Perfluorooctanoic acid (PFOA)-induced alterations of biomolecules in the wetland plant Alismaorientale

Novel insights on ecological responses of short- and long-chain perfluorocarboxylic acids in constructed wetlands coupled with modified basalt fiber bio-nest

The first investigation based on constructed wetlands coupled with modified basalt fiber bio-nest (MBF-CWs) was performed under exposure of short- and long-chain perfluorocarboxylic acids (PFCAs). In general, both perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) caused significant decline of chemical oxygen demand removal by 10.83 % and 4.73 %. However, only PFOA led to marked inhibition on total phosphorus removal by 12.51 % in whole duration. Suppression of removal performance resulted from side impacts on microbes by PFOA. For instance, activities of key enzymes like dehydrogenase (DHA), urease (URE), and phosphatase (PST) decreased by 52.77 %, 40.70 %, and 56.94 % in maximum under PFOA stress, while URE could alleviate over time. By contrast, distinct inhibition was only found on PST in later phases with PFBA exposure. PFCAs had adverse influence on alpha diversity of MBF-CWs, particularly long-chain PFOA. Both PFCAs caused enrichment of Proteobacteria, owing to increase of Gammaproteobacteria and Plasticicumulans by 22.04-35.79 % and 22.91-219.77 %. Nevertheless, some dominant phyla (like Bacteroidota and Acidobacteriota) and genera (like SC-I-84, Thauera, Subgroup_10, and Ellin6067) were only suppressed by PFOA, causing more hazards to microbial decontamination than PFBA did. As for plants, chlorophyll contents tend to decrease with PFOA treatment. Whereas, higher antioxidase activities and more lipid peroxidation products were uncovered in PFOA group, demonstrating more reactive oxygen species brought by long-chain PFCAs. This work offered new findings about ecological effects of MBF-CWs under PFCAs exposure, evaluating stability and sustainability of MBF-CW systems to treat sewage containing complex PFCAs.

Characterization and Statistical Optimization of Enterobatin Synthesized by Escherichia coli OQ866153

Microorganisms produce siderophores, which are secondary metabolites with a high affinity for iron. Siderophores have received significant attention due to their diverse applications in ecological and clinical research. In this study, siderophores production by Escherichia coli OQ866153 was optimized using two-stage statistical approach involving Plackett-Burman design (PBD) and response surface methodology (RSM) using central composite design (CCD). Out of 23 variables, succinate, tryptophan, Na2HPO4, CaCl2, agitation, and KH2PO4 were found to have the most significant effect on siderophores production in the first optimization stage with the highest SU% of 43.67%. In the second stage, RSM using CCD was utilized, and the optimal conditions were determined to be 0.3 g/l succinate, 0 g/l tryptophan, 6 g/l Na2HPO4, 0.1 g/l CaCl2, 150 RPM agitation, and 0.6 g/l KH2PO4, resulting in a maximum siderophore units (SU%) of 89.13%. The model was significant, as indicated by the model f-value of 314.14 (p-value = 0.0004) and coefficient of determination R2 of 0.9950. During validation experiments, the obtained maximum SU% was increased up to 87.1472%, which was two times as the value obtained under ordinary conditions (46.62%). The produced siderophores were purified and characterized using 1H, 13C NMR, IR spectroscopy. The obtained results indicated that the compound was enterobactin and entABCDEF genes were further detected in Escherichia coli OQ866153 extracted DNA. To our knowledge, this is the first report of statistical optimization for enterobactin synthesis by an E. coli strain isolated from a clinical source in Egypt.

PFOA accumulation in the leaves of basil (Ocimum basilicum L.) and its effects on plant growth, oxidative status, and photosynthetic performance

BACKGROUND

Perfluoroalkyl substances (PFASs) are emerging contaminants of increasing concern due to their presence in the environment, with potential impacts on ecosystems and human health. These substances are considered "forever chemicals" due to their recalcitrance to degradation, and their accumulation in living organisms can lead to varying levels of toxicity based on the compound and species analysed. Furthermore, concerns have been raised about the possible transfer of PFASs to humans through the consumption of edible parts of food plants. In this regard, to evaluate the potential toxic effects and the accumulation of perfluorooctanoic acid (PFOA) in edible plants, a pot experiment in greenhouse using three-week-old basil (Ocimum basilicum L.) plants was performed adding PFOA to growth substrate to reach 0.1, 1, and 10 mg Kg- 1 dw.

RESULTS

After three weeks of cultivation, plants grown in PFOA-added substrate accumulated PFOA at different levels, but did not display significant differences from the control group in terms of biomass production, lipid peroxidation levels (TBARS), content of α-tocopherol and activity of ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (POX) in the leaves. A reduction of total phenolic content (TPC) was instead observed in relation to the increase of PFOA content in the substrate. Furthermore, chlorophyll content and photochemical reflectance index (PRI) did not change in plants exposed to PFAS in comparison to control ones. Chlorophyll fluorescence analysis revealed an initial, rapid photoprotective mechanism triggered by PFOA exposure, with no impact on other parameters (Fv/Fm, ΦPSII and qP). Higher activity of glutathione S-transferase (GST) in plants treated with 1 and 10 mg Kg- 1 PFOA dw (30 and 50% to control, respectively) paralleled the accumulation of PFOA in the leaves of plants exposed to different PFOA concentration in the substrate (51.8 and 413.9 ng g- 1 dw, respectively).

CONCLUSION

Despite of the absorption and accumulation of discrete amount of PFOA in the basil plants, the analysed parameters at biometric, physiological and biochemical level in the leaves did not reveal any damage effect, possibly due to the activation of a detoxification pathway likely involving GST.

Bovine serum albumin-liposome stabilized high oil-phase emulsion: Effect of liposome ratio on interface properties and stability

This study aimed to solve the issue of poor lipophilicity of natural bovine serum albumin (BSA) by combining with liposomes (Lips) to stabilize high oil-phase emulsions (HOPEs). The interaction between BSA and Lips was mainly driven by hydrophobic forces, followed by hydrogen bonding. The secondary structure and tertiary structure of BSA were characterized and indicated that the addition of Lips promoted the structural expansion of BSA exposing the hydrophobic groups inside. Interfacial adsorption behaviours were assessed through dynamic interfacial tension, three-phase contact angle, and quartz crystal microbalance with dissipation. These results indicated that BSA-Lips crosslinking improved wettability, promoting adsorption and rearrangement at the oil-water interface, thereby resulting in a dense interfacial layer. The emulsifying efficacy of BSA-stabilized HOPEs also displayed a distinct Lips dependency. Varying the BSA-to-Lips ratio transformed their consistency from flowing to semi-solid, reinforcing the gel network. Under optimal conditions (BSA: Lips = 1:1), the droplet size of BSA-Lips stabilized HOPEs reached a minimum with a highly uniform distribution. Moreover, a 1:1 BSA to Lips ensured outstanding storage, thermal, and centrifugal stability for the HOPEs. This work provides valuable references for the interaction between protein and Lips, guiding the development of highly stable HOPEs stabilizers.

Occurrence, distribution, and risk assessment of antibiotics in a typical aquaculture area around the Dongzhai Harbor mangrove forest on Hainan Island

The trees of the Dongzhai Harbor mangrove forest suffer from antibiotic contamination from surrounding aquaculture areas. Despite this being one of the largest mangrove forests in China, few studies have focused on the antibiotic pollution status in these aquaculture areas. In the present study, the occurrence, distribution, and risk assessment of 37 antibiotics in surface water and sediment samples from aquaculture areas around Dongzhai Harbor mangrove forests were analyzed. The concentration of total antibiotics (∑antibiotics) ranged from 78.4 ng/L to 225.6 ng/L in surface water (except S14-A2) and from 19.5 ng/g dry weight (dw) to 229 ng/g dw in sediment. In the sediment, the concentrations of ∑antibiotics were relatively low (19.5-52.3 ng/g dw) at 75 % of the sampling sites, while they were high (95.7-229.0 ng/g dw) at a few sampling sites (S13-A1, S13D, S8D). The correlation analysis results showed that the Kd values of the 9 antibiotics were significantly positively correlated with molecular weight (MW), Kow, and LogKow. Risk assessment revealed that sulfamethoxazole (SMX) in surface water and SMX, enoxacin (ENX), ciprofloxacin (CFX), enrofloxacin (EFX), ofloxacin (OFX), and norfloxacin (NFX) in sediment had medium/high risk quotients (RQs) at 62.5 % and 25-100 %, respectively, of the sampling sites. The antibiotic mixture in surface water (0.06-3.36) and sediment (0.43-309) posed a high risk at 37.5 % and 66.7 %, respectively, of the sampling sites. SMX was selected as an indicator of antibiotic pollution in surface water to assist regulatory authorities in monitoring and managing antibiotic pollution in the aquaculture zone of Dongzhai Harbor. Overall, the results of the present study provide a comprehensive and detailed analysis of the characteristics of antibiotics in the aquaculture environment around the Dongzhai Harbor mangrove system and provide a theoretical basis for the source control of antibiotics in mangrove systems.

Single and combined toxicity effects of microplastics and perfluorooctanoic acid on submerged macrophytes and biofilms

Microplastics (MPs) and Perfluorooctanoic acid (PFOA) have contaminated nearly all types of ecosystems, including marine, terrestrial and freshwater habitats, posing a severe threat to the ecological environment. However, their combined toxicity on aquatic organisms (e.g., macrophytes) remains unknown. This study investigated single and combined toxic effects of polypropylene (PP), polyethylene (PE), polyvinylchloride (PVC), polyethylene terephthalate (PET) and PFOA on Vallisneria natans (V. natans) and associated biofilms. Results showed that MPs and PFOA significantly affected plant growth, while the magnitude of the effect was associated with concentrations of PFOA and the types of MPs, and antagonistic effects were induced at combined MPs and PFOA exposure. In addition, antioxidant responses in plants, such as promoted activities of SOD and POD, as well as increased content of GSH and MDA, were triggered effectively by exposure to MPs and PFOA alone and in combination. Ultrastructural changes revealed the stress response of leaf cells and the damage to organelles. Moreover, single and combined exposure to MPs and PFOA altered the diversity and richness of the microbial community in the leaf biofilms. These results indicated that the coexistence of MPs and PFOA can induce effective defense mechanisms of V. natans and change the associated biofilms at given concentrations in the aquatic ecosystems.

Effect and mechanism of perfluorooctanoic acid (PFOA) on anaerobic digestion sludge dewaterability

Perfluorooctanoic acid (PFOA) as nonbiodegradable organic pollutant, its presence and risks in wastewater treatment system has aroused wide concern. This study investigated the effect and underlying mechanism of PFOA on anaerobic digestion sludge (ADS) dewaterability. Long-term exposure experiments were set up to investigate the effect with various concentration of PFOA dosed. Experimental results suggested that the existence of high concentration PFOA (over 1000 μg/L) could deteriorate ADS dewaterability. The long-term exposure to 100,000 μg/L PFOA of ADS increased specific resistance filtration (SRF) by 81.57%. It was found that PFOA promoted the release of extracellular polymeric substances (EPS), which was strongly associated with sludge dewaterability. The fluorescence analysis revealed that the high PFOA concentration could significantly improve the percentage of protein-like substances and soluble microbial by-product-like content, and then further deteriorated the dewaterability. The FTIR results showed that long-term exposure of PFOA caused loose protein structure in sludge EPS, which led to loose sludge floc structure. The loose sludge floc structure aggravated the deterioration of sludge dewaterability. The solids-water distribution coefficient (K_d) decreased with the increase of initial PFOA concentration. Moreover, PFOA significantly affected microbial community structure. Metabolic function prediction results showed significant decrease of fermentation function exposed to PFOA. This study revealed that the PFOA with high concentration could deteriorated sludge dewaterability, which should be highly concerned.

Response mechanisms of Chlorella sorokiniana to microplastics and PFOA stress: Photosynthesis, oxidative stress, extracellular polymeric substances and antioxidant system

Co-pollution of microplastics and per- and polyfluoroalkyl substances (PFAS) is prevailing in the aquatic environment. However, the risks of coexisting microplastics and PFAS on organisms remain unknown. This study investigated the response mechanisms of Chlorella sorokiniana (C. sorokiniana) under polystyrene microplastics (PS-MPs) and perfluorooctanoic acid (PFOA) stress, including toxicity and defense mechanisms. C. sorokiniana was exposed to PS-MPs (10 mg/L) and PFOA (0.05, 0.5, and 5 mg/L) and their mixtures for 96 h, respectively. We found that the dominant toxicity mechanism of PFOA and PS-MPs to C. sorokiniana was dissimilar. PS-MPs mainly inhibited photosynthesis through shading effect, while PFOA mainly induced oxidative stress by reactive oxygen species. The co-exposure of PFOA and PS-MPs aggravated biotoxicity (maximum inhibition rate: 27.27 ± 2.44%), such as photosynthesis inhibition, physical damage, and oxidative stress, compared with individuals. To alleviate toxicity, C. sorokiniana activated defense mechanisms. Extracellular polymeric substances were the first barrier to protect cells, the effect on its secretion was ordered PS-MPs+5PFOA > PS-MPs > 5PFOA, and IBRv2 values were 2.37, 1.35, 1.11, respectively. Antioxidant system was thought of second defense pathway, the influence order of treatment groups was PS-MPs+5PFOA > 5PFOA > PS-MPs, and its IBRv2 values were 2.89, 1.69, 0.25, respectively. Our findings provide valuable information on the complex impacts of PFOA and PS-MPs, which facilitate the ecological risk assessment of multiple pollutants.

Screening of structural and functional alterations in duckweed (Lemna minor) induced by per- and polyfluoroalkyl substances (PFASs) with FTIR spectroscopy

As a class of common emerging pollutants, per- and polyfluoroalkyl substances (PFASs) and their alternatives have been widely detected in various environmental matrices, exhibiting a great threat to the ecological environment and human health. Nevertheless, changes in biomolecular structure and function of duckweed caused by PFASs and their alternatives remain unknown thus far. Herein, the effects of four PFASs, including two common legacy PFASs (perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA)) and two PFASs alternatives (perfluorobutane sulfonic acid (PFBS) and 1H,1H,2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)) on duckweed (Lemna minor) at biochemical level were investigated with Fourier transform infrared spectroscopy (FTIR). Although no obvious inhibitions were observed in the growth of L. minor with PFASs exposure at three levels of 1 μg L^-1, 100 μg L^-1, and 10 mg L^-1, significant structural and functional alterations were induced at the biochemical level. In response to PFASs exposure, lipid peroxidation, proteins aggregation and α-helix to β-sheet transformation of the protein conformation, as well as changes of DNA conformations were detected. Moreover, alterations in lipid, protein, and DNA were proved to be concentration-related and compound-specific. Compared to the two legacy PFASs (PFOS and PFOA), alternative ones exhibited greater effects on the biological macromolecules of L. minor. The findings of this study firstly reveal structural and functional alterations in L. minor induced by PFASs exposure, providing further understanding of their toxicity effects.

Complete mechanochemical defluorination of perfluorooctanoic acid using Al2O3 and Al powders through matching electron-mediated reduction with decarboxylation

This work reports a mechanochemical (MC) method for complete defluorination of perfluorooctanoic acid (PFOA) by using Al and Al₂O₃ as milling agents. Both the Al/Al₂O₃ molar ratio ( [Formula: see text] ) and the pre-thermal treatment of Al₂O₃ strongly influenced the defluorination of PFOA. When commercial γ-Al₂O₃ was pre-treated at 1200 °C, the use of Al and heat-treated γ-Al₂O₃ with [Formula: see text] of 1: 1 led to PFOA defluorination of 100% after ball milling for 26 min at 350 rpm, being much higher than those (8.3%-58.1%) for using singlet milling agents or binary milling agents containing γ-Al₂O₃ pre-heated at temperatures lower than 700 °C. It was clarified that the carboxylate-mediated adsorption of PFOA on Al₂O₃ was essential for the MC decarboxylation as a degradation initiation step, and the in-situ generated electron on milled Al consequently caused the reductive dissociation of C-F bonds in the decarboxylation intermediate. A larger [Formula: see text] increased the in-situ electron generation rate (r_e), and a higher heat-treatment temperature decreased OH^-/H₂O adsorbed on Al₂O₃ to low the PFOA decarboxylation rate (r_dec). The r_e/r_dec ratio determined defluorination pathways, and the percentage of the defluorination of PFOA in its total degradation including the generation of any degradation intermediates increased linearly with increasing r_e/r_dec.