Tris (2-ethylhexyl) phosphate (TEHP) is one of the most commonly used organophosphorus flame retardant (OPFR) analogues and is commonly detected in surface water and sediments. Limited information is available about the metabolic pathway or metabolite formation related to TEHP in fish. In this study, rare minnows (Gobiocyprisrarus) were exposed to TEHP in static water for 30 d to investigate the bioaccumulation and metabolite distribution in the fish muscle, liver, kidney, gill, GI-tract, ovary and testis. Based on the estimated kᵤₚ,ₚₐᵣₑₙₜ and kd,ₚₐᵣₑₙₜ values, the bioconcentration factors (BCFₚₐᵣₑₙₜ) of TEHP in fish tissues were calculated in the order of kidney > ovary ≈ liver ≈ testis > gill ≈ GI-tract > muscle; this finding was consistent with the results of our previous study on other alkyl-substituted OPFRs. In addition, this study identified the metabolic profiles of TEHP in the liver. TEHP was oxidatively metabolized by the fish to a dealkylated metabolite (di 2-ethylhexyl phosphate; DEHP) and hydroxylated TEHP (OH-TEHP). OH-TEHP further underwent extensive phase II metabolism to yield glucuronic acid conjugates. DEHP was mainly distributed in rare minnow in the following order: liver > GI-tract > kidney ≫ other tissues. However, the metabolite showed lower accumulation potential in fish tissues than TEHP, with metabolite parent concentration factors (MPCFs) for DEHP of less than 0.1 in all the investigated tissues. The BCFₚₐᵣₑₙₜ values of TEHP in various fish tissues were only 9.0 × 10⁻³-7.2 × 10⁻⁴ times its estimated tissue-water partition coefficient (Kₜᵢₛₛᵤₑ₋wₐₜₑᵣ) values based on tissue lipid, protein and water contents, which indicated the significance of biotransformation in reducing the bioaccumulation potential of TEHP in fish. The toxicokinetic data in the present study help in understanding the tissue-specific bioaccumulation and metabolism pathways of TEHP in fish and highlight the importance of toxicology research on TEHP metabolites in aquatic organisms.

Pyriproxyfen is a juvenile hormone analogue insecticide used worldwide. At present, the potential threat of pyriproxyfen to aquatic organism has not been well explored. In this work, the bioaccumulation, metabolic profile and toxicity of pyriproxyfen and its metabolites to zebrafish were studied, and the enantioselectivity of pyriproxyfen and the major chiral metabolites were also determined. Sixteen metabolites of pyriproxyfen in zebrafish were identified. Hydroxylation, ether linkage cleavage and oxidation in phase I metabolism, followed by sulfate and glucuronic acid conjugation. The bioconcentration factors ranged from 1175 to 1246. Hydroxylation metabolites of pyriproxyfen showed enantioselective behavior in zebrafish with enantiomer fractions (EFs) of 4′–OH– pyriproxyfen and 5″–OH– pyriproxyfen ranged from 0.50 to 0.71. Toxicological indexes including acute toxicity, joint toxicity and oxidative stress were tested. Among all the metabolites, 4′–OH– pyriproxyfen was found 2 folds more toxic to zebrafish than pyriproxyfen. (−)-Pyriproxyfen was found 2 folds more toxic than rac- and (+)-pyriproxyfen. Antagonistic effects were found in binary joint toxicity of pyriproxyfen and its hydroxylated metabolites. Pyriproxyfen and its metabolites also showed oxidative stress damage by inhibiting the activity of CAT and SOD and increasing MDA. This work provided deep insight into the metabolism and the potential risks of pyriproxyfen to aquatic organisms.

Recently, the increased use of monocyclic non-steroidal anti-inflammatory drugs has resulted in their presence in the environment. This may have potential negative effects on living organisms. The biotransformation mechanisms of monocyclic non-steroidal anti-inflammatory drugs in the human body and in other mammals occur by hydroxylation and conjugation with glycine or glucuronic acid. Biotransformation/biodegradation of monocyclic non-steroidal anti-inflammatory drugs in the environment may be caused by fungal or bacterial microorganisms. Salicylic acid derivatives are degraded by catechol or gentisate as intermediates which are cleaved by dioxygenases. The key intermediate of the paracetamol degradation pathways is hydroquinone. Sometimes, after hydrolysis of this drug, 4-aminophenol is formed, which is a dead-end metabolite. Ibuprofen is metabolized by hydroxylation or activation with CoA, resulting in the formation of isobutylocatechol. The aim of this work is to attempt to summarize the knowledge about environmental risk connected with the presence of over-the-counter anti-inflammatory drugs, their sources and the biotransformation and/or biodegradation pathways of these drugs.

This study used the enzymes extracted from an atrazine-degrading strain, Arthrobacter sp. DNS10, which had been immobilized by sodium alginate to rehabilitate atrazine-polluted soil. Meanwhile, a range of biological indices were selected to assess the ecological health of contaminated soils and the ecological security of this bioremediation method. The results showed that there was no atrazine detected in soil samples after 28 days in EN + AT (the soil containing atrazine and immobilized enzyme) treatment. However, the residual atrazine concentration of the sample in AT (the soil containing atrazine only) treatment was about 5.02 ± 0.93 mg kg(-1). These results suggest that the immobilized enzyme exhibits an excellent ability in atrazine degradation. Furthermore, the immobilized enzyme could relieve soil microbial biomass carbon and soil microbial respiration intensity to 772.33 ± 34.93 mg C kg(-1) and 5.01 ± 0.17 mg CO2 g(-1) soil h(-1), respectively. The results of the polymerase chain reaction-degeneration gradient gel electrophoresis experiment indicated that the immobilized enzyme also could make the Shannon-Wiener index and evenness index of the soil sample increase from 1.02 and 0.74 to 1.51 and 0.84, respectively. These results indicated that the immobilized enzymes not only could relieve the impact from atrazine on the soil, but also revealed that the immobilized enzymes did no significant harm on the soil ecological health.

Natural polymeric flocculant shows effectiveness in wastewater treatment without increasing the environmental burden. The extracellular substance produced by Paenibacillus mucilaginosus WL412 was identified as an anionic polysaccharide composed of five types of monosaccharides, namely, D-mannose, D-glucuronic acid, D-glucose, D-galactose, and L-fucose with the molar ratio of 2.8:1.2:2.0:1.8:0.8. The purified polysaccharide, POS412, presented high efficiency in flocculating coal washing wastewater and kaolin suspension without the assistance of inorganic coagulants. Addition of POS412 resulted in the polymer bridging phenomenon in suspensions, which was observed by means of scanning electron microscopic imaging, size grading, and ζ-potential analyses. More importantly, POS412 exhibited satisfactory stability after storage in various conditions. The flocculation rate was more than 91% for coal washing wastewater when POS412 was stored for 264 h in the wide range of pH (3–11) and temperature (20–50 °C) before use. Results indicate that POS412 is a competent bioflocculant for wastewater treatment.

A novel approach for the green synthesis of silver nanoparticles (AgNPs) from aqueous solution of AgNO₃using culture supernatant of phenol degraded broth is reported in this work. The synthesis was observed within 10 h, and AgNPs showed characteristic surface plasmon resonance around 410 nm. Spherical nanoparticles of size less than 30 nm were observed in transmission electron microscopy. X-ray diffraction pattern corresponding to 111, 200, 220, and 311 revealed the crystalline nature of the as-formed nanoparticles. It was found that the colloidal solution of AgNP suspensions exhibited excellent stability over a wide range of ionic strength, pH, and temperature. The effect of pH and ionic strength indicated that stabilization is due to electrostatic repulsion arising from the negative charge of the conjugate proteins. The AgNPs showed highly potent antimicrobial activity against Gram-positive, Gram-negative, and fungal microorganisms. The as-prepared AgNPs showed excellent catalytic activity in reduction of 4-nitrophenol to 4-aminophenol by NaBH₄. By manufacturing magnetic alginate beads, the reusability of the AgNPs for the catalytic reaction has been demonstrated.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) of proposed natural origin have been detected throughout the food web of the Baltic Sea. Some OH-PBDEs have been shown to disrupt oxidative phosphorylation and the thyroid hormone system in exposed organisms. This paper describes an investigation into the fate of OH-PBDEs in the Baltic Sea’s predominant specie, the blue mussel. The main focus was on the conjugation of OH-PBDEs with lipophilic moieties (e.g., fatty acids) and the potential role this transformation mechanism may have in heavily exposed mussels in nature. Analytical methods were developed to accurately determine the concentrations of these conjugates in blue mussels collected on different occasions during the summer in a coastal area of the Baltic proper. The measured concentrations of conjugated OH-PBDEs were compared to those of the unconjugated parent compounds, and it was found that in some cases, the levels of the conjugated derivatives can be equal or even higher than the levels of the unconjugated OH-PBDEs. This is, to our knowledge, the first study on lipid-soluble OH-PBDE conjugates, and the first study to investigate the occurrence of such conjugates of halogenated phenolic compounds in environmentally exposed mussels. The mussels were also found to contain hydrolysable water-soluble derivatives of OH-PBDEs (such as e.g., glucuronic acid and/or sulfate conjugates etc.). These were tentatively determined to be of lower concentration (by up to an order of magnitude) than that of the OH-PBDEs which were conjugated with lipophilic moieties.

Chromate-resistant bacterial strain isolated from the soil of tannery was studied for Cr(VI) bioaccumulation in free and immobilised cells to evaluate its applicability in chromium removal from aqueous solution. Based on the comparative analysis of the 16S rRNA gene, and phenotypic and biochemical characterization, this strain was identified as Paenibacillus xylanilyticus MR12. Mechanism of Cr adsorption was also ascertained by chemical modifications of the bacterial biomass followed by Fourier transform infrared spectroscopy analysis of the cell wall constituents. The equilibrium biosorption analysed using isotherms (Langmuir, Freundlich and Dubinin–Redushkevich) and kinetics models (pseudo-first-order, second-order and Weber–Morris) revealed that the Langmuir model best correlated to experimental data, and Weber–Morris equation well described Cr(VI) biosorption kinetics. Polyvinyl alcohol alginate immobilised cells had the highest Cr(VI) removal efficiency than that of free cells and could also be reused four times for Cr(VI) removal. Complete reduction of chromate in simulated effluent containing Cu²⁺, Mg²⁺, Mn²⁺ and Zn²⁺ by immobilised cells, demonstrated potential applications of a novel immobilised bacterial strain MR12, as a vital bioresource in Cr(VI) bioremediation technology.

Purpose Besides classical organic pollutants and pesticides, pharmaceuticals and their residues have nowadays become recognized as relevant environmental contaminants. The risks of these chemicals for aquatic ecosystems are well known, but information about the pharmaca-plant interactions and metabolic pathways is scarce. Therefore, we investigate the process of uptake of acetaminophen (N-Acetyl-4-aminophenol) by Brassica juncea, drug-induced defense responses and detoxification mechanisms in different plant parts. Material and methods Hydroponically grown Indian mustard (Brassica juncea L. Czern.) plants were treated with acetaminophen and root and leaf samples were collected after 24, 72, and 168 h of treatment. The uptake of acetaminophen and the formation of its metabolites were analyzed using LC-MS/MS technique and enzyme activities including glutathione S-transferases (GSTs) as well as several plant defense enzymes like catalase, ascorbat peroxidase, peroxidase, and glutathione reductase were assayed spectrophotometrically. Results We determined the uptake and the translocation of acetaminophen, and we tried to identify the steps of the detoxification process by assaying typical enzymes, supposing the involvement of the same- or similar enzymes and reactions as in the mammalian detoxification process. After 24-h exposure, effective uptake and translocation were observed to the upper part of plants followed by two independent conjugative detoxification pathways. Changes in antioxidant defense enzyme activities connected to the defense pathway towards reactive oxygen species indicate an additional oxidative stress response in the plants. Conclusions The major metabolic pathways in mammals are conjugation with activated sulfate and glucuronic acid, while a small amount of acetaminophen forms a chemically reactive and highly toxic, hydroxylated metabolite. We identified a glutathionyl and a glycoside conjugate, which refer to the similarities to mammalian detoxification. Increased GST activities in leaf tissues were observed correlated with the appearance of the acetaminophen-glutathione conjugate which shows the involvement of this enzyme group in the metabolism of acetaminophen in plants to organic pollutants and xenobiotics. High acetaminophen concentrations lead to oxidative stress and irreversible damages in the plants, which necessitates further investigations using lower drug concentrations for the deeper understanding of the induced detoxification—and defense processes.

Background, aim, and scope Polysaccharides are renewable resources representing an important class of polymeric materials of biotechnological interest, offering a wide variety of potentially useful products to mankind. Exopolysaccharides (EPSs) of microbial origin with a novel functionality, reproducible physico-chemical properties, stable cost and supply, became a better alternative to polysaccharides of algal origin. EPSs are believed to protect bacterial cells from desiccation, heavy metals or other environmental stresses, including hostimmune responses, and to produce biofilms, thus enhancing the cells chances of colonising special ecological niches. One of the most important stress factor is salt stress for microorganisms. The present investigation is aimed to determine correlation between salt resistance and EPS production by three cyanobacterial isolates (Synechocystis sp. BASO444, Synechocystis sp. BASO507 and Synechocystis sp. BASO511). It is also aimed to investigate the effect of salt concentrations on EPS production by cyanobacteria and effect of salt on monosaccharide composition of EPS. Materials and methods Cyanobacterial isolates were identified by 16 S rRNA analysis. Its salt (NaCl) tolerance and association with exopolysaccharides (EPSs) production in three cyanobacterial isolates were investigated. Also, EPS was analysed by HPLC for monomer characterization. Results Increased EPS production was associated with NaCl tolerance. The most tolerant isolate, Synechocystis sp. BASO444, secreted the most EPS (500 mg/L). EPS production by Synechocystis sp. BASO444, Synechocystis sp. BASO507 and Synechocystis sp. BASO511 was investigated following exposure to 0.2 and 0.4 M NaCl. Also, flasks containing medium without NaCl were inoculated in the same manner to serve as controls. The monosaccharide compositions of EPS produced by the three isolates following exposure to 0.2 M NaCl were analysed by HPLC. Control EPS of BASO444 was composed of glucose (97%) and galacturonic acid (3%). The composition of BASO511 (control) was glucose (95%), xylose (4.80%), arabinose (0.13%), glucuronic acid (0.03%) and galacturonic acid (0.04%). However, the composition of BASO507 (control) was glucose (0.98%), xylose (98.00%), arabinose (1.00%), glucuronic acid (0.01%) and galacturonic acid (0.01%). In the presence of 0.2 M NaCl, EPS compositions and ratios of three cyanobacterial isolates changed. Discussion Although hyperproduction of EPS in response to starvation, antiviral activity, thickening agent and cosmetic industry for product formulations has been reported for cyanobacteria, the effect of NaCl on EPS production in cyanobacteria is not a popular area of study. There are no clear reports correlating EPS production and NaCl tolerance. The gap in the data about the effect of NaCl on cyanobacterial EPS production was filled by this investigation, and the results of our study have important implications in both the industrial and environmental arenas. Conclusions Our results indicate that 1) exposure to elevated concentrations of NaCl affects the composition of EPS produced by Synechocystis sp. BASO444, Synechocystis sp. BASO507 and Synechocystis sp. BASO511, and 2) there is a correlation between NaCl tolerance and EPS production in some cyanobacteria. Recommendations and perspectives Differences in the monosaccharide composition and ratios of EPS may promote NaCl tolerance in these microorganisms. As well, these alternative composition polysaccharides may be important for industrial applications.