Microbial Community Analysis Research Articles

Nitrogen Removal Performance and Microbial Community Analysis of Anoxic and Oxic Process in Electrolytic Manganese Residue Leachate

Nitrogen Removal Performance and Microbial Community Analysis of Anoxic and Oxic Process in Electrolytic Manganese Residue Leachate

Identifying the specific pathways to improve nitrogen fixation of different straw biochar during chicken manure composting based on its impact on the microbial community

The application of straw biochar to chicken manure composting mitigated nitrogen loss. However, the impact of biochar derived from different types of straw on nitrogen fixation in chicken manure composting is discrepant, and the specific pathways remain unclear. Therefore, this study aimed to clarify the specific pathways of maize straw biochar (M) and rice straw biochar (R) to improve nitrogen fixation during chicken manure composting. The nitrogen losses in control (no addition, CK), M, and R composting were 51.84 %, 33.47 %, and 38.24 %, respectively, suggesting that adding straw biochar effectively improved nitrogen fixation. Microbial community analysis suggested that inhibiting denitrification and NH4+-N transformation by microorganisms was the primary means of improving nitrogen fixation. Meanwhile, biochar addition reduced the number of bacteria participating in nitrogen transformation and strengthened the NO3–-N and total organic nitrogen transformation processes, among which the effect of M composting was stronger. The stronger effect was attributed to the significant role of the core microorganisms in M composting in shifting the transformation processes of the nitrogen components (P < 0.05). Therefore, the function of different straw biochar was determined by its different impacts on the microbial community, highlighting the important role of microbial community variability.

Effects of an assistive electric field on heavy metal passivation during manure composting

Composting is one of main technologies for treating and thus utilizing livestock manure and sludge. However, heavy metals are major concerns in compost utilization due to their potential environmental hazards and health risks. This study aimed to investigate the effects of electric field-assisted composting on the variations of heavy metals and the affecting factors. The results showed that electric field significantly reduced the contents of bioavailable heavy metals including Mn, Zn, Cu, Ni, and Cd, with their bioavailable concentrations decreasing by 61.7, 63.8, 64.9, 83.7, and 63.8 %, respectively. The heavy metals being transformed into stable states were increased, indicating that the electric field also passivated these heavy metals and reduced their biological toxicity and stabilized their forms. Spearman's correlation analysis revealed that the changes in substances, temperature, and organic matter were the dominant environmental factors affecting the forms of heavy metals. Microbial community analysis indicated an increase in the abundance of metal-resistant bacteria such as Pseudomonas and Bacillus during electric field-assisted composting, with their relative abundances being increased to 2.66 % and 15.63 % in the pile of electric field-assisted composting, respectively, compared to the values of 1.88 % and 4.36 % respectively in the conventional composting. The current study suggests that electric field-assisted composting can significantly reduce the availability of heavy metals in the compost, and thus mitigate the health risks associated with its application.

Effects of zinc ion concentrations on the performance of SBR treating livestock wastewater and analysis of microbial community

Zinc ion (Zn2+) is a frequently occurring heavy metal in livestock wastewater. The effects of Zn2+ on the physicochemical properties and the microbial distribution of activated sludge are essential to controlling nitrogen removal performance. Nevertheless, there are raw studies on the effects of Zn2+ on nitrogen removal. This study investigated the effect of Zn2+ on the treatment performance of livestock wastewater in a sequencing batch reactor (SBR). The results indicated the low Zn2+ concentrations could improve nitrogen removal performance. However, as the Zn2+ concentration increased, the total nitrogen (TN) removal performance of the reactor gradually deteriorated. When the Zn2+ concentration was 90.00 mg/L, the TN removal efficiency was the lowest, only 2.40%. The contents of the Extracellular polymeric substance (EPS) presented a trend of first increasing and then decreasing with the increase of Zn2+ concentration, and the main reason was the decrease of protein-like and tryptophan-like. The 16SrRNA analysis indicated that Zn2+ within a specific concentration could increase the operational taxonomic units (OTUs) number, microbial richness, and diversity of microorganisms in the SBR. However, with Zn2+ concentration exceeding 10.00 mg/L, the relative abundance of denitrification functional bacteria (Dechloromonas, Nitrospira, and Thauera) decreased.

Highly efficient and rapid removal of Malathion using non-aerated algae bacteria consortia: Performance, kinetic, and microbial mechanisms

The frequent use of pesticides in human activities introduce Malathion into water， which caused serious environmental pollutants. However, the treatment of these wastewaters is expensive and inefficiency. In this study, two photo-sequencing batch reactors (PSBRs) were established to treat Malathion-containing wastewater using algae bacteria consortia (ABC) in aerated (R1) and non-aerated (R2) conditions, respectively. The removal rates of Malathion by ABC in R1 and R2 after stabilization were 83.6 % and 71.9 %, respectively. The microbial community analysis results indicated that Burkholderia was the dominant population in ABC, which was response for the main Malathion degradation. Furthermore, the investigation of degradation pathways of Malathion discovered that the ABC converted Malathion into inorganic phosphorus. The conversion rates of inorganic phosphorus in the two reactors were 16.9 % and 21.6 %. The results demonstrated that non-aerated ABC have a strong potential adaption on Malathion stress and can removal Malathion from wastewater economically and efficiently.

Modified polymer electrolyte membrane for microbial fuel cell: Performance analysis, investigation on anti-biofouling effect, and microbial community analysis on biofouled membrane

Sulphonation is limited in Sulphonated Polyether Ether Ketone (SPEEK) due to its solubility in water beyond an extent. However, to enhance performance of polymer electrolyte membrane (PEM) in microbial fuel cell (MFC), more functional groups are required. To facilitate effective proton transfer, styrene sulphonic acid (SSA) is grafted onto SPEEK, resulting in SPEEK/SSA, to increase the number of functional groups. Based on membrane properties, 5 wt% SSA is found to be the optimum grafting for further filler addition. Copper oxide doped reduced graphene oxide (CuO@rGO) is used as membrane filler at various concentrations to enhance anti-biofouling effect. Swelling is excessive in SPEEK/SSA (30.2%), whereas it is only 17.3% in SPEEK/SSA+1.5 wt%CuO@rGO. As evidenced by the zone of inhibition assay, biofilm inhibition test, and Bradford protein assay, the membrane's anti-biofouling impact is improved by the inherent hydrophilicity of SPEEK/SSA and antibacterial activity of CuO@rGO. The MFC with 1.5 wt% CuO@rGO membrane shows highest maximum power density of 186 ± 5 mW m−2 and Chemical Oxygen Demand removal of 81.23%. Phylogenetic analysis on biofouled membrane shows the predominance of Pseudomonas, Acidovorax and Flavobacterium. The research demonstrates that despite biofouling, the synthesized grafted PEM exhibits high resistance to it and hence performs better.

Effects of Al3+ on the microbial community, metabolic pathways, and morphological analysis of activated sludge

Al3+ generated during aluminum mining, electrolytic industry, and aluminum-based coagulant production enters sewage treatment plants and interacts with activated sludge, interfering with microbial growth and community succession. An anaerobic-anoxic-oxic (A2O) process was used to investigate the effect of Al3+ on biological denitrification, the metal form, and the microbial community structure. The results showed that a low concentration of Al3+ improved removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) as well as biological activity. However, a high concentration of Al3+ reduced the COD and TN removal efficiencies. The removal efficiencies of COD, TN, and NH4+-N were the highest, and the INT-ETS values in the anaerobic, anoxic, and oxic zones were 93.21, 91.36, and 94.44 mg·INTF/(g·TSS·h) in the 10 mg/L Al3+ concentration treatment. Regardless of the change in Al3+ concentration, aluminum in the sludge mainly existed in the form of stable organic aluminum. Microbial richness and diversity decreased under the high concentration of Al3+. However, the relative abundance of Bacteroidetes and Chitinophagales increased, which was coincident with the change in microbial aluminum tolerance capacity. The dominant flora included Proteobacteria, Gammaproteobacteria, Betaproteobacteriales, Rhodocyclaceae, and Thauera. Amino acid and carbohydrate metabolism, as well as membrane transport and replication and repair, were the main metabolic pathways. K03088, K03406, and K02014 exhibited good adaptability under the high Al3+ concentration, which ensured effective removal of COD and TN.

Investigate the anaerobic degradation of high-acetone latex wastewater with magnetite supplement

This study evaluated the effects of acetone on the anaerobic degradation of synthetic latex wastewater, which was simulated from the wastewater of the deproteinized natural rubber production process, including latex, acetate, propionate, and acetone as the main carbon sources, at a batch scale in 5 cycles of a total of 60 days. Fe3O4 was applied to accelerate the treatment performance from cycle 3. Acetone was added in concentration ranges of 0%, 0.05%, 0.1%, 0.15%-included latex, and 0.15%-free latex (w/v). In the Fe3O4-free cycles, for latex-added vials, soluble chemical oxygen demand (sCOD) was removed at 43.20%, 43.20%, and 12.65%, corresponding to the input acetone concentrations varying from 0.05% to 0.15%, indicating the interference of acetone for COD reduction. After adding Fe3O4, all flasks reported a significant increase in COD removal efficiency, especially for acetone-only and latex-only vials, from 36.9% to 14.30%–42.95% and 83.20%, respectively. Other highlighted results of COD balance showed that Fe3O4 involvement improved the degradation process of acetate, propionate, acetone, and the other COD parts, including the intermediate products of latex reduction. Besides, during the whole batch process, the order of reduction priority of the carbon sources in the synthetic wastewater was acetate, propionate and acetone. We also found that the acetate concentration appeared to be strongly related to reducing other carbon sources in natural rubber wastewater. Microbial community analysis revealed that protein-degrading bacteria Bacteroidetes vadinHA17 and Proteinniphilum and methylotrophic methanogens might play key roles in treating simulated deproteinized-natural-rubber wastewater.

Intensifying anaerobic digestion of 5-hydroxymethylfurfural via granular activated carbon supplementation

5-hydroxymethylfurfural (5-HMF) is typically found in hydrolysate produced by thermal pretreatment and wastewater streams, and its presence can significantly inhibit anaerobic digestion (AD) performance. This study comprehensively investigates the impact of adding 1–5 g/L granular activated carbon (GAC) on the AD of 0.5–4 g/L 5-HMF. The innovation of this study is to clarify the mechanism of direct interspecies electron transfer (DIET) in the AD system with 5-HMF as the sole source. Compared to the control group, adding 5 g/L GAC shows the most significant promotion effect, which increases the electron transfer activity of the sludge by 27.0%–75.0% and enhances the methane production peak rate by 27.5%–68.1%. GAC supplementation can rapidly reduce the concentration of 5-HMF by adsorption and alleviate its inhibition of microorganisms. SEM and microbial community analyses show that GAC enriches electroactive microbes and can promote AD by establishing the DIET pathway.

Enhanced degradation of petroleum in saline soil by nitrogen stimulation and halophilic emulsifying bacteria Bacillus sp. Z-13

Remediation of petroleum-contaminated soil is a widely concerned challenge. As an ecofriendly method, the performance improvement of indigenous microbial degradation is facing the bottleneck. In this study, a strain with high efficiency of petroleum degradation was isolated from the petroleum-contaminated soil and identified and named as Bacillus sp. Z-13. The strain showed the ability to produce lipopeptide surfactant which could improve 66% more petroleum hydrocarbons eluted. Strain Z-13 and its biosurfactant exhibited broad environmental adaptability to salinity (0–8%), pH (6−9) and temperature (15–45 °C). With the addition of strain Z-13 and the stimulation of NH4Cl, up to 59% of the petroleum in the contaminated soil was removed at the carbon to nitrogen ratio of 10. Microbial community analysis showed that petroleum-degrading bacteria, represented by Bacillus, became the dominant species at genus level and played an important role in the remediation. Additionally, ammonium stimulation facilitated both pathways of ammonium assimilation and nitrification in native microorganisms to achieve efficient degradation of petroleum hydrocarbons. This study could provide a promising approach for stable, environmental-friendly and efficient remediation of petroleum-contaminated soil.

Biogeochemical transformation of mercury driven by microbes involved in anaerobic digestion of municipal wastewater

Anaerobic digestion (AD) with municipal wastewater contained heavy metal mercury (Hg) highly affects the utilization of activated sludge, and poses severe threat to the health of human beings. However, the biogeochemical transformation of Hg during AD remains unclear. Here, we investigated the biogeochemical transformation and environmental characteristics of Hg and the variations of dominant microbes during AD. The results showed that Hg(II) methylation is dominant in the early stage of AD, while methylmercury (MeHg) demethylation dominates in the later stage. Dissolved total Hg (DTHg) in the effluent sludge decreased with time, while THg levels enhanced to varying degrees at the final stage. Sulfate significant inhibits MeHg formation, reduces bioavailability of Hg(II) by microbes and thus inhibits Hg(II) methylation. Microbial community analysis reveals that strains in Methanosarcina and Aminobacterium from the class of Methanomicrobia, rather than Deltaproteobacteria, may be directly related to Hg(II) methylation and MeHg demethylation. Overall, this research provide insights into the biogeochemical transformation of Hg in the anaerobic digestion of municipal wastewater treatment. This work is beneficial for scientific treatment of municipal wastewater and effluent sludge, thus reducing the risk of MeHg to human beings.

Hybrid biofilm system based on corncob coupling with scrap iron for synergistic nitrogen removal and phosphorus recovery in low-carbon source wastewater

Low-carbon source wastewater (LCSW) challenged the nutrients removal capability of traditional wastewater treatment techniques, becoming a hidden problem of eutrophic waters. Thus, a hybrid biofilm system (HBS) was developed based on corncob coupled with scrap iron for synergistic nitrogen removal and phosphorus recovery in LCSW. Corncob provided the sustainable carbon source by hydrolyzing and fermenting coupling with dissimilatory iron reduction (DIR) process, resulting in a maximum release of over 191.2 mg/L COD and supporting nitrogen removal of 83.5 % in HBS with HRT at 6 h. Meanwhile, scrap iron supported the DIR process and chemical precipitation by Fe3+ release, generating vivianite with Fe2+ for phosphate recovery (97.1 %) in HBS. By microbial community analysis, heterotrophic denitrification was the primary process for nitrogen removal, which benefitted from hydrolyzing and fermenting bacteria. After chemical precipitation, phosphorus recovery was realized by biological solubilization and DIR process, which were functioned by Acinetobacter calcoaceticus, Bacillus aryabhattai and Bacillus sp. X12014, etc. The DIR process was the critical driving force that coupled organics degradation with synergistic removal of N and P.

Applicability of Rice Husk Residue Generated by the Silica Extraction Process to Anaerobic Digestion for Methane Production

Rice husks are a feedstock of biogenic silica because of their high silica content. After silica extraction, a solid residue comprising mostly carbohydrates is present. Solid residue valorization is important for closed-loop systems using rice husk and has minimal negative environmental impacts. In this study, we used solid rice husk that was generated by silica extractionto anaerobic digestion for producing biomethane. The rice husk residue was characterized in terms of total solids, volatile solids, pH, composition, and particle size. Changing the characteristics increased biogas production by 2.48-fold compared to that of raw rice husk. The residue produced 166.4 mL-biogas g−1 vs. and 100.4 mL CH 4 g−1 VS, much more than previously reported. Microbial community analysis, which was conducted to investigate the biological reasons for increased biogas and methane, found increased Bacteroidetes levels in the rice husk samples. Among archaeal communities, Bathyarchaeota was more abundant in all rice husk samples than in the inoculum. The rice husk residue contained more operational taxonomic units than other samples. These changes in the microbial community significantly influenced the anaerobic digestion of the rice husk residue and improved methane production. Our findings provide a basis for the cleaner utilization of rice husk residue to produce renewable energy.

Acceleration of nitrogen removal performance in a biofilm reactor augmented with Pseudomonas sp. using polycaprolactone as carbon source for treating low carbon to nitrogen wastewater

Heterotrophic nitrification-aerobic denitrification (HN-AD) process was achieved in a moving bed biofilm reactor after 180-days acclimation using PCL as carbon source for low C/N wastewater treatment. A novel HN-AD strain, JQ-H3, with ability of PCL degradation was augmented to improve nitrogen removal. TN removal efficiencies of 82.31%, 90.05%, and 93.16% were achieved in the augmented reactor (R2), at different HRTs of 24 h, 20 h, and 16 h, while in the control reactor (R1), the TN removal efficiencies were 59.24%, 74.61%, and 76.68%. The effluent COD in R2 was 10.17 mg/L, much lower than that of 42.45 mg/L in R1. Microbial community analysis revealed that JQ-H3 has successfully proliferated with a relative abundance of 4.79%. Relative abundances of functional enzymes of nitrogen cycling remarkably increased due to bioaugmentation based on the analysis of PICRUSt2. This study provides a new approach for enhancing nitrogen removal in low C/N sewage treatment via the HN-AD process.

Nano-hydroxyapatite/carbon nanotube: An excellent anode modifying material for improving the power output and diclofenac sodium removal of microbial fuel cells

Anode material and surface properties have a crucial impact on the performance of MFCs. Designing and fabricating various modified carbon-based anodes with functional materials is an effective strategy to improve anode performance in MFCs. Anode materials with excellent bioaffinity can promote bacterial attachment, growth, and extracellular electron transfer. In this study, positively charged nano hydroxyapatite (nHA) with remarkable biocompatibility combined with carbon nanotubes (CNTs) with unique structure and high conductivity were used as anode modifying material. The nHA/CNTs modified carbon brush (CB) exhibited improved bacteria adsorption capacity, electrochemical activity and reticular porous structure, thus providing abundant sites and biocompatible microenvironment for the attachment and growth of functional microbial and accelerating extracellular electron transfer. Consequently, the nHA/CNTs/CB-MFCs achieved the maximum power density of 4.50 ± 0.23 mW m−2, which was 1.93 times higher than that of the CB-MFCs. Furthermore, diclofenac sodium (DS), which is a widely used anti-inflammatory drug and is also a persistent toxic organic pollutant constituting a serious threat to public health, was used as the model organic pollutant. After 322 days of long-term operation, enhanced diclofenac sodium removal efficiency and simultaneous bioelectricity generation were realized in nHA/CNTs/CB-MFCs, benefiting from the mature biofilm and the diverse functional microorganisms revealed by microbial community analysis. The nHA/CNTs/CB anode with outstanding bioaffinity, electrochemical activity and porous structure presents great potential for the fabrication of high-performance anodes in MFCs.

Spatial distribution and assembly processes of bacterial communities in northern Florida freshwater springs

Freshwater microorganisms are an essential component of the global biogeochemical cycle and a significant contributory factor in water quality. Unraveling the mechanisms controlling microbial community spatial distribution is crucial for the assessment of water quality and health of aquatic ecosystems. This research provided a comprehensive analysis of microbial communities in Florida freshwater springs. The 16S rRNA gene sequencing and bioinformatics analyses revealed the bacterial compositional heterogeneity as well as numerous unique ASVs and biomarkers in different springs. Statistical analysis showed both geographic distance and environmental variables contributed to regional bacterial community variation, while nitrate was the dominant environmental stressor that shaped the bacterial communities. The phylogenetic bin-based null model characterized both deterministic and stochastic factors contributing to community assembly in Florida springs, with the majority of bins dominated by ecological drift. Mapping of predicted pathways to the MetaCyc database revealed the inconsistency between microbial taxonomic and functional profiles, implying the functional redundancy pattern. Collectively, our work sheds insights into the microbial spatial distribution, community assembly, and function traits in one of the world's most productive aquifers. Therefore, this work provides a unique view of the health of Florida's artesian springs and offers new perspectives for freshwater quality assessment and sustainable management.

Effects of cold isostatic press pretreatment of rice straw on microstructure and efficiency of anaerobic digestion for methane production

In this study, rice straw was pretreated using by cold isostatic pressure to disrupt its microstructure and improve the performance of anaerobic digestion, and the optimal process parameters were optimized using the response surface methodology. The results showed that cold isostatic pressure pretreatment under optimal conditions (pressure of 400 MPa and holding time of 9 min) was effective in disrupting the structure of rice straw and improving its biodegradability. The cumulative methane production of the cold isostatic pressure pretreatment group increased by 76% compared to the untreated group. In addition, microbial community analysis showed that the relative abundance of Firmicutes, Halobacterota, DMER64 and Methanosaeta was higher in groups pretreated with cold isostatic pressure than in untreated groups. This study demonstrated the potential of pretreatment of rice straw with cold isostatic pressure to increase methane production during anaerobic digestion.

Bioelectricity generation by using cellulosic waste and spent engine oil in a concentric photobioreactor-microbial fuel cell

Microbial fuel cells (MFC) can be a potential technique to harvest energy from waste organic biomass. Organic waste is a good source of carbon in the form of simple and complex polysaccharides. In this study, newspaper powder, dried dead microalgae biomass and mixed fruit peel powder were separately targeted as substrate for the growth of an isolated cellulolytic bacteria inside the anode chamber of three different MFCs. At cathode, bold basal medium with spent engine oil was used as catholyte. An isolated and acclimatized microalgae was used as cathode biocatalyst in order to perform bioremediation of spent engine oil wastewater at cathode chamber. The MFC with newspaper powder showed highest maximum power density of 34.88 ± 1.00 mW/m2. Both fruit peel powder and dried microalgae powder-based MFCs achieved almost parallel maximum power densities of 15.57 ± 0.49 mW/m2 (at 161.1 ± 2.54 mA/m2) and 16.00 ± 0.32 (at 163.3 ± 1.66 mA/m2), respectively. The anode chambers of all MFCs reflected chemical oxygen demand (COD) removal efficiencies in range of 65–86 %. At anode chamber, maximum COD removal of 86.25 % was achieved by microalgae powder based MFC. The removal percentage of oil and grease at cathode chamber were 37.7 %, 42.3 % and 29.1 % for fruit peel, newspaper powder and microalgae powder based MFCs respectively. Up to 76–80 % nitrate-nitrogen, 96–97 % ammonium-nitrogen, 90–94 % phosphate-phosphorous removal were observed at cathode chamber in all the MFCs. Microbial community analysis revealed that Proteobacteria, Firmicutes and Bacteroidetes were the dominant phyla present in all the three anodic biofilms.

Biodesulfurization of Consortia Immobilized on Oil Palm Frond Biochar in Biotrickling Filters under Anoxic Conditions

Biodesulfurization using biotrickling filters (BTFs) under anoxic conditions is a cost-effective method for biogas clean-up. To improve the performance of BTFs, the microbial consortia from the anaerobic pond of a swine farm (SW), the denitrification pond of a tuna factory (DN), and the UASB of the concentrated latex industry (LW) were immobilized on BTFs. In this study, the efficiency of BTFs immobilized with the microbial consortia for the reduction of H2S gas combined with the reduction of nitrate contained in wastewater was investigated. The results showed that H2S was completely removed at the inlet H2S concentration of 207.8–1476 ppmv with wastewater circulation under anoxic conditions. However, only the DN-BTF achieved H2S removal of 95.2% at an inlet concentration of 2500 ppmv. An increase in the N/S ratio (0.356–2.07 mol/mol) improved the H2S removal of the SW-BTF, LW-BTF, and DN-BTF but not the BTF-C. Moreover, the DN-BTF had the highest nitrate removal rate (71.1%) with an N/S ratio of 2.07 mol/mol. When oxygen was supplied in wastewater at DO = 3.60 ± 0.41 mg/L, sulfate was generated at a higher rate, but nitrite production was lower than at DO~0. After microbial community analysis, Proteobacteria were the main phyla involved in the biodesulfurization process.

Fe/Mn modified biochar as electrode particles in electrochemical system for efficient anaerobic sludge digestion

Electrochemical pretreatment (EPT) of sewage sludge demonstrates an aggressive effect on extracellular polymeric substance destruction and sludge solubilization. While the low efficiency of methane production does not match the initial dissolution of the sludge after EPT. Here we proposed a novel method, using Fe-Mn-modified biochar (FMBC) strengthening electrochemical pretreatment, aiming at improving the methanogenic efficiency. The strengthening mechanism of FMBC was studied according to the physicochemical parameters of sludge at different concentrations and the change of microbial community. Experimentally, with the addition of 2 g/L FMBC, the methane production increased by 7.96% and 10.06% compared with electrochemical pretreatment alone and the control group. The sludge organic matter solubilization varied from 344.6 mg/L in E0 to 383.4 mg/L in E2 after pretreatment. Simultaneously, analysis of microbial communities showed that the addition of 2 g/L FMBC obviously increased the relative abundance of Methanofastidiosum and Methanosaeta from 5.5% and 20.9% in CK to 16% and 28.7% in E2, respectively. The addition of FMBC also intensified the acetoclastic methanogenesis and methylotrophic methanogenesis. This study provides new ideas for the enhancement of electrochemical pretreatment of sludge.