Toxicity mechanisms and synergies of silver nanoparticles in 2,4-dichlorophenol degradation by Phanerochaete chrysosporium

Metagenomic insights into the diversity of 2,4-dichlorophenol degraders and the cooperation patterns in a bacterial consortium

2,4-Dichlorophenol, which is largely employed in herbicides and industrial production, is frequently detected in ecosystems and poses risks to human health and environmental safety. Microbial communities are thought to perform better than individual strains in the complete degradation of organic contaminants. However, the synergistic degradation mechanisms of the microbial consortia involved in 2,4-dichlorophenol degradation are still not widely understood. In this study, a bacterial consortium named DCP-2 that is capable of degrading 2,4-dichlorophenol was obtained. Metagenomic analysis, cultivation-dependent functional verification, and co-occurrence network analysis were combined to reveal the primary 2,4-dichlorophenol degraders and the cooperation patterns in the consortium DCP-2. Metagenomic analysis showed that Pseudomonas, Achromobacter, and Pigmentiphaga were the primary degraders for the complete degradation of 2,4-dichlorophenol. Thirty-nine phylogenetically diverse bacterial genera, such as Brucella, Acinetobacter, Aeromonas, Allochromatium and Bosea, were identified as keystone taxa for 2,4-dichlorophenol degradation by keystone taxa analysis of the co-occurrence networks. In addition, a stable synthetic consortium of isolates from DCP-2 was constructed, consisting of Pseudomonas sp. DD-13 and Brucella sp. FZ-1; this synthetic consortium showed superior degradation capability for 2,4-dichlorophenol in both mineral salt medium and wastewater compared with monoculture. The findings provide valuable insights into the practical bioremediation of 2,4-dichlorophenol-contaminated sites.

Head dysgenesis and disruption of cranial neural crest stem cells behaviour by 4-octylphenol in fire-bellied toad Bombina orientalis embryos

Alkylphenolic endocrine disruptors (Eds) have been known to affect development of the descendants of multipotent neural crest cells (NCCs) in amphibian embryos. To unravel the mechanism of head dysgenesis induced by alkylphenols in amphibians, the effect of 4-octylphenol (OP) on the differentiation of cranial NCCs in developing embryos and tadpoles, ex vivo NC explant, and isolated NCCs was examined in fire-bellied toad Bombina orientalis with 0, 1, 2, 5, 10, 25 and 50 μM concentrations. Following OP treatment, head cartilages were frequently absent together with the decreased col2a1 mRNA level in tadpoles. While the lipid hydroperoxide (LPO), endoplasmic reticulum stress (ERS), apoptosis, and DNA fragmentation were significantly increased in stage 22 neulurae and heads of stage 45 tadpoles. In stage 22 neulurae, OP decreased sox9 mRNA, the master transcription factor for chondrogenic differentiation and increased undifferentiated NCC markers. The ectopic NCCs were found in endoderm while mesodermal SOX10(+) cells were decreased. In cranial NCCs isolated from stage 22 embryos, OP treatment decreased cellular survival and increased apoptosis, epithelial-mesenchymal transition (EMT) and cell migration. In chondrogenic induced cranial NC explants, OP treatment decreased SOX9(+) chondrocytes and cartilage development. Together, OP potentiated oxidative damage, apoptosis, EMT, and ectopic migration of NCCs. Considering that tissue differentiation requires stem cells to activate the molecular mechanism of differentiation at the correct location during embryonic development, these changes caused by OP may inhibit sox9-dependent chondrogenic differentiation of cranial NCCs, leading to head dysgenesis in B. orientalis embryos. Therefore, developing multipotent NCCs could be an important target of OP, provides new direction for the estimation of the risk of EDs exposure in human and wildlife animals.

Exploring the mechanism of enhanced Cr(VI) removal by Lysinibacillus cavernae microcapsules loaded with synthetic nano-hydroxyapatite

In this study, nano-scale hydroxyapatite (HAP) powder was successfully synthesized from waste eggshells and combined with Lysinibacillus cavernae CR-2 to form bio-microcapsules, which facilitated the enhanced removal of Cr(VI) from wastewater. The effects of various parameters, such as bio-microcapsule dosage, HAP dosage, and initial Cr(VI) concentration on Cr(VI) removal, were investigated. Under different treatment conditions, the Cr(VI) removal followed the order of LC@HAP (90.95%) > LC (78.15%) > Free-LC (75.61%) > HAP (6.56%) > NM (0.23%) at the Cr(VI) initial concentration of 50 mg L-1. Relative to other reaction systems, the LC@HAP treatment exhibited a considerable decrease in total Cr content in the solution, with removal rates surpassing 70%. Additionally, the bio-microcapsules maintained significant biological activity after reacting with Cr(VI). Further characterization using SEM, FTIR, XPS, and XRD revealed that the Cr(VI) removal mechanisms by bio-microcapsules primarily involved biological reduction and HAP adsorption. The adsorption of Cr(III) by HAP predominantly occurred through electrostatic interactions and surface complexation, accompanied by an ion exchange process between Cr(III) and Ca(II). Hence, bio-microcapsules, created by combining L. cavernae with HAP, represent a promising emerging material for the enhanced removal of Cr(VI) pollutants from wastewater.

Antifungal Activity of Juglans-regia-Mediated Silver Nanoparticles (AgNPs) against Aspergillus-ochraceus-Induced Toxicity in In Vitro and In Vivo Settings

Aflatoxins produced by some species of Aspergillus are considered secondary toxic fungal by-products in feeds and food. Over the past few decades, many experts have focused on preventing the production of aflatoxins by Aspergillus ochraceus and also reducing its toxicity. Applications of various nanomaterials in preventing the production of these toxic aflatoxins have received a lot of attention recently. The purpose of this study was to ascertain the protective impact of Juglans-regia-mediated silver nanoparticles (AgNPs) against Aspergillus-ochraceus-induced toxicity by exhibiting strong antifungal activity in in vitro (wheat seeds) and in vivo (Albino rats) settings. For the synthesis of AgNPs, the leaf extract of J. regia enriched with high phenolic (72.68 ± 2.13 mg GAE/g DW) and flavonoid (18.89 ± 0.31 mg QE/g DW) contents was used. Synthesized AgNPs were characterized by various techniques, including TEM, EDX, FT-IR, and XRD, which revealed that the particles were spherical in shape with no agglomeration and fine particle size in the range of 16-20 nm. In vitro antifungal activity of AgNPs was tested on wheat grains by inhibiting the production of toxic aflatoxins by A. ochraceus. According to the results obtained from High-Performance Liquid Chromatography (HPLC) and Thin-Layer Chromatography (TLC) analyses, there was a correlation between the concentration of AgNPs and a decrease in the production of aflatoxin G1, B1, and G2. For in vivo antifungal activity, Albino rats were administrated with different doses of AgNPs in five groups. The results indicated that the feed concentration of 50 µg/kg feed of AgNPs was more effective in improving the disturbed levels of different functional parameters of the liver (alanine transaminase (ALT): 54.0 ± 3.79 U/L and aspartate transaminase (AST): 206 ± 8.69 U/L) and kidney (creatinine 0.49 ± 0.020 U/L and BUN 35.7 ± 1.45 U/L), as well as the lipid profile (LDL 22.3 ± 1.45 U/L and HDL 26.3 ± 2.33 U/L). Furthermore, the histopathological analysis of various organs also revealed that the production of aflatoxins was successfully inhibited by AgNPs. It was concluded that the harmful effects of aflatoxins produced by A. ochraceus can be successfully neutralized by using J. regia-mediated AgNPs.

Controlled Synthesis of Ag-SnO2/α-Fe2O3 Nanocomposites for Improving Visible-Light Catalytic Activities of Pollutant Degradation and CO2 Reduction

The key to developing highly active α-Fe2O3-based photocatalysts is to improve the charge separation and efficiently utilize the electrons with sufficient thermodynamic energy. Herein, α-Fe2O3 nanosheets (FO) were synthesized using a metal-ion-intervened hydrothermal method and then coupled with SnO2 nanosheets (SO) to obtain SO/FO nanocomposites. Subsequently, nanosized Ag was selectively loaded on SO using the photo-deposition method to result in the ternary Ag-SO/FO nanocomposites. The optimal nanocomposite could realize the efficient aerobic degradation of 2,4-dichlorophenol as a representative organic pollutant under visible-light irradiation (>420 nm), exhibiting nearly six-fold degradation rates of that for FO. Additionally, the Ag-SO/FO photocatalyst is also applicable to the visible-light degradation of other organic pollutants and even CO2 reduction. By using steady-state surface photovoltage spectroscopy, fluorescence spectroscopy, and electrochemical methods, the photoactivity enhancement of Ag-SO/FO is principally attributed to the improved charge separation by introducing SO as an electron platform for the high-energy-level electrons of FO. Moreover, nanosized Ag on SO functions as a cocatalyst to further improve the charge separation and facilitate the catalytic reduction. This work provides a feasible design strategy for narrow-bandgap semiconductor-based photocatalysts by combining an electron platform and a cocatalyst.

Construction of a novel Cu1.8S/NH2-La MOFs decorated Black-TNTs photoanode electrode for high-efficiently photoelectrocatalytic degradation of 2, 4-dichlorophenol

Photoelectrocatalysis (PEC) has long been regarded as an efficient and green method to eliminate various organic pollutants from wastewater. However, the lack of highly photoelectrocatalytic active and stable electrodes limits the development of the PEC technologies. Herein, a novel hierarchical photo-electrode with hollow Cu_1.8S/NH₂-La MOFs decorated black titanium dioxide nanotubes (Cu_1.8S/NH₂-La MOFs/Black TNTs) was fabricated by a two-step water-heating method. The prepared photoelectrode was used to degradation of 2, 4-dichlorophenol (2, 4-DCP). Analysis of photoelectrocatalytic degradation process of 2, 4-DCP was evaluated using UV-Vis absorption spectroscopy and the main degradation paths were analyzed by LC-MS. The results showed that 99.3% of the pollutant could be rapidly degraded within 180 min. Furthermore, the Cu_1.8S/NH₂-La MOFs/Black TNTs photoelectric pole exhibited excellent stability after 15 cycling experiments.

Enhanced adsorption of aqueous chlorinated aromatic compounds by nitrogen auto-doped biochar produced through pyrolysis of rubber-seed shell

The adsorption of chlorinated aromatic compounds (CACs) on pristine biochar was often limited. Surface modification can greatly improve the adsorption capacity of biochar. In this work, by pyrolysis activation of rubber-seed shell wastes, nitrogen auto-doped biochar (RSS-NBC) was synthesized and used for purifying CACs-containing wastewater. Systematic characterization results showed that after proper treatment, the as-prepared RSS-NBC had high specific surface area, abundant surface oxygen- and nitrogen-containing functional groups, and nano-scale pore structure. Batch adsorption experiments were conducted with using three typical CACs probing pollutants, i.e. 1,2-dichlorobenzene (1,2-DCB), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorobenzoic acid (2,4-DCBA). The adsorption experiments results showed that the maximum adsorption amounts of 1, 2-DCB, 2,4-DCP, and 2,4-DCBA could reach 2284, 1921, and 1142 mg/g at 298.15 K. Moreover, 90% of the equilibrium adsorption amount can be reached within 0.5 h. The adsorption kinetic results showed that the adsorption processes of the three CACs followed the pseudo-second-order rate model and were dominated by chemisorption. Also, the adsorption isotherms of 1, 2-DCB and 2, 4-DCP belonged to the Freundlich model and were valid for multilayer adsorption, while the adsorption of 2,4-DCBA followed Langmuir model and single-layer adsorption. The thermodynamics data indicated that the spontaneous adsorption process of 1, 2-DCB and 2, 4-DCP was endothermic while that of 2,4-DCBA was exothermic. After 5 cycles of adsorption-regeneration, the removal efficiency of RSS-NBC particles still remained more than 80% for the three typical CACs, indicating that it could be reused as an effective and retrievable adsorbent in the treatment of CACs-containing effluents.

Oxygen vacancy-mediated peroxydisulfate activation and singlet oxygen generation toward 2,4-dichlorophenol degradation on specific CuO1-x nanosheets

Durable and stable removal of 2,4-dichlorophenpl (2,4-DCP) by CuO_1-x nanosheets is reported. CuO_1-x nanosheets were fabricated by a simple defect engineering strategy and greatly increased the efficiency of peroxydisulfate (PDS) activation to improve 2,4-DCP removal by introducing abundant oxygen vacancy (V_o) to produce an electron-rich surface. Results showed that CuO_1-x nanosheets exposed more V_o as active sites for PDS activation as compared with that of CuO nanoparticles, giving rise to dramatic enhancement of catalytic performance with ultrahigh reaction rate that is qualified for serving in flow filtration system, completely degrading 100 mg L^-1 of 2,4-DCP within 3 s of residence time. Besides, experimental studies confirmed that ¹O₂ generated by V_o - mediated PDS activation plays the dominate role in the degradation of contaminants. Relative to the previously reported CuO/PDS systems, the obtained CuO_1-x nanosheets demonstrated 2.7 times higher specific PDS activity and 67 times higher specific CuO activity for 2,4-DCP removal. Our study not only improves the fundamental understanding of active sites in morphologically tunable metal oxides but also proposes a guideline for future research and engineering application of persulfate.

Recyclable Fe/S co-doped nanocarbon derived from metal-organic framework as a peroxymonosulfate activator for efficient removal of 2,4-dichlorophenol

In this study, a recyclable Fe/S co-doped nanocarbon (Fe/S-NC) was successfully prepared by the pyrolysis of ZIF-8 confined with Fe(II) and added S. Characterization showed that a highly graphitized carbon-based material co-doped with sulfur and iron was successfully prepared. This Fe/S-NC can efficiently activate PMS to remove organic pollutants in water. The effect of different synthesis conditions on the degradation efficiency of 2,4-DCP was studied by orthogonal experiments. The optimized Fe/S-NC/PMS system exhibited excellent catalytic performance and could degrade more than 99.7% of 2,4-DCP within 30 min. Even after 5 cycles, the degradation efficiency could still be maintained above 96.3%, which proved that the catalytic system had good cycle performance. In addition, the effect of pH on catalytic performance showed that the degradation rate of 2,4-DCP exceeds 96.7% in the pH range of groundwater (pH = 5-9). We had confirmed that the free radicals that caused 2,4-DCP degradation were SO₄^·-, ·OH, O₂^·-, and ¹O₂, which played important roles in degrading organic pollutants. These research results show that the Fe/S-NC/PMS system can be used as an efficient, stable, and environmentally friendly system to treat organic pollutants in groundwater.

Environmental impact assessment of nanofluids containing mixtures of surfactants and silica nanoparticles

Due to widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable and toxic for biota and/or wastewater treatment processes. Because of concerns over the environmental impacts of nanofluids, studies of the fate and environmental impacts, hazards, and toxicities of nanoparticles are beginning. However, interactions between nanoparticles and surfactants and the biodegradability of these mixtures have been little studied until now. In this work, the environmental impacts of nanofluids containing mixtures of surfactants and silica nanoparticles were valuated. The systems studied were hydrophilic silica nanoparticles (sizes 7 and 12 nm), a nonionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The ultimate aerobic biodegradation and the interfacial and adsorption properties of surfactants, nanoparticles, and mixtures during biodegradation were also evaluated. Ultimate biodegradation was studied below and above the CMCs of the individual surfactants. The interfacial and adsorption properties of surfactant solutions containing nanoparticles were influenced by the addition of silica particles. It was determined that silica nanoparticles reduced the capability of the nonionic surfactant alkyl polyglucoside to decrease the surface tension. Thus, silica NPs promoted a considerable increase in the surfactant CMC, whereas the effect was opposite in the case of the anionic surfactant ether carboxylic acid. Increasing concentrations of surfactant and nanoparticles in the test medium caused decreases in the maximum levels of mineralization reached for both types of surfactants. The presence of silica nanoparticles in the medium reduced the biodegradability of binary mixtures containing nonionic and anionic surfactants, and this effect was more pronounced for larger nanoparticles. These results could be useful in modelling the behaviour of nanofluids in aquatic environments and in selecting appropriate nanofluids containing nanoparticles and surfactants with low environmental impact.

Remediation of chromium, zinc, arsenic, lead and antimony contaminated acidic mine soil based on Phanerochaete chrysosporium induced phosphate precipitation

Microbial induced phosphate precipitation (MIPP) is an advanced bioremediation technology to reduce the mobility and bioavailability of heavy metals (HMs), but the high level of HMs would inhibit the growth of phosphate solubilizing microbes. This study proposed a new combination system for the remediation of multiple HMs contaminated acidic mine soil, which included hydroxyapatite (HAP) and Phanerochaete chrysosporium (P. chrysosporium, PC) that had high phosphate solubilizing ability and HMs tolerance. Experimental data suggested that in HAP/PC treatment after 35 d of remediation, labile Cr, Zn and As could be transformed into the stable fraction with the maximum immobilization efficiencies increased by 53.01 %, 22.43 %, and 35.65 %, respectively. The secretion of organic acids by P. chrysosporium was proved to promote the dissolution of HAP. Besides, the pH value, available phosphorus (AP) and organic matter (OM) increased in treated soil than in original soil, which also indicated the related dissolution-precipitation mechanism of HMs immobilization. Additionally, characterization results revealed that adsorption and ion exchange also played an important role in the remediation process. The overall results suggested that applying P. chrysosporium coupled with HAP could be considered as an efficient strategy for the remediation of multiple HMs contaminated mine soil and laid a foundation for the future exploration of soil microenvironment response during the remediation process.

Insights into the recent advances in nano-bioremediation of pesticides from the contaminated soil

In the present scenario, the uncontrolled and irrational use of pesticides is affecting the environment, agriculture and livelihood worldwide. The excessive application of pesticides for better production of crops and to maintain sufficient food production is leading to cause many serious environmental issues such as soil pollution, water pollution and also affecting the food chain. The efficient management of pesticide use and remediation of pesticide-contaminated soil is one of the most significant challenges to overcome. The efficiency of the current methods of biodegradation of pesticides using different microbes and enzymes depends on the various physical and chemical conditions of the soil and they have certain limitations. Hence, a novel strategy is the need of the hour to safeguard the ecosystem from the serious environmental hazard. In recent years, the application of nanomaterials has drawn attention in many areas due to their unique properties of small size and increased surface area. Nanotechnology is considered to be a promising and effective technology in various bioremediation processes and provides many significant benefits for improving the environmental technologies using nanomaterials with efficient performance. The present article focuses on and discusses the role, application and importance of nano-bioremediation of pesticides and toxic pollutants to explore the potential of nanomaterials in the bioremediation of hazardous compounds from the environment.

Bioremediation of organic pollutants by white rot fungal cytochrome P450: The role and mechanism of CYP450 in biodegradation

Cytochrome P450 (CYP450) is a well-known protein family that is widely distributed in many organisms. Members of this family have been implicated in a broad range of reactions involved in the metabolism of various organic compounds. Recently, an increasing number of studies have shown that the CYP450 enzyme also participates in the elimination and degradation of organic pollutants, by white rot fungi (WRF), a famous group of natural degraders. This paper reviews previous investigations of white rot fungal CYP450 involved in the biodegradation of organic pollutants, with a special focus on inhibitory experiments, and the direct and indirect evidence of the role of white rot fungal CYP450 in bioremediation. The catalytic mechanisms of white rot fungal CYP450, its application potential, and future prospect for its use in bioremediation are then discussed.

Laccase immobilized on amino-functionalized magnetic Fe3O4-SiO2 core-shell material for 2,4-dichlorophenol removal

In this study, an amino-functionalized magnetic silica microsphere material (Fe₃O₄-SiO₂-NH₂) was prepared. Using glutaraldehyde as a cross-linking agent, Trametes versicolor laccase was adsorbed-covalently bonded and immobilized on the material to prepare Laccase @ Fe₃O₄-SiO₂. In addition, the materials were characterized and analysed by SEM, TEM, XRD, FT-IR and VSM. Finally, the thermal inactivation dynamics of immobilized laccase in polar/non-polar/toxic systems and the adsorption and degradation of 2,4-DCP were studied. The results showed that Laccase @ Fe₃O₄-SiO₂ under the optimal conditions (pH 6, temperature 65°C, initial concentration of 2,4-DCP 10 mg/L), the removal rate was as high as 81.6%. Moreover, compared with free laccase, immobilized laccase had good tolerance under low pH and high-temperature conditions, and storage stability was also greatly improved. After repeated use for 7 times, Laccase @ Fe₃O₄-SiO₂ can still maintain 59% removal rate of 2,4-DCP, which gives it the potential for industrial applications.

Biomass-derived nanocellulose aerogel enable highly efficient immobilization of laccase for the degradation of organic pollutants

Laccase is a promising biocatalyst for pollutant degradation and water purification. However, laccase can only improve the stability of enzyme activity and achieve its significant catalytic effect after effective immobilization. Herein, we report a general strategy to integrate nanocellulose aerogel and laccase for high-efficiency degradation of organic pollutants. Biomass-derived functional bacterial cellulose (BC) aerogel with a nanonetwork structure and high porosity was prepared by biosynthesis, solvent replacement, and atom transfer radical polymerization (ATRP) procedures. Subsequently, a biocatalyst platform was fabricated by "coupling" ATRP-modified BC aerogel with abundant active sites with laccase through ion coordination. The results demonstrated the biocatalyst platform not only has good biological affinity, but also has high enzyme load and structural stability. Meanwhile, the degradation rates of reactive red X-3B and 2, 4-dichlorophenol reached 94.5% and 85.2% within 4 h, respectively. The strategy disclosed herein could provide a practical method for the degradation of organic pollutants.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

Toxicity of Nanoparticles of AgO, La₂O₃, CuO, AgO-Fe₃O₄, Ag-Graphene, and GO-Cu-AgO to the Fungus Moniliella wahieum Y12T Isolated from Degraded Biodiesel and the Bacterium Escherichia coli

Moniliella wahieum Y12^T (M. wahieum Y12^T), a fungal isolated from biodiesel caused serious biodiesel contamination and resulting in biofouling and corrosion, especially during storage. Nanoparticles (NPs) composed of silver, copper, iron, and graphene or their binary mixtures were examined as environmental inhibitors against the fungus Moniliella wahieum Y12^T, a biodiesel contaminant. Exposure of M. wahieum Y12^T and Escherichia coli (E. coli) to low concentrations of Ag-based nanoparticles (from 0.01 to 0.05 mg mL^-1) resulted in excellent growth inhibition. The half-maximal inhibitory concentration (IC₅₀) of M. wahieum Y12^T by La₂O₃ NPs was 138 times greater when compared with silver (AgO). The median effective concentration (EC₅₀) of La₂O₃ NPs on E. coli was 379 times more than M. wahieum Y12^T. At this same concentration, E. coli was uninhibited after exposure to the NPs. However, a fluorescein diacetate analysis showed the Ag-based NPs (including AgO, AgO-Fe₃O₄ and GO-Cu-AgO) significantly reduced the metabolic activity for both of the compared organisms. Compared with other metal oxide NPs, AgO and AgO-Fe₃O₄ NPs display strong bactericidal effect with higher stability and dispersibility, with the zeta potential of -22.27 mV and poly-dispersity index (PDI) values of 0.36. These results demonstrate the broad-spectrum biological inhibition that occurs with both Ag-based bimetallic and graphene oxide nanoparticles and the combined utilization of Ag-based NPs paves a new way for inhibits the biodegradation of biodiesel.

Mesoporous ferrihydrite-supported Pd nanoparticles for enhanced catalytic dehalogenation of chlorinated environmental pollutant

Organic chlorides are a group of ubiquitous environmental pollutants that have attracted wide attention because of their carcinogenetic effect on human. Catalytic hydrodechlorination represents one of the most promising methods for the removal of these contaminants, but it suffers from drawbacks such as catalytic inefficiency and/or instability, and the danger of using H₂ as hydrogen source. The relationship between the catalyst structure and its dehalogenation activity has not been completely understood. By combining the advantages of Pd nanocatalyst and mesoporous ferrihydrite (Fh) with its distinctive structure, here we present a new composite material with Pd nanoparticles (NPs) supported onto the Fh (Pd/Fh), which has excellent catalytic dehalogenation performance with a rapid, complete dechlorination of chlorophenol (turnover frequency 25.2 min^-1) and the ability to perform well over a wide range of pH and temperature. The superior catalytic property of Pd/Fh can be attributed to the three unique functions of Fh, including: 1) having abundant hydroxyl groups that provide interaction sites with metals for incorporating highly dispersed small Pd NPs; 2) facilitating the fast adsorption of chlorophenol onto the catalyst surface via hydrogen bonding and importantly, 3) working as an electron mediator to greatly enhance the electron transfer from iron or chemicals (e.g., NaBH₄) to the catalyst, thereby achieving a synergistic effect between Pd catalyst and support, and an enhanced dechlorination activity. In essence, this work presents a promising catalyst for the efficient dehalogenation of chlorinated environmental pollutants and provides an insight into the relationship between catalyst structure and dehalogenation activity.

Mineralization of lead by Phanerochaete chrysosporium microcapsules loaded with hydroxyapatite

In this study, microcapsules assembled with Phanerochaete chrysosporium (P. chrysosporium, PC) and hydroxyapatite (HAP) were successfully prepared and applied for Pb(II) immobilization in aqueous solution. The effect of different conditions on Pb(II) removal was investigated, such as pH, temperature, dosages of microcapsules and HAP, and initial concentrations of Pb(II). The removal efficiency of Pb(II) was in order of HAP+PC > HAP > PC > CK (control check) at the Pb(II) initial concentration of 100 mg L^-1, which were 87.7%, 82.82%, 63.67% and 2.06%, respectively. Under HAP+PC treatment, P. chrysosporium secreted plentiful organic acids like formic, oxalic and citric acids, when the addition dose of HAP increased from 5 g L^-1 to 15 g L^-1, the production of formic acid increased remarkably from 32.37 g L^-1 to 66.02 g L^-1. After reaction, P. chrysosporium kept a good biological activity evidenced by the live/dead stain test. The characterization results indicated that the insoluble apatite could transform to soluble phosphate due to the secreted organic acids, then reacted with Pb(II) to form pyromorphite [Pb₁₀(PO₄)₆Cl₂] and lead phosphate hydroxide [Pb₁₀(PO₄)₆(OH)₂]. The overall results clearly demonstrated that combining P. chrysosporium with HAP could be used as a promising technology to accelerate lead immobilization.

Trends in microbial degradation and bioremediation of emerging contaminants

Modernization and modern ways of living demands more improved products from pharmaceuticals, cosmetics, and food processing industries. Moreover, industries like pesticides, fertilizers, dyeing, paints, detergent etc., also needs improvised products as per demand. As the new product emerges, the pollutants from these industries also constitute new type of danger to the environment and serious health risks to the living organisms. These emerging contaminants (ECs) are from different category of sources such as personal care products (PCPs), pharmaceuticals (Phcs), endocrine disrupting chemicals (EDCs), etc. These ECs can easily escape from the conventional water treatment and eventually get discharged in to the surface water and thus enters in to the ground water, soil, sediments, and also into the oceans. When these contaminants emerge we also require progress in tremendous process for preventing these hazardous chemicals by effective removal and treatment. For the past 50 years, both developed and developing countries are working on this treatment process and found that Microbial degradation and bioremediation are very useful for effective treatment to prevent their emissions. This treatment can be designed for any sort of ECs since the microbial members are so versatile to redesign their metabolic pathways when subject to exposure. However, implementing bioremediation is not alone efficient to degrade ECs and hence, combination of bioremediation, nanotechnology and physical treatment method will also provide sustainable, potent and fast degradation process. In this Book Chapter, we discuss in detail about the ECs, sources of microbial degradation process and its usefulness in the bioremediation of these ECs.

A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants

Environmental problems resultant from organic pollutants are a major current challenge for modern societies. White rot fungi (WRF) are well known for their extensive organic compound degradation abilities. The unique oxidative and extracellular ligninolytic systems of WRF that exhibit low substrate specificity, enable them to display a considerable ability to transform or degrade different environmental contaminants. In recent decades, WRF and their ligninolytic enzymes have been widely applied in the removal of polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds (PhACs), endocrine disruptor compounds (EDCs), pesticides, synthetic dyes, and other environmental pollutants, wherein promising results have been achieved. This review focuses on advances in WRF-based bioremediation of organic pollutants over the last 10 years. We comprehensively document the application of WRF and their lignocellulolytic enzymes for removing organic pollutants. Moreover, potential problems and intriguing observations that are worthy of additional research attention are highlighted. Lastly, we discuss trends in WRF-remediation system development and avenues that should be considered to advance research in the field.

Physarum polycephalum macroplasmodium exhibits countermeasures against TiO2 nanoparticle toxicity: A physiological, biochemical, transcriptional, and metabolic perspective

Concerns about the environmental and human health implications of TiO₂ nanoparticles (nTiO₂) are growing with their increased use in consumer and industrial products. Investigations of the underlying molecular mechanisms of nTiO₂ tolerance in organisms will assist in countering nTiO₂ toxicity. In this study, the countermeasures exhibited by the slime mold Physarum polycephalum macroplasmodium against nTiO₂ toxicity were investigated from a physiological, transcriptional, and metabolic perspective. The results suggested that the countermeasures against nTiO₂ exposure include gene-associated metabolic rearrangements in cellular pathways involved in amino acid, carbohydrate, and nucleic acid metabolism. Gene-associated nonmetabolic rearrangements involve processes such as DNA repair, DNA replication, and the cell cycle, and occur mainly when macroplasmodia are exposed to inhibitory doses of nTiO₂. Interestingly, the growth of macroplasmodia and mammal cells was significantly restored by supplementation with a combination of responsive metabolites identified by metabolome analysis. Taken together, we report a novel model organism for the study of nTiO₂ tolerance and provide insights into countermeasures taken by macroplasmodia in response to nTiO₂ toxicity. Furthermore, we also present an approach to mitigate the effects of nTiO₂ toxicity in cells by metabolic intervention.

4-Octylphenol induces developmental abnormalities and interferes the differentiation of neural crest cells in Xenopus laevis embryos

Developmental toxicity of 4-octylphenol (OP), an estrogenic endocrine disruptor was verified using frog embryo teratogenesis assay Xenopus. LC₅₀, EC_{50Malformtion} and EC_{50Melanocyte-dysgenesis} of OP were 9.9, 10.5, and 2.4 μM, respectively. In tadpoles, despite the low teratogenic index, 2 μM OP significantly inhibited head cartilage development and tail malformation. The total length of tadpole was significantly increased at 5 μM and decreased at 10 μM OP. In OP-treated tadpoles, head cartilages were frequently missed and col2a1 mRNA was decreased at 2 μM, indicating a chondrogenic defect in developing head. In the head skin of 1 μM OP-treated tadpoles, number of melanocytes and melanogenic pathway genes expression were significantly decreased. In the head-neck junction of stage 22 embryos, OP increased foxd3 and sox10 mRNA and SOX10(+) neural crest cells (NCCs) in somite mesoderm and endoderm, indicating the inhibition of chondrogenic differentiation, ectopic migration to endoderm, and undifferentiation of NCCs by OP. Together, OP-induced head dysplasia and inhibition of melanogenesis may be attributable to deregulation of neural crest cells in embryos. In tadpoles, OP at 1 μM significantly increased lipid hydroperoxide and induced spliced xbp1 mRNA, an IRE1 pathway endoplasmic reticulum stress (ERS) marker and p-eIF2α protein, a PERK pathway ERS marker. OP at 10 μM induced CHOP mRNA, pro-apoptotic genes expression, DNA fragmentation, and cleaved caspase-3, suggesting that OP differentially induced ERS and apoptosis according to the concentration in embryos. In 5-10 μM OP-treated stage 22 embryos and stage 45 tadpole heads, Ki67 was significantly increased, suggesting the apoptosis-induced proliferation of embryonic cells in the OP-treated embryos. Together, OP should be managed as a developmental toxicant altering the behavior of NCCs in vertebrates.

A new method for the preconcentrations of U(VI) and Th(IV) by magnetized thermophilic bacteria as a novel biosorbent

This paper proposes the use of Anoxybacillus flavithermus SO-15 immobilized on iron oxide nanoparticles (NPs) as a novel magnetized biosorbent for the preconcentrations of uranium (U) and thorium (Th). The SPE procedure was based on biosorption of U(VI) and Th(IV) on a column of iron oxide NPs loaded with dead and dried thermophilic bacterial biomass prior to U(VI) and Th(IV) measurements by ICP-OES. The biosorbent characteristicswere explored using FT-IR, SEM, and EDX. Significant operational factors such as solution pH, volume and flow rate of the sample solution, amounts of dead bacteria and iron oxide nanoparticles, matrix interference effect, eluent type, and repeating use of the biosorbent on process yield were studied. The biosorption capacities were found as 62.7 and 56.4 mg g^-1 for U(VI) and Th(IV), respectively. The novel extraction process has been successfullyapplied to the tap, river, and lake water samples for preconcentrations of U(VI) and Th(IV).

A Concise Review on Multidimensional Silver Nanoparticle Health Aids and Threats

Benefits and Risk:

AgNps have beneficial approaches for cancer treatment and angiogenesisrelated diseases like rheumatoid arthritis, atherosclerosis, diabetic psoriasis, retinopathy, endometriosis, and adiposity.

Result:

The advancing nanotechnology-based therapy needs to be devised better, and it should offload the hitches of prevailing treatment approaches. Essential studies are required to explain the synergistic effect of two different cytotoxic agents.

Adsorption, degradation, and mineralization of emerging pollutants (pharmaceuticals and agrochemicals) by nanostructures: a comprehensive review

This review discusses a fresh pool of research findings reported on the multiple roles played by metal-based, magnetic, graphene-type, chitosan-derived, and sonicated nanoparticles in the treatment of pharmaceutical- and agrochemical-contaminated waters. Some main points from this review are as follows: (i) there is an extensive number of nanoparticles with diverse physicochemical and morphological properties which have been synthesized and then assessed in their respective roles in the degradation and mineralization of many pharmaceuticals and agrochemicals, (ii) the exceptional removal efficiencies of graphene-based nanomaterials for different pharmaceuticals and agrochemicals molecules support arguably well a high potential of these nanomaterials for futuristic applications in remediating water pollution issues, (iii) the need for specific surface modifications and functionalization of parent nanostructures and the design of economically feasible production methods of such tunable nanomaterials tend to hinder their widespread applicability at this stage, (iv) supplementary research is also required to comprehensively elucidate the life cycle ecotoxicity characteristics and behaviors of each type of engineered nanostructures seeded for remediation of pharmaceuticals and agrochemicals in real contaminated media, and last but not the least, (v) real wastewaters are extremely complex in composition due to the mix of inorganic and organic species in different concentrations, and the presence of such mixed species have different radical scavenging effects on the sonocatalytic degradation and mineralization of pharmaceuticals and agrochemicals. Moreover, the formulation of viable full-scale implementation strategies and reactor configurations which can use multifunctional nanostructures for the effective remediation of pharmaceuticals and agrochemicals remains a major area of further research.

Citrate-silver nanoparticles and their impact on some environmental beneficial fungi

Colloidal suspensions of silver nanoparticles (AgNPs) with surface modified by capping with citrate ions were synthesized by chemical reduction method. Transmission and Scanning Electron Microscopy as well as darkfield Optical Microscopy provided information on the nanoparticle morphology, with fine symmetrical grains and log-normal fitted size distribution. Small Angle X-ray Scattering method allowed theoretical confirmation of colloidal silver nanoparticle fine granularity, based on measurements in the native fluid sample. UV–Vis spectrophotometry allowed studying the Localized Surface Plasmon Resonance band versus the stability of the citrate-AgNP sample after storage and after UV-C exposure. The colloidal AgNP impact on Phanerochaete chrysosporium environmental microorganisms was studied by specific biochemical investigations. Silver released from the colloidal suspension of AgNPs was supposed to induce changes in some antioxidant enzymes and in some enzymes of Krebs’ cycle. Catalase activity was moderately changed (an increase with over 50%) as well as superoxide dismutase activity, while the diminution of the activities of four dehydrogenases synthesized in the fungus mycelium was emphasized also: a decrease with about 60% for malate dehydrogenase, with over 50% for isocitrate dehydrogenase and succinate dehydrogenase and with about 40% for alpha-ketoglutarate dehydrogenase. These findings suggested the nano-toxicological issues of citrate-AgNPs impact on the environmental beneficial microorganisms.

Developments in the Application of Nanomaterials for Water Treatment and Their Impact on the Environment

Nanotechnology is an uppermost priority area of research in several nations presently because of its enormous capability and financial impact. One of the most promising environmental utilizations of nanotechnology has been in water treatment and remediation where various nanomaterials can purify water by means of several mechanisms inclusive of the adsorption of dyes, heavy metals, and other pollutants, inactivation and removal of pathogens, and conversion of harmful materials into less harmful compounds. To achieve this, nanomaterials have been generated in several shapes, integrated to form different composites and functionalized with active components. Additionally, the nanomaterials have been added to membranes that can assist to improve the water treatment efficiency. In this paper, we have discussed the advantages of nanomaterials in applications such as adsorbents (removal of dyes, heavy metals, pharmaceuticals, and organic contaminants from water), membrane materials, catalytic utilization, and microbial decontamination. We discuss the different carbon-based nanomaterials (carbon nanotubes, graphene, graphene oxide, fullerenes, etc.), and metal and metal-oxide based nanomaterials (zinc-oxide, titanium dioxide, nano zerovalent iron, etc.) for the water treatment application. It can be noted that the nanomaterials have the ability for improving the environmental remediation system. The examination of different studies confirmed that out of the various nanomaterials, graphene and its derivatives (e.g., reduced graphene oxide, graphene oxide, graphene-based metals, and graphene-based metal oxides) with huge surface area and increased purity, outstanding environmental compatibility and selectivity, display high absorption capability as they trap electrons, avoiding their recombination. Additionally, we discussed the negative impacts of nanomaterials such as membrane damage and cell damage to the living beings in the aqueous environment. Acknowledgment of the possible benefits and inadvertent hazards of nanomaterials to the environment is important for pursuing their future advancement.

Biological Removal and Fate Assessment of Diclofenac Using Bacillus subtilis and Brevibacillus laterosporus Strains and Ecotoxicological Effects of Diclofenac and 4′-Hydroxy-diclofenac

Since bacterial consortia involved in conventional wastewater treatment processes are not efficient in removing diclofenac (DCF), an emerging pollutant frequently detected in water bodies, the identification of microorganisms able to metabolise this pharmaceutical compound is relevant. Thus, DCF removal was investigated using bacteria isolated from aqueous stock solutions of this micropollutant and identified as Bacillus and Brevibacillus species using 16S rRNA gene sequencing. A 100% DCF removal was achieved after 17 hours of experiment at 20°C in a nutrient medium; the biodegradation kinetic followed a pseudo-first order (kbiol = 11 L·gSS−1·d−1). Quantitative assessment of DCF removal showed that its main route was biotic degradation. The main degradation product of DCF, 4′-hydroxy-diclofenac (4′-OH-DCF), was identified using liquid chromatography-electrospray ionisation high-resolution mass spectrometry. Since the ecotoxicological impact of 4′-hydroxy-diclofenac was not reported in the literature, the ecotoxicity of DCF and its metabolite were tentatively evaluated using Vibrio fischeri bioassays. Results from these tests showed that this metabolite is not more toxic than its parent compound and may hopefully be an intermediate product in the DCF transformation. Indeed, no significant difference in ecotoxicity was observed after 30 min between DCF (50 should be writtten in subscript all along the manuscript in EC50 = 23 ± 4 mg·L−1) and 4′-hydroxy-diclofenac (EC50 = 19 ± 2 mg·L−1). Besides, the study highlighted a limit of the Microtox® bioassay, which is largely used to assess ecotoxicity. The bioluminescence of Vibrio fischeri was impacted due to the production of microbial activity and the occurrence of some carbon source in the studied medium.

A hybrid lipid membrane coating "shape-locks" silver nanoparticles to prevent surface oxidation and silver ion dissolution

The controlled synthesis of stable silver nanoparticles (AgNPs), that do not undergo surface oxidation and Ag+ ion dissolution, continues to be a major challenge. Here the synthesis of robust hybrid lipid-coated AgNPs, comprised of l-α-phosphatidylcholine (PC) membranes anchored by a stoichiometric amount of long-chained hydrophobic thiols and sodium oleate (SOA) as hydrophobic binding partners, that do not undergo surface oxidation and Ag+ ion dissolution, is described. UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometry (ICP-MS) demonstrate that in the presence of strong oxidants, such as potassium cyanide (KCN), the hybrid lipid-coated AgNPs are stable and do not undergo surface oxidation even in the presence of membrane destabilizing surfactants. UV-Vis studies show that the stability of hybrid lipid-coated AgNPs of various sizes and shapes is dependent on the length of the thiol hydrocarbon chain and can be ranked in the order of increasing stability as follows: propanethiol (PT) < hexanethiol (HT) ≤ decanethiol (DT). UV-Vis and ICP-MS studies show that the hybrid lipid-coated AgNPs do not change in size or shape confirming that the AgNPs do not undergo surface oxidation and Ag+ ion dissolution when placed in the presence of strong oxidants, chlorides, thiols, and low pH. Long-term stability studies, over 21 days, show that the hybrid lipid-coated AgNPs do not release Ag+ ions and are more stable. Overall, these studies demonstrate hybrid membrane encapsulation of nanomaterials is a viable method for stabilizing AgNPs in a "shape-locked" form that is unable to undergo surface oxidation, Ag+ ion release, aging, or shape conversion. More importantly, this design strategy is a simple approach to the synthesis and stabilization of AgNPs for a variety of biomedical and commercial applications where Ag+ ion release and toxicity is a concern. With robust and shielded AgNPs, investigators can now evaluate and correlate how the physical features of AgNPs influence toxicity without the confounding factor of Ag+ ions present in samples. This design strategy also provides an opportunity where the membrane composition can be tuned to control the release rate of Ag+ ions for optimizing antimicrobial activity.

Alleviating the toxicity of quantum dots to Phanerochaete chrysosporium by sodium hydrosulfide and cysteine

Quantum dots (QDs) have caused large challenges in clinical tests and biomedical applications due to their potential toxicity from nanosize effects and heavy metal components. In this study, the physiological responses of Phanerochaete chrysosporium (P. chrysosporium) to CdSe/ZnS QDs with either an inorganic sulfide NaHS or an organic sulfide cysteine as antidote have been investigated. Scanning electron microscope analysis showed that the hyphal structure and morphology of P. chrysosporium have obviously changed after exposure to 100 nM of COOH CdSe/ZnS 505, NH₂ CdSe/ZnS 505, NH₂ CdSe/ZnS 565, or NH₂ CdSe/ZnS 625. Fourier transform infrared spectroscopy analysis indicated that the existence of hydroxyl, amino, and carboxyl groups on cell surface could possibly conduct the stabilization of QDs in an aqueous medium. However, after NaHS or cysteine treatment, the cell viability of P. chrysosporium exposed to CdSe/ZnS QDs increased as compared to control group, since NaHS and cysteine have assisted P. chrysosporium to alleviate oxidative damage by regulating lipid peroxidation and superoxide production. Meanwhile, NaHS and cysteine have also stimulated P. chrysosporium to produce more antioxidant enzymes (superoxide dismutase and catalase), which played significant roles in the defense system. In addition, NaHS and cysteine were used by P. chrysosporium as sulfide sources to promote the glutathione biosynthesis to relieve CdSe/ZnS QDs-induced oxidative stress. This work revealed that sulfide sources (NaHS and cysteine) exerted a strong positive effect in P. chrysosporium against the toxicity induced by CdSe/ZnS QDs.

Effects of different simulated seasonal temperatures on the fermentation characteristics and microbial community diversities of the maize straw and cabbage waste co-ensiling system

Ensiling is considered as a suitable method to preserve seasonal agricultural residues to enable long-term supply for wastes valorization. In this study, the effects of simulated seasonal temperatures (-3, 18 and 34 °C) on the organic compositions, ensiling fermentation characteristics, and microbial community evolution during 120 days co-ensiling of maize straw and cabbage wastes were investigated. Successful storage performance was obtained at all these three temperatures. Comparatively, silages at 18 and 34 °C showed lower ammonia nitrogen, lower pH and more intensive lactic acid bacteria fermentation than that at -3 °C. Both silages at -3 and18 °C were well-preserved for 120 days with higher biodegradation potential (BDP), accompanied by lower content of acid detergent lignin (ADL). However, the silages at 34 °C could only preserved for 90 days due to low carbohydrate, low BDP and higher ADL content than that at -3 or18 °C. The storage temperature is a critical parameter that significantly affected the silage quality by influencing the microbial community diversity in silages. Proteobacteria and Firmicutes were dominant bacteria at phylum level for all silages while the dominant lactic acid bacteria at genus level were Lactobacillus and Leuconostoc, which restrained the undesirable microbes such as Enterobacteriaceae, Pseudomonas, Flavobacterium, and Pantoea during co-ensiling. Co-ensiling of maize straw with vegetable wastes may provide a promising strategy for long-term preservation of air-dried crop straw while using vegetable wastes as regulatable supplement to achieve silages of desired quality. This study could provide valuable information for conservation and management of agricultural wastes.

Biodegradation and toxicity reduction of nonylphenol, 4-tert-octylphenol and 2,4-dichlorophenol by the ascomycetous fungus Thielavia sp HJ22: Identification of fungal metabolites and proposal of a putative pathway

Research on the biodegradation of emerging pollutants is gained great focus regarding their detrimental effects on the environment and humans. The objective of the present study was to evaluate the ability of the ascomycetes Thielavia sp HJ22 to remove the phenolic xenobiotics nonylphenol (NP), 4-tert-octylphenol (4-tert-OP) and 2,4-dichlorophenol (2,4-DCP). The strain showed efficient degradation of NP and 4-tert-OP with 95% and 100% removal within 8 h of incubation, respectively. A removal rate of 80% was observed with 2,4-DCP within the same time. Under experimental conditions, the degradation of the tested pollutants concomitantly increased with the laccase production and cytochrome P450 monooxygenases inhibition. This study showed the involvement of laccase in pollutants removal together with biosorption mechanisms. Additionally, results demonstrated the participation of cytochrome P450 monooxygenase in the elimination of 2,4-DCP. Liquid chromatography-mass spectrometry analysis revealed several intermediates, mainly hydroxylated and oxidized compounds with less harmful effects compared to the parent compounds. A decrease in the toxicity of the identified metabolites was observed using Aliivibrio fischeri as bioindicator. The metabolic pathways of degradation were proposed based on the identified metabolites. The results point out the potential of Thielavia strains in the degradation and detoxification of phenolic xenobiotics.

Mechanism and performance of singlet oxygen dominated peroxymonosulfate activation on CoOOH nanoparticles for 2,4-dichlorophenol degradation in water

Peroxymonosulfate (PMS) has gained attention as oxidant for SR-AOPs. It is essential to develop a stable heterogeneous catalyst with strong hydrophilicity and high electron transfer capability for PMS activating. In this study, cobalt oxyhydroxide (CoOOH) was synthesized and activated PMS for degradation of 2,4-dichlorophenol (2,4-DCP) aiming to assess the feasibility of CoOOH/PMS system. 50 mg/L of 2,4-DCP could be 100% degraded within 120 min with 0.20 g/L CoOOH and 6 mM PMS. CoOOH/PMS system possessed a high degradation efficiency (0.0462 min^-1), which was about 10 and 4 times higher than Co₃O₄/PMS and CoFe₂O₄/PMS system, respectively. Furthermore, it was found that CoOOH/PMS system displayed effective catalytic performance over broad pH range (e.g. 3-9). Importantly, the quenching tests revealed that ¹O₂ was identified as dominant reactive oxygen species (ROS). Co (Ⅲ) was rapidly reduced to Co (Ⅱ) owing to the efficient electron transfer rate performance of CoOOH in the catalytic reaction. Then, the regeneration of Co (Ⅱ) facilitated CoOH⁺ owing to the surface of CoOOH with sufficient hydroxyl group, which is crucial for PMS activation and reactive oxygen species-ROS generation. This study proposed an alternative technology based on peroxymonosulfate catalyzed by cobalt-based hydroxide for waste water treatment.

Antimicrobial efficacy and mechanisms of silver nanoparticles against Phanerochaete chrysosporium in the presence of common electrolytes and humic acid

In this study, influences of cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺), anions (NO₃^-, Cl^-, and SO₄^2-), and humic acid (HA) on the antimicrobial efficacy of silver nanoparticles (AgNPs)/Ag⁺ against Phanerochaete chrysosporium were investigated by observing cell viability and total Ag uptake. K⁺ enhanced the antimicrobial toxicity of AgNPs on P. chrysosporium, while divalent cations decreased the toxicity considerably, with preference of Ca²⁺ over Mg²⁺. Impact caused by a combination of monovalent and divalent electrolytes was mainly controlled by divalent cations. Compared to AgNPs, however, Ag⁺ with the same total Ag content exhibited stronger antimicrobial efficacy towards P. chrysosporium, regardless of the type of electrolytes. Furthermore, HA addition induced greater microbial activity under AgNP stress, possibly originating from stronger affinity of AgNPs over Ag⁺ to organic matters. The obtained results suggested that antimicrobial efficacy of AgNPs was closely related to water chemistry: addition of divalent electrolytes and HA reduced the opportunities directly for AgNP contact and interaction with cells through formation of aggregates, complexes, and surface coatings, leading to significant toxicity reduction; however, in monovalent electrolytes, the dominating mode of action of AgNPs could be toxic effects of the released Ag⁺ on microorganisms due to nanoparticle dissolution.

Ecofriendly laccases treatment to challenge micropollutants issue in municipal wastewaters

In this study, a multidisciplinary approach investigated the enzymatic degradation of micropollutants in real, not modified, municipal wastewaters of a plant located in Italy. Stir Bar Sorptive Extraction combined to Gas Chromatography-Mass Spectrometric detection (SBSE-GC-MS) was applied to profile targeted pollutants in wastewaters collected after the primary sedimentation (W1) and the final effluent (W2). Fifteen compounds were detected at ng/L - μg/L, including pesticides, personal care products (PCPs) and drugs. The most abundant micropollutants were bis(2-ethylhexyl) phthalate, diethyl phthalate and ketoprofen. Laccases of Trametes pubescens MUT 2400 were very active against all the target micropollutants: except few cases, their concentration was reduced more than 60%. Chemical analysis and environmental risk do not always come together. To verify whether the treated wastewaters can represent a stressor for the aquatic ecosystem, toxicity was also evaluated. Raphidocelis subcapitata and Lepidium sativum tests showed a clear ecotoxicity reduction, even though they did not evenly respond. Two in vitro tests (E-screen test and MELN assay) were used to evaluate the estrogenic activity. Treatments already operating in the plant (e.g. activated sludge) partially reduced the estradiol equivalent concentration, and it was almost negligible after the laccases treatment. The results of this study suggest that laccases of T. pubescens are promising biocatalysts for the micropollutants transformation in wastewaters and surface waters.

Application of natural mixed bacteria immobilized carriers to different kinds of organic wastewater treatment and microbial community comparison

Although many literatures have reported that biomass materials had been used for water treatment, most of the biomass materials were directly used for adsorbing toxic or organic substances. In this research, modified pine bark and corn straw were used to prepare the high-efficiency and low-cost activated sludge immobilized materials. By treating phenol wastewater and ordinary organic wastewater, various factors influencing the treatment effect were investigated. The results showed that the immobilized biological carriers had good effects on the treatment of two kinds of wastewater. The removal efficiency of the phenol wastewater reached 100% in 24 h, and the removal efficiency of ordinary organic wastewater reached 95.5% in 96 h. The results of microbial community analysis showed that the abundance of the immobilized carrier and that of the original sludge was similar. But when treating different wastewater, the number and proportion of microorganisms were significantly different.

Effects of nonylphenols on embryonic development and metamorphosis of Xenopus laevis: FETAX and amphibian metamorphosis toxicity test (OECD TG231)

Nonylphenols (NPs) are a group of endocrine-disrupting surfactants that mimic estrogen. To determine the developmental toxicity and thyroid-disrupting effect of NPs, the effects of exposure to nonylphenol (NP), 4-nonylphenol (4-NP), and nonylphenol ethoxylate (NP-12) were examined according to the frog embryo teratogenesis assay-Xenopus (FETAX) and Organization for Economic Co-operation and Development test guidelines 231 (TG231). In FETAX, the LC₅₀ values of NP, 4-NP, and NP-12 were 59.14 mg/L, 10.13 mg/L, and 14.60 mg/L, respectively. At 10.0 mg/L, NP, 4-NP, and NP-12 significantly decreased the total length of tadpoles, and NP and 4-NP increased gut malformation and bent tails. In surviving tadpoles, the EC₅₀ values for malformation of NP, 4-NP, and NP-12 were 4.66, 6.51, and 13.08 mg/L, respectively. The teratogenic indices of NP, 4-NP, and NP-12 were 12.69, 1.56, and 1.08, respectively, suggesting the teratogenic potential of NP and 4-NP. In a range-finder assay for TG231, the 96-h LC₅₀ values of NP, 4-NP, and NP-12 were 2.0, 2.0, and 10.57 mg/L, respectively. When NF stage 51 larvae were exposed for 21 days, larval growth was inhibited by NP, 4-NP, and NP-12 at 0.67, 0.07, and 0.37 mg/L, respectively. 4-NP at 0.07 mg/L accelerated the developmental stage and significantly increased hind limb length, while 0.67 mg/L 4-NP delayed the developmental stage and decreased hind limb length, suggesting a bimodal effect of 4-NP on metamorphosis. NP and NP-12 at test concentrations did not alter the larval stage, but NP-12 at 0.37 mg/L significantly decreased total length and tail length, suggesting growth inhibition in larvae. The total colloid area of thyroid follicles was significantly increased by 0.07 mg/L 4-NP but not by NP and NP-12, suggesting that 4-NP may interfere with thyroid function. Together, the developmental toxicity of NPs was in the following order: 4-NP, NP-12, and NP. 4-NP may alter metamorphosis driven by thyroid hormones in X. laevis.

Toxicity of perfluorooctane sulfonate on Phanerochaete chrysosporium: Growth, pollutant degradation and transcriptomics

As a persistent organic pollutant listed in the Stockholm Convention, perfluorooctane sulfonate (PFOS) is extremely refractory to degradation under ambient conditions. Its potential ecotoxicity has aroused great concerns and research interests. However, little is known about the toxicity of PFOS on fungus. In this study, the white rot fungus Phanerochaete chrysosporium (P. chrysosporium) was adopted to assess the toxicity of PFOS in liquid culture. The addition of 100 mg/L PFOS potassium salt significantly decreased the fungal biomass by up to 76.4% comparing with un-amended control during the incubation period. The hyphostroma of P. chrysosporium was wizened and its cell membrane was thickened, while its vesicle structure was increased, based on the observation with scanning electron microscope (SEM) and transmission electron microscope (TEM). Nevertheless, the PFOS dosage of below 100 mg/L did not show a considerable damage to the growth of P. chrysosporium. The degradation of malachite green (MG) and 2,4-dichlorophenol (2,4-DCP) by P. chrysosporium was negatively affected by PFOS. At the initial dosage of 100 mg/L PFOS, the decolorization efficiency of MG and the degradation efficiency of 2,4-DCP decreased by 37% and 20%, respectively. This might be attributed to the inhibition of PFOS on MnP and LiP activities. The activities of MnP and LiP decreased by 20.6% and 43.4%, respectively. At a high dosage PFOS (100 mg/L), P. chrysosporium could show a high adsorption of MG but lose its pollutant degradation ability. Transcriptome analysis indicated that PFOS contamination could lead to the change of gene expression in the studied white rot fungus, and the genes regulating membrane structure, cell redox process, and cell transport, synthesis and metabolism were impacted. Membrane damage and oxidative damage were the two main mechanisms of PFOS' toxicity to P. chrysosporium.