagenomic next-generation sequencing can identify multiple pathogens (viral, bacterial, fungal, or parasitic) from samples based on DNA and/or RNA sequences and has advantages in diagnosing anaerobic infections of the central nervous system. Prompt empirical antimicrobial therapy is essential for the prognosis of the patients.

In this study, voltage was used as a disturbance factor to investigate the relationship between microbial community and methane (CH 4 ) production flux in a microbial electrolytic cell coupled anaerobic digestion (MEC-AD). Metabolic flux analysis (MFA) was used to explore the relationship between the CH 4 metabolic flux produced and the microbes. The results showed that both methane production flux and hydrogen production flux changed significantly upon voltage disturbance, while the voltage disturbance had little effect on acetic acid production flux. The maximum CH 4 production flux under 0.6 V disturbance was 0.522±0.051, which increased by 77% and 32%, respectively, compared with that of the control group under 1.0 V (0.295±0.013) and under 1.4 V (0.395±0.029). In addition, an average of 15.7%±2.9% of H 2 (flux) was used to reduce CO 2 to produce CH 4 and acetic acid, and an average of 27.7%±6.9% of acetic acid (flux) was converted to CH 4 . Moreover, the abundance of Lachnospiraceae significantly affected the flux of acetic acid. The flux of CH 4 production is positively correlated with the abundances of Petrimonas , Syntrophomonas , Blvii 28, and Acinetobacter , and negatively correlated with the abundances of Tuzzerella and Sphaerochaeta . The species that affected the flux of H 2 and CH 4 were similar, mostly belonging to Bacteroides , Clostridium , Pseudomonas and Firmicutes . Furthermore, the interspecies interaction is also an important factor affecting the MEC-AD methanogenesis flux.

Anaerobic ammonia oxidation (ANAMMOX) process is an efficient and low-cost biological nitrogen removal process. However, it still faces some challenges in mainstream applications due to the limitation of substrate types and nitrate accumulation. In recent years, the combined process of anammox has been widely studied to solve the above problems. In this paper, the combined processes of anammox developed in recent years are reviewed, and discussed from the process principle, advantages and disadvantages, influencing factors, process extensibility and the key bottlenecks existing in the promotion and application, as well as the relevant work of the subject group. Finally, we take an outlook on the development of the combined anaerobic ammonia oxidation process in municipal domestic wastewater treatment.

The feasibility for nitrogen removal in a two-stage ANAMMOX biofilm reactor promoted by Fe 2+ under low nitrogen concentration was investigated. The results showed that the ANAMMOX reaction could be effectively promoted by a ρ (Fe 2+ ) of 5, 10, and 15 mg·L -1 . A ρ (Fe 2+ ) of 10 mg·L -1 presented the highest promotion for the ANAMMOX reaction, with the highest nitrogen removal efficiency (NRE) of 81.71% under a ρ (TN) of 150 mg·L -1 and a nitrogen loading rate (NLR) of 0.62 kg·(m 3 ·d) -1 . Fe 2+ promoted the secretion of extracellular polymeric substance (EPS) and the synthesis of heme c in the ANAMMOX system. Batch test results further verified the positive effects by Fe 2+ on the activity of anaerobic ammonium oxidizing bacteria (AnAOB). The specific ANAMMOX activity (SAA) of 10 mg·L -1 ρ (Fe 2+ ) was 3.6 times as high as that of the control group[ ρ (Fe 2+ )=0 mg·L -1 ], whereas the activity of AnAOB was significantly inhibited with ρ (Fe 2+ ) increased to 20 mg·L -1 . High-throughput sequencing results showed that the addition of Fe 2+ increased the abundance of Candidatus&#95;Kuenenia . When ρ (Fe 2+ ) was 10 mg·L -1 , the relative abundance of Candidatus&#95;Kuenenia in reactor 1 and reactor 2 increased to 16.18% and 4.22%, respectively. The stable operation of the two-stage ANAMMOX biofilm process promoted by Fe 2+ provides an alternative technology for low-strength nitrogen wastewater.

Cytochrome c is a type of heme proteins that are widely distributed in living organisms. It consists of heme and apocytochrome c, and has potential applications in bioelectronics, biomedicine and pollutant degradation. However, heterologous overexpression of cytochrome c is still challenging. To date, expression of the cytochrome c from uncultured anaerobic methanotrophic archaea has not been reported, and nothing is known about the function of this cytochrome c. A his tagged cytochrome c was successfully expressed in E. coli by introducing a thrombin at the N-terminus of CytC4 and co-expressing CcmABCDEFGH, which is responsible for the maturation of cytochrome c. Shewanella oneidensis , which naturally has enzymes for cytochrome c maturation, was then used as a host to further increase the expression of CytC4. Indeed, a significantly higher expression of CytC4 was achieved in S. oneidensis when compared with in E. coli . The successful heterologous overexpression of CytC4 will facilitate the exploitation of its physiological functions and biotechnological applications.

In order to realize the rapid recovery of ANAMMOX sludge bacterial activity after long-term room temperature storage, three groups of reactors were added to ANAMMOX sludge that had been stored without substrate at room temperature (15-30℃) for 9 months. Among the three groups of reactors, comet fiber carrier and K3 carrier were added to R2 and R3 reactors, respectively, as biological carriers. The effects of different carriers on the recovery rate of ANAMMOX sludge bacterial activity were investigated. The results showed that ANAMMOX reactions in the R2 and R3 reactors began taking place on the 8th and 10th day, respectively, with respective TIN removal rates of 82.25% and 80.92%, which were significantly improved compared with that in the R1 reactor, in which no carrier was added (ANAMMOX reaction started occurring on the 15th day with a TIN removal rate of 80.26%). After 42 days with influent, ρ (NH 4 + -N) and ρ (NO 2 - -N) respectively increased to 300 mg·L -1 and 396 mg·L -1 , and the TIN removal rates of the three groups of reactors were respectively 78.96%, 84.92%, and 84.66%. Microbial community structure analysis showed that the relative abundances of ANAMMOX bacteria in the R2 and R3 reactor were respectively 6.85% and 6.06%, two to four times that in the R1 reactor. The predominant ANAMMOX bacteria in the sludge was Candidatus Jettenia , whose relative abundances in the three groups of reactors were respectively 1.62%, 5.74%, and 5.21%. The results show that ANAMMOX biofilm-granular sludge complex systems constructed by adding carriers can considerably shorten the time for recovering ANAMMOX sludge bacterial activity after long-term room temperature storage without substrate. The carriers effectively promoted the relative abundances of ANAMMOX bacteria in the reactors, whereas the promoting effect of comet fiber carrier was slightly more significant than that of the K3 carrier.

For the ambient and low-temperature operation of the anaerobic ammonium oxidation (ANAMMOX) process, sequence batch biofilm reactors (SBBR) with non-woven fabric and modified polyurethane foam as carriers, respectively, were used to treat nitrogenous wastewater. Nitrogen removal performances of both reactors were investigated while the temperature decreased from 35℃ to 15℃. When the nitrogen loading rate (NLR) was 110 mg·(L·d) -1 , the average total nitrogen (TN) removal rate of the non-woven fabric reactor increased from 71.16% (35℃) to 76.19% (30℃) and then decreased to 61.11% (15℃). The average TN removal rate of the modified polyurethane foam reactor increased from 78.71% (35℃) to 81.75% (20℃) and then decreased to 75.68% (15℃). Compared with the non-woven fabric, the modified polyurethane foam provided a more stable nitrogen removal performance and could be used as the preferred carrier. High-throughput sequencing of the modified polyurethane foam biofilm indicated that Candidatus Kuenenia was the dominant ANAMMOX genus, with relative abundances of 8% (35℃), 5% (25℃), and 16% (15℃). Candidatus Kuenenia still grew and enriched at low temperatures. The decrease in temperature significantly affected the biofilm microbial community structure.

Paddy fields are one of the most important methane sources, which have great impacts on climate change. The nitrite-dependent anaerobic methane oxidation, by NC10 phylum bacteria- Candidatus Methylomirabilis oxyfera ( M. oxyfera )-like bacteria, is a new process regulating methane emission from paddy fields. However, little is known about the spatial and temporal variations of M. oxyfera -like bacterial communities and the regulating factors in paddy soils. We investigated the community composition, diversity, and abundance of M. oxyfera -like bacteria in 0-40 cm depth of paddy soils at key growth stages of rice, including tillering, jointing, flowering, and milky stages. Results of high-throughput sequencing showed that community composition of M. oxyfera -like bacteria differed significantly among different soil layers, while no significant variation was observed among different rice growth stages. The diversity of M. oxyfera -like bacteria increased with soil depth. Real-time quantitative PCR showed that the 16S rRNA gene abundance of M. oxyfera -like bacteria ranged from 5.73×10 6 to 2.56×10 7 copies·g -1 (dry weight), with the highest gene abundance in the 10-20 cm layer. Further, the abundance of these bacteria showed a decreasing trend with rice growth. Soil organic carbon content and soil pH were correlated with the M. oxyfera -like bacterial community structures and abundance. In all, our results suggested a certain degree of heterogeneity of spatial and temporal distribution of M. oxyfera -like bacterial communities in paddy soils, which was largely influenced by soil organic carbon and soil pH.

The facultative anaerobic and strict anaerobic microorganisms enriched and acclimated during the anaerobic digestion process are crucial for the efficiency of the anaerobic digestion system. Most of the problems encountered during running anaerobic digestion processes could be effectively improved via stimulation of microbial metabolic activity. Benefited from the rapid development of microbiome techniques, deeper insights into the microbial diversity in anaerobic digestion systems, e.g. the microbe-microbe interactions and microbe-environment interactions, have been gained. A complex and intricate metabolic network exists in the anaerobic digestion system of solid organic wastes. However, little is known about these interactions and the underlying mechanisms. This review briefly summarized the representative interactions between microbial communities during anaerobic digestion process discovered to date. In addition, typical issues encountered during the anaerobic digestion of solid organic wastes and how microbes can tackle and alleviate these issues were discussed. Finally, future priorities on microbiome research were proposed based on present contribution of microbiome analysis in anaerobic digestion system.

The genus Dehalogenimonas (Dhgm) is a recently discovered taxonomic group within the class Dehalococcoidia of the phylum Chloroflexi. To date, Dhgm consists of three formally described species including Dehalogenimonas lykanthroporepellens, Dehalogenimonas alkenigignens and Dehalogenimonas formicexedens. All isolates of these three Dhgm species are obligate organohalide-respiring bacteria. They use hydrogen and formate as electron donors and chlorinated ethanes (e.g., 1,2,3-trichloropropane, 1,2-dichloropropane, 1,2-dichloroethane) as electron acceptors in energy-conserving reductive dechlorination reaction. Chlorinated ethanes are common groundwater contaminants in China. The unique metabolic capacities of Dhgm strains implicate it may play important roles in site remediation. The recently reported Dhgm sp. strain WBC-2 and 'Candidatus Dehalogenimonas etheniformans' strain GP are capable of dechlorinating certain chlorinated ethenes. More importantly, strain GP can completely detoxify the carcinogenic vinyl chloride (VC) to ethene. These findings expand the diversity of microorganisms involved in the respiratory VC reductive dechlorination and improve the understanding of Dhgm's ecological functions. Here, we summarize the advances in physiological and biochemical characteristics, ecological functions and genomic features of Dhgm, with the aim to develop effective and sustainable strategies to facilitate the bioremediation of chlorinated compounds contaminated sites.

We cultivated simultaneous partial nitrification, anaerobic ammonium oxidizing(ANAMMOX), and denitratation granular sludge in a novel air-lift internal circulation reactor using low C/N wastewater as the substrate and ANAMMOX sludge matched with ordinary activated sludge as the inoculum. The results showed that the mature and stable granular sludge could be cultivated after 225 d of continuous operation, and the total nitrogen removal rate was as high as 91.4%. Compared with flocculated sludge, the ANAMMOX activity in the granular sludge increased significantly, and the ANAMMOX activity was highest among the four nitrogen removal processes followed by partial nitrification, and the specific denitratation activity was 2.1-times higher than the specific nitrite reduction activity. High-throughput sequencing results showed that the dominant bacteria in partial nitrification and ANAMMOX were Nitrosomonas and Candidatus&#95;Brocadia , respectively, compared to flocculated sludge, with abundances increasing to 0.70% and 0.57%, respectively. Thauera may also be the potential dominant bacteria for denitratation, with an abundance of up to 0.26%. RT-qPCR analysis showed that compared to the inoculation stage, the transcript levels of the amoA and hao genes for partial nitrification increased 3.5-and 1.5-fold, respectively, and the transcript levels of the hzsA gene for ANAMMOX increased 2.1-fold. During denitrataion, the overall abundance of napA and narG transcript levels was 4.8-times higher than that of nirK and nirS . The results of this study provide new insights for the treatment of low C/N wastewater.

A sequencing batch reactor-anaerobic sequencing batch reactor(SBR-ASBR) process was used to treat domestic sewage. In the SBR, the effects of the anoxic/aerobic time ratio and temperature on the realization of partial nitritation(PN) were investigated. In the ASBR, the effects of different COD/NO 2 - -N(C/N) ratios on the removal of nitrogen and carbon using anaerobic ammonia oxidation(ANAMMOX) and denitrification were studied. The results illustrated that:① After three single cycles and on the 22 nd day, the NO 2 - -N accumulation rate(NiAR) was 98.06%, and the nitrate nitrogen generation rate(SNiPR, calculated as N/VSS) was 0.28g·(g·d) -1 , and simultaneous nitrification and denitrification removal the TN and COD were 12.29 and 110.36mg·L -1 , respectively(temperature=25℃, anoxic/aerobic time ratio=30 min:30 min). ② At an anoxic/aerobic time ratio of 30 min:30 min, the filamentous sludge bulked, the sludge activity decreased, and sludge settleability was poor at 15℃. Furthermore, the conversion rate of NH 4 + -N to NO 2 - -N was 86.83%, indicating that the effluent NH 4 + -N concentration was too low to provide suitable matrix concentrations for ANAMMOX at 30℃. The effluent concentrations of NH 4 + -N and NO 2 - -N were 31.58 mg·L -1 and 35.04mg·L -1 , respectively, matching the ratio of the ANAMMOX substrate at 25℃. ③ The SBR-ASBR combined process showed good denitrification performance; the effluent TN, NH 4 + -N, and COD concentrations were stable at 13.13, 4.83, and 69.96mg·L -1 , respectively, and the removal rates were 83.10%, 93.64%, and 75.11%, respectively. When the influent C/N of the ASBR was 2.5, 2.0, and 1.5, respectively, anaerobic ammonia oxidation and denitrification showed the best performance with respect to nitrogen and carbon removal with a C/N of 2.0. The effluent NH 4 + -N, NO 2 - -N, NO 3 - -N, and COD were 0.09, 0.25, 1.04, and 32.73 mg·L -1 , respectively.

Actual domestic sewage has a complex composition and relatively low carbon and nitrogen content. Anaerobic plug-flow influent can enhance the utilization of COD by aerobic granular sludge by providing a locally high concentration of substrate. In this study, intermittent aeration was used to cultivate aerobic granular sludge in a sequencing batch reactor (SBR), and actual domestic sewage was used as the feed water to inoculate the sewage plant sludge. In the R1 experiment, rapid anaerobic feeding was adopted, while in R2, anaerobic plug-flow feeding was adopted, to explore the impact of different feeding modes on the aerobic granular sludge system of domestic sewage. Under rapid anaerobic feeding in R1, the particle structure appeared earlier, but particle breakage occurred after 71 days of operation; the particle structure generated in R2 was denser than that of R1, the particle surfaces were smoother, and the denitrifying phosphorous accumulating organisms (DPAO) had a more enriching effect. In the final R1 and R2 reactors, the proportion of DPAO to phosphorous accumulating organisms (PAO) was 14.17% and 22.07%, respectively. The results show that the anaerobic plug-flow feeding mode can enhance the use of influent COD by granular sludge, which is conducive to enriching DPAO, generating denser and more stable particles, realizing "one carbon dual purpose" operation, and removing more nitrogen and phosphorus.

In order to understand the characteristics and interactions of the microbial community during the anaerobic ferric ammonium oxidation (FEAMMOX) process, this study investigated the effects of various forms of chelated iron on nitrogen removal efficiency and microbial community structure. After 77 days of reactor operation, the removal efficiency of total nitrogen was 83.32% for the ferric humate group, 43.67% for the ferric citrate group, 55.07% for the ferric sodium ethylene diamine tetraacetate group, and 12.65% for the ferric ammonium triacetate group. After the experiment, the abundance of denitrifying bacteria Comamonadaceae in ferric humate group was 17.57%, the abundance of Clostridium in ferric citrate group was 47.70%; and the abundance of denitrifying bacteria Thermomonas in the ferric sodium ethylene diamine tetraacetate group was 20.11%. This indicates that ferric humate is a more effective electron acceptor for the FEAMMOX process. The result of function prediction shows that the iron, sulfur, and nitrogen cycles are all closely related, with iron and sulfur metabolism playing an important role in nitrogen removal. In the humate group, iron respiration and the nitrogen cycle are more strongly correlated than other groups. Co-occurrence network analysis showed that the keystone species in the FEAMMOX process is Tessaracoccus .

Bacterial communities are vital for efficient nitrogen removal in an anaerobic ammonium oxidation (ANAMMOX) system. However, the diversity and functional characteristics of a bacterial community during the start-up of ANAMMOX has not been reported. In this study, an up-flow anaerobic sludge bed reactor was used to start-up the ANAMMOX system, and 16S rRNA high-throughput gene sequencing, combined with PICRUSt2-based functional prediction analysis, was used to investigate the dynamic changes in diversity and function of the bacterial community at different times (d0, d30, d60, and d90) during the start-up. The results showed that 48 phyla, 111 classes, 269 orders, 457 families, 840 genera, and 1497 species were present during the start-up of ANAMMOX. Candidatus Brocadia and Candidatus&#95;Kuenen ia were the main detected ANAMMOX bacteria, and their relative abundance was significantly different at different times during the start-up of ANAMMOX ( P <0.05). During the start-up, the alpha diversity indices of the bacterial community were significantly decreased ( P <0.05), and the structure of the bacterial community exhibited significant spatial differentiation ( R =0.846, P <0.01). Functional prediction analysis with PICRUSt2 revealed that the bacterial community was active in organic systems and metabolism at hierarchy level 1, implying abundant functional diversity. Further, the abundance of functional genes was significantly different at hierarchy level 2, during the start-up of ANAMMOX. Forty-nine functional genes involving metabolic nitrogen were detected. The abundance of functional genes, involved in nitrification, denitrification, ANAMMOX, and nitrate and nitrite assimilatory/dissimilatory reduction, changed significantly during the start-up of ANAMMOX.

In this study, a SBR reactor was selected to explore the effect of nitrogen and phosphorus removal by aerobic granular sludge under different initial anaerobic time using intermittent gradient aeration (decreasing dissolved oxygen concentration in each aeration section) and actual domestic wastewater with low C/N ratio as the influent matrix. The results showed that the initial anaerobic stage of intermittent gradient aeration increased from 50 min to 90 min, which increased the carbon source reserves in granular sludge. This improved delayed anaerobic condition led to the improvement of nitrogen and phosphorus removal efficiency of granular sludge. When delayed to 70 and 90 min, the removal efficiency of COD, TN, and TP reached 84.74%, 70.05%, and 89.7% and 86.65%, 78.81%, and 85.5%, respectively. However, after the first anaerobic phase time was increased to 110 min, the sludge loss was more severe owing to the disintegration of some cells, leading to a decrease in internal carbon source reserves by about 13.6%. Owing to this, the pollutant removal efficiency decreased. In the process of prolonging the first anaerobic phase time from 50 min to 90 min, the content of PS in LB-EPS changed minimally; when it was delayed to 110 min, the content of PS increased to about 7.18 mg·g -1 , and the PN content increased to about 5.56 mg·g -1 . The contents of PN and PS in TB-EPS were stable, which indicated that the effect of internal carbon storage on LB-EPS was greater than that of TB-EPS, and the decrease in sludge settling performance was closely related to the increase in PS content in LB-EPS. The proportion of DPAOs in granular sludge increased as the first anaerobic phase time increased, and the proportion of DPAOs reached 51.5% when the first anaerobic phase time was 70 min.

To investigate the effects of temperature and stirring on antibiotic resistance genes (ARGs) and microbial communities during the anaerobic digestion of dairy manure, mesophilic and thermophilic anaerobic digestion experiments were performed with and without stirring. Two-way analysis of variance indicated that temperature affected biogas production more strongly than stirring ( η 2 =0.934>0.911), and thermophilic and stirring increased the total biogas yield by 13.93% and 12.63%, respectively. The effect of temperature on the removal of ARGs was also stronger than that of stirring ( η 2 =0.992>0.920), where thermophilic conditions enhanced the reduction of ARGs and MGEs to 0.09-1.53 (logarithm), while stirring had no significant effects. When temperature was altered from mesophilic to thermophilic, the microbial communities shifted, with Firmicutes becoming the dominant phylum after thermophilic anaerobic digestion, with a relative abundance of >86%. Network analysis demonstrated that eight genera including Sedimentibacter , Sphaerochaeta , and Pseudomonas were the hosts of ARGs and MGEs, and the redundancy analysis suggested that physicochemical parameters play important roles in shaping microbial communities, especially TAN and TVFAs, which indirectly affected the ARGs by altering their host bacteria.

Gaseous nitrogen (N) emission [nitric oxide (NO), nitrous oxide (N 2 O), and nitrogen (N 2 )] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the 15 N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N 2 O and N 2 production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total 15 N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added 15 N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N 2 O and N 2 respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N 2 O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N 2 O production. For N 2 production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N 2 O and N 2 production. Our results demonstrated that the 15 N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.

The organic fraction of municipal solid waste (OFMSW) has become one of the sources and reservoirs of antibiotic resistance genes (ARGs). It is essential to explore the fate of ARGs during biological treatment of OFMSW. Therefore, the changes in several types of ARGs and integron genes during anaerobic digestion of the OFMSW were analyzed by quantitative PCR. Furthermore, the effects of different particle sizes of activated carbon on the behaviors of the target genes and the potential microbial mechanisms of ARGs dynamics were investigated. The results showed that the total ARGs in the initial system were reduced after anaerobic digestion with or without the presence of activated carbon. The removal rate of the absolute abundance of total ARGs was 29.95%-63.40%. In the final system of anaerobic digestion of the OFMSW, the abundance of total ARGs in powdered activated carbon (PAC) groups was significantly higher than that in the control group ( P <0.05). The supplementation of PAC inhibited the reduction of ARGs, and the supplementation of granular activated carbon had no significant effect on the change in ARGs. The potential host bacteria of ARGs were mainly Clostridia, Bacteroidia, and Synergistia during anaerobic digestion. The enrichment of host bacteria caused by PAC addition was the main reason for the increase in the target genes. Moreover, Clostridia might have been the main driving factor for the growth and decline of ARGs. These results will help us to understand the dissemination of ARGs and the impacts of activated carbon addition on ARGs during anaerobic digestion of the OFMSW.

The effects of polyether sulfone (PES) microplastics and 2,4-dichlorophenol (2,4-DCP) on the loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound EPS (TB-EPS) of anaerobic granular sludge were investigated. In addition, high-throughput sequencing technology was used to analyze the changes in the microbial community and gene functions in the anaerobic granular sludge. The results revealed that the chemical oxygen demand (COD) removal rates of the 2,4-DCP and PES+2,4-DCP experimental groups were 35% and 37%, which were 57% and 55% lower than that of the blank control group, while the COD removal rates of the PES experimental group remained around 90%. After the addition of the PES microplastics and 2,4-DCP, the protein and polysaccharide contents in the LB-EPS decreased compared with the control group, and the polysaccharide content in TB-EPS increased the least. In presence of the PES microplastics and 2,4-DCP, the activity of coenzyme F 420 was inhibited. Through high-throughput sequencing, the microbial richness and diversity of the anaerobic granular sludge in the experimental group were reduced with the addition of the PES microplastics or 2,4-DCP. In the control group and the experimental group, the dominant bacteria at the phylum level were Proteobacteria (13.45%-44.47%), Firmicutes (6.86%-21.67%), and Actinobacteria (3.16%-18.11%). The abundance of β -Proteobacteria in the PES+2,4-DCP experimental group was reduced by 15.28%, while the abundance of γ -Proteobacteria increased by 28.44% compared with the control group. Based on the phylogenetic investigation of the communities using the reconstruction of unobserved states (PICRUSt) analysis, it was found that in the experimental group with the PES microplastics or 2,4-DCP, the genes related to the sludge energy metabolism function were 0.25%-0.72% more than the control group; therefore, the abundance of genes related to the transport function group decreased significantly.

In order to clarify the characteristics of anaerobic ammonia oxidizing (ANAMMOX) sludge and the succession rule of bacteria based on particle size differentiation, the performance change and microbial community structure of ANAMMOX floc sludge during the formation of particles in the reaction system of a high ammonia-nitrogen biofilter were studied. The results indicated that the specific activity (SAA) and tolerance of the ANAMMOX granular sludge (AnGS) were significantly improved by increasing the particle size, and the SAA of R4(>4.75 mm) was up to 426.8 mg·(g·d) -1 , but it also had adverse effects on mass transfer. The results of the high-throughput sequencing showed that dynamic changes between bacterial genera were common. When the particle size was less than 4.75 mm, the increase in particle size strengthened the stability of the bacterial flora, the ammonia oxidizing bacteria (AOB) with more flocs were eliminated, and the nitrogen removal ratio gradually stabilized. R3 (2.8-4.75 mm) exhibited the most specific flora composition, and the functional bacteria Candidatus Kuenenia accounted for 52.7%, while the R4 community complexity increased. Furthermore, the proportion of functional bacteria decreased, and the abundance of heterotrophic bacteria increased, which negatively affected the particle structure. In addition, the R3 microorganism has the best gene function expression level, which is significantly better than small particles in gene replication repair and energy conversion. Finally, the evolution of AnGS was analyzed through the OTU matrix between the samples. These results have some guiding significance for the optimization of the AnGS system and will be helpful for the application of the ANAMMOX process.

Sulfate reduction with ammonium oxidation (SRAO) in laboratory ANAMMOX reactors was considered as an autotrophic process mediated by ANAMMOX bacteria (AnAOB), in which ammonium, as an electron donor, was oxidized by the electron acceptor sulfate. This process was developed based on the transformations of nitrogenous and sulfurous compounds observed in natural environments. Reported results vary widely for conversion mole ratios (ammonium/sulfate) as do intermediate and final products of the sulfate reduction. Thus, hypotheses surrounding biological conversion pathways of ammonium and sulfate in ANAMMOX consortia are implausible. In this study, continuous reactor experiments and batch tests were conducted under micro-aerobic (-100 mV < ORP < 0 mV, 0.5 mg·L -1 < DO < 1 mg·L -1 ), anoxic (-300 mV < ORP < -100 mV, 0.2 mg·L -1 < DO < 0.5 mg·L -1 ) and anaerobic (ORP < -300 mV, DO < 0.2 mg·L -1 ) conditions with different inoculated sludge (ANAMMOX sludge and mixed sludge) to verify the SRAO phenomena and identify possible pathways of substrate conversion. The key findings were that SRAO occurred only where SRB existed under anoxic condition, and was absent under anaerobic conditions with ANAMMOX consortia. The analysis of the microbial community and functional gene expression showed that ammonium oxidation by AAOB coupled with sequential ANAMMOX is possibly responsible for the loss of ammonium under anoxic condition. Organic substances released through microbial decay contributed to heterotrophic sulfate conversion by SRB. AnAOB do not possess the ability to oxidize ammonium with sulfate as the electron acceptor. SRAO could, in fact, involve a combination of aerobic ammonium oxidation, ANAMMOX, and heterotrophic sulfate reduction processes, which are mediated via AOB, AnAOB, and SRB.

Resource utilization is an effective way to cope with the rapid increase of kitchen waste and excess sludge, and volatile fatty acids produced by anaerobic fermentation is an important way of recycling organic waste. However, the single substrate limits the efficient production of volatile fatty acids. In recent years, volatile fatty acids produced by anaerobic co-fermentation using different substrates has been widely studied and applied. In this paper, we analyze the characteristics of fermentation to produce acid using kitchen waste and excess sludge alone or mixture. Influences of environmental factors and microbial community structure on the type and yield of volatile fatty acids in the anaerobic fermentation system are discussed in detail. Moreover, we propose future research directions, to provide a reference for recycling kitchen waste and excess sludge.

Polyhydroxyalkanoates (PHA) synthesis by activated sludge using volatile fatty acids (VFAs) in fermentation liquid of excess sludge as carbon source is a hotspot in the field of environmental biotechnology. However, there is no unified conclusion on the effects of non-VFAs, mainly dissolved organic matter (DOM), on PHA production. Thus, this critical review mainly introduces the main characteristics and common analysis methods of DOM in anaerobic fermentation liquid. The effects of DOM on PHA production are analyzed from the aspects of microbiology, metabolic regulation and sludge properties. The results of different studies showed that high concentration of DOM is bad for PHA production, but an appropriate amount of DOM is conducive to the stability of sludge properties, reducing the final PHA purification cost. Finally, suitable strategies were proposed to regulate the PHA synthesis by activated sludge with DOM for PHA production by anaerobic fermentation liquid.

The waste sludge of municipal wastewater treatment plants is an important reservoir for antibiotic resistance genes (ARG). It is necessary to explore the fate of ARG, microbial community succession, and the correlations between them. Therefore, the distribution of ARG and the microbial community structure of waste sludge from wastewater treatment plants with A 2 O and A 2 O-MBR processes during microwave pretreatment and anaerobic digestion were studied in this research. The results showed that the occurrence of ARG and the microbial community structure were quite different in the waste sludge of A 2 O and A 2 O-MBR processes. The microwave pretreatment did not change the microbial community much, whereas the community structure of the digested sludge with pretreatment showed significant differences. Anaerobic digestion had a conformity effect on the distribution of ARG and MGE in the digested sludge with or without pretreatment. Among genes, ermF , qnrS , and bla NDM-1 were the most difficult to be reduced ARG and were prone to propagation during anaerobic digestion. The influence of biomass, ammonia nitrogen, and phosphorus on the distribution of ARG and MGE was higher than that of other environmental factors. The sludge characteristics also showed important impacts on the microbial community, especially on some genera with specific functions. These results could help people to better understand the spread and control of ARG during sludge anaerobic digestion.

In order to explore the microbial communities and functions of activated sludge in an Anaerobic-anoxic-oxic (A²/O) process under the start-up of Actinic reaction enzyme system (ARES) system and to understand the impact of the ARES system in domestic sewage treatment process, the activated sludge microbial community structure in the A²/O process system before and after ARES system start-up was analyzed by Illumina-HiSeq 2000 high-throughput sequencing platform. By combining with the main parameters related to the effect of sewage treatment, we analyzed the environmental functions of the microbial communities. The microbial community structure of activated sludge was significantly different before and after the ARES system start-up. There were 9 main bacterial phyla in the system (average relative abundance ≥1%), accounting for 96%-98% of the total bacteria sequenced. After the ARES system was started, the relative abundance of Betaproteobacteria and Chlorobi increased by 3.45%-3.85% and 0.45%-2.61%, respectively. In the anaerobic unit, the relative abundance of Bacteroidetes increased by 12.97%, while the Actinobacteria and Firmicutes decreased by 9.60% and 1.45%, respectively. At the genus level of bacteria, the relative abundance of Denitratisoma increased by 0.80%-3.27%, while the Haliangium and Arcobacter decreased by 3.36%-4.52% and 1.48%-3.45%, respectively. The relative abundance of bacteria was significantly different before and after the ARES system start-up. There were 7 abundant fungi phyla (average relative abundance ≥1%) in the system. After the ARES system was started, the relative abundance of Rozellomycota decreased by 42.71%-46.77%. In the anaerobic unit, the relative abundance of Ascomycota decreased by 13.39%, while the relative abundance of Glomeromycota increased by 13.86%. At the genus level of fungi. The relative abundance of Entomophthoraceae sp. and Glomcromycota sp. increased by 31.35%-36.50% and 6.27%-13.84%, respectively, while the Rozellomycota sp. and Xylochrysis lucida decreased by 42.71%-46.77% and 3.67%-5.54%, respectively. Our results showed that the application of ARES system caused the response of the microbial community to environmental changes, especially for the fungi communities, in the meanwhile, improved the effluent quality, especially the removal rate of total nitrogen.

To understand the changes in microbial community characteristics during the enrichment of anaerobic ammonium oxidation (ANAMMOX) bacteria, an ASBR reactor was used to culture the ANAMMOX bacteria. The composition, diversity, and species co-occurrence network of the microbial community were investigated under different cultivation times. The results showed that the ANAMMOX bacteria were enriched by gradually increasing the substrate concentration, with removal efficiencies for NH 4 + -N, NO 2 - -N, and total nitrogen of 97.6%, 95.4%, and 84.9%, respectively. The high-throughput sequencing found that the dominant phyla (relative abundance>5%) were Proteobacteria, Bacteroidetes, Chloroflexi, Planctomycetes, Armatimonadetes, and Actinobacteria in the whole culture process. Candidatus Brocadia was the main ANAMMOX bacteria in the reactor, with its relative abundance increasing from 1.42% to 24.66%. During the cultivation process, the composition of the dominant microbial community did not change, while the relative abundance showed a significant difference ( P <0.05). The alpha diversity of the microbial community significantly increased first and then decreased ( P <0.05), and the beta diversity of the microbial community was significantly spatially differentiated ( R =0.5672, P <0.01) during the culture process. Species network densities were 0.188, 0.068, 0.059, 0.18, and 0.0735 at different times during the culture process. Although the enrichment culture process resulted in weaker correlations between microorganisms, the related group of microorganisms in the phylum Aspergillus became the main node in the network. The enrichment process weakened the correlation between microorganisms; however, the microbial taxa related to the phylum Planctomycetes became the key node in the network.

Membrane fouling is the biggest challenge of membrane bioreactor industrialization. In this study, a bio-electrochemical system (BES)-anaerobic membrane bioreactor (AnMBR) system was constructed, and the effect of nano-zero-valent iron (nZVI) on membrane anti-fouling ability and methane production was investigated. The results showed that the BES-AnMBR system was stable and the chemical oxygen demand (COD) removal rate was maintained at approximately 95%. The optimum condition was observed to be nZVI 0.1 g·g -1 (VS). Under this condition, transmembrane pressure (TMP) was reduced by 28.1%, the membrane flux had a slight improvement, and methane production was up to 81.3 mL·g -1 (COD removed ). This was 12.1% higher than that of the control. In addition, a further analysis of extracellular polymeric substances (EPS) fraction and membrane resistance showed that nZVI enhanced EPS decomposition, promoted the formation of an iron-rich layer of inorganic and organic matters on the membrane surface, and changed the distribution of organics and inorganics, thereby significantly alleviating membrane fouling. This study will enrich basic theory of conventional AnMBR and provide a new solution for efficient sludge treatment and resource utilization.

Anaerobic digestion is widely used for sewage sludge stabilization. Different anaerobic digestion methods have different impacts on the speciation and stability of heavy metals in sludge. This study investigated the response of the speciation and stability of heavy metals in sludge to the treatment of mesophilic anaerobic digestion-mechanical dewatering and thermal hydrolysis pre-treatment-thermophilic anaerobic digestion. The results showed that the process of mesophilic anaerobic digestion increased the contents of Cd, Cr, Cu, Ni, and Zn in the sludge, increasing its contamination level and potential ecological risks. In contrast, the thermophilic anaerobic digestion process increased the contents of Cd, Cr, and Pb in the sludge, reducing the level of heavy metal contamination and potential ecological risks. It was found that the main contaminated metals were Cd and Zn in Plant N and Cd in Plant S. Cd has the highest risk factor and is the highest risk contributor to the potential ecological risk of all the types of sludge. The sum of reducible and the exchangeable fractions of Cd, Ni, Pb, and Zn reduced, and the residual fraction of Cd, Cr, Cu, and Ni decreased after mesophilic anaerobic digestion. This indicated that the process of mesophilic anaerobic digestion changed the proportion of potential toxicity and steady state of the heavy metals into direct toxicity. After thermophilic anaerobic digestion, the exchangeable proportion of Cd, Cr, Cu, Pb, and Zn decreased, and the steady state of Cd, Cr, Cu, Ni, Pb, and Zn decreased. After the thermophilic anaerobic digestion process, the proportions of bio-availability and mobility of heavy metals therefore decreased, and the proportions of steady state also reduced. The potential toxicity increased.

A continuous flow reactor was inoculated at 25-28℃ with mature partial nitrification granular sludge. In order to avoid the granular sludge being crushed because of the sludge backflow through the peristaltic pump, a built-in sedimentation zone was used for internal backflow. The experiment investigated the influence of the different anaerobic time to aeration time ratio (1:1, 2:1, and 1:2) on the stability of a continuous-flow partial nitrification granular sludge system. The results showed that when the controlled anaerobic time to aeration time ratio was 1:1 and 2:1, the partial nitrification performance was good and the nitrite accumulation rates were 85.2% and 94.5%, respectively. When the controlled anaerobic time to aeration time ratio was 1:2, the partial nitrification performance gradually deteriorated, and the ammonia nitrogen removal rate and nitrite accumulation rate at the end of the stage decreased to 64.1% and 58.7%, respectively. Batch test results showed that intermittent aeration and continuous aeration can better inhibit the relative activity of NOB in the partial nitrification system to a certain extent. The longer the anaerobic time, the better the NOB activity inhibition. However, too long an anaerobic time will also lead to ammonia nitrogen removal rate. In the process of partial nitrification, the long-term stable operation of continuous flow partial nitrification process can be realized by 1:1 and coordinated control of other control conditions. An analysis of sludge performance indicated that in the anaerobic time to aeration time ratio range of 1:1-1:2, the longer the anaerobic time, the more stable the granular sludge structure. The shorter the anaerobic time, the smaller the selection pressure in the reactor, resulting in poor sludge sedimentation performance and partial disintegration of partial nitrification granular sludge. An EPS chemical analysis and a three-dimensional fluorescence spectroscopic analysis showed that the PN content was higher and the PN/PS value was higher when the anaerobic time and aeration time ratio was 2:1.

The greenhouse gas N 2 O is released during the biological nitrogen removal process. ANAMMOX (anaerobic ammonium oxidation) is regarded as a promising nitrogen removal process for treating municipal wastewater, and the N 2 O emission patterns and mechanisms need further investigation. In this study, batch tests were performed to study the release of N 2 O at different temperatures and substrate concentrations, and the microbial mechanisms of N 2 O emission were discussed. The results showed that the increase of the influent substrate concentration of the ANAMMOX process promoted the release of N 2 O. At 35℃, when the influent nitrite increased from 40 mg·L -1 to 60 mg·L -1 , 120 mg·L -1 , the maximum accumulated concentration of N 2 O increased from 0.5 mg·L -1 to 1.5 mg·L -1 and 2.4 mg·L -1 , accounting for 0.85%, 1.43%, and 1.11% of the total nitrogen removal, respectively. Lowering temperature had an obvious inhibitory effect on ANAMMOX activity. The specific ANAMMOX activity at 15℃ was only 6% of that at 30℃. Furthermore, the intracellular ATP concentration was reduced. At 15℃, the intracellular ATP concentration was 4% of that at 30℃. The decrease in temperature led to a decrease in the release of N 2 O in the ANAMMOX process. When the temperature decreased, the denitrification rate would decrease, leading to a lower N 2 O production rate and lower N 2 O accumulation. 16S rRNA amplicon sequencing showed that ANAMMOX bacteria Candidatus Brocadia and Ca. Jettenia were enriched, accounting for 6.9%-13.8% and 1.4%-2.6% of microbial community, respectively. Abundant heterotrophic bacteria were also found in the microbial community. The accumulation of N 2 O in the ANAMMOX process was mainly attributed to denitrifying bacteria producing and consuming N 2 O. This study provides support for controlling N 2 O emission during the ANAMMOX process for treating municipal wastewater.

Municipal wastewater methanogenesis is one of the ways to utilize municipal wastewater resources.In this study, a biofilter used to treat actual municipal wastewater was employed to investigate the methanogenesis in a pilot-scale reactor. The method of rapid start-up, the influence of temperature on the reactor performance, and the changes in the microbial structure were investigated in the pilot-scale study. The rapid start-up of the biofilter reactor was achieved by the combination of intermittent and continuous operations. The effluent concentration of SCOD was 60 mg ·L -1 at the stable operation stage. The biofilter was operated steadily at a temperature higher than 14℃, the accumulation of volatile fatty acids (VFA) was low, and the effluent concentrations of SCOD and TCOD were 69 mg ·L -1 and 90 mg ·L -1 , respectively. In addition, the metabolism of hydrolysis and methanogenesis tended to balance off under such conditions. However, the abundance of microorganisms that can hydrolyze organic matter and produce methane decreased. The abundance of Peptostreptococcaceae increased even the temperature was lower than 10℃, which typically increases VFA production. Therefore, the concentrations of effluent VFA and TCOD increased, but methane production decreased. The effluent concentration of SCOD was relatively stable. The microbial abundance and diversity were the richest at 19℃ in the reactor. The acetolactic methanogens were the dominant methanogens at low temperatures. The anaerobic biological filter for the treatment of urban sewage starts quickly and can resist the impact of continuous temperature reduction. Moreover, it does not need backwashing after running for nine months, and it is not easily clogged.Therefore,the functions of biological contact oxidation and filtration retention of the biological filter can be more fully utilized.

A laboratory-scale anaerobic membrane bioreactor (AnMBR) was used for the co-digestion of sewage sludge and food waste to investigate its organic matter removal characteristics, biogas production performance, and microbial community composition. The results showed that the degradation rate of volatile solids (VS) increased from 17.5% for a single digestion to 40% for the total digestion, and that the COD removal was 95.3% when the organic loading rate (OLR) was stabilized at 0.59-0.64 kg·(m 3 ·d) -1 . The solids content of the digested sludge increased by a factor of 3.9. The final CH 4 content was 60% and the CH 4 yield was 78.7 mL·g -1 of COD added . The transmembrane pressure (TMP) and average flux were maintained at between -3.1 and -2.7 kPa and 0.106 L·(m 2 ·h) -1 , respectively, and membrane fouling was not serious. According to an analysis of the microbial diversity using 16S rRNA, the anaerobic bacterium in the AnMBR were mainly phylum Proteobacteria, Bacteroidetes, and Cloacimonetes, and the dominant methanogens included the Methanobacterium family, Methanosaeta genus, and Methanolinea genus. This study provides a strong theoretical basis for research into the stability and performance of AnMBRs for the co-treatment of sludge and other high-solid waste streams, and provided an effective solution for biomass resource utilization and the energy crisis.

Ammonia inhibition is an important factor impacting methane production efficiency during the anaerobic digestion of high-solid organic wastes. This study investigated the effect of micro-sized zero-valent iron (m-ZVI) on the anaerobic digestion of excess sewage sludge and thermal hydrolyzed sludge using batch mode experiments. The effect of m-ZVI on ammonia inhibition mitigation was also studied. Results showed that the kinetic characteristics of the methane production rate, lag phase, and methane production potential of the anaerobic digestion of excess sludge and thermal hydrolyzed sludge were not impacted by the addition of m-ZVI at a dosage of 4 g·L -1 and 10 g·L -1 . However, during the inhibited anaerobic digestion process with a high ammonia concentration, the addition of 4 g·L -1 and 10 g·L -1 of m-ZVI was able to shorten the lag phase from 18.61 d (the control) to 17.22 d and 16.18 d, respectively. Moreover, the maximum methane production rate (based on the VS) increased from 6.34 mL·(d·g) -1 (the control) to 7.84 mL·(d·g) -1 (4 g·L -1 m-ZVI) and 7.39 mL·(d·g) -1 (10 g·L -1 m-ZVI). The pH buffer system was not influenced by the chemical reaction of m-ZVI in the anaerobic digestion, although the relative abundance of the dominant methanogenic archaea ( Methanosarcina ) improved greatly from 30.71% (the control) to 53.50% (4 g·L -1 m-ZVI) and 60.30% (10 g·L -1 m-ZVI) at 27 d. This study proved that m-ZVI was incapable of improving the methane production potential of sewage sludge, while the mitigation of ammonia inhibition during anaerobic digestion was enhanced by the stimulating effect on methanogenic archaea.