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1.
Environ Pollut ; 263(Pt B): 114381, 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-32203859

RESUMO

Estrogens, which are extensive in the eco-environments, are a category of high-toxic emerging contaminants that induce metabolic disorders and even carcinogenic risks in wildlife and humans. Here we investigate whether fungus-secreted laccase can be used as a green catalyst to eliminate a representative estrogen, 17ß-estradiol (E2). A white-rot fungus Trametes hirsuta La-7 with high laccase-productivity, was isolated from pig manure-contaminated soil. Extracellular laccase activity expressed by strain La-7 was 65.4 U·mL-1 for a 3 d inoculation under the optimal fermentation parameters. The concentrated-crude laccase from Trametes hirsuta La-7 (CC-ThLac) was capable of effectively metabolizing E2 at pH 4-6, and the apparent pseudo first-order reaction rate constant and half-life values were respectively 0.027-0.055 min-1 and 25.86-12.67 min (R2 > 0.98). The mass measurement of high-resolution mass spectrometry in combination with 13C-isotope labeling identified that the main by-products of E2 metabolism were dimers, trimers, and tetramers, which are consistent with radical-driven C-C and/or C-O-C covalent coupling pathway, involving the initial enzymatic production of phenoxy radical intermediates and then the successive oxidative-oligomerization of radical intermediates. The formation of oligomers dramatically reduced the estrogenic activity of E2. Additionally, CC-ThLac also exhibited high-efficiency metabolism capability toward E2 in the natural water and pig manure, with more than 94.4% and 91.0% of E2 having been metabolized, respectively. These findings provide a broad prospect for the clean biotechnological applications of Trametes hirsuta La-7 in estrogen-contaminated ecosystems.

2.
J Hazard Mater ; 393: 122393, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-32120219

RESUMO

Nanozymes, which display the bifunctional properties of nanomaterials and natural enzymes, are useful tools for environmental remediation. In this research, nano-MnO2 was selected for its intrinsic enzyme-like activity to remove 17ß-estradiol (E2). Results indicated that nano-MnO2 exhibited laccase-like activity (7.22 U·mg-1) and removed 97.3 % of E2 at pH 6. Humic acid (HA) impeded E2 removal (only 72.4 %) by competing with E2 for the catalytic sites of the MnO2 nanozyme surface, and there was a good linear correlation between the kinetic constants and HA concentrations (R2 = 0.9489). Notably, the phenolic -OH of E2 interacted with HA to yield various polymeric products via radical-driven covalent coupling, resulting in ablation of phenolic -OH but increase of ether groups in the polymeric structure. Intermediate products, including estrone, E2 homo-/hetero-oligomers, E2 hydroxylated and quinone-like products, as well as aromatic ring-opening species, were identified. Interestingly, HA hindered the extent of E2 oxidation, homo-coupling, and decomposition but accelerated E2 and HA hetero-coupling. A reasonable catalytic pathway of E2 and HA involving MnO2 nanozyme was proposed. These findings provide novel insights into the influence of HA on MnO2 nanozyme-driven E2 radical polymerization and decomposition, consequently favoring the ecological water restoration and the global carbon cycle.

3.
Sci Total Environ ; 706: 135711, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31791784

RESUMO

The environmental toxicity of silver nanoparticles (AgNPs) is currently the focus of intensive research. However, the mechanisms underlying the cytotoxic effects of AgNPs on denitrifying microbes have yet to be explicitly demonstrated. Herein, Pseudomonas stutzeri was used to explore the effects of AgNPs on denitrification and cytotoxicity. The denitrification efficiency decreased from 94.91% in the AgNP-free treatment to 87.66%, 60.51% and 36.10% with treatments of 3.125, 6.25 and 12.5 mg/L AgNPs, respectively. The inhibition and delay in the denitrification process from treatment with AgNPs likely occurred through alteration of the viability and metabolic activity of P. stutzeri. Flow cytometry analysis indicated that the early apoptotic rates of P. stutzeri were 8.72%, 30.60%, and 48.60% with treatments of 3.125, 6.25, and 12.5 mg/L AgNPs, respectively. Results for scanning electron microscope (SEM) imaging, ζ-potential analysis, lactate dehydrogenase (LDH) release and malondialdehyde (MDA) production assays demonstrated adsorption of AgNPs on the cell surface, which altered membrane potential and mediated lipid peroxidation; these events eventually resulted in the aberration of cell morphology. Transmission electron microscopy (TEM) images and measurements of Ag content distribution by ICP-MS indicated that AgNPs were easily internalized by P. stutzeri, which increased the accumulation of reactive oxygen species (ROS). Furthermore, the presence of AgNPs also greatly inhibited expression of genes napA, nirS, cnorB, and nosZ, thereby reducing the activities of nitrate reductase (NAR) and nitrite reductase (NIR). These findings will help further our understanding of the mechanism underlying AgNPs cytotoxicity, and provide the means to evaluate the negative effect of nanoparticles in the environment.

4.
Huan Jing Ke Xue ; 40(6): 2939-2947, 2019 Jun 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854689

RESUMO

In order to study the effect of nanosilver on soil nitrification microorganisms and nitrogen transformation, soil culture experiments were carried out. Yellow brown soil and paddy soil were first spiked with different doses of nanosilver (10, 50, 100 mg·kg-1) and silver ions (1, 5, 10 mg·kg-1). Then, the number of nitrifying bacteria, activity of soil invertase, amoA gene abundance, NH4+-N content, NO3--N content, and soil potential ammonia oxidation rate were determined. The results showed that the number of nitrite bacteria and nitrate bacteria decreased significantly when the soils were treated with nanosilver and silver ions. Soil invertases were inhibited, and the effect on urease was greater than that on catalase. The amoA gene abundances of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) decreased, and the effect on the gene abundance of AOB was greater than that of AOA. When (NH4)2SO4 was added to the soil, nanosilver and silver ion pollutants caused NH4+-N to accumulate, and the contents of NO3--N were reduced, the rate of ammonia oxidation decreased, and the transformation of ammonium nitrogen to nitrate nitrogen was inhibited. This research suggests that nanosilver and silver ions can have toxic effects on soil nitrification microorganisms and ammonium nitrogen conversion, and the degree of influence was found to be related to the soil physical and chemical properties.

5.
Environ Sci Pollut Res Int ; 26(36): 36410-36422, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31728944

RESUMO

This study demonstrated, for the first time, Fe(III)/peroximonosulphate (PMS) could be an efficient advanced oxidation process (AOP) for wastewater treatment. Bisphenol A (BPA) was chosen as a model pollutant in the present study. Fe(III)-activated PMS system proved very effective to eliminate 92.18% of BPA (20 mg/L) for 30-min reaction time at 0.50 mM PMS, 1.5 g/L Fe(III), pH 7.0. The maximum degradation of BPA occurred at neutral pH, while it was suppressed at both strongly acidic and alkaline conditions. Organic and inorganic ions can interfere with system efficiency either positively or negatively, so their interaction was thoroughly investigated. Furthermore, the presence of organic acids also affected BPA degradation rate, especially the addition of 10 mM citric acid decreased the degradation rate from 92.18 to 66.08%. Radical scavenging experiments showed that SO4•- was the dominant reactive species in Fe(III)/PMS system. A total of 5 BPA intermediates were found by using LC/MS. A possible degradation pathway was proposed which underwent through bridge cleavage and hydroxylation processes. Acute toxicity of the BPA degradation products was assessed using Escherichia coli growth inhibition test. These findings proved to be promising and economical to deal with wastewater using iron mineral for the elimination of organic pollutants. Graphical abstract.


Assuntos
Compostos Benzidrílicos/análise , Compostos Férricos/química , Peróxidos/química , Fenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Oxirredução
6.
Water Res ; 166: 115040, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31505307

RESUMO

Estrogens are a category of non-degradable organic pollutants prevalent in aquatic environments with reported health risks in human and wildlife reproduction. A biotechnological approach is proposed for utilizing fungal laccase-mediated humification reactions (L-MHRs) to remove estrogens from water. Through a reactive radical-mediated C-C, C-O-C, or C-N-C covalent coupling mechanism, multifarious complex polymeric structures are generated having limited solubilities, which significantly reduces their estrogenic activity and ecotoxicity. This review highlights the available literature associated with the self/cross-coupling mechanism of fungal L-MHRs in catalyzing the single-electron oxidation of estrogens and humic acid (HA). Advances in identifying unknown estrogen-HA cross-coupling products using high-resolution mass spectrometry combined with 13C-isotope labeling and 13C NMR may provide key research directions beneficial to aquatic ecological restoration measures.


Assuntos
Estrogênios , Poluentes Químicos da Água , Ecossistema , Estrona , Substâncias Húmicas , Lacase
7.
Nanoscale ; 11(34): 15783-15793, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31432841

RESUMO

Phenolic contaminants (R-OH) are a category of highly toxic organic compounds that are widespread in aquatic ecosystems and can induce carcinogenic risk to wildlife and humans; natural enzymes as green catalysts are capable of step-polymerizing these compounds to produce diverse macromolecular self-coupling products via radical-mediated C-C and C-O-C bonding at either the ortho- or para-carbon position, thereby evading the bioavailability and ecotoxicity of these compounds. Intriguingly, certain artificial metal and metal-oxide nanomaterials are known as nanozymes. They not only possess the unique properties of nanomaterials but also display intrinsic enzyme-mimicking activities. These artificial nanozymes are expected to surmount the shortcomings, such as low stability, easy inactivation, difficult recycling, and high cost, of natural enzymes, thus contributing to eco-environmental restoration. This review highlights the available studies on the enzymatic characteristics and catalytic mechanisms of natural enzymes and artificial metal and metal-oxide nanozymes in the removal and transformation of R-OH. These advances will provide key research directions beneficial to the multifunctional applications of artificial nanozymes in aquatic ecosystems.


Assuntos
Materiais Biomiméticos , Ecossistema , Poluentes Ambientais/química , Metais/química , Nanoestruturas/química , Óxidos/química , Oxirredutases/química , Benzoatos/química , Catálise , Humanos
8.
Bull Environ Contam Toxicol ; 103(1): 181-186, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31049596

RESUMO

Silver nanoparticles (AgNPs) is widely used as an antibacterial agent, but the specific antibacterial mechanism is still conflicting. This study aimed to investigate the size dependent inhibition of AgNPs and the relationship between inhibition and reactive oxygen species (ROS). Azotobactervinelandii and Nitrosomonaseuropaea were exposed to AgNPs with different particles size (10 nm and 50 nm). The ROS production was measured and the results showed that the generation of ROS related to the particle size and concentrations of AgNPs. At 10 mg/L of 10 nm Ag particles, the apoptosis rate of A. vinelandii and N. europaea were 20.23% and 1.87% respectively. Additionally, the necrosis rate of A. vinelandii and N. europaea reached to 15.20% and 42.20% respectively. Furthermore, transmission electron microscopy images also indicated that AgNPs caused severely bacterial cell membrane damage. Together these data suggested that the toxicity of AgNPs depends on its particle size and overproduction of ROS.


Assuntos
Azotobacter vinelandii/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Prata/toxicidade , Apoptose/efeitos dos fármacos , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Espécies Reativas de Oxigênio/metabolismo
9.
Environ Sci Technol ; 53(7): 3802-3810, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30861341

RESUMO

The increasing use of silver-containing nanoparticles (NPs) in commercial products has led to NP accumulation in the environment and potentially in food webs. Identifying the uptake pathways of different chemical species of NPs, such as Ag2S-NP and metallic AgNPs, into plants is important to understanding their entry into food chains. In this study, soybean Glycine max L. was hydroponically exposed to Ag2S-NPs via their roots (10-50 mg L-1) and stable-isotope-enriched 109AgNPs via their leaves [7.9 µg (g fresh weight)-1]. Less than 29% of Ag in treated leaves (in direct contact with 109AgNP) was accumulated from root uptake of Ag2S-NPs, whereas almost all of the Ag in soybean roots and untreated leaves sourced from Ag2S-NPs. Therefore, Ag2S-NPs are phytoavailable and translocate upward. During trophic transfer the Ag isotope signature was preserved, indicating that accumulated Ag in snails most likely originated from Ag2S-NPs. On average, 78% of the Ag in the untreated leaves was assimilated by snails, reinforcing the considerable trophic availability of Ag2S-NPs via root uptake. By highlighting the importance of root uptake of Ag2S-NPs in plant uptake and trophic transfer to herbivores, our study advances current understanding of the biogeochemical fate of Ag-containing NPs in the terrestrial environment.


Assuntos
Nanopartículas Metálicas , Prata , Cadeia Alimentar , Isótopos , Soja
10.
World J Microbiol Biotechnol ; 35(4): 64, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30923928

RESUMO

Chromate is one of the hazardous toxic pollutants. Reduction of Cr(VI) to Cr(III) has shown to reduce the toxicity of chromate. This work examined the reduction of Cr(VI) using an anaerobic batch cultures of Shewanella oneidensis MR-1 containing Fe(III). To do so, 10 mg/L Cr(VI) was reduced to Cr(III) within 3 days along with the oxidization of Fe(II) to Fe(III). The removal rate of Cr(VI) increased with increasing the concentration of Fe(III). In the absence of Cr(VI), the Fe(II) concentration of the batch culture increased with the growth of S. oneidensis MR-1. These data showed that S. oneidensis MR-1 could reduce Fe(III) into Fe(II), resulting in reduction of Cr(VI) to Cr(III). During this process, the anthraquinone-2,6-disulfonate (AQDS) acted as an electron shuttle. Microscopic analysis showed that Cr(VI) had toxic effects on S. oneidensis MR-1 due to the appearance of Cr species on the bacterial surface. Cr2O3 or Cr(OH)3 precipitates formed during Cr(VI) reduction was identified using X-ray photoelectron spectroscopy. The AQDS as an electron shuttle enhanced the Cr(VI) reduction by S. oneidensis MR-1. Microbial reduction of Cr(VI) can be a useful technique for Cr detoxification.


Assuntos
Cromo/metabolismo , Elétrons , Compostos Férricos/metabolismo , Shewanella/metabolismo , Antraquinonas/metabolismo , Técnicas de Cultura Celular por Lotes , Biodegradação Ambiental , Cromatos/toxicidade , Transporte de Elétrons , Oxirredução , Shewanella/citologia , Shewanella/crescimento & desenvolvimento
11.
Chemosphere ; 225: 745-754, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30903848

RESUMO

Laccase-mediated humification processes (L-MHPs) can be used to polymerize and transform phenolic pollutants in water. However, the mechanism on Cu2+ impacts the self-polymerization of multi-purpose antimicrobial agent triclosan during L-MHPs is less understood. Here, the influence of divalent metal ions (DMIs) on Trametes versicolor laccase activity was investigated. Particularly, the performance of Cu2+-assisted laccase in polymerizing and transforming triclosan was systematically characterized. Compared with DMI-free, the activity of laccase was obviously accelerated with Cu2+ present due to copper is a vital component of laccase catalytic center. It was found that Cu2+-assisted laccase was effective in transforming triclosan, and the enzymatic reaction kinetic constants increased from 0.28 to 0.73 h-1 as the Cu2+ concentration increased (0-3.0 mM). Identification of intermediate products revealed that laccase oxidation predominantly generated triclosan dimers, trimers, and tetramers. The presence of Cu2+ reinforced self-polymerization of triclosan via forming more triclosan oligomers relative to the Cu2+-free, which likely attributed to the enhancement of laccase activity and stability with Cu2+ present in L-MHPs. A possible transformation mechanism was proposed as follows: Laccase initially catalyzed the oxidation of triclosan to generate phenoxy radical intermediates, which self-coupled to each other subsequently by radical-mediated CC and COC covalent binding, forming oligomers and polymers. The growth inhibitory assays of freshwater microalgae (Chlamydomonas reinhardtii and Scenedesmus obliquus) demonstrated that the self-polymerized triclosan by L-MHPs had lower toxicity than the parent compound. These findings implied that Cu2+-assisted laccase was an effective strategy for rapidly self-polyreaction and detoxication of triclosan from Cu2+-triclosan combined polluted wastewater.


Assuntos
Cobre/química , Lacase/química , Trametes/patogenicidade , Triclosan/química
12.
Environ Sci Pollut Res Int ; 26(14): 14350-14361, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30868464

RESUMO

In this study, a novel Fe-Mn binary oxide (FMBO), which combined the oxidation capability of iron and manganese oxides, was constructed to remove sulfamethoxazole (SMX) effectively using the simultaneous co-precipitation and oxidation methods, and the reaction products were probed by liquid chromatography-mass spectrometry (LC/MS). Particularly, FMBO-mediated transformation mechanisms of SMX were explored using radical scavengers and electron paramagnetic resonance (EPR). Results indicated that the best removal efficiency was obtained at a pH of 4.0, with the H2O2 of 6.0 mmol/L and the FMBO dosage of 2.0 g/L, giving 97.6% removal of 10 mg/L SMX within 60 min. More importantly, we found that the hydroxyl (•OH) radicals generated by FMBO through Fenton-like reaction were responsible for the SMX oxidation. EPR studies were confirmed that the peak intensities of hydroxyl adduct decreased remarkably with increasing pH values. Moreover, the four SMX degradation intermediate products were detected by LC/MS and a reaction pathway for the possible mineralization of SMX, with •OH radicals as the main oxidant, was proposed. These findings provide a novel insight into the removal of SMX by FMBO-mediated radical reactions in aquatic environments. Moreover, this research suggested that FMBO can act as an efficient catalyst to remove SMX in hospital wastewater.


Assuntos
Compostos Férricos/química , Radical Hidroxila/química , Compostos de Manganês/química , Óxidos/química , Sulfametoxazol/análise , Poluentes Químicos da Água/análise , Peróxido de Hidrogênio/química , Modelos Teóricos , Oxidantes/química , Oxirredução , Sulfametoxazol/química , Poluentes Químicos da Água/química
13.
R Soc Open Sci ; 6(1): 181769, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30800404

RESUMO

As a simple and feasible method for acute biotoxicity assessment, personal glucose meter (PGM) can be successfully applied in the early warning of environmental pollutants in sewage. In this paper, the acute biotoxicity of single and joint heavy metals in sewage and real sludge samples was systematically described based on the glucose metabolism of Escherichia coli (E. coli). Results indicated that the biotoxicity order of five single heavy metals in sewage was Hg2+ > As3+ > Cu2+ > Zn2+ > Cd2+. The joint heavy metals of Cu2+ + Zn2+, Cu2+ + Cd2+, and Cu2+ + Hg2+ produced synergistic effects, while Cu2+ + As3+ and Cd2+ + Zn2+ possessed antagonistic effects for the combined biotoxicity. In spiked sludge, Cd2+ and Zn2+ owned higher biotoxicity than Cu2+ and As3+. Notably, the electroplate factory and housing estate sludge respectively showed the highest and lowest inhibition rates as 57.4% and 17.7% under the real sludge biotoxicity assessment. These results demonstrated that PGM was a sensitive and portable method, which could be widely used for acute biotoxicity assessment of heavy metals in sewage sludge.

14.
PLoS One ; 13(12): e0209020, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30566461

RESUMO

The influence of nanomaterials on the ecological environment is becoming an increasingly hot research field, and many researchers are exploring the mechanisms of nanomaterial toxicity on microorganisms. Herein, we studied the effect of two different sizes of nanosilver (10 nm and 50 nm) on the soil nitrogen fixation by the model bacteria Azotobacter vinelandii. Smaller size AgNPs correlated with higher toxicity, which was evident from reduced cell numbers. Flow cytometry analysis further confirmed this finding, which was carried out with the same concentration of 10 mg/L for 12 h, the apoptotic rates were20.23% and 3.14% for 10 nm and 50 nm AgNPs, respectively. Structural damage to cells were obvious under scanning electron microscopy. Nitrogenase activity and gene expression assays revealed that AgNPs could inhibit the nitrogen fixation of A. vinelandii. The presence of AgNPs caused intracellular reactive oxygen species (ROS) production and electron spin resonance further demonstrated that AgNPs generated hydroxyl radicals, and that AgNPs could cause oxidative damage to bacteria. A combination of Ag content distribution assays and transmission electron microscopy indicated that AgNPs were internalized in A. vinelandii cells. Overall, this study suggested that the toxicity of AgNPs was size and concentration dependent, and the mechanism of antibacterial effects was determined to involve damage to cell membranes and production of reactive oxygen species leading to enzyme inactivation, gene down-regulation and death by apoptosis.


Assuntos
Apoptose/efeitos dos fármacos , Azotobacter vinelandii/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Compostos de Prata/toxicidade , Azotobacter vinelandii/crescimento & desenvolvimento , Azotobacter vinelandii/metabolismo , Azotobacter vinelandii/ultraestrutura , Proteínas de Bactérias/metabolismo , Poluentes Ambientais , Expressão Gênica/efeitos dos fármacos , Radical Hidroxila/metabolismo , Nanopartículas Metálicas/química , Fixação de Nitrogênio/efeitos dos fármacos , Tamanho da Partícula , Espécies Reativas de Oxigênio/metabolismo , Compostos de Prata/química
15.
Environ Toxicol Pharmacol ; 62: 156-163, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30029095

RESUMO

The ability of anthraquinone-2,6-disulfonate (AQDS) and riboflavin to enhance the sulfamethoxazole (SMX) degradation coupled with the Fe(III) reduction by Shewanella oneidensis MR-1 was investigated. The results indicated that the SMX degradation rate was 38.5% with an initial SMX concentration at 0.04 mM. For the overall performance of AQDS and riboflavin mediated SMX degradation and iron reduction, the SMX degradation rate was gradually increased with the enhancement of iron reduction. Riboflavin had a stronger enhancement on SMX degradation and iron reduction than AQDS, but the enhancement was not positively correlated with electron shuttles concentration. A quantitative characterization of the electron transfer capacity (ETC) of the electron shuttles showed that the ETC was higher for riboflavin than AQDS. The S. oneidensis MR-1 16S rRNA gene copies results indicated that electron shuttles had a positive effect on the microbial activity of S. oneidensis MR-1. The LCMS result indicated that the products of the SMX biodegradation were 3-amino-5-methylisoxazole and 4-aminobenzenesulfonic acid, which suggested that the SMX biodegradation was caused by SN bond cleavage. This study indicates that the biochemical mechanisms play a vital role in SMX transformation and Fe(II) generation in this system.


Assuntos
Antraquinonas/farmacologia , Ferro/metabolismo , Riboflavina/farmacologia , Shewanella/efeitos dos fármacos , Sulfametoxazol/metabolismo , Biodegradação Ambiental/efeitos dos fármacos , Elétrons , Oxirredução , RNA Ribossômico 16S , Shewanella/genética , Shewanella/metabolismo
16.
Biodegradation ; 29(2): 129-140, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29302823

RESUMO

Because of extensive sulfonamides application in aquaculture and animal husbandry and the consequent increase in sulfonamides discharged into the environment, strategies to remediate sulfonamide-contaminated environments are essential. In this study, the resistance of Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 to the sulfonamides sulfapyridine (SPY) and sulfamethoxazole (SMX) were determined, and sulfonamides degradation by these strains was assessed. Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 were resistant to SPY and SMX concentrations as high as 60 mg/L. After incubation for 5 days, 23.91 ± 1.80 and 23.43 ± 2.98% of SPY and 59.88 ± 1.23 and 63.89 ± 3.09% of SMX contained in the medium were degraded by S. oneidensis MR-1 and Shewanella sp. strain MR-4, respectively. The effects of the initial concentration of the sulfonamides and initial pH of the medium on biodegradation, and the degradation of different sulfonamides were assessed. The products were measured by LC-MS; with SPY as a substrate, 2-AP (2-aminopyridine) was the main stable metabolite, and with SMX as a substrate, 3A5MI (3-amino-5-methyl-isoxazole) was the main stable metabolite. The co-occurrence of 2-AP or 3A5MI and 4-aminobenzenesulfonic acid suggests that the initial step in the biodegradation of the two sulfonamides is S-N bond cleavage. These results suggest that S. oneidensis MR-1 and Shewanella sp. strain MR-4 are potential bacterial resources for biodegrading sulfonamides and therefore bioremediation of sulfonamide-polluted environments.


Assuntos
Shewanella/metabolismo , Sulfonamidas/metabolismo , Biodegradação Ambiental , Resistência Microbiana a Medicamentos , Concentração de Íons de Hidrogênio , Shewanella/crescimento & desenvolvimento , Sulfametoxazol/química , Sulfametoxazol/metabolismo , Sulfapiridina/química , Sulfapiridina/metabolismo , Sulfonamidas/química
17.
Environ Pollut ; 222: 50-57, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28089465

RESUMO

With the increasing application in antimicrobial products, silver nanoparticles (AgNP) are inevitably released into the terrestrial environment, and pose potential risks to invertebrates such as land snails Achatina fulica, which take up AgNP from food and water. Here we differentiate Ag uptake biodynamic between Ag forms (i.e., PVP-AgNP vs. AgNO3) and between exposure pathways. Snails assimilated Ag efficiently from lettuce leaves pre-exposed to AgNP, with assimilation efficiencies (AEs) averaging 62-85% and food ingestion rates of 0.11 ± 0.03 g g-1 d-1. Dietary Ag bioavailability was independent on Ag forms, as revealed by comparable AEs between AgNP and AgNO3. However, the uptake rate constant from water was much lower for AgNP relative to AgNO3 (2 × 10-4 vs. 0.12 L g-1 d-1). The elimination rate constants were 0.0093 ± 0.0037 d-1 for AgNP and 0.019 ± 0.0077 d-1 for AgNO3. Biodynamic modeling further showed that dietary exposure was the dominant uptake pathway for AgNP in most circumstances, while for AgNO3 the relative importance of waterborne and dietary exposure depended on Ag concentrations in food and water. Our findings highlight the importance of dietary uptake of AgNP during bioaccumulation, which should be considered in the risk assessment of these nanoparticles.


Assuntos
Disponibilidade Biológica , Alface/química , Nitrato de Prata/metabolismo , Prata/metabolismo , Caramujos/metabolismo , Animais , China , Nanopartículas Metálicas
18.
Huan Jing Ke Xue ; 37(4): 1330-6, 2016 Apr 15.
Artigo em Chinês | MEDLINE | ID: mdl-27548953

RESUMO

Mercury is harmful to the environment, which has gradually become one of the research hotspots. Sediments, as a main repository of pollutants, have an important impact on water quality and the internal organisms, which deserves our research. In this paper, we focused on Hefei landscape water sediment and tried to investigate the status of inorganic mercury and methylmercury pollutions in the sediment. To study the conversion process from inorganic mercury to methylmercury and their enrichment levels and mechanism, we established the ecological chain of "sediment-water-grass-fish" through analog microcosm examination. The results were as follows: from ten water and sediment samples in Hefei landscape water sediment, we found that the contents of inorganic mercury and methylmercury ranged 11.74-13.12 µg · kg⁻¹ and 0.37-2.23 µg · kg⁻¹, respectively. The microcosm examination showed that: with increasing culture time, inorganic mercury in sediments gradually decreased. There was a phenomenon that the content of methylmercury increased at first and then decreased to reach the balance later. Both the inorganic mercury and methylmercury in water change showed an increasing trend. The enrichment contents of inorganic mercury in Egeria densa Planch, and golden mandarin fish (Siniperca scherzeri Steindachner) were low while their enrichment of methylmercury could he great. In addition, we found that both the bioaccumulation ability and the enrichment coefficient of methylmercury in the body of golden mandarin fish were the maximum during the same period.


Assuntos
Monitoramento Ambiental , Mercúrio/análise , Compostos de Metilmercúrio/análise , Poluentes Químicos da Água/análise , Animais , Peixes , Sedimentos Geológicos/química , Masculino , Poaceae/química , Água/química
19.
Water Sci Technol ; 73(12): 2913-20, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27332836

RESUMO

The effects of solid-state NaOH pretreatment on the efficiency of methane production from semi-dry anaerobic digestion of rose (Rosa rugosa) stalk were investigated at various NaOH loadings (0, 1, 2, and 4% (w/w)). Methane production, process stability and energy balance were analyzed. Results showed that solid-state NaOH pretreatment significantly improved biogas and methane yields of 30-day anaerobic digestion, with increases from 143.7 mL/g volatile solids (VS) added to 157.1 mL/g VS -192.1 mL/g VS added and from 81.8 mL/g VS added to 88.8 mL/g VS-117.7 mL/g VS added, respectively. Solid-state NaOH pretreatment resulted in anaerobic digestion with higher VS reduction and lower technical digestion time. The 4% NaOH-treated group had the highest methane yield of 117.7 mL/g VS added, which was 144% higher compared to the no NaOH-treated group, and the highest net energy recovery. Higher rate of lignocellulose breakage and higher process stability of anaerobic digestion facilitated methane production in the NaOH-pretreated groups.


Assuntos
Biocombustíveis/análise , Metano/biossíntese , Rosa/química , Hidróxido de Sódio/química , Anaerobiose , Caules de Planta/química
20.
Chemosphere ; 150: 79-89, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26891360

RESUMO

The human population boom, urbanization and rapid industrialization have either directly or indirectly resulted in the serious environmental toxification of the soil-food web by metal exposure from anthropogenic sources in most of the developing industrialized world. The present study was conducted to analyze concentrations of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in soil and vegetables in the urban-periurban areas influenced by emerging industry. Vegetables and their corresponding soil samples were collected and analyzed for heavy metals contents from six random sites. According to the results, the potential health risks from metals to the local communities were assessed by following the methodology described by the US-EPA. In general, the total non-carcinogenic risks were shown to be less than the limits set by the US-EPA. However, the potential risk of developing carcinogenicity in humans over a lifetime of exposure could be increased through the dietary intake of Cd, Cr and Ni. In some cases, Pb was also marginally higher than the safe level. It was concluded that some effective remedial approaches should be adopted to mitigate the risks of Cd, Cr, Ni and Pb in the study area because these metal levels have exceeded the safe limits for human health. However, new studies on gastrointestinal bioaccessibility in human are required to heighten our understanding about metals exposure and health risk assessment.


Assuntos
Exposição Ambiental/análise , Contaminação de Alimentos/análise , Metais Pesados/análise , Poluentes do Solo/análise , População Suburbana , População Urbana , Humanos , Indústrias , Paquistão , Distribuição Aleatória , Medição de Risco , Solo/química , Verduras/química
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