Bacterium Photobacterium Phosphoreum Research Articles

Cytotoxic and radical activities of metal-organic framework modified with iron oxide: Biological and physico-chemical analyses

Metal-organic framework (MOF) modified with iron oxide, Fe3O4-MOF, is a perspective drug delivery agent, enabling magnetic control and production of active hydroxyl radicals, •OH, via the Fenton reaction. This paper studies cytotoxic and radical activities of Fe-containing nanoparticles (NPs): Fe3O4-MOF and its components – bare Fe3O4 and MOF (MIL-88B). Luminous marine bacteria Photobacteriumphosphoreum were used as a model cellular system to monitor bioeffects of the NPs. Neither the NPs of Fe3O4-MOF nor MOF showed cytotoxic effects in a wide range of concentrations (<10 mg/L); while Fe3O4 was toxic at >3·10−3 mg/L. The NPs of Fe3O4 did not affect the bacterial bioluminescence enzymatic system; their toxic effect was attributed to cellular membrane processes. The integral content of reactive oxygen species (ROS) was determined using a chemiluminescence luminol assay. Bacteria mitigated excess of ROS in water suspensions of Fe3O4-MOF and MOF, maintaining bioluminescence intensity closer to the control; this resulted in low toxicity of these NPs. We estimated the activity of •OH radicals in the NPs samples with physical and chemical methods – spin capture technology (using electron paramagnetic resonance spectroscopy) and methylene blue degradation. Physico-chemical interpretation of cellular responses is provided in terms of iron content, iron ions release and •OH radical production.

Toxicity of individual and mixture of organic compounds to P. Phosphoreum and S. Capricornutum using interpretable simple structural parameters

Human and environmental ecosystem beings are exposed to multicomponent compound mixtures but the toxicity nature of compound mixtures is not alike to the individual chemicals. This work introduces four models for the prediction of the negative logarithm of median effective concentration (pEC50) of individual chemicals to marine bacteria Photobacterium Phosphoreum (P. Phosphoreum) and algal test species Selenastrum Capricornutum (S. Capricornutum) as well as their mixtures to P. Phosphoreum, and S. Capricornutum. These models provide the simplest approaches for the forecast of pEC50 of some classes of organic compounds from their interpretable structural parameters. Due to the lack of adequate toxicity data for chemical mixtures, the largest available experimental data of individual chemicals (55 data) and their mixtures (99 data) are used to derive the new correlations. The models of individual chemicals are based on two simple structural parameters but chemical mixture models require further interaction terms. The new model's results are compared with the outputs of the best accessible quantitative structure–activity relationships (QSARs) models. Various statistical parameters are done on the new and comparative complex QSAR models, which confirm the higher reliability and simplicity of the new correlations.

Mathematical modeling of quorum sensing dynamics in batch culture of luminescent bacterium Photobacterium phosphoreum 1889.

At the beginning of the paper, the level of necessary phenomenology of complex models is discussed. When working with complex systems, which of course include living organisms and ecological systems, it is necessary to use a phenomenological description. An illustration of the phenomenological approach is given, which captures the most significant general principles or patterns of interactions; the specific values of the parameters cannot be calculated from the first principles, but are determined empirically. An appropriate interpretation is also chosen empirically and pragmatically. However, in order to simulate a wider range of situations, it becomes necessary to lower the level of phenomenology, switch to a more detailed description of the system, introducing interaction between selected elements of the system. The requirements for a system model combining ecological, metabolic and genetic levels of cell culture description are formulated. A mathematical model of quorum sensing dynamics during the growth of batch culture of luminescent bacteria at different concentrations of the nutrient substrate has been developed. The model contains four blocks describing ecological, energy, quorum and luminescent aspects of bacterial culture growth. The model demonstrated good agreement with the experimental data obtained. When analyzing the model, three oddities in the behavior of the culture were noted, which presumably can change the idea of some processes taking place during the development of a culture of luminescent bacteria. The results obtained suggest the presence of some additional control system for the luminescent reaction via the synthesis pathways of FMN · Н2 or aliphatic aldehyde. In this case, the generalized description of the contribution of energy metabolism to luminescence only through ATP is too strong a simplification. As a result of comparing the model dynamics with the experiment, a discrepancy arose between the concentration of the substrate (peptone) measured in the experiment and its effective influence on the bacterial population growth. This discrepancy seems to indicate peptone is not the leading substrate, and growth is limited by nutrients contained in the yeast extract, the concentration of which did not change in these experiments. The discrepancies noted between the expectations and the results of experimental data processing, together with the assumptions about the causes of these discrepancies, set the direction for further experimental and theoretical studies of quorum sensing mechanisms in a culture of luminescent bacteria.

Enzyme Inhibition-Based Assay to Estimate the Contribution of Formulants to the Effect of Commercial Pesticide Formulations.

Pesticides can affect the health of individual organisms and the function of the entire ecosystem. Therefore, thorough assessment of the risks associated with the use of pesticides is a high-priority task. An enzyme inhibition-based assay is used in this study as a convenient and quick tool to study the effects of pesticides at the molecular level. The contribution of formulants to toxicological properties of the pesticide formulations has been studied by analyzing effects of 7 active ingredients of pesticides (AIas) and 10 commercial formulations based on them (AIfs) on the function of a wide range of enzyme assay systems differing in complexity (single-, coupled, and three-enzyme assay systems). Results have been compared with the effects of AIas and AIfs on bioluminescence of the luminous bacterium Photobacterium phosphoreum. Mostly, AIfs produce a considerably stronger inhibitory effect on the activity of enzyme assay systems and bioluminescence of the luminous bacterium than AIas, which confirms the contribution of formulants to toxicological properties of the pesticide formulation. Results of the current study demonstrate that "inert" ingredients are not ecotoxicologically safe and can considerably augment the inhibitory effect of pesticide formulations; therefore, their use should be controlled more strictly. Circular dichroism and fluorescence spectra of the enzymes used for assays do not show any changes in the protein structure in the presence of commercial pesticide formulations during the assay procedure. This finding suggests that pesticides produce the inhibitory effect on enzymes through other mechanisms.

Adaptation of a Bacterial Bioluminescent Assay to Monitor Bioeffects of Gold Nanoparticles.

Our current study aimed to adapt a bioluminescent bacteria-based bioassay to monitor the bioeffects of gold nanoparticles (AuNPs). Luminous marine bacteria Photobacterium phosphoreum and AuNPs modified with polyvinylpyrrolidone were employed; low-concentration (≤10−3 g/L) bioeffects of AuNPs were studied. Bioluminescence intensity was used as an indicator of physiological activity in bacteria. Two additional methods were used: reactive oxygen species (ROS) content was estimated with a chemiluminescent luminol method, and bacterial size was monitored using electron microscopy. The bacterial bioluminescent response to AuNPs corresponded to the “hormesis” model and involved time-dependent bioluminescence activation, as well as a pronounced increase in the number of enlarged bacteria. We found negative correlations between the time courses of bioluminescence and the ROS content in bacterial suspensions, demonstrating the relationship between bioluminescence activation and bacterial ROS consumption. The combined effects of AuNPs and a beta-emitting radionuclide, tritium, revealed suppression of bacterial bioluminescent activity (as compared to their individual effects) and a reduced percentage of enlarged bacteria. Therefore, we demonstrated that our bacteria-based bioluminescence assay is an appropriate tool to study the bioeffects of AuNPs; the bioeffects can be further classified within a unified framework for rapid bioassessment.

Safflower and bitter melon extracts on suppression of biogenic amine formation by fish spoilage bacteria and food borne pathogens

Safflower (Carthamus tinctorius) and bitter melon (Momordica charantia L.) ethanolic extracts for controlling growth of fish spoilage bacteria (Acinetobacter lwoffii, Pseudomonas oryzihabitans, Enterobacter cloacae, Shigella spp., Morganella psychrotolerans and Photobacterium phosphoreum) and food-borne pathogens (Staphylococcus aureus, Klebsiella pneumoniae and Salmonella Paratyphi A), and their biogenic amine production were examined in anchovy infusion decarboxylase broth (AIDB). Bacterial load in AIDB was between 8.1 and 8.9 log CFU/ml. Bitter melon generally restricted growth of bacteria (p < 0.05). Bacterial load in the medium was not associated well with biogenic amine production. All bacteria had a high ability to form biogenic amines in AIDB. Significant discrepancies were noticed among groups in ammonia and biogenic amine production by bacteria (p < 0.05). A. lwoffii and P. phosphoreum were main bacteria produced the highest level of histamine (254.05 vs. 234.39 mg/L). Among food-borne pathogens, S. aureus was found stronger tyramine producer, with value of 736.53 mg/L. Bitter melon and safflower extract led approximately 9 and 12 fold lower histamine accumulation by S. aureus. The study result showed that bitter melon extract had more obvious effect, particularly for suppressing ammonia and toxicologically important biogenic amines production by bacteria, and thus could be suitable antimicrobial agent in food systems.

Resazurin as an indicator of reducing capacity for analyzing the physiologic status of deep-sea bacterium Photobacterium phosphoreum ANT-2200

Resazurin (RZ) is a weakly fluorescent blue dye and can be reduced irreversibly to highly fluorescent pink resorufin (RF) that is reduced reversibly to colorless dihydroresorufin (hRF) by photo, deoxygenation, chemical reaction and reductive organic compounds produced through cell metabolism. Because of the reliable and sensitive fluorescence-color change and noninvasive features, RZ has been used widely as a redox indicator in cell viability/proliferation assays for bacteria, yeast, and mammalian cells. However, RZ is used rarely for physiological characterization of marine microorganisms. Here, we developed a custom-made irradiation and absorption-analysis device to assess the reducing capacity and physiologic status of marine bacterial cultures. We measured the absorption spectra of RZ, RF, and hRF in the presence of the reducing compound Na2S and under visible-light irradiation. After establishing appropriate parameters, we monitored the color changes of RZ and its reduced derivatives to evaluate the coherence between reducing capacity, bioluminescence and growth of the deep-sea bacterium Photobacterium phosphoreum strain ANT-2200 under various conditions. Emission of bioluminescence is an oxidation process dependent upon cellular reducing capacity. Growth and bioluminescence of ANT-2200 cell cultures were impeded progressively with increasing concentrations of RZ, which suggested competition for reducing molecules between RZ at high concentration with reductive metabolism. Therefore, caution should be applied upon direct addition of RZ to growth media to monitor redox reactions in cell cultures. Analyses of the instantaneous reduction velocity of RZ in ANT-2200 cell cultures showed a detrimental effect of high hydrostatic pressure and high coherence between the reducing capacity and bioluminescence of cultures. These data clearly demonstrate the potential of using RZ to characterize the microbial metabolism and physiology of marine bacteria.

High-Pressure Inactivation of Histamine-Forming Bacteria Morganella morganii and Photobacterium phosphoreum

The effects of high hydrostatic pressure (HHP) treatments on histamine-forming bacteria (HFB) Morganella morganii and Photobacterium phosphoreum in phosphate buffer and tuna meat slurry were investigated using viability counting and scanning electron microscopy. The first-order model fits the destruction kinetics of high pressure on M. morganii and P. phosphoreum during the pressure hold period. The D-values of M. morganii (200 to 600 MPa) and P. phosphoreum (100 to 400 MPa) in phosphate buffer ranged from 16.4 to 0.08 min and 26.4 to 0.19 min, respectively, whereas those in tuna meat slurry ranged from 51.0 to 0.09 min and 71.6 to 0.19 min, respectively. M. morganii had higher D-values than P. phosphoreum at the same pressure, indicating it was more resistant to HHP treatment. HFB had a higher D-value in tuna meat slurry compared with that in phosphate buffer, indicating that the HFB were more resistant to pressure in tuna meat slurry. The Zp values (pressure range that results in a 10-fold change in D-value) of M. morganii and P. phosphoreum were 162 and 140 MPa in phosphate buffer and 153 and 105 MPa in tuna meat slurry, respectively. Damage to the cell wall and cell membrane by HHP treatments can be observed by scanning electron microscopy. To our knowledge, this is the first report to demonstrate that HHP can be applied to inactivate the HFB M. morganii and P. phosphoreum by inducing morphological changes in the cells.

HPTLC-bioautography/SERS screening nifedipine adulteration in food supplement based on Ginkgo biloba

Ginkgo biloba was a popular phytomedicine as the essential ingredient of many food supplement. In this work, a bio-inspired HPTLC method was proposed for the visualized screening of nifedipine adulteration in food supplement based on Gingko biloba. To customize the visualization of the analyte by inhibiting bacterium (Photobacterium phosphoreum) bioluminescence, the silica gel plate that gives the highest detectability was selected as the stationary phase of separation. Thereafter, the HPTLC procedure (toluene and ethyl acetate 8/2, v/v, as the mobile phase, to a distance of 60 mm) was optimized and standardized as a sample cleanup tool to exclude noises caused by bioactive co-extracts. Then, the separation result fixed on the plate layer was selectively visualized as dark bands against the white background, only after 6 min exposure. To achieve quantitation of the obtained HPTLC images, an enhanced quantitative analysis was optimized via software (ImageJ) facilitated pixel scanning, offered remarkable sensitivity (LOD=24.0 μg/g), linearity (R2=0.9985 within 50–300 ng/band) and precision (RSD<7.2%). Further, the developed method was validated with real samples (recovery rates within 81.0–92.8%). In conjunction with image quantitation, in-situ surface enhance Raman spectroscopy was incorporated into the analysis, using silver nanoparticles as the active substrate and He:Ne 633 nm lamp the incident laser source. The obtained SERS spectra displayed highly characteristic fingerprint patterns, enabling unambiguous confirmation of effect-directed results.

A new HPTLC platformed luminescent biosensor system for facile screening of captan residue in fruits

This study presented a HPTLC platformed luminescent biosensor system for screening captan residue. First, the potential bio-effects of layers materials on the detectability of a luminescent bacteria Photobacterium phosphoreum (ATCC 11040) as the sensor cell were assessed. From comparison, it was noteworthy that the combination of sensor cells with normal silica gel layer exclusively gave outstanding detectability (<10 ng/zone). On this basis, HPTLC mediated separation and biosensing was further optimized. Then, the obtained graphic results were digitally quantified via software processing, offering satisfactory selectivity, linearity (R2 = 0.9901 within 10–80 ng/zone) and sensitivity (0.5 mg/kg against MRLs ≥ 6 mg/kg). Additionally, the performance of the established method was validated with different fruits (recover rates 75–96%, RSD < 11.8%). Meanwhile, it was demonstrated that detectability of this hybrid system would be tuneable by altering the combination of bacteria strains and layer materials, which was meaningful to strengthen the usability of microbial biosensors.

Environmentally persistent free radical generation on contaminated soil and their potential biotoxicity to luminous bacteria

Environmentally persistent free radicals (EPFRs) are detected in the clay, mineral or humic part of the soil, especially in soil contaminated with phenolic compounds. To clarify the detailed information on the formation of EPFRs, we used the contaminated soil with catechol to mimic their formation process in laboratory scale and tested their biotoxicity with luminescent bacteria (Photobacterium phosphoreum, P. phosphoreum). Our results showed that the concentration of EPFRs reached the maximum at pyrolysis temperature of 300 °C, and EPFRs could significantly inhibit the luminescence of P. phosphoreum. Based on the detection of OH radicals in the aquatic system we used, we speculated that the generation of OH may be a crucial contributor to the toxicity of EPFRs. Our results aid to understand the detailed process on the formation of EPFRs in contaminated soil, as well as the basic biotoxicity data of EPFRs, which will be helpful and essential for their potential environmental risk assessments.

The Use of Luminos Bacteria Photobacterium phosphoreum as a Bioindicator of Geomagnetic Activity

Background. An actual problem is determination of features of different micro-organisms for the activity bioindication of environment geophysical parameter state.Objective. The aim of the paper is to determine correlation dependences between values of luminescence intensity of bacteria Photobacterium phosphoreum and factors determining geomagnetic activity.Methods. The optimum parameters of suspension were determined for research of bioluminescence intensity as a bioindicator of the geomagnetic field state. The monitoring of specific intensity of bacteria luminescence has been carried out for 2 months and it was compared to the daily values of activity of the geomagnetic field in the conditions of Kiev, during the research of bioluminescence. Vari­ation determination of the geomagnetic field was conducted from data of Space Environment Center, NOAA & U.S. Air Force. Description of sun activity was conducted with the use of the Wolf numbers and flux of sun radio radiation at a wavelength 10,7 сm.Results. The correlation coefficients of changes of bacteria bioluminescence intensity daily values were calculated and compared to the K-index and Ap-index values, Wolf numbers, and flux of sun radio radiation. The inverse proportional reliable average correlation was defined R = -0,41 between the values of specific bacterial luminescence and the K-indexes of the geomagnetical field, and with the values of flux of sun radio radiation – reliable directly proportional correlation. It is shown, that at the geomagnetic field variation intensity increase there is reduction of values of bacteria bioluminescence specific intensity.Conclusions. The presence of reliable inverse dependence between K-indexes of geomagnetic field is shown and specific intensity of the P. rhosphoreum luminescence, the correlation coefficient in months with increased geomagnetic activity was R = -0,51. The use of the automated system of the luminescent bacteria luminescence intensity monitoring allows better forecasting in time the manifestations of indignations of the Earth’s magnetic field.

The Effect of K-Lactate Salt and Liquid Smoke on Bacterial Growth in a Model System

ABSTRACTThe effects of a commercial lactate salt formulation—containing potassium lactate (KL) and potassium acetate (KA)—and liquid smoke (LS) on the growth of selected lactic acid bacteria (LAB; Carnobacterium maltaromaticum, Carnobacterium inhibens, Lactococcus lactis, Lactobacillus curvatus, and Enterococcus faecalis), fish spoilage bacteria (Photobacterium phosphoreum, Pseudomonas putida, and Vibrio vulnificus), and Listeria innocua, were examined in a tryptic soy broth model system at 20ºC based on BioScreen data. The most pronounced inhibition effect on growth of bacteria was seen in the presence of 6% KL + 0.4% KA, used either combined with LS or alone. Only a minor inhibition effect on growth was found in the presence of LS alone. The only exception was Lactobacillus curvatus, which grew quite well in the presence of LS compared to control medium. The growth of Vibrio vulnificus was prevented in 6% KL + 0.4% KA, and significantly inhibited in the presence of 3% KL + 0.2% KA. When V. vulnificus was grown in NaCl, KA, and KL + KA, it was observed that KL + KA had a better inhibition effect than sodium salt within the same concentration range.

THE EFFECTS OF MICROWAVE ELECTROMAGNETIC RADIATION ON THE LUMINESCENCE INTENSITY OF PHOTOBACTERIUM PHOSPHOREUM

For an objective assessment of environment pollution by physical factors the adequate test systems and bio-indicators are necessary. It is used bacteria Photobacterium phosphoreum as indicator of exposure to low-intensity microwave electromagnetic field. Registration of the bacteria physiological activity changes was carried out by luminescence intensity. It has been shown that Ph. phosphoreum have sensitive to the effects of low-intensity microwave electromagnetic field (1 GHz, 70 mW / cm2).

Exposure of luminous marine bacteria to low-dose gamma-radiation

The study addresses biological effects of low-dose gamma-radiation. Radioactive 137Cs-containing particles were used as model sources of gamma-radiation. Luminous marine bacterium Photobacterium phosphoreum was used as a bioassay with the bioluminescent intensity as the physiological parameter tested. To investigate the sensitivity of the bacteria to the low-dose gamma-radiation exposure (≤250 mGy), the irradiation conditions were varied as follows: bioluminescence intensity was measured at 5, 10, and 20°С for 175, 100, and 47 h, respectively, at different dose rates (up to 4100 μGy/h). There was no noticeable effect of gamma-radiation at 5 and 10°С, while the 20°С exposure revealed authentic bioluminescence inhibition. The 20°С results of gamma-radiation exposure were compared to those for low-dose alpha- and beta-radiation exposures studied previously under comparable experimental conditions. In contrast to ionizing radiation of alpha and beta types, gamma-emission did not initiate bacterial bioluminescence activation (adaptive response). As with alpha- and beta-radiation, gamma-emission did not demonstrate monotonic dose-effect dependencies; the bioluminescence inhibition efficiency was found to be related to the exposure time, while no dose rate dependence was found. The sequence analysis of 16S ribosomal RNA gene did not reveal a mutagenic effect of low-dose gamma radiation. The exposure time that caused 50% bioluminescence inhibition was suggested as a test parameter for radiotoxicity evaluation under conditions of chronic low-dose gamma irradiation.

Oxidative degradation of triclosan by potassium permanganate: Kinetics, degradation products, reaction mechanism, and toxicity evaluation

In this study, we systematically investigated the potential applicability of potassium permanganate for removal of triclosan (TCS) in water treatment. A series of kinetic experiments were carried out to study the influence of various factors, including the pH, oxidant doses, temperature, and presence of typical anions (Cl−, SO42−, NO3−), humic acid (HA), and fulvic acid (FA) on triclosan removal. The optimal reaction conditions were: pH = 8.0, [TCS]0:[KMnO4]0 = 1:2.5, and T = 25 °C, where 20 mg/L of TCS could be completely degraded in 120 s. However, the rate of TCS (20 μg/L) oxidation by KMnO4 ([TCS]0:[KMnO4]0 = 1:2.5) was 1.64 × 10−3 mg L−1·h−1, lower than that at an initial concentration of 20 mg/L (2.24 × 103 mg L−1·h−1). A total of eleven products were detected by liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-Q-TOF-MS) analysis, including phenol and its derivatives, benzoquinone, an organic acid, and aldehyde. Two main reaction pathways involving CO bond cleavage (−C(8)O(7)−) and benzene ring opening (in the less chlorinated benzene ring) were proposed, and were further confirmed based on frontier electron density calculations and point charges. Furthermore, the changes in the toxicity of the reaction solution during TCS oxidation by KMnO4 were evaluated by using both the luminescent bacteria Photobacterium phosphoreum and the water flea Daphnia magna. The toxicity of 20 mg/L triclosan to D. magna and P. phosphoreum after 60 min was reduced by 95.2% and 43.0%, respectively. Phenol and 1,4-benzoquinone, the two representative degradation products formed during permanganate oxidation, would yield low concentrations of DBPs (STHMFP, 20.99–278.97 μg/mg; SHAAFP, 7.86 × 10−4−45.77 μg/mg) after chlorination and chloramination. Overall, KMnO4 can be used as an effective oxidizing agent for TCS removal in water and wastewater treatment.

Kinetic and mechanism studies of musk tonalide reacted with hydroxyl radical and the risk assessment of degradation products

Tonalide was extensively used as fragrances in various personal care products and recognized as emerging contaminant recently. In this study, the transient reactions of hydrophobic tonalide with hydroxyl radical (OH), one of highly reactive oxygen species (ROSs), was firstly investigated in acetonitrile through direct observation using laser flash photolysis. Two transient intermediates were formed with the peak centered at 360 and 450nm, and the bimolecular reaction rate constants of tonalide with OH were determined in both water and acetonitrile solutions with values of 4.04×109 and 1.95×109M−1s−1, respectively. Then, the photocatalytic experiments in a heterogeneous TiO2 system were carried out to study the decomposition kinetics of tonalide with OH, which was confirmed as the dominant ROSs in photocatalytic system. Five degradation products were identified with molecule weight of 260, 272 and 274. Finally, the potential risks of reaction products formed through the reactions of tonalide with OH were further investigated. It is found that the toxicity towards luminescent bacterium (Photobacterium phosphoreum) was not changed so much, and the estrogenic activity increased a little bit during the degradation of tonalide by OH.

Comparative assessment of toxic effects of surfactants using biotesting methods

This study assesses the comparative sensitivity and possibility of obtaining fast results of various methods of biotesting for several surfactants: Tween 85, sodium dodecyl sulfate (SDS), Fairy dishwashing gel, and Mif washing powder. The following test organisms are used for the study: luminescent bacteria Photobacterium phosphoreum (Beijerinck), preparation of Ecolum luminescent bacteria, unicellular algae Scenedesmus quadricauda (G.M. Smith), infusorian Paramecium caudatum (Ehrenberg), and crustacean Daphnia magna (Straus). It has been revealed that Fairy dishwashing gel possesses the strongest toxicity against the studied test objects. Daphnia and algae are most sensitive to the effects of Fairy and SDS, protozoan and luminescent bacteria are most sensitive to SDS, and Ecolum is most sensitive to Mif washing powder. The tested aquatic organisms and Ecolum are most tolerant to the effect of Tween 85.

The investigation of different pollutants and operation processes on sludge toxicity in sequencing batch bioreactors

ABSTRACTThe influence of different target pollutants and operation modes in sequencing batch bioreactors (SBRs) on sludge toxicity was compared in this study. Sludge toxicity was characterized by the inhibiting luminosity through using luminescent bacterium Photobacterium phosphoreum (P. phosphoreum) during either gradual acclimation or impaction processes with synthetic wastewater containing high-strength bisphenol A (BPA) or N, N-dimethylformamide (DMF). When the activated sludge was first acclimated with either 120 mg/L DMF or 20 mg/L BPA, and then respectively increased to 200 mg/L DMF and 40 mg/L BPA it was defined as gradual acclimation process, whereas when the activated sludge was, respectively, injected with 200 mg/L DMF and 40 mg/L BPA directly it was defined as impaction process. Results showed that the toxicity of the impacted sludge was greater than that of the gradual acclimated sludge, especially in the initial stage before 10 d. Activated sludge treating BPA synthetic wastewater exhibited higher toxicity due to the more inhibition of BPA to sludge activity compared to that of DMF. The proteomics analysis indicated that the stress responses of activated sludge to DMF and BPA stimulation were both significant. In turn, the secretions from two kinds of sludge under stress conditions contributed to sludge toxicity.

Ozonation of the UV filter benzophenone-4 in aquatic environments: Intermediates and pathways

The occurrence of benzophenone-4 (BP-4) in water environments may pose a serious public health hazard due to its potential endocrine disrupting effects. In this work, the intermediates, probable degradation pathways and toxicity changes during ozonation of BP-4 in aqueous solution were systematically investigated. Results revealed that alkaline conditions favored the oxidation of BP-4. However, inorganic anions (Cl−, NO3−, SO42−), cations (K+, Ca2+, Mg2+) and humic acid had no remarkable effect on BP-4 removal within the tested concentrations. Ozonation was also effective for the fast removal of BP-4 in real waters. The TOC suggested a low mineralization rate, even after the complete BP-4 removal. Meanwhile, the treated mixtures exhibited an obvious inhibition to the bioluminescent bacteria Photobacterium phosphoreum, indicating the formation of transformation products with higher toxicities. Furthermore, fourteen products were identified by means of liquid chromatography-mass spectrometry. Notably, seven of them have not been reported previously. The quenching test indicated that the degradation processes probably were dominated by OH. Next, possible degradation pathways were proposed and further justified by theoretical calculations of frontier electron densities. This investigation will contribute to the systematic elucidation of the ozonation process of UV filters in aquatic environments.