Bio-degraded of sulfamethoxazole by microbial consortia without addition nutrients: Mineralization, nitrogen removal, and proteomic characterization.

Sulfamethoxazole (SMX) is widely employed as an antibiotic, while its residue in environment has become a common public concern. Using 100 mg/L SMX as the sole nutrient source, the acclimated sludge obtained by this study displayed an excellent SMX degradation performance. The addition of SMX resulted in significant microbiological differentiation within the acclimated sludge. Microbacterium (6.6%) was identified as the relatively dominant genera in metabolism group that used SMX as sole carbon source. Highly expressed proteins from this strain strongly suggested its essential role in SMX degradation, while the degradation of SMX by other strains (Thaurea 78%) in co-metabolism group appeared to also rely on this strain. The interactions of differentially expressed proteins were primarily involved in metabolic pathways including TCA cycle and nitrogen metabolism. It is concluded that the sulfonamides might serve not only as the carbon source but also as the nitrogen source in the reactor. A total of 24 intermediates were identified, 13 intermediates were newly reported. The constructed pathway suggested the mineralizing and nitrogen conversion ability towards SMX. Batch experiments also proved that the acclimated sludge displayed ability to biodegrade other sulfonamides, including SM2 and SDZ and SMX-N could be removed completely.

Dimorphism of Candida tropicalis and its effect on nitrogen and phosphorus removal and sludge settleability.

Candida tropicalis PNY, a novel dimorphic strain with the capacity of simultaneous carbon, nitrogen and phosphorus removal in anaerobic and aerobic conditions, was isolated from activated sludge. Dimorphism of C. tropicalis PNY had effect on removing nitrogen and phosphorous and slightly affected COD removal under aerobic condition. Sample with high hypha formation rate (40 ± 5%) had more removal efficiencies of NH4+-N (50 mg/L) and PO43--P (10 mg/L), which could achieve 82.19% and 97.53%, respectively. High hypha cells dosage exhibited good settleability and filamentous overgrowth was not observed. According to label-free quantitative proteomics assays. Up-regulated proteins involved in the mitogen-activated protein kinase (MAPK) pathway indicated the active growth and metabolism process of sample with high hypha formation rate (40 ± 5%). And proteins concerning about glutamate synthetase and SPX domain-contain protein explain for the nutrient removal mechanism including assimilation of ammonia and polyphosphates synthesis.

Adsorbed copper on urea modified activated biochar catalyzed H2O2 for oxidative degradation of sulfadiazine：Degradation mechanism and toxicity assessment.

The combined pollution of heavy metals and organic compounds usually occurs simultaneously and induces high toxicity. The technology of simultaneous removal of combined pollution is lacking and the removal mechanism is not clear. Sulfadiazine (SD), a widely used antibiotic, was used as a model contaminant. Urea modified sludge-based biochar (USBC) was prepared and used to catalyze H2O2 to remove the combined pollution of Cu2+ and sulfadiazine (SD) without causing secondary pollution. After 2 h, the removal rates of SD and Cu2+ were 100 and 64.8%, respectively. Cu2+ adsorbed on the surface of USBC accelerated the activation of H2O2 by the USBC catalyzed by CO bond to produce hydroxyl radical (•OH) and single oxygen (1O2) to degrade SD. Twenty-three intermediate products were detected, most of which were completely decomposed into CO2 and H2O. The toxicity was significantly reduced in the combined polluted system. This study highlights the potential of the low-cost technology based on sludge reuse and its inherent significance in reducing the toxic risk of combined pollution in the environment.

Perchlorate reduction kinetics and genome-resolved metagenomics identify metabolic interactions in acclimated saline lake perchlorate-reducing consortia.

Perchlorate is a widely detected environmental contaminant in surface and underground water, that seriously impacts human health by inhibiting the uptake of thyroidal radioiodine. Perchlorate reduction due to saline lake microorganisms is not as well understood as that in marine environments. In this study, we enriched a perchlorate-reducing microbial consortium collected from saline lake sediments and found that the perchlorate reduction kinetics of the enriched consortium fit the Michaelis-Menten kinetics well, with a maximum specific substrate reduction rate (qmax) of 0.596 ± 0.001 mg ClO4-/mg DW/h and half-saturation constant (Ks) of 16.549 ± 0.488 mg ClO4-/L. Furthermore, we used improved metagenome binning to reconstruct high-quality metagenome-assembled genomes from the metagenomes of the microbial consortia, including the perchlorate-reducing bacteria (PRB) Dechloromonas agitata and Wolinella succinogenes, with the genome of W. succinogenes harboring complete functional genes for perchlorate reduction being the first recovered. Given that the electrons were directly transferred to the electronic carrier cytochrome c-553 from the quinone pool, the electron transfer pathway of W. succinogenes was shorter and more efficient than the canonical pattern. This finding provides a theoretical basis for microbial remediation of sites contaminated by high concentrations of perchlorate. Metagenomic binning and metatranscriptomic analyses revealed the gene transcription variation of perchlorate reductase pcr and chlorite dismutase cld by PRB and the synergistic metabolic mechanism.

Advanced simultaneous nitrogen and phosphorus removal for non-sterile wastewater through a novel coupled yeast-sludge system: Performance, microbial interaction, and mechanism.

A novel coupled yeast-sludge system (CYSS) was constructed by the yeast Candida sp. PNY integrated with activated sludge to treat non-sterile mainstream wastewater. After 240-day cultivation, compared with single activated sludge, simultaneous removal efficiency of total organic carbon (TOC), nitrogen and phosphorus increased by 19.5% (176.34 mg TOC g-1 d-1), 21.3% (11.25 mg TN g-1 d-1) and 15.0% (6.95 mg TP g-1 d-1), respectively, while the amount of sludge reduced by 50%. Amplicon sequencing analysis showed that the abundance of Nitrosomonas, Nitrospira, Zoogloea, Dechloromonas, and Candidatus Accumulibacter significantly decreased to 0% on Day 200. Abundance of nirS and nirK for denitrification significantly decreased in CYSS by quantitative PCR (qPCR), and the copies of nirS and nirK were 3.37-fold and 1.71-fold decrease from Day 0 to Day 240, respectively. The results of Fluorescence in situ hybridization and co-occurrence network showed that Candida sp. PNY predominated its distribution in CYSS, and strongly connected with environmental variables based on network analysis. Furthermore, this study reconstructed the carbon, nitrogen and phosphorus metabolic pathways of the CYSS based on metagenomics.

Biodegradation of phenol by Candida tropicalis sp.: Kinetics, identification of putative genes and reconstruction of catabolic pathways by genomic and transcriptomic characteristics.

Candida tropicalis sp. was isolated with predominant biodegradation capability to phenol compounds, even with high concentration or in acid environment. The biodegradation of phenol was evaluated at the following concentrations 10-1750 mg L-1, the strain exhibited well biodegradation efficiency. The maximum specific growth rate was 0.660 h-1 and the specific biodegradation rates was 0.47 mg (phenol) [(mg (VSS) h]-1. Differentially expressed genes were screened out, and results revealed a complete process of energy and carbon metabolism. The genes' arrangements and phylogenetic information showed the unique genetic characteristics of the strain. Catabolic pathways were reconstructed and some key phenol-degrading genes were obviously upregulated, including pheA, catA, OXCT and fadA. A notable detail that CMBL encoding carboxymethylenebutenolidase was speculated to be involved in a shortened pathway of phenol biodegradation, thereby contributing to the reconstruction of the novel phenol catabolic pathway through the hydrolases of dienelactone. Finally, key enzymes were verified by the analysis of specific activity.

High-concentration COD wastewater treatment with simultaneous removal of nitrogen and phosphorus by a novel Candida tropicalis strain: Removal capability and mechanism.

Aerobic and anaerobic continuous stirred-tank reactor (CSTR), up-flow anaerobic sludge blanket (UASB) were set up and inoculated with newly isolated Candida tropicalis. Reactors were operated at high concentrations of chemical oxygen demand (COD) (8000 mg/L), the modified UASB expressed better COD removal rate simultaneously removal of nitrogen and phosphate than other two reactors. Notably, under both aerobic or anaerobic conditions, large amounts of organic acids and alcohol were generated. Transcriptomic analysis showed that carbon metabolism under anaerobic conditions shared the same pathway with aerobic conditions by regulating and inhibiting some functional genes. Experiments utilizing different carbon sources proved that our strain has excellent performances in utilizing organic materials, which were verified by transcriptomic analysis. Finally, the strain was applied to treat four types of sugar-containing wastewaters. Among them, our strain exerts the best removal capability of COD (90%), nitrogen (89%), and phosphate (82%) for brewery wastewater.

Efficient biodegradation of tetrabromobisphenol A by the novel strain Enterobacter sp. T2 with good environmental adaptation: Kinetics, pathways and genomic characteristics.

T2, a gram-positive bacterium capable of rapidly degrading tetrabromobisphenol A (TBBPA), and affiliated with the genus Enterobacter, was isolated for the first time from sludge that had been contaminated for several years. The TBBPA degradation data fitted the first-order model well. Under optimal conditions (pH of 7, temperature of 31 °C, TBBPA concentration of 5 mg L-1, and inoculum size of 5%), 99.4% of the initially added TBBPA was degraded after 48 h. TBBPA degradation fitted the first-order model with the half-life of 3.3 h. These results illustrated that the TBBPA degradation capability of strain T2 was significantly better than that of previously reported bacteria. A total of 17 intermediates were detected, among which five were reported for the first time. Whole-genome sequencing revealed that strain T2 had a chromosome with the total length of 4 854 376 bp and a plasmid with the total length of 21 444 bp. It harbored essential genes responsible for debromination, such as cyp450, gstB, gstA, and HADH, and genes responsible for subsequent complete mineralization, such as bioC, yrrM, Tam, and Ubil. A key protein of haloacid dehalogenases responsible for the biodegradation of TBBPA may also be involved in the regulation of TBBPA degradation in natural environment. In soil bioremediation experiments, strain T2 showed excellent environmental adaptation. It was able to biodegrade TBBPA and its typical intermediate bisphenol A efficiently. Therefore, it could potentially be applied to treat TBBPA-contaminated sites.

Candida tropicalis prompted effectively simultaneous removal of carbon, nitrogen and phosphorus in activated sludge reactor: Microbial community succession and functional characteristics.

A new Candida tropicalis that simultaneously remove nitrogen and phosphorus, and degrade organic matters was isolated. Three continuous stirred tank reactors inoculated with C. tropicalis, activated sludge, and their co-existing system in aerobic condition were operated for 150 days. Results demonstrated that the inoculation of C. tropicalis in the co-existing system remarkably improved the carbon, nitrogen, and phosphorus removal efficiencies. The co-existing system had increased carbon, nitrogen, and phosphorus removal efficiencies (92%, 73%, and 63%, respectively); decreased biomass (reduced from 1200 mg/L to 500 mg/L); and C. tropicalis as the dominant strain. The relative abundance of traditional nitrogen- and phosphorus-removing microorganisms, such as Mycobacterium, Flavonifactor, and Devsia, increased in the co-existing system. Metagenomic analysis showed that the presence of the PCYT2, EPT1, and phnPP genes and more complexed metabolism pathways in the co-existing system might be responsible for the more activated metabolism process.

Socioeconomic Status and Risk-Taking Behavior Among Chinese Adolescents: The Mediating Role of Psychological Capital and Self-Control.

Risk-taking behavior is particularly widespread during adolescence, and negatively impacts the healthy growth and social adaptation of adolescents. Utilizing problem-behavior theory (PBT) and the family stress model (FSM), the current study examined the relationship between socioeconomic status (SES) and adolescents' risk-taking behavior, as well as the mediating role of psychological capital and self-control. A total of 1,156 Chinese adolescent students (Mage = 15.51, 48% boys) completed a series of questionnaires anonymously. The results showed that: (1) Socioeconomic status was negatively correlated with adolescents' risk-taking behavior; (2) Both psychological capital and self-control mediated the relationship between SES and adolescents' risk-taking behavior independently; and (3) Psychological capital and self-control also mediated the relationship between SES and the risk-taking behavior of adolescents sequentially. This study reveals the internal mechanism of risk-taking behavior during adolescence and provides theoretical support and empirical evidence for preventing and reducing such behavior in this age group.

N-doped biochar from sewage sludge for catalytic peroxydisulfate activation toward sulfadiazine: Efficiency, mechanism, and stability.

Sewage sludge-derived biochar (SBC) could remove organic contaminants in environment and reuse the sludge effectively. In this study, urea-doped SBC (NSBC) was prepared, characterized, and applied as heterogeneous catalytics to peroxydisulfate (PDS) activation. Sulfadiazine (SD), a widely used antibiotic, was used as a model pollutant to evaluate the efficiency and mechanism of this system. The degradation rate of SD increased to 100% after 4 h when 1 g/L of NSBC was added to the system with a SD concentration of 20 mg/L. In this study, it was confirmed that there were two important pathways in the degradation of SD by NSBC/PDS system: the free radical on the surface of NSBC and the nonradical (1O2) in the solution. The doping of N atoms makes neighboring C atoms positively charged, thereby making the direct transfer of electrons with S2O82- and the generation of 1O2 via nonradical pathway easy. In addition, the CO functional group formed during the pyrolysis of NSBC can produce 1O2 in a similar way. A total of 22 SD degradation products were identified, and 4 possible pathways were proposed. This study provide supplement for the degradation mechanism of organic compounds by carbon-based materials.

Kinetics, pathways and toxicity of hexabromocyclododecane biodegradation: Isolation of the novel bacterium Citrobacter sp. Y3.

This research investigated the biodegradation kinetics, pathways and ecological risk of hexabromocyclododecane (HBCD) by a novel bacterium Citrobacter sp. Y3. Results showed the biodegradation followed a first-order model. The specific degradation rate constant of HBCD were obviously higher in batch experiments with combined carbon sources (k: 0.156-0.290 d-1) than those using HBCD as the sole carbon source (k: 0.055 d-1). Correspondingly, the degradation half-life became much shorter (T1/2: 2.39-4.44 d vs T1/2: 13.7 d). HBCD could be degraded through dehydrobromination and dehalohydroxylation, of which six possible degradation products were detected. To evaluate the ecological risk of HBCD biodegradation products, acute toxicity tests were assessed for the first time. The acute toxicity decreased slowly during treatment for 3-5 d and then decreased sharply. In general, treatment by Strain Y3 is not only a biodegradation process but also a detoxification process, thus it shows potential for bioremediation of HBCD contaminated sites.

Triclosan in contact with activated sludge and its impact on phosphate removal and microbial community.

Triclosan (TCS) is applied in a wide range of pharmaceutical and personal care products to prevent or reduce bacterial growth. In this study, the effects of TCS on phosphate removal and bacterial community shifts of activated sludge, especially on functional bacteria variation, were investigated. Compared with the control group (R-control), the treatment group (R-TCS) with 100 µg/L TCS inhibited the microbial growth. In addition, the phosphorus removal efficiency of PO43--P and total phosphorus removal rates declined by 15.99% and 7.81%, respectively. Proteobacteria gradually dominated the microorganisms. The growths of Proteobacteria and Bacteroidetes were inhibited when 150 µg/L of TCS was added. Moreover, the differences in the microbial community structures of the R-control and R-TCS groups gradually expanded, no obvious difference was observed in the final stage, and the interrelationships of microbes in the latter weakened. The long-term addition of TCS impairs the growth of polyphosphate-accumulating organisms (PAOs).

Facile synthesis of polyoxometalate-modified metal organic frameworks for eliminating tetrabromobisphenol-A from water.

Removal of tetrabromobisphenol-A (TBBPA) from wastewater is of significance to protect the aquatic life. The present study reports the facile preparation of polyoxometalate-modified metal-organic framework (MOFs) materials for TBBPA removal from water. The polyoxometalate-modified MOFs exhibited significantly higher affinity towards TBBPA than the control MOFs. The experimental data were fitted with the Langmuir, Freundlich and Dubinin-Radushkevich models. The TBBPA adsorption onto modified MOFs fitted the pseudo-second-order kinetic model. The equilibrium adsorption isotherms showed that the adsorption of TBBPA can be fitted by the Langmuir model. The maximum adsorption capacity of adsorbent composites reached 3.65 mg/g, with 95 % removal of TBBPA. The thermodynamic parameters indicated that adsorption was spontaneous. A blue shift of phosphorus peaks obtained from XPS spectra implied the formation of intrinsic chemical bonding between TBBPA and MOFs composites. Moreover, response surface methodology was employed to characterize the TBBPA adsorption in the co-existence of different factors. BPA had strong competition for TBBPA adsorption in a wide range of pH, but not at the middle level of Ca2+ concentration. Polyoxometalate-modified MOFs can easily be recycled using a simple organic solvent washing. This study provides a novel strategy for developing cost effective adsorbents to remove TBBPA from contaminated water.

Debromination of Hexabromocyclododecane by Anaerobic Consortium and Characterization of Functional Bacteria.

A microbial consortium which can efficiently remove hexabromocyclododecane (HBCD) under anaerobic condition have been successfully enriched over 300 days. Under the optimal conditions, the degradation efficiency was 92.4% removal after treatment of 12 days with original addition of 500 µg/L HBCD, yielding 321.7 µg/L bromide in total as well. A typical debromination product, dibromocyclododecadiene (DBCD), was detected during the degradation process. The debromination profiles of three main HBCD diastereomers fitted well with first-order model (R2: 0.96-0.99), with the rate constants ranging from 1.3 × 10-1 to 1.9 × 10-1. The microbial community analysis by high throughput sequencing showed that the composition of the microbial communities varied dynamically with time and the population of functional bacteria increase sharply after enrichment. The population of Bacteroidetes increased from 5 to 47%. And some bacteria which are relatively minority in population at the beginning, such as Azospira oryzae (OTU2), Microbacterium (OTU13), and Achromobacter insolitus (OTU39) increased more than 22 times after enrichment (from 0.5 to 13%, 12%, and 11%, respectively). However, no reported dehalogenating bacteria were found after enrichment. And the contribution for debromination may come from new dehalogenating bacteria. All in all, the present study provided in-depth information on anaerobic microbial communities for HBCD removal by debromination.

Novel approach for removing brominated flame retardant from aquatic environments using Cu/Fe-based metal-organic frameworks: A case of hexabromocyclododecane (HBCD).

Cu and Fe based metal-organic frameworks (Cu-BTC and Fe-BTC) were synthesized via a simple solvothermal method and innovatively utilized to remove a typical nonionic brominated flame retardant, hexabromocyclododecane (HBCD), from aquatic environment. Results show that over 80% of HBCD was removed by Cu-BTC within 5h, which is 1.3 times higher than removal by Fe-BTC. Thermodynamic analysis confirms spontaneous adsorption of HBCD onto the metal-organic frameworks (MOFs). Furthermore, the Gibbs free energy of Cu-BTC (-9.11kJ/mol) is more negative than that of Fe-BTC (-5.04kJ/mol). Both adsorption isotherms of HBCD onto Cu-BTC and Fe-BTC followed the Langmuir model, indicating a typical monomolecular-layer adsorption mechanism. In addition, the water stability test of these MOFs shows that the collapse of the Cu-BTC crystal structure is significantly hindered in the aquatic environment due to adsorption of the hydrophobic HBCD. The proposed adsorption mechanism includes van der Waals and hydrophobic interactions. These findings demonstrate that Cu/Fe-BTC are promising adsorbents for the removal of hydrophobic organic pollutants from aquatic environments, and may further improve the understanding of MOF materials for environmental applications.

Biodegradation of tetrabromobisphenol A in the sewage sludge process.

Anaerobic sewage sludge capable of rapidly degrading tetrabromobisphenol A (TBBPA) was successfully acclimated in an anaerobic reactor over 280days. During the period from 0 to 280days, the TBBPA degradation rate (DR), utilization of glucose, and VSS were monitored continuously. After 280days of acclimation, the TBBPA DR of active sludge reached 96.0% after 20days of treatment in batch experiments. Based on scanning electron microscopy (SEM) observations and denaturing gradient gel electrophoresis (DGGE) determinations, the diversity of the microorganisms after 0 and 280days in the acclimated anaerobic sewage sludge was compared. Furthermore, eleven metabolites, including 2-bromophenol, 3-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, tribromophenol and bisphenol A, were identified by gas chromatography-mass spectrometry (GC-MS). Moreover, the six primary intermediary metabolites were also well-degraded by the acclimated anaerobic sewage sludge to varying degrees. Among the six target metabolites, tribromophenol was the most preferred substrate for biodegradation via debromination. These metabolites degraded more rapidly than monobromide and bisphenol A. The biodegradation data of the intermediary metabolites exhibited a good fit to a pseudo-first-order model. Finally, based on the metabolites, metabolic pathways were proposed. In conclusion, the acclimated microbial consortia degraded TBBPA and its metabolites well under anaerobic conditions.

Efficient degradation of tetrabromobisphenol A by synergistic integration of Fe/Ni bimetallic catalysis and microbial acclimation.

This study provides a novel technology for the degradation of tetrabromobisphenol A (TBBPA) via an interaction of Fe redox and a shift of functional microbial community. TBBPA was degraded by integration of synthesized Fe-Ni bimetallic particles and enriched microbial consortium within an aqueous system. This cooperative integration yielded the best TBBPA-degrading capacity (100% removal after treatment for 2 h) and highest TOC-removing efficiency (94.5% removal after treatment for 96 h), as well as the lowest toxicity to Vibrio fischeri (almost 0% growth inhibition during reaction). The synergistic mechanism of integrated system was clarified based on systematical analyses of the degradation processes as well as the shifts in microbial community. Owing to the microbial metabolism and the Fenton-like process of leaked Fe2+, Fe3+ and Ni2+ from Fe-Ni bimetallic catalyst, reactive oxidative species (ROS), including superoxide (O2-), hydroxyl radicals (OH) and hydrogen peroxide (H2O2) were produced and evaluated by multiple techniques. Moreover, the quenching experiments indicated that OH was the major ROS leading to TBBPA degradation, rather than H2O2 or O2-. Based on the analysis of the 12 detected intermediates, three parallel pathways were proposed. It was clearly revealed that reductive and oxidative debromination, hydroxylation, and ß-scission simultaneously occurred in the integrated system. Fe non-randomly accelerated the enrichment of TBBPA-degrading microbes (e.g. Pseudomonas sp. and Citrobacter sp., etc.). Above all, this novel technology has great promise for field-applications for remediation of TBBPA-contaminated field.

Isolation of a non-fermentative bacterium, Pseudomonas aeruginosa, using intracellular carbon for denitrification and phosphorus-accumulation and relevant metabolic mechanisms.

A newly designed pilot-scale system was developed to enrich denitrifying phosphate-accumulating organisms (DNPAOs) for nitrogen and phosphorus nutrient removal synchronously. A strain of DNPAOs was isolated and its biochemical characteristics and metabolic mechanisms of this bacterial strain were analyzed. The results showed that compared with previously reported system, this newly designed system has higher removal rates of nutrients. Removal efficiencies of NH3-N, TN, TP, and COD in actual wastewater were 82.64%, 79.62%, 87.22%, and 90.41%, respectively. Metabolic activity of DNPAOs after anoxic stage in this study even reached 94.64%. Pseudomonas aeruginosa is a strain of non-fermentative DNPAOs with strong nitrogen and phosphorus removal abilities. Study on the metabolic mechanisms suggested that intracellular PHB of P. aeruginosa plays dual roles, supplying energy for phosphorus accumulation and serving as a major carbon source for denitrification.

Study of novel pure culture HBCD-1, effectively degrading Hexabromocyclododecane, isolated from an anaerobic reactor.

In this study, two pure strains, named HBCD-1 and HBCD-2, were isolated from a continuous anaerobic reactor over 300-days acclimation, which processed high capability of biodegrading Hexabromocyclododecane. Both of the two strains degraded HBCD diastereomers in different extents, especially strain HBCD-1, which interestingly degraded α-HBCD effectively. All of the degrading results were well fitted with the first-order kinetics model. By morphological observation and 16S rRNA gene sequence analysis, the strain HBCD-1 showed highest similarity with Achromobacter sp. Under the optimal culturing conditions of 30°C, pH 7 and the initial HBCD concentration of 500µg/L, the biodegradation rate of HBCD-1 reached 90% after 8days treatment. Moreover, during the biodegradation process by HBCD-1 strain, the concentration of bromide ion was lower than the theoretical value. Finally, 4 metabolites were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as well as a biodegradation pathway was proposed.