Aerobic degradation of BDE-209 by Enterococcus casseliflavus: Isolation, identification and cell changes during degradation process

Mitigation of Nitrogen Losses in a Plant-Soil System through Incorporation of Nanocellulose and Zinc-Modified Nanocellulose

Most nitrogen (N) applied to plants as fertilizer is lost through leaching. Here, nanocellulose was used in mitigating N leaching loss. Lettuce-cropped soil was treated with unmodified or Zn-modified nanocellulose (1-2% by wt) in combination with NPK, compared with urea and NPK-only treatments. Consecutive leaching, plant growth, plant N uptake, and soil nitrogen retention were assessed. Nanocellulose + NPK significantly (p ≤ 0.05) reduced N leaching, compared with urea and NPK-only. 1-and-2 wt % nanocellulose, as well as Zn-modified 1-and-2 wt % nanocellulose, reduced N leaching by 45, 38, 39, and 49% compared with urea and by 43, 36, 37, and 47% compared with NPK-only, respectively. Nitrogen leached mainly as NO3- (98.4%). Compared with urea and NPK, lettuce shoot mass was significantly (p ≤ 0.05) increased by 30-42% and by 44-57%, respectively, by all nanocellulose treatments, except for the Zn-modified 1 wt % nanocellulose. Leached N negatively correlated to biomass yield. Soil N retention was enhanced by the pristine and Zn-modified nanocelluloses between 27 and 94%. Demonstrably, nanocellulose can be utilized for mitigating N loss in soil and supporting crop production, resource management, and environmental sustainability.

Enhanced degradation of enrofloxacin in mariculture wastewater based on marine bacteria and microbial carrier

This study aimed to isolate marine bacteria to investigate their stress response, inhibition mechanisms, and degradation processes under high-load conditions of salinity and enrofloxacin (ENR). The results demonstrated that marine bacteria exhibited efficient pollutant removal efficiency even under high ENR stress (up to 10 mg/L), with chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN) and ENR removal efficiencies reaching approximately 88%, 83%, 61%, and 73%, respectively. The predominant families of marine bacteria were Bacillaceae (50.46%), Alcanivoracaceae (32.30%), and Rhodobacteraceae (13.36%). They responded to ENR removal by altering cell membrane properties, stimulating the activity of xenobiotic-metabolizing enzymes and antioxidant systems, and mitigating ENR stress through the secretion of extracellular polymeric substance (EPS). The marine bacteria exhibited robust adaptability to environmental factors and effective detoxification of ENR, simultaneously removing carbon, nitrogen, phosphorus, and antibiotics from the wastewater. The attapulgite carrier enhanced the bacteria's resistance to the environment. When treating actual mariculture wastewater, the removal efficiencies of COD and TN exceeded 80%, TP removal efficiency exceeded 90%, and ENR removal efficiency approached 100%, significantly higher than reported values in similar salinity reactors. Combining the constructed physical and mathematical models of tolerant bacterial, this study will promote the practical implementation of marine bacterial-based biotechnologies in high-loading saline wastewater treatment.

Integrated influence of sulfide modification on the reactivity of nanoscale zero-valent iron towards decabromodiphenyl ether under an electromagnetic field

Individual application of sulfide modification and electromagnetic field (EMF) can enhance the reactivity of nanoscale zero-valent iron (nZVI), yet the potential of both in combination is not clear. This work found that the reactivity of nZVI towards decabromodiphenyl ether was significantly enhanced by the combined effect of sulfidation and EMF. The specific reaction rate constant of nZVI increased by 7 to 10 times. A series of characterization results revealed that the sulfidation level not only affects the inherent reactivity but also the magnetic-induced heating (MIH) and corrosion (MIC) of nZVI. These collectively influence the degradation efficiency of nZVI under EMF. Sulfidation generally diminished the MIH effect. The low degree of sulfidation (S/Fe = 0.1) slightly reduced the MIC effect by 21.4%. However, the high degree of sulfidation (S/Fe = 0.4) led to significantly enhanced MIC effect by 107.1%. For S/Fe = 0.1 and 0.4, the overall enhancement in the reactivity resulting from EMF was alternately dominated by the contributions of MIH and MIC. This work provides valuable insights into the MIH and MIC effects about the sulfidation level of nZVI, which is needed for further exploration and optimization of this combined technology.

Bioadsorption, bioaccumulation and biodegradation of antibiotics by algae and their association with algal physiological state and antibiotic physicochemical properties

Bioadsorption, bioaccumulation and biodegradation processes in algae, play an important role in the biomagnification of antibiotics, or other organic pollutants, in aquatic food chains. In this study, the bioadsorption, bioaccumulation and biodegradation of norfloxacin [NFX], sulfamethazine [SMZ] and roxithromycin [RTM]) is investigated using a series of culture experiments. Chlorella vulgaris was exposed to these antibiotics with incubation periods of 24, 72, 120 and 168 h. Results show the bioadsorption concentration of antibiotics in extracellular matter increases with increasing alkaline phosphatase activity (AKP/ALP). The bioaccumulation concentrations of NFX, SMZ and RTM within cells significantly increase after early exposure, and subsequently decrease. There is a significant positive antibiotics correlation to superoxide dismutase (SOD), the photosynthetic electron transport rate (ETR) and maximum fluorescence after dark adaptation (Fv/Fm), while showing a negative correlation to malondialdehyde (MDA). The biodegradation percentages (Pb) of NFX, SMZ and RTM range from 39.3 - 97.2, 41.3 - 90.5, and 9.3 - 99.9, respectively, and significantly increase with increasing Fv/Fm, density and chlorophyll-a. The accumulation of antibiotics in extracellular and intracellular substances of C. vulgaris is affected by antibiotic biodegradation processes associated with cell physiological state. The results succinctly explain relationships between algal growth during antibiotics exposure and the bioadsorption and bioaccumulation of these antibiotics in cell walls and cell matter. The findings draw an insightful understanding of the accumulation of antibiotics in algae and provide a scientific basis for the better utilization of algae treatment technology in antibiotic contaminated wastewaters. Under low dose exposures, the biomagnification of antibiotics in algae is affected by bioadsorption, bioaccumulation and biodegradation.

Modulation in growth, oxidative stress, photosynthesis, and morphology reveals higher toxicity of alpha-cypermethrin than chlorpyrifos towards a non-target green alga at high doses

Considering the frequent detection of pesticides in the aquatic environment, the ecotoxicological effects of Chlorpyrifos (CHP), an organophosphate, and alpha-cypermethrin (ACM), a pyrethroid, on freshwater microalgae were compared for the first time in this study. High concentrations of both CHP and ACM significantly suppressed the growth of test microalga Graesiella emersonii (p < 0.05). The 96-h EC50 of CHP and ACM were 54.42 mg L-1 and 29.40 mg L-1, respectively. Sub-inhibitory doses of both pesticides increased ROS formation in a concentration-dependent manner, which was accompanied by changes in antioxidant enzymes activities, lipid peroxidation, and variations in photosynthetic pigment concentration. Furthermore, both pesticides influenced photosystem II performance, oxygen-evolving complex efficiency and, intracellular ATP levels. Scanning electron microscopy analysis revealed that high concentrations of both CHP and ACM caused considerable morphological changes in the microalga. In comparison, CHP was more toxic than ACM at low concentrations, whereas ACM was more toxic at high concentrations.

A critical review on BDE-209: Source, distribution, influencing factors, toxicity, and degradation

As the most widely used polybrominated diphenyl ether, BDE-209 is commonly used in polymer-based commercial and household products. Due to its unique physicochemical properties, BDE-209 is ubiquitous in a variety of environmental compartments and can be exposed to organisms in various ways and cause toxic effects. The present review outlines the current state of knowledge on the occurrence of BDE-209 in the environment, influencing factors, toxicity, and degradation. BDE-209 has been detected in various environmental matrices including air, soil, water, and sediment. Additionally, environmental factors such as organic matter, total suspended particulate, hydrodynamic, wind, and temperature affecting BDE-209 are specifically discussed. Toxicity studies suggest BDE-209 may cause systemic toxic effects on living organisms, reproductive toxicity, embryo-fetal toxicity, genetic toxicity, endocrine toxicity, neurotoxicity, immunotoxicity, and developmental toxicity, or even be carcinogenic. BDE-209 has toxic effects on organisms mainly through epigenetic regulation and induction of oxidative stress. Evidence regarding the degradation of BDE-209, including biodegradation, photodegradation, Fenton degradation, zero-valent iron degradation, chemical oxidative degradation, and microwave radiation degradation is summarized. This review may contribute to assessing the environmental risks of BDE-209 to help develop rational management plans.

Is it really safe to replace decabromodiphenyl ether (BDE209) with decabromodiphenyl ethane (DBDPE)?: A perspective from hepatotoxicity

In this paper, the hepatocytotoxicity and aryl hydrocarbon receptor (AHR) activity of decabromodiphenyl ethane (DBDPE), decabromodiphenyl ether (BDE209) and other 18 analogues were evaluated in vitro using human normal liver cell L02. These dioxin-like compounds showed differential hepatocytotoxicity (EC₅₀  = 0.38-17.87 mg/L) and AHR activity (EROD activity = 4.53-46.35 U/μg). In silico study indicated the distance of π-π bonds between the benzene ring of compounds and residue Phe234 of AHR played a key role in the binding of AHR, and the substituents on the benzene ring also influenced the activity. Combining molecular biology and bioomics, the comprehensive investigations on the hepatotoxic mechanisms have demonstrated the AHR signaling pathway was the key mediation mechanism for the hepatotoxicity of DBDPE/BDE209. The cytochrome P450s (CYP2 family) mediated formation of reactive oxygenated intermediates might be the dominant toxic mechanism, which could produce oxidative stress or cause genotoxicity. Although the experimental toxicity of DBDPE was smaller relative to BDE209, the health risk of DBDPE may be much greater than we expected, due to the high potential to form a variety of dioxin-like intermediates by microbial oxidation of ethyl group. Therefore, whether it is really safe to replace BDE209 with DBDPE is a debatable question, and more ecotoxicological and health data are needed to clarify this issue.

Biotransformation of sulfamethoxazole by a novel strain, Nitratireductor sp. GZWM139: Characterized performance, metabolic mechanism and application potential

A novel strain, Nitratireductor sp. GZWM139 capable of efficient removal of SMX was isolated from mariculture sewage, and Nitratireductor was reported to conduct the removal of antibiotics for the first time. Strain GZWM139 exhibited desirable adaptations to environmental factors with SMX removal efficiencies more than 90 % at temperatures of 28-38 °C, pH values of 4.5-8.5, salinities of 20-30 ‰, SMX levels of 1-5 mg/L and shaking speeds of 20-260 rpm. SMX removal was a cooperated process implemented by intracellular enzymes and extracellular enzymes, and was achieved through four proposed biotransformation pathways with the occurrences of demethylation, hydroxylation, nitration, formylation, oxidation, bond cleavage and ring opening. Strain GZWM139 responded to the SMX removal process by altering properties of cell membrane and motivating activities of xenobiotic-metabolizing enzymes and antioxidant system. Genomic analysis proved the existence of functional genes relevant to the SMX removal in strain GZWM139 and provided echoing genetic insights for revealing the SMX removal mechanism. Strain GZWM139 performed efficient detoxification of SMX and accomplished simultaneous removal of SMX and nitrogen in both mariculture sewage and domestic sewage. The findings are significant to the effective elimination of SMX pollution and comprehensive cognitions on metabolic mechanisms of SMX removal.

Mechanisms of flame retardant tris (2-ethylhexyl) phosphate biodegradation via novel bacterial strain Ochrobactrum tritici WX3-8

Tris (2-ethylhexyl) phosphate (TEHP) is a common organophosphorus flame retardant analog with considerable ecological toxicity. Here, novel strain Ochrobactrum tritici WX3-8 capable of degrading TEHP as the sole C source was isolated. Our results show that the strain's TEHP degradation efficiency reached 75% after 104 h under optimal conditions, i.e., 30 °C, pH 7, bacterial inoculum 3%, and Collapse

Key Words

• Biodegradation
• Metabolic pathway
• Ochrobactrum tritici
• Organic pollutants

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MESH Headings Collapse

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Affiliation(s)

Jiamei He College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
Zeyu Wang Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China
Fengzhen Zhen College of Biological and Environmental Engineering, Zhejiang Shuren University, Hangzhou, 310015, China
Zhaoyun Wang College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
Zhongdi Song Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China
Jun Chen Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China.
Dzmitry Hrynsphan Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk, 220030, Belarus
Savitskaya Tatsiana Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk, 220030, Belarus

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Aerobic Degradation Characteristics and Mechanism of Decabromodiphenyl Ether (BDE-209) Using Complex Bacteria Communities

Complex bacteria communities that comprised Brevibacillus sp. (M1) and Achromobacter sp. (M2) with effective abilities of degrading decabromodiphenyl ether (BDE-209) were investigated for their degradation characteristics and mechanisms under aerobic conditions. The experimental results indicated that 88.4% of 10 mg L^-1 BDE-209 could be degraded after incubation for 120 h under the optimum conditions of pH 7.0, 30 °C and 15% of the inoculation volume, and the addition ratio of two bacterial suspensions was 1:1. Based on the identification of BDE-209 degradation products via liquid chromatography-mass spectrometry (LC-MS) analysis, the biodegradation pathway of BDE-209 was proposed. The debromination, hydroxylation, deprotonation, breakage of ether bonds and ring-opening processes were included in the degradation process. Furthermore, intracellular enzymes had the greatest contribution to BDE-209 biodegradation, and the inhibition of piperyl butoxide (PB) for BDE-209 degradation revealed that the cytochrome P450 (CYP) enzyme was likely the key enzyme during BDE-209 degradation by bacteria M (1+2). Our study provided alternative ideas for the microbial degradation of BDE-209 by aerobic complex bacteria communities in a water system.

Microalgae cultivation for antibiotic oxytetracycline wastewater treatment

Microalgae-based technology provides a potential approach to biologically treating oxytetracycline (OTC) wastewater due to its environmental friendliness, low cost, and high efficiency. However, the OTC degradation and transformation characteristics by microalgae are still unclear and need further exploration. This study used microalgae Chlorella sorokiniana MB-1 for OTC wastewater treatment. The OTC with an initial concentration less than 50 mg L^-1 promoted microalgae growth, while OTC with a concentration higher than 100 mg L^-1 inhibited microalgae growth significantly. More than 99% OTC was removed with the biomass productivity up to 1.8 g L^-1 when treated OTC with 10 mg L^-1 initial concentration for 7 days. Chlorophyll and total sugar contents decreased, while protein and lipid contents increased compared to the control without OTC. The malondialdehyde content firstly reduced but subsequently enhanced when increased OTC concentration, while superoxide dismutase content gradually enhanced, manifesting that traces of OTC stimulate microalgae antioxidant capacity, while the increasing OTC caused further oxidative damage to microalgae cells. The removal pathways of OTC mainly include photolysis (75.8%), biodegradation (17.8%), biosorption (3.6%), and hydrolysis (2.7%). Overall, removing OTC by microalgae was confirmed to be an excellent technology for treating antibiotics wastewater whilst accumulating microalgae biomass.

Transcriptome Profiling of Stenotrophomonas sp. Strain WZN-1 Reveals Mechanisms of 2,2',4,4'-Tetrabromodiphenyl Ether (BDE-47) Biotransformation

The brominated flame retardant 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is extensively used, stable, and difficult to degrade in the environment. The existence of BDE-47 could pose a certain risk to the environment and human health. However, the biotransformation mechanisms of BDE-47 by microorganisms remain unclear. In this study, aerobic degradation of BDE-47 by Stenotrophomonas sp. strain WZN-1 and transcriptome analysis were carried out. BDE-47 degradation by Stenotrophomonas sp. strain WZN-1 was mainly through the biological action of intracellular enzymes via the route of debromination and hydroxylation. The results of the transcriptome sequencing indicated the differentially expressed genes were related to transport, metabolism, and stress response. The key processes involved the microbial transmembrane transportation of BDE-47, energy anabolism, synthesis, and metabolism of functional enzymes, stress response, and other biological processes of gene regulation. In particular, bacterial chemotaxis played a potential role in biodegradation of BDE-47 by Stenotrophomonas sp. strain WZN-1. This study provides the first insights into the biotransformation of Stenotrophomonas sp. strain WZN-1 to BED-47 stress and shows potential for application in remediation of polluted environments.

Development of a calcium alginate-cellulose nanocrystal-based coating to reduce the impact of oil spills on shorelines

It is well known that oil stranded on shoreline substrates can be difficult to remove and cause serious environmental effects. To address this issue, a calcium alginate-cellulose nanocrystal (CA-CNC)-based coating with a unique surface structure and superhydrophobic properties was developed to reduce the extent of shoreline oiling. The results of batch washing test showed that not only did the introduction of CNC not reduce the oil removal efficiency; it also improved the environmental stability of the coating to resist the effects associated with seawater immersion and erosion (especially in the case of 0.4 wt% of CNC). The oil-repellent performance of the coated gravels implied that both oscillation time and oil concentration had almost no effects on the amount of adhered oil. Assessment of oiling prevention based on the laboratory shoreline tank simulator proved the coated gravel performed very well as more oil floated and less oil remained on substrates and penetrated into the subsurface. Biotoxicity analysis showed that the coating powders reduced impacts on the toxicity of the oil to algae at low doses. There is a good potential for the use of this CA-CNC based coating technique to improve shoreline oil spill response.

Aerobic Degradation Characteristics of Decabromodiphenyl ether through Rhodococcus ruber TAW-CT127 and Its Preliminary Genome Analysis

Decabromodiphenyl ether (BDE-209), a polybrominated diphenyl ether (PBDE) homolog, seriously threatens human health. In this study, a Rhodococcus ruber strain with high BDE-209 degradation activity, named TAW-CT127, was isolated from Tong’an Bay, Xiamen. Under laboratory conditions, the strain’s optimal growth temperature, pH, and salinity are 45 °C, 7.0, and 0–2.5%, respectively. Scanning electron microscopy (SEM) analysis shows that TAW-CT127 is damaged when grown in manual marine culture (MMC) medium with BDE-209 as the sole carbon source instead of eutrophic conditions. In the dark, under the conditions of 28 °C, 160 rpm, and 3 g/L (wet weight) TAW-CT127, the degradation rate of 50 mg/L BDE-209 is 81.07%. The intermediate metabolites are hexabromo-, octabromo-, and nonabromo-diphenyl ethers. Through whole-genome sequencing, multiple dehalogenases were found in the genome of TAW-CT127; these may be involved in the production of lower-brominated diphenyl ethers. Additionally, biphenyl-2,3-dioxygenase (BDO) in TAW-CT127 may catalyze the debromination reaction of BDE-209. Our research provides a new high-efficiency strain for bioremediation of BDE-209 pollution, and lays the foundation for the preliminary exploration of genes associated with BDE-209 degradation.

Metabolomic analysis and oxidative stress response reveals the toxicity in Escherichia coli induced by organophosphate flame retardants tris(2-chloroethyl) phosphate and triphenyl phosphate

Organophosphate flame retardants (OPFRs) are emerging environmental pollutants that are increasingly being used in consumer commodities. The adverse effects on biota induced by tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) have become a growing concern. Unfortunately, toxic mechanisms at the molecular level for OPFRs in organisms are still lacking. Herein, Escherichia coli (E.coli) was exposed to TCEP and TPHP for 24 and 48 h to reveal oxidative stress response and molecular toxicity mechanisms. The results indicated that promotion of ROS overload occurred at higher dosages groups. The levels of SOD and CAT were significantly elevated along with the increase of MDA attributed to lipid peroxidation. Additionally, apoptosis rates increased, accompanied by a decline in membrane potential and Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase contents, signifying that E. coli cytotoxicity induced by TCEP and TPHP was mediated by oxidative stress. Based on metabolomic analysis, different metabolic pathways were disrupted, including glycolysis/gluconeogenesis, pentose phosphate metabolism, purine metabolism, glutathione metabolism, amino acid biosynthesis, butanoate metabolism, alanine and aspartate metabolism. Most differentially expressed metabolites were downregulated, indicating an inhibitory effect on metabolic functions and key metabolic pathways. These findings generated new insights into the potential environmental risks of OPFRs in aquatic organisms.

Chelating surfactant N-lauroyl ethylenediamine triacetate enhanced electrokinetic remediation of copper and decabromodiphenyl ether co-contaminated low permeability soil: Applicability analysis

In this study, chelating surfactant N-lauroyl ethylenediamine triacetate (N-LED3A) was used as strengthening agent for electrokinetic (EK) remediation of copper (Cu) and decabromodiphenyl ether (BDE209) co-contaminated low permeability soil. The results indicated that negligible amount of N-LED3A would be adsorbed on the experimental soil. The synchronous elution efficiencies (SEEs) of Cu and BDE209 had reached 65.4% and 49.9%, respectively, when the concentration of N-LED3A was 4000 mg/L, and they kept almost unchanged as the concentration of N-LED3A further increased. Meanwhile, the optimal SEEs were obtained at the pH condition within 6-8. The removal efficiencies of Cu (55.3%-65.8%) and BDE209 (31.4%-46.4%) would be increased with the applied voltage gradient and concentration of N-LED3A. In addition, BDE209 and Cu contaminants were also detected in the catholyte and anolyte, respectively, and their concentrations still showed an uptrend by the end of the experiments. While in the control experiments, the removal efficiency of Cu was in the range of 18.2%-23.6%, and almost no BDE209 was migrated out. The electric current would be increased with N-LED3A concentration increased, further resulting in the enhancement of cumulative electro-osmotic flow (EOF). However, the increment of EOF was limited after an 8-day treatment due to the declined capacity of the soil water supply, and the removal efficiency of BDE209 did not change proportionally to the cumulative EOF as a consequence. The accumulated (21 days) energy consumption under the optimal operation conditions (voltage gradient 1 V/cm, N-LED3A 1 g/L) was 377.28 KWh/m³. Efficiently synchronous removal of BDE209 and Cu could be achieved by the N-LED3A enhanced EK technique, exhibiting a promising application potential in the organic pollutant and heavy metal co-contaminated soil remediation.

Increasing oxytetracycline and enrofloxacin concentrations on the algal growth and sewage purification performance of an algal-bacterial consortia system

Oxytetracycline (OTC) and enrofloxacin (EFX) pollution in surface water are very common. Using the algal-bacterial consortia system to remove antibiotics remains to be further studied. In this study, the algal growth and sewage purification performance were studied in an algal-bacterial consortia system with different concentrations of antibiotics. The enzyme activity, malondialdehyde content, chlorophyll-a content, extracellular polysaccharide, and protein content of algae were also tested. It was found that the algal growth was promoted by low-dose antibiotics, 21.83% and 22.11% promotion at 0.1 mg L^-1 OTC and EFX, respectively. The nutrients and antibiotics removals of the low-dose groups (OTC <5 mg L^-1, EFX <1 mg L^-1) were not affected significantly. More than 70% of total organic carbon and total phosphorus, and 97.84-99.76% OTC, 42.68-42.90% EFX were removed in the low-dose groups. However, the algal growth was inhibited, and the nutrients removals performance also declined in the high-concentration groups (10 mg L^-1 OTC, 5 mg L^-1 EFX). The superoxide dismutase and catalase activity, and malondialdehyde content increased significantly (P < 0.05), indicating the increased activity of reactive oxygen species. In addition, the decreased chlorophyll-a content, thylakoid membrane deformation, starch granules accumulation, and plasmolysis showed that the algal physiological functions were affected. These results showed that the algal-bacterial consortia system was more suitable to treat low-concentration antibiotics and provided basic parameters for the consortia application.

Microplastics habituated with biofilm change decabrominated diphenyl ether degradation products and thyroid endocrine toxicity

Microplastics (MPs) are rapidly colonized by microbial biofilms in a natural aquatic environment, and the nature of the microbial community and type of MP can result in different degradation products of organic pollutants. Here, we quantified the degradation products of a ubiquitously detected pollutant, decabrominated diphenyl ether (BDE-209), under both light-only and biota conditions and in the absence or presence of three kinds of MPs, styrofoam polystyrene, hard polyamide, and polypropylene film. The results showed that the BDE-209 concentration increased by 0.7-2.8 fold in the presence of MPs, probably due to the "sustained release" desorption effect. Under light-only conditions, the penta- and hexa-BDE concentrations in the presence of styrofoam or hard MPs were significantly reduced, which can be deemed a beneficial effect. However, when biota were present, the debromination products increased with the addition of MPs, particularly in the presence of styrofoam MPs. These products caused a 1.7-fold upregulation in triiodothyronine content and a 5.9-fold upregulation of thyroid stimulating hormone β expression in zebrafish larvae. The increase in debromination products could be attributed to the distinct high abundance of the bacteria Chloroflexi, Proteobacteria, and Basidiomycotina on styrofoam MPs that can participate in pollutant degradation. Collectively, our results indicate that MPs can alter the degradation pathways of BDE-209 and increase the toxicity to the endocrine system and the thyroid in aquatic organisms.

Comparison of decabromodiphenyl ether degradation in long-term operated anaerobic bioreactors under thermophilic and mesophilic conditions and the pathways involved

Anaerobic digestion of decabromodiphenyl ether was carried out and compared in two continuously stirred anaerobic bioreactors for 210 days under thermophilic and mesophilic conditions. Results show that the degradation of decabromodiphenyl ether followed the first-order reaction kinetics, which exhibited a higher removal rate in the thermophilic reactor when compared to the mesophilic one, reaching its maximum of 1.1 μg·day^-1. The anaerobic digestion of decabromodiphenyl ether was found to involve the replacement of bromines from polybrominated diphenyl ether by hydrogen atoms, gradually forming nona-, octa- and hepta-brominated diphenyl ether, respectively. Under the thermophilic condition, the reactors were dominated by Bacillus sp. and Methanosarcina sp. with high bioactivity and high concentrations of debromination microorganisms.

Aerobic degradation of decabrominated diphenyl ether through a novel bacterium isolated from municipal waste dumping site: Identification, degradation and metabolic pathway

In the present study, a novel bacterium capable of degrading BDE-209 aerobically was isolated from a municipal waste dumping site and identified as Bacillus tequilensis strain BDE-S1 through 16S rRNA gene sequencing. A correlation between BDE-209 and bromide concentration, COD, TOC, and cell biomass was established. 65% of 50 mg/L initial concentration of BDE-209 was degraded within eight days of incubation by BDE-S1 strain. Two hexa, two penta, one tetra-BDE congener, and benzamide were detected as metabolites. The bromide release, COD, TOC and cell biomass were found to be significantly correlated parameters with BDE-209 degradation. Based on the metabolite analysis, ortho and meta debromination, cleavage of diphenyl ether bond and ring-opening were suggested as possible degradation pathways. This is the first study demonstrating the use of indigenously isolated Bacillus tequilensis strain BDE-S1 for aerobic degradation of BDE-209, which could provide new comprehension for bioremediation of PBDEs from contaminated environments.

Biotechnology-based microbial degradation of plastic additives

Plastic additives are agents responsible to the flame resistance, durability, microbial resistance, and flexibility of plastic products. High demand for production and use of plastic additives is associated with environmental accumulation and various health hazards. One of the suitable methods of depleting plastic additive in the environment is bioremediation as it offers cost-efficiency, convenience, and sustainability. Microbial activity is one of the effective ways of detoxifying various compounds as microorganisms can adapt in an environment with high prevalence of pollutants. The present review discusses the use and abundance of these plastic additives, their health-related risks, the microorganisms capable of degrading them, the proposed mechanism of biodegradation, and current innovations capable of improving the efficiency of bioremediation.

Current progress in degradation and removal methods of polybrominated diphenyl ethers from water and soil: A review

The widespread of polybrominated diphenyl ethers (PBDEs) in the environment has caused rising concerns, and it is an urgent endeavor to find a proper way for PBDEs remediation. Various techniques such as adsorption, hydrothermal and thermal treatment, photolysis, photocatalytic degradation, reductive debromination, advanced oxidation processes (AOPs) and biological degradation have been developed for PBDEs decontamination. A comprehensive review of different PBDEs remediation techniques is urgently needed. This work focused on the environmental source and occurrence of PBDEs, their removal and degradation methods from water and soil, and prospects for PBDEs remediation techniques. According to the up-to-date literature obtained from Web of Science, it could be concluded that (i) photocatalysis and photocatalytic degradation is the most widely reported method for PBDEs remediation, (ii) BDE-47 and BDE-209 are the most investigated PBDE congeners, (iii) considering the recalcitrance nature of PBDEs and more toxic intermediates could be generated because of incomplete degradation, the combination of different techniques is the most potential solution for PBDEs removal, (iv) further researches about the development of novel and effective PBDEs remediation techniques are still needed. This review provides the latest knowledge on PBDEs remediation techniques, as well as future research needs according to the up-to-date literature.

Removal of pharmaceutical and personal care products (PPCPs) from wastewater using microalgae: A review

Pharmaceuticals and personal care products (PPCPs) are a group of emerging micro-pollutants causing detrimental effects on living organisms even at low doses. Previous investigations have confirmed the presence of PPCPs in the environment at hazardous levels, mainly due to the inefficiency of conventional wastewater treatment plants (CWWTPs). Their stable structure induces longer persistence in the environment. Microalgae are currently used to bioremediate numerous pollutants of different characteristics and properties released from the domestic, industrial, agricultural, and farm sectors. CO₂ mitigation during culture and the use of biomass as feedstock for biodiesel or biofuel production are, briefly, other benefits of microalgae-mediated treatment over CWWTPs. This review provides a comprehensive summary of recent literature, an overview of approaches and treatment systems, and breakthrough in the field of algal-mediated removal of PPCPs in wastewater treatment processes. The mechanisms involved in phycoremediation, along with their experimental approaches, have been discussed in detail. Factors influencing the removal of PPCPs from aqueous media are comprehensively described and assessed. A comparative study on microalgal strains is analyzed for a more efficient implementation of future processes. The role of microalgae to mitigate the most severe environmental impacts of PPCPs and the generation of antibiotic-resistant bacteria is discussed. Also, a detailed assessment of recent research on potential toxic effects of PPCPs on microalgae was conducted. The current review highlights microalgae as a promising and sustainable approach to efficiently bio-transform or bio-adsorb PPCPs.

Nephrotoxicity and possible mechanisms of decabrominated diphenyl ethers (BDE-209) exposure to kidney in broilers

The flame retardant decabrominated diphenyl ether (BDE-209) is a widely used chemical in a variety of products and exists extensively in the environment. BDE-209 has been reported to induce kidney injury and dysfunction. However, the causes and mechanisms of its nephrotoxicity are still under investigation. In this study, 150 male broilers were exposed to BDE-209 concentrations of 0, 0.004, 0.04, 0.4, 4.0 g/kg for 42 days. The relative kidney weight, histopathology, markers of renal injury, oxidative stress, inflammation, apoptosis and the expression of MAPK signaling pathways-related proteins were assessed. The results showed that the concentrations of blood urea nitrogen (BUN), creatinine (CRE) and the neutrophil gelatinase-associated lipocalin (NGAL), significantly increased after exposure to BDE-209 with the doses more than 0.04 g/kg. Similarly, severe damage of renal morphology was observed, including atrophy and necrosis of glomeruli, and swelling and granular degeneration of the renal tubular epithelium. In the renal homogenates, the oxidative stress was evidenced by the elevated concentrations of MDA and NO, and decreased levels of GSH-Px, GSH and SOD. Due to the inflammatory response, the level of NF-κB and the pro-inflammatory cytokines TNF-α, IL-1β, IL-18 were remarkably upregulated, while the content of the anti-inflammatory cytokine IL-10 decreased. Additionally, the apoptotic analysis showed notable upregulations of Bax/Bcl-2 ratio, the relative expression of p-ERK1/2 and p-JNK1/2, and the expression of Bax, cytochrome c and caspase 3. The present study indicates that BDE-209 exposure can cause nephrotoxicity in broilers through oxidative stress and inflammation, which activate the phosphorylation of key proteins of the MAPK signaling pathways, and subsequently induce mitochondria-mediated kidney apoptosis.

Desorbing of decabromodiphenyl ether in low permeability soil and the remediation potential of enhanced electrokinetic

In this study, desorption kinetic was determined for decabromodiphenyl ether (BDE209) in a low permeability soil, and the remediation potential of hydroxypropyl-β-cyclodextrin (HPCD) enhanced electrokinetic (EK) technique was investigated. The results indicated that the release rate of BDE209 in slowly and very slowly desorbing process was accounted for 31% and 68% in the whole desorption process, respectively. The final desorption rate of BDE209 was 20.7% after 70 h treatment with 5% HPCD in an ideal solution reaction system (without electric field). However, the removal efficiency of BDE209 in section S5 (near anode) of EK1 and EK2 had reached 22% and 20% after 14 days treatment, respectively. Thus it can be assumed that the interaction between BDE209 (on soil particles) and HPCD had been promoted under the electric field. A higher cumulative EOF did not remove more BDE209 with HPCD as facilitating agent, which might due to the low viscosity of HPCD and it did not react completely with BDE209 in soils. In addition, the removal efficiency of BDE209 in section S5 of CK1 and CK2 (without HPCD) had reached 6% and 10%, respectively, which might attribute to the desorption promoting effect of the uniform electric field on hydrophobic organic contaminants. In summary, it is feasible to use the EK to remove BDE209 in low permeability soils using HPCD as solubilizing agent, and the technique key is maintaining sufficient EOF and ensuring the contact reaction efficiency between HPCD and BDE209 synchronously.

The Potential for Bio-Sustainable Organobromine-Containing Flame Retardant Formulations for Textile Applications-A Review

This review considers the challenge of developing sustainable organobromine flame retardants (BrFRs) and alternative synergists to the predominantly used antimony III oxide. Current BrFR efficiencies are reviewed for textile coatings and back-coatings with a focus on furnishing and similar fabrics covering underlying flammable fillings, such as flexible polyurethane foam. The difficulty of replacing them with non-halogen-containing systems is also reviewed with major disadvantages including their extreme specificity with regard to a given textile type and poor durability.The possibility of replacing currently used BrFRs for textiles structures that mimic naturally occurring organobromine-containing species is discussed, noting that of the nearly 2000 such species identified in both marine and terrestrial environments, a significant number are functionalised polybrominated diphenyl ethers, which form part of a series of little understood biosynthetic biodegradation cycles.The continued use of antimony III oxide as synergist and possible replacement by alternatives, such as the commercially available zinc stannates and the recently identified zinc tungstate, are discussed. Both are effective as synergists and smoke suppressants, but unlike Sb₂0₃, they have efficiencies dependent on BrFR chemistry and polymer matrix or textile structure. Furthermore, their effectiveness in textile coatings has yet to be more fully assessed.In conclusion, it is proposed that the future of sustainable BrFRs should be based on naturally occurring polybrominated structures developed in conjunction with non-toxic, smoke-suppressing synergists such as the zinc stannates or zinc tungstate, which have been carefully tailored for given polymeric and textile substrates.

Establishment and application of a novel fluorescence-based analytical method for the rapid detection of viable bacteria in different samples

A rapid method for readily detecting the total numbers of viable bacterial cells in numerous samples (including surface water, solid inoculants, and soil samples) is reported using a newly developed hand-held fluorometer and a fluorescent dye Calcein UltraGreen™ AM. Compared to the traditional plate counting method that requires 48 hours of cultivation, the newly established method does not require any incubation time, making the detection method faster and more convenient. The portable rapid detection fluorometer has a wide dynamic range of relative fluorescence intensity from 45 to 30 133. It can detect bacterial concentration ranging from 10⁵ to 10¹⁰ cells per mL. This newly established method has good applicability for accurately and quickly detecting the cell number of viable bacteria in various samples. The results of the fluorescence-based method were compared with those of the traditional plate counting method, and it was found that the relative standard deviation was less than 6%. This new rapid measurement system provides a robust method for the rapid on-site detection of viable bacteria.

A polystyrene-degrading Acinetobacter bacterium isolated from the larvae of Tribolium castaneum

Polystyrene (PS) has been widely used in various fields, whereas this thermoplastic material is generally considered to be resistant to biodegradation. Tribolium castaneum (Coleoptera: Tenebrionidae), a common pest of stored agricultural products, is a powerful model organism for general insect research. In this study, the larvae of T. castaneum were observed chewing and eating extruded polystyrene foam (XPS). Investigation of the gut microbiome of plastic- and bran-fed T. castaneum larvae showed that Acinetobacter sp. was strongly associated with PS ingestion. Additionally, one bacterial strain capable of PS degradation, was successfully isolated from the gut of these larvae and identified as Acinetobacter sp. AnTc-1 by its 16S rDNA sequence. Gel penetration chromatography (GPC), ¹H nuclear magnetic resonance (¹H NMR) spectroscopy, thermo gravimetric analysis (TGA) and scanning electron microscope (SEM) were employed to characterize the PS degradation. After incubation with AnTc-1 for 60 days, the mass weight (12.14%) and molecular weight (13%/25%, weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of PS powder were significantly reduced. The results indicated that the isolated strain of Acinetobacter sp. AnTc-1 has PS-degrading capacity. The isolated strain may play a role in the larval gut for biodegradation of PS and has potential to be applied for petroleum-based plastic degradation study and development of remediation approaches.

Aerobic biodegradation pathways of pentabromobiphenyl ethers (BDE-99) and enhanced degradation in membrane bioreactor system

A bacterial strain capable of efficiently degrading pentabromobiphenyl ether (BDE-99) was isolated from activated sludge and named as NLPSJ-22. This strain was highly close to Pseudomonas asplenii with 100% similarity. The degradation products of BDE-99 were analyzed by gas chromatography mass spectrometry. The biochemical degradation pathways analysis indicated that BDE-99 gradually transformed to diphenyl ether by meta-, para- and ortho-debromination. It became phenol under the action of ring-opening cracking and finally entered the tricarboxylic acid cycle. The degradation of BDE-99 by strain NLPSJ-22 conformed to the first-order reaction kinetics. Rhamnolipid significantly improved the cell-surface hydrophobicity and the degradation of BDE-99. The highest degradation efficiency (96%) was achieved when diphenyl ether as co-metabolic substrate was added. In the bioaugmentation membrane bioreactor (MBR) system, BDE-99 was intensively degraded, and the reactor reached a steady state in about 35 days. The degradation rate of BDE-99 was over 80%, which was significantly higher than that of the control system. MiSeq sequencing results indicated that the genera of Rhodococcus, Bacillus, Pseudomonas, Burkholderia, and Sphingobium were the predominant bacterial communities responsible for BDE-99 biodegradation in the MBR. Pseudomonas increased significantly in the bioaugmented reactor with the relative abundance increasing from 5% to 24%.

Cellular changes of microbial consortium GY1 during decabromodiphenyl ether (BDE-209) biodegradation and identification of strains responsible for BDE-209 degradation in GY1

Microbial consortium remediation has been considered to be a promising technique for BDE-209 elimination in water, soil and sediment. Herein, we studied malondialdehyde (MDA), membrane potential (MP), and reactive active species (ROS) of a microbial consortium GY1 exposed to BDE-209. The results indicated that the microbial antioxidant defense system was vulnerable by BDE-209. Both early and late apoptosis of microbial consortium induced by BDE-209 were observed. The sequencing results revealed that Stenotrophomonas, Microbacterium and Sphingobacterium in GY1 played major roles in BDE-209 degradation. Moreover, a novel facultative anaerobic BDE-209 degrading strain named Microbacterium Y2 was identified from GY1, by which approximately 56.1% of 1 mg/L BDE-209 was degraded within 7 days, and intracellular enzymes of which contributed great to the result. Overall, the current study provided new insights to deeply understand the mechanisms of BDE-209 degradation by microbial consortium.

Effect of rhamnolipid on the physicochemical properties and interaction of bacteria and fungi

Bacterial adhesion on surfaces is an essential initial step in promoting bacterial mobilization for soil bioremediation process. Modification of the cell surface is required to improve the adhesion of bacteria. The modification of physicochemical properties by rhamnolipid to Pseudomonas putida KT2442, Rhodococcus erythropolis 3586 and Aspergillus brasiliensis ATCC 16404 strains was analysed using contact angle measurements. The surface energy and total free energy of adhesion were calculated to predict the adhesion of both bacteria strains on the A. brasiliensis surface. The study of bacterial adhesion was carried out to evaluate experimental value with the theoretical results. Bacteria and fungi physicochemical properties were modified significantly when treated with rhamnolipid. The adhesion rate of P. putida improved by 16% with the addition of rhamnolipid (below 1 CMC), while the increase of rhamnolipid concentration beyond 1 CMC did not further enhance the bacterial adhesion. The addition of rhamnolipid did not affect the adhesion of R. erythropolis. A good relationship has been obtained in which water contact angle and surface energy of fungal surfaces are the major factors contributing to the bacterial adhesion. The adhesion is mainly driven by acid-base interaction. This finding provides insight to the role of physicochemical properties in controlling the bacterial adhesion on the fungal surface to enhance bacteria transport in soil bioremediation.

Ecotoxicological effects of alpha-cypermethrin on freshwater alga Chlorella sp.: Growth inhibition and oxidative stress studies

Alpha-cypermethrin (ACy) is a synthetic pyrethroid insecticide commonly used in agricultural practices for controlling a broad range of insect pests particularly belonging to the order Lepidoptera and Coleoptera. The present study aims to evaluate the toxic effect of ACy on microalgae by studying its influence on Chlorella sp. According to our knowledge, this is the first detailed study of ACy toxicity on microalgae. Significant growth inhibition of Chlorella sp. was observed at high ACy concentration (6-48 mg L^-1) during the entire 96 h bioassay. The 96 h median effective concentration (EC₅₀) of ACy was estimated to be 11.00 mg L^-1. Flow cytometry analysis showed an enhanced generation of reactive oxygen species (ROS) and intracellular lipid accumulation after 96 h exposure to 11.00 mg L^-1 of ACy. Further, the same ACy concentration showed a significant decrease in photosynthetic pigment content and an increase in antioxidant enzyme activity and malondialdehyde (MDA) content in Chlorella sp.

Biodegradation of triphenyl phosphate using an efficient bacterial consortium GYY: Degradation characteristics, metabolic pathway and 16S rRNA genes analysis

Triphenyl phosphate (TPHP) was frequently detected in various environment, which has caused wide attention out of its adverse effects on organisms. Hence, an effective and reasonable method is in urgent demand for removing TPHP. In this study, microbial consortium GYY with efficient capacity to degrade TPHP has been isolated, which could degrade 92.2% of TPHP within 4 h under the optimal conditions (pH 7, inoculum size 1 g/L wet weight, 30 °C, TPHP initial concentration 3 μmol/L). Some intermediate products such as diphenyl phosphate (DPHP), phenyl phosphate (PHP), OH-TPHP, and methoxylation products were identified, suggesting that TPHP was metabolized by hydrolysis, methoxylation after hydrolysis, and methoxylation after hydroxylation pathways. The sequencing analysis demonstrated that Pseudarthrobacter and Sphingopyxis were the dominant genera in consortium GYY during the process of TPHP biodegradation. Also, Sphingopyxis (GY-1) that degraded 98.9% of TPHP (3 μmol/L) within 7 days was further isolated and identified. Overall, this study provides a new insight on TPHP metabolic transformation by consortium and theoretical basis of developing bioremediation technology for TPHP contamination.

Proteomic mechanism of decabromodiphenyl ether (BDE-209) biodegradation by Microbacterium Y2 and its potential in remediation of BDE-209 contaminated water-sediment system

The investigation of BDE-209 degradation by Microbacterium Y2 under different condition was conducted. Cell membrane permeability, cell surface hydrophobicity (CSH), membrane potential (MP) and reactive oxygen species (ROS) production were altered under BDE-209 stress. Eleven debrominated congeners were identified, suggesting that BDE-209 biodegradation by Microbacterium Y2 was dominantly a successive debromination process. Proteome analysis showed that the overexpression of haloacid dehalogenases, glutathione S-transferases (GSTs) and ATP-binding cassette (ABC) transporters might occupy important roles in BDE-209 biotransformation. Meanwhile, heat shock proteins (HSPs), ribonuclease E, oligoribonuclease (Orn) and ribosomal protein were activated to counter the BDE-209 toxicity. The up-regulated pyruvate dehydrogenase E1 component beta subunit and dihydrolipoamide dehydrogenase suggested that the pyruvate metabolism pathway was activated. Bioaugmentation of BDE-209 polluted water-sediments system with Microbacterium Y2 could efficiently improve BDE-209 removal. The detection of total 16S rRNA genes in treatment system suggested that Microbacterium (25.6 %), Luteimonas (14.3 %), Methylovorus (12.6 %), Hyphomicrobium (9.2 %) were the dominant genera and PICRUSt results further revealed that the diminution of BDE-209 was owed to cooperation between the introduced bacteria and aboriginal ones.

Ecotoxicological effects of sulfonamide on and its removal by the submerged plant Vallisneria natans (Lour.) Hara

The extensive application of sulfonamides (SAs) raises concern regarding its negative environmental effects. In aquatic environments, macrophytes may not only be affected by various pollutants, they may also help to reduce the concentrations in the surrounding environment. We studied both the ecotoxicological effects of sulfonamide (SN) on and its removal by Vallisneria natans (Lour.) Hara, an important submerged macrophyte in Chinese lakes and rivers. The toxic effect and oxidative stress caused by SN resulted in a reduction of total chlorophyll (chl.a and b) and autofluorescence of chloroplast. Meanwhile, the levels of reactive oxygen species (ROS, including O₂^- and H₂O₂) and peroxidase (POD) increased with increasing SN concentration and duration of exposure. After 20 days' exposure, a reduction in the relative growth rate (RGR) and leaf length of V. natans was found under SN stress, but SN had only a weak effect on root length. Although high SN concentrations had toxic effects on the growth of V. natans, the plant was overall resistant to the SN doses that we used. We studied the effect of V. natans on sulfonamide removal in an additional 13-day exposure experiment with focus on the dynamics of dissolved oxygen (DO), the oxidation-reduction potential (ORP) and microbial communities in the water column, as well as in the periphyton on V. natans surfaces. The results show that presence of V. natans significantly improved the SN removal efficiency likely by increasing DO, ORP and bacterial diversity in the water column. The presence of V. natans led to higher relative abundances of Saccharimonadales and Rhizoniales. Lefse analysis showed that Saccharimonadales, Micrococcales, Sphingobacteriales, Bacteroidales, Obscuribacterales, Flavobacteriales, Pseudomonadaceae and Myxococcales, which are considered to be SN-resistant bacteria, increased significantly in the V + S+ (V. natans and SN) treatment compared with the V + S- (V. natans and no SN) treatment and V-S+ (no V. natans and SN) treatment. As far as we know, ours is the first study of the ecotoxicological effects of sulfonamide and its removal by submerged vascular plants (here V. natans). Thus, our results add to the understanding of the antibiotic removal mechanism of macrophytes in freshwater systems and help to clarify the linkages between antibiotics and macrophyte-microbe systems; thereby providing new insight into ecological-based removal of antibiotics in aquatic systems.

Degradation mechanism, intermediates and toxicology assessment of tris-(2-chloroisopropyl) phosphate using ultraviolet activated hydrogen peroxide

Organophosphate flame retardants (OPFRs), one kind of emerging flame retardants, have received prevalent attention owing to their ubiquity in aquatic matrices and their characteristics of being refractory to biodegradation. In current research, the degradation mechanism of tris-(2-chloroisopropyl) phosphate (TCPP), one of OPFRs, and its toxicological evaluation using UV-driven hydroxyl radical oxidation were investigated. A pseudo-first order reaction was fitted with an apparent rate constant (K_obs) of 0.1328 min^-1 on transformation of TCPP in the case of CH₂O₂ 0.1 mM, pH 6.6-7.1 and 4.7 mW cm^-2 UV irradiation. High resolution mass spectroscopy analyses identified nine degradation products (eg., C₆H₁₃Cl₂O₄P (m/z 251.0002), C₉H₁₇Cl₂O₅P (m/z 307.0266), C₉H₁₇Cl₂O₆P (m/z 323.0217), C₉H₁₈Cl₃O₅P (m/z 343.0033)) during transformation of TCPP. The removal efficiency dropped by inhibitory effect of natural organic matters and anions, implying that the complete mineralization of TCPP may be difficult in actual water treatment process. The toxicity assessment has shown an decrease in reactive oxygen species (ROS) and apoptosis, membrane potential (MP) elevation of Escherichia coli, and biological molecular function revision (eg., metabolism and DNA biosynthesis), indicating that toxicity of degradation products were conspicuously decreased in comparison with intact TCPP. To sum up, effective detoxification of TCPP can be realized by a UV driving radical-based oxidation, which will provide an alternative safe treatment method to control TCPP in water matrix.

Exogenous Zn2+ enhance the biodegradation of atrazine by regulating the chlorohydrolase gene trzN transcription and membrane permeability of the degrader Arthrobacter sp. DNS10

Enhancing the biodegradation efficiency of atrazine, a kind of commonly applied herbicide, has been attracted much more concern. Here, Zn²⁺ which has long been considered essential in adjusting cell physiological status was selected to investigate its role on the biodegradation of atrazine by Arthrobacter sp. DNS10 as well as the transmembrane transport of atrazine during the biodegradation period. The results of gas chromatography showed that the atrazine removal percentages (initial concentration was 100 mg L^-1) in 0.05 mM Zn²⁺ and 1.0 mM Zn²⁺ treatments were 94.42% and 86.02% respectively at 48 h, while there was also 66.43% of atrazine left in the treatment without exogenous Zn²⁺ existence. The expression of atrazine chlorohydrolase gene trzN in the strain DNS10 cultured with 0.05 mM and 1.0 mM Zn²⁺ was 7.30- and 4.67- times respectively compared with that of the non-zinc treatment. In addition, the flow cytometry test suggests that 0.05 mM of Zn²⁺ could better adjust the membrane permeability of strain DNS10, meanwhile, the amount of atrazine accumulation in the strain DNS10 co-cultured with this level Zn²⁺ was 2.21 times of that of the strain without Zn²⁺. This study may facilitate a better understanding of the mechanisms that exogenous Zn²⁺ enhances the biodegradation of atrazine by Arthrobacter sp. DNS10.

Temporal and spatial surveys of polybromodiphenyl ethers (PBDEs) contamination of soil near a factory using PBDEs in northern Taiwan

Polybrominated diphenyl ethers (PBDEs), previously commonly used as flame retardants, should be monitored in the environment since some are listed as persistent organic pollutants. A contaminated site near a northern Taiwan factory using decabrominated diphenyl ether (deca-BDE) was identified based on a vegetable PBDEs monitoring project in 2013. The subsequent spatial and temporal survey of that contaminated site shows the contamination ingredients in soils were close to ones used by the factory, indicating that contamination was from the factory, possibly through an exhaust vent. The average concentration of deca-BDE in the main contaminated soil was 615 μg/kg d. w. (dry weight) soil in 2015, slightly decreasing to 604 μg/kg d. w. soil in 2016, increasing to 844 μg/kg d. w. soil in 2017, and then slightly decreasing to 670 μg/kg d. w. soil in 2018. The slight change of deca-BDE and the minor change in low brominated congener level indicate a low degradation rate. The contamination of peripheral sites was around 5000 μg/kg d. w. soil for one PBDEs sampling site that was higher than those around or within the main contaminated farm, indicating serious pollution. Concentrations of PBDEs in different soil depths show that depth 2-15 cm accounted for the greatest PBDEs accumulation, indicating that deca-BDE pollution had been present over time and transported into deeper soil. There can be PBDEs uptake by crops consumed by humans, as shown in our previous studies, so continuous monitoring of PBDEs in this site is important and treatments should be established urgently.

Adaptive Evolution of Sphingobium hydrophobicum C1T in Electronic Waste Contaminated River Sediment

Electronic waste (e-waste) has caused a severe worldwide pollution problem. Despite increasing isolation of degradative microorganisms from e-waste contaminated environments, the mechanisms underlying their adaptive evolution in such habitats remain unclear. Sphingomonads generally have xenobiotic-degrading ability and may play important roles in bioremediation. Sphingobium hydrophobicum C1^T, characterized with superior cell surface hydrophobicity, was recently isolated from e-waste contaminated river sediment. To dissect the mechanisms driving its adaptive evolution, we evaluated its stress resistance, sequenced its genome and performed comparative genomic analysis with 19 other Sphingobium strains. Strain C1^T can feed on several kinds of e-waste-derived xenobiotics, exhibits a great resistance to heavy metals and possesses a high colonization ability. It harbors abundant genes involved in environmental adaptation, some of which are intrinsic prior to experiencing e-waste contamination. The extensive genomic variations between strain C1^T and other Sphingobium strains, numerous C1^T-unique genes, massive mobile elements and frequent genome rearrangements reflect a high genome plasticity. Positive selection, gene duplication, and especially horizontal gene transfer drive the adaptive evolution of strain C1^T. Moreover, presence of type IV secretion systems may allow strain C1^T to be a source of beneficial genes for surrounding microorganisms. This study provides new insights into the adaptive evolution of sphingomonads, and potentially guides bioremediation strategies.

Oxidation degradation of tris-(2-chloroisopropyl) phosphate by ultraviolet driven sulfate radical: Mechanisms and toxicology assessment of degradation intermediates using flow cytometry analyses

Organophosphate flame retardants (OPFRs) were frequently detected in biotic and abiotic matrix owing to their persistence and recalcitrant degradation. Some specific OPFRs, such as tris-(2-chloroisopropyl) phosphate (TCPP), pose a significant potential risk to human health due to their high water solubility. Therefore, an environmentally sound and high efficient technique is in urgent need of controlling TCPP. This research is focused on degrading TCPP using ultraviolet-persulfate (UV/PS) technique. The degradation reaction of TCPP followed a pseudo-first order kinetics with an apparent rate constant (k_obs) at 0.1653 min^-1. As the photocatalytic reaction proceeded, TCPP was transformed to twelve degradation intermediates via the selective electron-transfer reactions induced by activated sulfate radical. Anions existence and pH value significantly inhibited the degradation efficiency, implying that it was hard for TCPP to reach up to complete mineralization in actual water treatment process. Additionally, toxicological assessment of degradation intermediate mixture was conducted using Flow cytometry (FCM) analyses, and the result showed that the intracellular reactive oxygen species (ROS) and cell apoptotic rates significantly declined, and membrane potential (MP) increased in comparison with original TCPP. On the other hand, the negative impacts of these degradation products on DNA biosynthesis in Escherichia coli were weakened based on cell cycle analysis, all of which indicated that toxicity of these degradation intermediates was obviously reduced via UV/PS treatment. To summarize, an appropriate mineralization is effective for TCPP detoxification, suggesting the feasibility of TCPP control using UV/PS treatment in water matrix.

Biodegradation of tricresyl phosphate isomers by Brevibacillus brevis: Degradation pathway and metabolic mechanism

Tricresyl phosphates (TCPs), a typical sort of organophosphate flame retardants, has received extensive concerns due to its potential adverse effects. However, limited information is available on the efficient and safe removal methods of TCPs. In this regard, TCPs were tentatively biodegraded with Brevibacillus brevis. A probable degradation pathway was further proposed with the cellular reactions discussed in detail. Experiments showed that B. brevis at 2 g L^-1 could degrade 1 mg L^-1 tri-m-cresyl phosphate, tri-p-cresyl phosphate, and tri-o-cresyl phosphate by 82.91%, 93.91%, and 53.92%, respectively, within five days. In the process of biodegradation, B. brevis metabolism caused the release of Na⁺ and Cl^- as well as the absorption of some nutrient ions including K⁺, PO₄^3-, Mg²⁺, and SO₄^2-; the presence of oxalic acid, citric acid, acetic acid, and malonic acid was also detected. Similar metabolic pathways were found among different TCPs isomers, but tri-o-cresyl phosphate induced more reactive oxygen species than the other two did. This work develops novel insights into the potential mechanisms of TCPs biodegradation by microorganisms.

Reductive debromination of decabromodiphenyl ether by iron sulfide-coated nanoscale zerovalent iron: mechanistic insights from Fe(II) dissolution and solvent kinetic isotope effects

The mechanism that iron sulfide-coated nanoscale zero valent iron (S-nZVI) has better reduction activity towards organic pollutants than nanoscale zero-valent iron (nZVI) has long been debated. In this work, a systematic study was investigated to compare differences of main influences, BDE-209 degradation pathway, degradation kinetics and reduction mechanism of BDE-209 between nZVI and S-nZVI systems. The observed transformation rate of BDE-209 (k_obs) by S-nZVI was 58.3 and 7.1 times greater than that by S^2- and nZVI, respectively. The valence change of Fe and S on S-nZVI surface before and after BDE-209 degradation process based on XPS characterization confirmed that both Fe⁰ and iron sulfide were the reduction entity of the surface-mediated reaction. The presence of tetrahydrofuran (THF) promoted the surface contact of BDE-209 with S-nZVI, thus accelerating the BDE-209 degradation process. Compared with nZVI, the iron sulfide coated on the Fe⁰ core surface could not only greatly reduce unnecessary electron loss via Fe⁰ corrosion with water, but also accelerate the transmission of electrons from Fe⁰ core to organic pollutants according to Fe(II) dissolution and solvent kinetic isotope effects investigations. These findings help to clarify the synergistic degradation mechanism between Fe⁰ core and iron sulfide shell layer.

The role of surface copper content on biofilm formation by drinking water bacteria

Copper alloys demonstrated comparable or higher performance than elemental copper in biofilm control. The alloy containing 96% copper was the most promising surface in biofilm control and regrowth prevention.

Cell changes and differential proteomic analysis during biodegradation of decabromodiphenyl ether (BDE-209) byPseudomonas aeruginosa

BDE-209 is a persistent organic pollutant. To promote microbial biodegradation of BDE-209 and gain further insight into its mechanism, cell changes and differential proteomic analysis ofP. aeruginosaduring biodegradation were studied.

Biodegradation of decabromodiphenyl ether (BDE 209) by a newly isolated bacterium from an e-waste recycling area

Polybrominated diphenyl ethers (PBDEs) have become widespread environmental pollutants all over the world. A newly isolated bacterium from an e-waste recycling area, Stenotrophomonas sp. strain WZN-1, can degrade decabromodiphenyl ether (BDE 209) effectively under aerobic conditions. Orthogonal test results showed that the optimum conditions for BDE 209 biodegradation were pH 5, 25 °C, 0.5% salinity, 150 mL minimal salt medium volume. Under the optimized condition, strain WZN-1 could degrade 55.15% of 65 μg/L BDE 209 under aerobic condition within 30 day incubation. Moreover, BDE 209 degradation kinetics was fitted to a first-order kinetics model. The biodegradation mechanism of BDE 209 by strain WZN-1 were supposed to be three possible metabolic pathways: debromination, hydroxylation, and ring opening processes. Four BDE 209 degradation genes, including one hydrolase, one dioxygenase and two dehalogenases, were identified based on the complete genome sequencing of strain WZN-1. The real-time qPCR demonstrated that the expression level of four identified genes were significantly induced by BDE 209, and they played an important role in the degradation process. This study is the first to demonstrate that the newly isolated Stenotrophomonas strain has an efficient BDE 209 degradation ability and would provide new insights for the microbial degradation of PBDEs.

Ecotoxicological effects of enrofloxacin and its removal by monoculture of microalgal species and their consortium

Enrofloxacin (ENR), a fluoroquinolone antibiotic, has gained big scientific concern due to its ecotoxicity on aquatic microbiota. The ecotoxicity and removal of ENR by five individual microalgae species and their consortium were studied to correlate the behavior and interaction of ENR in natural systems. The individual microalgal species (Scenedesmus obliquus, Chlamydomonas mexicana, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri) and their consortium could withstand high doses of ENR (≤1 mg L^-1). Growth inhibition (68-81%) of the individual microalgae species and their consortium was observed in ENR (100 mg L^-1) compared to control after 11 days of cultivation. The calculated 96 h EC₅₀ of ENR for individual microalgae species and microalgae consortium was 9.6-15.0 mg ENR L^-1. All the microalgae could recover from the toxicity of high concentrations of ENR during cultivation. The biochemical characteristics (total chlorophyll, carotenoid, and malondialdehyde) were significantly influenced by ENR (1-100 mg L^-1) stress. The individual microalgae species and microalgae consortium removed 18-26% ENR at day 11. Although the microalgae consortium showed a higher sensitivity (with lower EC₅₀) toward ENR than the individual microalgae species, the removal efficiency of ENR by the constructed microalgae consortium was comparable to that of the most effective microalgal species.

Effect of copper ion and soil humic acid on biodegradation of decabromodiphenyl ether (BDE-209) by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a good environmental microorganism capable of degrading decabromodiphenyl ether (BDE‐209). This paper studied the effect of Cu²⁺ and humic acid (HA) extracted from e‐waste contaminated soils on biodegradation of BDE‐209 by P. aeruginosa. The adsorption isotherms of Cu²⁺ on HA, the crude enzyme activity, cell surface morphology, and biodegradation pathway were also investigated. The results showed that BDE‐209 biodegradation by P. aeruginosa was inhibited at Cu²⁺ concentrations above 5 mg L⁻¹, but exhibited the best effect at the condition of 40 mg L⁻¹ Cu²⁺ + 3 g L⁻¹ HA. At the condition of 40 mg L⁻¹ Cu²⁺ + 3 g L⁻¹ HA, 97.35 ± 2.33% of the initial BDE‐209 was degraded after 5 days, debromination efficiency was 72.14 ± 1.89%, crude enzyme activity reached the maximum of 0.519 ± 0.022U g⁻¹ protein, cell surface of P. aeruginosa was smooth with normal short‐rod shapes, and biodegradation pathway mainly include debromination, hydroxylation, and cleavage of the diphenyl ether bond. It was suggested that soil HA could eliminate the toxic effect of high Cu²⁺ concentrations and biodegradation of BDE‐209 was improved by synergistic effect of HA and Cu²⁺.