Community In Bioreactor Research Articles

Changes in the bacterial and microeukaryotic communities in the bioreactor upon increasing heavy metal concentrations

Heavy metals are necessary at low concentration for biological activity, but they are often toxic for microorganisms at high concentrations. Amplicon sequencing of 16S rRNA and 18S rRNA was used to investigate changes in the bacterial and microeukaryotic communities in an activated sludge bioreactor incrementally contaminated with nickel (Ni), copper (Cu), and zinc (Zn) with an IC50 value ranging from 0% to 100%, as previously determined, while an uncontaminated bioreactor served as a control. The chemical oxygen demand (COD) was on average 90% in the uncontaminated bioreactor but dropped to 49% when the heavy metal concentration was 100% IC50. The bacterial community in the uncontaminated bioreactor was dominated by Alphaproteobacteria (mostly Agrobacterium and Brevundimonas) when the heavy metal concentrations were low and Bacteroidetes (mostly Sphingobacterium) when the highest amounts of heavy metal concentrations were applied. The members of Ciliophora, Ascomycota, and Basidiomycota alternatively dominated in the uncontaminated bioreactor, while Ascomycota (mostly Fusarium) dominated in the contaminated bioreactor. The results revealed that increased concentrations of Ni, Cu, and Zn altered the bacterial and microeukaryotic communities and some putative metabolic functions.

Metagenomic Analysis of Bacterial, Archaeal and Fungal Diversity in Two-Stage Anaerobic Biodegradation for Production of Hydrogen and Methane from Corn Steep Liquor.

The main purpose of this study was to identify the microbial communities (bacterial, archaeal and fungal) in a two-stage system of anaerobic bioreactors for the production of hydrogen and methane from the waste substrate-corn steep liquor. Wastes from the food industry are valuable resources with potential in biotechnological production because of their high organic matter contents. In addition, the production of hydrogen and methane, volatile fatty acids, reducing sugars and cellulose content was monitored. Two-stage anaerobic biodegradation processes were performed by microbial populations in the first hydrogen generating bioreactor (working volume of 3 dm3) and in the second methane-generating reactor (working volume of 15 dm3). Cumulative hydrogen yield reached 2000 cm3 or 670 cm3/L a day, while the methane production reached a maximum quantity of 3300 cm3 or 220 cm3/L a day. Microbial consortia in anaerobic digestion systems play an essential role for process optimization and biofuel production enhancement. The obtained results showed the possibility of conducting two separate processes-the hydrogenic (hydrolysis and acidogenesis) and methanogenic (acetogenesis and methanogenesis)-as two stages of anaerobic digestion to favor energy production under controlled conditions with corn steep liquor. The diversity of microorganisms as main participants in the processes in the bioreactors of the two-stage system was followed using metagenome sequencing and bioinformatics analysis. The obtained metagenomic data showed that the most abundant phylum in both bacterial communities was Firmicutes-58.61% and 36.49% in bioreactors 1 and 2, respectively. Phylum Actinobacteria were found in significant quantities (22.91%) in the microbial community in Bioreactor 1, whereas in Bioreactor 2, they were 2.1%. Bacteroidetes are present in both bioreactors. Phylum Euryarchaeota made up 0.4% of the contents in the first bioreactor and 11.4% in the second. As the dominant genera among methanogenic archaea are Methanothrix (8.03%) and Methanosarcina (3.39%), the main fungal representatives were Saccharomyces cerevisiae. New knowledge of anaerobic digestion mediated by novel microbial consortia could be widely used to convert different wastes to green energy.

Comparison of metagenomes from fermentation of various agroindustrial residues suggests a common model of community organization.

The liquid residue resulting from various agroindustrial processes is both rich in organic material and an attractive source to produce a variety of chemicals. Using microbial communities to produce chemicals from these liquid residues is an active area of research, but it is unclear how to deploy microbial communities to produce specific products from the different agroindustrial residues. To address this, we fed anaerobic bioreactors one of several agroindustrial residues (carbohydrate-rich lignocellulosic fermentation conversion residue, xylose, dairy manure hydrolysate, ultra-filtered milk permeate, and thin stillage from a starch bioethanol plant) and inoculated them with a microbial community from an acid-phase digester operated at the wastewater treatment plant in Madison, WI, United States. The bioreactors were monitored over a period of months and sampled to assess microbial community composition and extracellular fermentation products. We obtained metagenome assembled genomes (MAGs) from the microbial communities in each bioreactor and performed comparative genomic analyses to identify common microorganisms, as well as any community members that were unique to each reactor. Collectively, we obtained a dataset of 217 non-redundant MAGs from these bioreactors. This metagenome assembled genome dataset was used to evaluate whether a specific microbial ecology model in which medium chain fatty acids (MCFAs) are simultaneously produced from intermediate products (e.g., lactic acid) and carbohydrates could be applicable to all fermentation systems, regardless of the feedstock. MAGs were classified using a multiclass classification machine learning algorithm into three groups, organisms fermenting the carbohydrates to intermediate products, organisms utilizing the intermediate products to produce MCFAs, and organisms producing MCFAs directly from carbohydrates. This analysis revealed common biological functions among the microbial communities in different bioreactors, and although different microorganisms were enriched depending on the agroindustrial residue tested, the results supported the conclusion that the microbial ecology model tested was appropriate to explain the MCFA production potential from all agricultural residues.

Effect of quorum quenching on biofouling control and microbial community in membrane bioreactors by Brucella sp. ZJ1

Quorum quenching (QQ) has been demonstrated to be a novel technique for controlling biofouling in membrane bioreactors (MBRs), as it can significantly inhibit biofilm formation by disrupting quorum sensing (QS). The exploration of new QQ bacterial strains and the evaluation of their performance in mitigating membrane fouling in MBR systems is significant. In this study, an efficient QQ strain, Brucella sp. ZJ1 was encapsulated in alginate beads and evaluated for its ability to mitigate biofouling. The findings revealed that MBR with QQ beads extended the operation time by 2–3 times without affecting pollutant degradation. QQ beads maintained approximately 50% QQ activity after more than 50 days operation, indicating a long-lasting and endurable QQ effect. The QQ effect reduced extracellular polymeric substance (EPS) production especially in terms of polysaccharide and protein by more than 40%. QQ beads in the MBR also reduced the cake resistance and the irreversible resistance of membrane biofouling. Metagenomic sequencing suggests that QQ beads suppressed the QS effect and increased the abundance of QQ enzyme genes, ultimately inducing efficient membrane biofouling control.

The impact of sunlight on fouling behaviors and microbial communities in membrane bioreactors

Membrane fouling is a significant obstacle to applying membrane bioreactors (MBRs) for wastewater treatment. Here we report the impact of sunlight irradiation on membrane fouling, biopolymers, signal molecules, and microbial communities in MBRs. The degradation of signal molecules, which induce membrane biofouling, occurred through solar photolysis in batch tests. However, MBR sludge exposed to sunlight exhibited different biological behaviors creating more soluble microbial products (SMP) and signal molecules (particularly autoinducer-2). Cell lysis and deflocculation occurred when the MBR mixed liquor was exposed to sunlight. MBR fouling rates coincided with the temporal concentration profiles of SMP and signal molecules. Sunlight caused drastic changes in the MBR microbial community, stimulating the preferential growth of specific bacteria (e.g., Deinococcus Runella, Flavitalea, Glaiimonas, and Rurimicrobium). The nonmetric multidimensional scaling analysis of the MBR community structures with and without sunlight irradiation showed two distinct microbial community clusters and their reversibility. Network analysis based on Spearman's rank correlations revealed that with sunlight irradiation, fouling rates had significant positive connections with SMP proteins and the Flavitalea genus. The findings of this study demonstrate that sunlight is a considerable factor affecting membrane fouling and microbial ecology in MBRs, needing shade for fouling mitigation and sustainable operation.

Quantitative and Qualitative Changes in the Genetic Diversity of Bacterial Communities in Anaerobic Bioreactors with the Diatomaceous Earth/Peat Cell Carrier.

This paper analyses the impact of the diatomaceous earth/peat (DEP; 3:1) microbial carrier on changes in the bacterial microbiome and the development of biofilm in the anaerobic digestion (AD) of confectionery waste, combined with digested sewage sludge as inoculum. The physicochemical properties of the carrier material are presented, with particular focus on its morphological and dispersion characteristics, as well as adsorption and thermal properties. In this respect, the DEP system was found to be a suitable carrier for both mesophilic and thermophilic AD. The evaluation of quantitative and qualitative changes in the genetic diversity of bacterial communities, carried out using next-generation sequencing (NGS), showed that the material has a modifying effect on the bacterial microbiome. While Actinobacteria was the most abundant cluster in the WF-control sample (WF—waste wafers), Firmicutes was the dominant cluster in the digested samples without the carrier (WF-dig.; dig.—digested) and with the carrier (WF + DEP). The same was true for the count of Proteobacteria, which decreased twofold during biodegradation in favor of Synergistetes. The Syntrophomonas cluster was identified as the most abundant genus in the two samples, particularly in WF + DEP. This information was supplemented by observations of morphological features of microorganisms carried out using fluorescence microscopy. The biodegradation process itself had a significant impact on changes in the microbiome of samples taken from anaerobic bioreactors, reducing its biodiversity. As demonstrated by the results of this innovative method, namely the BioFlux microfluidic flow system, the decrease in the number of taxa in the digested samples and the addition of DEP contributed to the microbial adhesion in the microfluidic system and the formation of a stable biofilm.

Exploiting the Potential of Bioreactors for Creating Spatial Organization in the Soil Microbiome: A Strategy for Increasing Sustainable Agricultural Practices

Industrial production of synthetic nitrogen fertilizers and their crop application have caused considerable environmental impacts. Some eco-friendly alternatives try to solve them but raise some restrictions. We tested a novel method to produce a nitrogen bioinoculant by enriching a soil microbial community in bioreactors supplying N2 by air pumping. The biomass enriched with diazotrophic bacteria was diluted and applied to N-depleted and sterilized soil of tomato plants. We estimated microbial composition and diversity by 16S rRNA metabarcoding from soil and bioreactors at different run times and during plant uprooting. Bioreactors promoted the N-fixing microbial community and revealed a hided diversity. One hundred twenty-four (124) operational taxonomic units (OTUs) were assigned to bacteria with a greater Shannon diversity during the reactor’s steady state. A total of 753 OTUs were found in the rhizospheres with higher biodiversity when the lowest concentration of bacteria was applied. The apparent bacterial abundance in the batch and continuous bioreactors suggested a more specific functional ecological organization. We demonstrate the usefulness of bioreactors to evidence hidden diversity in the soil when it passes through bioreactors. By obtaining the same growth of inoculated plants and the control with chemical synthesis fertilizers, we evidence the potential of the methodology that we have called directed bioprospecting to grow a complex nitrogen-fixing microbial community. The simplicity of the reactor’s operation makes its application promising for developing countries with low technological progress.

Distinct comammox Nitrospira catalyze ammonia oxidation in a full-scale groundwater treatment bioreactor under copper limited conditions

Microbial ammonia oxidation is the initial nitrification step used in biological nitrogen-removal during water treatment processes, and the discovery of complete ammonia-oxidizing (comammox) bacteria added a novel member to this functional group. It is important to identify and understand the predominant microorganisms responsible for ammonium removal in biotechnological process design and optimization. In this study, we used a full-scale bioreactor to treat ammonium in groundwater (9.3 ± 0.5 mg NH4+-N/L) and investigated the key ammonia-oxidizing prokaryotes present. The groundwater ammonium was stably and efficiently oxidized throughout ∼700 days of bioreactor operation. 16S rRNA gene amplicon sequencing of the bioreactor community showed a high abundance of Nitrospira (12.5–45.9%), with the dominant sequence variant (3.5–37.8%) most closely related to Candidatus Nitrospira nitrosa. Furthermore, analyses of amoA, the marker gene for ammonia oxidation, indicated the presence of two distinct comammox Nitrospira populations, however, the relative abundance of only one of these populations was strongly correlated to ammonia oxidation rates and was robustly expressed. After 380 days of operation copper wires were immersed into the reactor at 0.04–0.06 m2/m3 tank, which caused a gradual abundance increase of one discrete comammox Nitrospira population. However, further increase of the copper dosing (0.08 m2/m3 tank) inverted the most abundant ammonia-oxidizing population to Nitrosomonas sp. These results indicate that comammox Nitrospira were capable of efficient ammonium removal in groundwater without exogenous nutrients, but copper addition can stimulate comammox Nitrospira or lead to dominance of Nitrosomonas depending on dosage.

Microbial communities in full-scale woodchip bioreactors treating aquaculture effluents

Woodchip bioreactors are being successfully applied to remove nitrate from commercial land-based recirculating aquaculture system (RAS) effluents. In order to understand and optimize the overall function of these bioreactors, knowledge on the microbial communities, especially on the microbes with potential for production or mitigation of harmful substances (e.g. hydrogen sulfide; H2S) is needed. In this study, we quantified and characterized bacterial and fungal communities, including potential H2S producers and consumers, using qPCR and high throughput sequencing of 16S rRNA gene. We took water samples from bioreactors and their inlet and outlet, and sampled biofilms growing on woodchips and on the outlet of the three full-scale woodchip bioreactors treating effluents of three individual RAS. We found that bioreactors hosted a high biomass of both bacteria and fungi. Although the composition of microbial communities of the inlet varied between the bioreactors, the conditions in the bioreactors selected for the same core microbial taxa. The H2S producing sulfate reducing bacteria (SRB) were mainly found in the nitrate-limited outlets of the bioreactors, the main groups being deltaproteobacterial Desulfobulbus and Desulfovibrio. The abundance of H2S consuming sulfate oxidizing bacteria (SOB) was 5–10 times higher than that of SRB, and SOB communities were dominated by Arcobacter and other genera from phylum Epsilonbacteraeota, which are also capable of autotrophic denitrification. Indeed, the relative abundance of potential autotrophic denitrifiers of all denitrifier sequences was even 54% in outlet water samples and 56% in the outlet biofilm samples. Altogether, our results show that the highly abundant bacterial and fungal communities in woodchip bioreactors are shaped through the conditions prevailing within the bioreactor, indicating that the bioreactors with similar design and operational settings should provide similar function even when conditions in the preceding RAS would differ. Furthermore, autotrophic denitrifiers can have a significant role in woodchip biofilters, consuming potentially produced H2S and removing nitrate, lengthening the operational age and thus further improving the overall environmental benefit of these bioreactors.

Optimal start-up conditions for the efficient treatment of acid mine drainage using sulfate-reducing bioreactors based on physicochemical and microbiome analyses

Typically, sulfate-reducing bioreactors used to treat acid mine drainage (AMD) undergo an initial incubation period of a few weeks to acclimatize sulfate-reducing bacteria (SRB), although necessity of this preincubation has rarely been evaluated. To reduce time and economic cost, we developed an SRB acclimatization method using the continuous flow of AMD into bioreactors fed with rice bran, and compared with the conventional acclimatization method. We found that the SRB sufficiently acclimatized without the preincubation phase. Furthermore, we examined the performance and SRB communities in bioreactors operated for >200 days under seven different conditions, in which the amount of rice bran added and hydraulic retention times (HRTs) were varied. A comparison of the various bioreactor conditions revealed that the lowest rice bran amount (50 g) and the shortest HRT (6 h) caused a deterioration in reactor performance after day 144 and 229, respectively. In both cases, relatively aerobic environments developed due to the lack of organic matter seemed to inhibit sulfate reduction. Of the conditions tested, operation of the bioreactors with 200 g of rice bran and an HRT of 12.5 h was the most effective in treating AMD, showing a sulfate reduction rate of 20.7–77.9% during days 54–242. Data and materials availabilityAll data needed to evaluate the conclusions of this study are presented in the paper and/or the appendix.

Denitrification performance and microbial community of bioreactor packed with PHBV/PLA/rice hulls composite

In this study, a novel biodegradable PHBV/PLA/rice hulls (PPRH) composite was applied and tested as biofilm attachment carrier and carbon source in two bioreactors for biological denitrification process. The denitrification performance, effect of operational conditions and microbial community structure of PPRH biofilm were evaluated. The batch experiment results showed that PPRH-packed bioreactor could completely remove 50 mg L−1 of NO3−-N at natural pH (ca. 7.5) and room temperature. The continuous flow experiments indicated that high NO3−-N removal efficiency (77%–99%) was achieved with low nitrite (<0.48 mg L−1) and ammonia (<0.81 mg L−1) accumulation, when influent NO3−-N concentration was 30 mg L−1 and hydraulic retention time was 2–6 h. Furthermore, the microbial community analysis indicated that bacteria belonging to genus Diaphorobacter in phylum Proteobacteria were the most dominant and major denitrifiers in denitrification. In summary, PPRH composite was a promising carbon source for biological nitrate removal from water and wastewater.

Methane-dependent selenate reduction by a bacterial consortium.

Methanotrophic microorganisms play a critical role in controlling the flux of methane from natural sediments into the atmosphere. Methanotrophs have been shown to couple the oxidation of methane to the reduction of diverse electron acceptors (e.g., oxygen, sulfate, nitrate, and metal oxides), either independently or in consortia with other microbial partners. Although several studies have reported the phenomenon of methane oxidation linked to selenate reduction, neither the microorganisms involved nor the underlying trophic interaction has been clearly identified. Here, we provide the first detailed evidence for interspecies electron transfer between bacterial populations in a bioreactor community where the reduction of selenate is linked to methane oxidation. Metagenomic and metaproteomic analyses of the community revealed a novel species of Methylocystis as the most abundant methanotroph, which actively expressed proteins for oxygen-dependentmethane oxidation and fermentation pathways, but lacked the genetic potential for selenate reduction. Pseudoxanthomonas, Piscinibacter, and Rhodocyclaceae populations appeared to be responsible for the observed selenate reduction using proteins initially annotated as periplasmic nitrate reductases, with fermentation by-products released by the methanotrophs as electron donors. The ability for the annotated nitrate reductases to reduce selenate was confirmed by gene knockout studies in an isolate of Pseudoxanthomonas. Overall, this study provides novel insights into the metabolic flexibility of the aerobic methanotrophs that likely allows them to thrive across natural oxygen gradients, and highlights the potential role for similar microbial consortia in linking methane and other biogeochemical cycles in environments where oxygen is limited.

Clostridioides difficile is Chemoattracted to Oligosaccharides Released by Mucin‐ Degrading Microbes

Background Clostridioides difficile is an enteric pathogen causing post-antibiotic diarrhea and colitis. It is widely accepted that C. difficile exploits an intestinal environment with an altered microbiota, but the details of these microbe-microbe interactions are not well characterized. Several pathogens have been demonstrated to adhere and colonize the intestinal mucus layer. However, few studies have addressed this interplay with C. difficile. We hypothesized that C. difficile would adhere to the human mucin MUC2 and that mucin-associated microbes, which can liberate mucin glycan oligosaccharides, would promote C. difficile growth. Methods & Results Using CFDA-SE fluorescently tagged bacteria, we demonstrated in vitro that C. difficile is capable of adhering to human MUC2 glycans. In vivo we identified co-localization of C. difficile with colonic MUC2 in infected mice and surgical resections from C. difficile infected patients. To identify microbes that may be interacting with C. difficile we generated bioreactor communities with human stool with the addition of mucin-coated inserts. 16S rRNA sequencing identified that C. difficile formed biofilms with several mucin-degrading microbes. We reasoned that these microbes may be releasing mucin monosaccharides that might serve as a chemoattractant. C. difficile chemotaxed towards human MUC2 as well as mucin monosaccharides fucose, mannose, galactose, GalNAc, GlcNAc and sialic acid. The highest chemotaxis was observed with mannose and GlcNAc. We confirmed our chemotaxis phenotype using live cell imaging. To address whether C. difficile was capable of cleaving mucin glycans, we queried 35 C. difficile genomes and found that all C. difficile strains lacked the specific glycosyl hydrolases required to enzymatically cleave mucin O-linked glycans. In contrast, the genomes of mucin degrading microbes identified from our 16S sequencing harbored an extensive repertoire of mucin-degrading glycosyl hydrolases. In vitro, we confirmed that C. difficile was unable to degrade mucin glycans and use them as a primary carbon source for growth. However, co-cultures with the mucin-degrading Akkermansia muciniphila, Ruminococcus torques and Bacteroides thetaioatomicron promoted C. difficile growth in media containing purified MUC2, but lacking glucose. qPCR analysis of chemotaxis and adherence genes revealed an upregulation of key genes in response to both MUC2 and microbe-mucin metabolites. Consistent with changes in chemotaxis genes, we observed that C. difficile chemotaxed toward mucin oligosaccharides released by A. muciniphila and B. thetaioatomicron. Conclusions These studies suggest that C. difficile is chemoattracted to and adheres to mucins, where it interacts with mucin-degrading microbes which likely promote its colonization.

A pilot-scale sulfur-based sulfidogenic system for the treatment of Cu-laden electroplating wastewater using real domestic sewage as electron donor

Elemental sulfur (S0) reduction process has been demonstrated as an attractive and cost-efficient approach for metal-laden wastewater treatment in lab-scale studies. However, the system performance and stability have not been evaluated in pilot- or large-scale wastewater treatment. Especially, the sulfide production rate and microbial community structure may significantly vary from lab-scale system to pilot- or large-scale systems using real domestic sewage as carbon source, which brings questions to this novel technology. In this study, therefore, a pilot-scale sulfur-based sulfidogenic treatment system was newly developed and applied for the treatment of Cu-laden electroplating wastewaters using domestic sewage as carbon source. During the 175-d operation, >99.9% of Cu2+ (i.e., 5580 and 1187 mg Cu/L for two types of electroplating wastewaters) was efficiently removed by the biogenic hydrogen sulfide that produced through S0 reduction. Relatively high level of sulfide production (200 mg S/L) can be achieved by utilizing organics in raw domestic sewage, which was easily affected by the organic content and pH value of the domestic sewage. The long-term feeding of domestic sewage significantly re-shaped the microbial community in sulfur-reducing bioreactors. Compared to the reported lab-scale bioreactors, higher microbial community diversity was found in our pilot-scale bioreactors. The presence of hydrolytic, fermentative and sulfur-reducing bacteria was the critical factor for system stability. Accordingly, a two-step ecological interaction among fermentative and sulfur-reducing bacteria was newly proposed for sulfide production: biodegradable particulate organic carbon (BPOC) was firstly degraded to dissolved organic carbon (DOC) by the hydrolytic and fermentative bacteria. Then, sulfur-reducing bacteria utilized the total DOC (both DOC degraded from BPOC and the original DOC present in domestic sewage) as electron donor and reduced the S0 to sulfide. Afterwards, the sulfide precipitated Cu2+ in the post sedimentation tank. Compared with other reported technologies, the sulfur-based treatment system remarkable reduced the total chemical cost by 87.5‒99.6% for the same level of Cu2+ removal. Therefore, this pilot-scale study demonstrated that S0 reduction process can be a sustainable technology to generate sulfide for the co-treatment of Cu-laden electroplating wastewater and domestic sewage, achieving higher Cu2+removal and higher cost-effectiveness than the conventional technologies.

Database Mining to Unravel the Ecology of the Phylum Chloroflexi in Methanogenic Full Scale Bioreactors.

Although microbial communities of anaerobic bioreactors have been extensively studied using DNA-based tools, there are still several knowledge gaps regarding the microbiology of the process, in particular integration of all generated data is still limited. One understudied core phylum within anaerobic bioreactors is the phylum Chloroflexi, despite being one of the most abundant groups in anaerobic reactors. In order to address the abundance, diversity and phylogeny of this group in full-scale methanogenic reactors globally distributed, a compilation of 16S ribosomal RNA gene sequence data from 62 full-scale methanogenic reactors studied worldwide, fed either with wastewater treatment anaerobic reactors (WTARs) or solid-waste treatment anaerobic reactors (STARs), was performed. One of the barriers to overcome was comparing data generated using different primer sets and different sequencing platforms. The sequence analysis revealed that the average abundance of Chloroflexi in WTARs was higher than in STARs. Four genera belonging to the Anaerolineae class dominated both WTARs and STARs but the core populations were different. According to the phylogenetic analysis, most of the sequences formed clusters with no cultured representatives. The Anaerolineae class was more abundant in reactors with granular biomass than in reactors with disperse biomass supporting the hypothesis that Anaerolineae play an important role in granule formation and structure due to their filamentous morphology. Cross-study comparisons can be fruitfully used to understand the complexity of the anaerobic digestion process. However, more efforts are needed to standardize protocols and report metadata information.

Hydrolyzed polyacrylamide-containing wastewater treatment using ozone reactor-upflow anaerobic sludge blanket reactor-aerobic biofilm reactor multistage treatment system.

Polymer flooding is one of the most important enhanced oil recovery techniques. However, a large amount of hydrolyzed polyacrylamide (HPAM)-containing wastewater is produced in the process of polymer flooding, and this poses a potential threat to the environment. In this study, the treatment of HPAM-containing wastewater was analyzed in an ozonic-anaerobic-aerobic multistage treatment process involving an ozone reactor (OR), an upflow anaerobic sludge blanket reactor (UASBR), and an aerobic biofilm reactor (ABR). At an HPAM concentration of 500mgL-1 and an ozone dose of 25g O3/g TOC, the HPAM removal rate reached 85.06%. With fracturing of the carbon chain, high-molecular-weight HPAM was degraded into low-molecular-weight compounds. Microbial communities in bioreactors were investigated via high-throughput sequencing, which revealed that norank_c_Bacteroidetes_vadinHA17, norank_f_Cytophagaceae, and Meiothermus were the dominant bacterial groups, and that Methanobacterium, norank_c_WCHA1-57, and Methanosaeta were the key archaeal genera. To the best of our knowledge, this is the first study in which HPAM-containing wastewater is treated using an ozonic-anaerobic-aerobic multistage treatment system. The ideal degradation performance and the presence of keystone microorganisms confirmed that the multistage treatment process is feasible for treatment of HPAM-containing wastewater.

A metagenomic assessment of microbial communities in anaerobic bioreactors and sediments: Taxonomic and functional relationships

The present study used metagenomic sequencing, metagenome assembly and physical-chemical analysis to describe taxonomically and functionally 3 anaerobic bioreactors treating manure (LI), brewery (BR) and cornmeal (CO) wastes, and an anaerobic estuarine sediment (ES). Proteobacteria, Firmicutes, Euryarchaeota and Bacteroidetes were the most abundant Phyla in all metagenomes. A bacteria/archaea ratio of 3.4 was found in the industrial full-scale anaerobic bioreactors BR and CO, while ratios greater than 10 were found for LI and ES. Canonical correspondence analysis showed that environmental variables such as chemical oxygen demand, lipid content, and ammonium nitrogen influenced the ordination of taxonomic groups. Mesotoga prima was linked to high-temperature conditions, particularly in the BR bioreactor, along with the presence of heat shock proteins genes. Likewise, the hydrogenotrophic methanogen, Methanoregula formicica, was associated with high ammonium concentration in LI bioreactor. The interactions of microbes with specific methanogenic pathways were identified using Clusters of Orthologous Groups (COG) functions, while metagenome-assembled genomes (MAGs) further confirmed relationships between taxa and functions. Our results provide valuable information to understand microbial processes in anaerobic environments.

Evaluating the effect of air flow rate on hybrid and conventional membrane bioreactors: Implications on performance, microbial activity and membrane fouling

This study addressed the impact of air flow rate on the performance, membrane fouling behaviour and microbial community of a sequencing batch conventional membrane bioreactor (SB-MBR) and a sequencing batch hybrid membrane bioreactor (SB-HMBR) with carrier media for biofilm growth. Two different scenarios were evaluated: high (6.4 L min−1) and low (1.6 L min−1) air flow rates, associated with high (4.5 mg L−1) and low (1.5 mg L−1) dissolved oxygen (DO) concentrations and specific aeration demand per membrane area (SADm) of 0.426 and 0.106 m3 m−2 h−1, respectively. Both reactors were subjected to alternating non-aerated and aerated conditions for organic matter (as chemical oxygen demand - COD), nitrogen and phosphate removal from a municipal wastewater. From the bacterial community analysis, the key players in nutrient removal processes were assessed. The results showed that COD removal efficiencies were above 95% in both MBRs, regardless of the aeration intensity, while complete ammonium removal was observed at the higher DO. However, nitrifying activity was adversely affected under low DO levels. High nitrification levels were re-established faster in the hybrid MBR, thanks to the presence of biofilm, where nitrifying activity was favoured and the bacterial community profile did not exhibit substantial changes upon DO reduction. A higher denitrification potential was found for the carrier-based MBR, resulting in lower effluent nitrate concentrations. Regarding phosphorus removal, a slight improvement was observed in the SB-HMBR at reduced DO, while in the SB-MBR it remained practically constant. Moreover, the specific phosphate uptake rate exhibited a significant increase, especially in the hybrid MBR, reaching 44.6 mgP gVSS−1 h−1. At lower aeration rate, however, worse filterability and higher membrane fouling rates were observed, especially in the conventional MBR. Overall, the results demonstrated that the hybrid MBR better withstood the reduced air flow rate and DO as compared to the conventional counterpart.

Antibiotic-induced role interchange between rare and predominant bacteria retained the function of a bacterial community for denitrifying quinoline degradation.

Quinoline is a recalcitrant pollutant in coking wastewater which has been broadly investigated with many isolates possessing aerobic quinoline-degrading ability. However, studies on anaerobic degradation and the corresponding bacteria are very scarce. This study attempted to investigate the role of diverse functional members and the redundancy of quinoline degradation in a lab-scale quinoline denitrifying bioreactor. Antibiotics were added to the batch culture under denitrifying conditions to disturb the microbial community of the quinoline-degrading bioreactor. According to the results, the nitrate removal rate remained stable, and the quinoline removal rate increased by 9·7% after treatment with streptomycin. However, PCoA analysis of 16S rRNA gene sequencing data of these samples indicated a significant shift in microbial community structures. Specifically, 12 operational taxonomic units (OTUs), including OTU1 (Pseudomonas) and OTU2 (Achromobacter), were significantly enriched. OTU1 replaced OTU8 (Thauera) as the most predominant denitrifying quinoline-degrading member. However, OTU8 and other predominant OTUs (Comamonas and Pseudoxanthomonas), which were hypothesized to contribute essentially to quinoline degradation in the origin bioreactor, became almost undetectable. Functional redundancy due to high biological diversity allowed the role reversal of predominant quinoline-degrading bacteria and other rare bacteria when disturbed by antibiotic stress. Although the abundance of OTU1 was much lower initially, it replaced the essential role of the predominant member OTU8 in the bioreactor community for quinoline degradation once the environmental condition changed. This study indicated that the high biological diversity in a wastewater treatment bacterial community is crucial for maintaining the degrading function of organic pollutants, especially in a changing environment due to external disturbance or stress.

Carbon emission and energy potential of a novel spatiotemporally anaerobic/semi-aerobic bioreactor for domestic waste treatment

The biogas generation mechanism and its utilization potential in a novel spatiotemporally anaerobic/semi-aerobic bioreactor (STASAB) system with three activated bioreactors (C1, C2 and C3) was analyzed. Methane generation potential was obtained by measurements and estimation methods with similar values of 23.38 and 27.79 kg CH4/t waste, respectively. CH4 and CO2 production was quickly achieved in the STASAB, and the total amount of CH4 and CO2 was low due to the mixed leachate-recirculation operation process among bioreactors, which were at different stages of operation. The microbial communities in different bioreactors were diverse. The leachate-recirculation operation was a critical parameter to effectively enhance the microbial community structure in the STASAB, which can regulate CH4, CO2 and N2O production with global warming potential of 7.479 kg CO2e/(t·d). The STASAB had higher energy potential of 1.011 kWh/(t·d) compared with that of conventional landfills and sequentially anaerobic/semi-aerobic bioreactors. Moreover, direct electricity production in the STASAB is recommended for energy utilization with 38.38% GHG emission reduction, and with 131.43 million CNY (Chinese Yuan) benefit per year for national rural waste disposal via utilization of biogas from the STASAB for power generation. Hence, the STASAB shows a notable potential for treating domestic waste in rural areas.