Removal of oxytetracycline from wastewater by biochar modified with biosynthesized iron oxide nanoparticles and carbon nanotubes: Modification performance and adsorption mechanism.

The pollution problem of oxytetracycline (OTC) from wastewater becomes more serious, so an efficient, economical, and green adsorption material is urgently explored. In this study, the multilayer porous biochar (OBC) was prepared by coupling carbon nanotubes with iron oxide nanoparticles synthesized by Aquabacterium sp. XL4 to modify corncobs under medium temperature (600 °C) conditions. The adsorption capacity of OBC could reach 72.59 mg g-1 after preparation and operation parameters were optimized. In addition, various adsorption models suggested that OTC removal resulted from the combined effect of chemisorption, multilayer interaction, and disordered diffusion. Meanwhile, the OBC was fully characterized and exhibited a large specific surface area (237.51 m2 g-1), abundant functional groups, stable crystal structure, high graphitization, and mild magnetic properties (0.8 emu g-1). The OTC removal mechanisms mainly included electrostatic interactions, ligand exchange, π-π bonding reactions, hydrogen bonds, and complexation. pH and coexistence substance experiments revealed that the OBC possesses a wide pH adaptation range and excellent anti-interference ability. Finally, the safety and reusability of OBC were confirmed by repeated experiments. In summary, OBC as a biosynthetic material shows considerable potential for application in the field of purifying new pollution from wastewater.

Removal of oxytetracycline from water by liquid-phase plasma process with an iron precipitated TiO2 photocatalyst.

This study developed a new water treatment method using liquid-phase plasma (LPP) process that can decompose oxytetracycline (OTC) remaining in the aquatic environment. Relatedly, the OTC causes damage to the human body and cannot be removed by traditional water treatment methods. The study also prepared Fe/TiO2 photocatalyst responding to visible light using the LPP process. In particular, the OTC decomposition efficiency of the LPP process improved by more than 10% with the use of the Fe/TiO2 photocatalyst as compared to that of the one with the use of bare TiO2 photocatalyst. Further, the optimal LPP process parameters and Fe/TiO2 photocatalyst amount in the LPP process for OTC decomposition were established in the study. Finally, the degradation pathway of the OTC in the LPP process was found based on the five intermediates of the LPP reaction that were detected by the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis. In particular, the decomposition pathway was estimated to be involving the mineralization of the OTC through demethylation, deamination, dehydration, and ring cleavage.

A study of the effect of reactive oxygen species induced by violet and blue light from oxytetracycline on the deactivation of Escherichia coli.

Oxytetracycline (OTC), a tetracycline antibiotic, is a broad-spectrum antibacterial agent. In this investigation, liquid chromatography-mass spectrometry (LC-MS) is utilized to determine the effects of blue light (λ = 448 nm) illumination (BLIA) and violet light (λ = 403 nm) illumination (VLIA) on conformational changes in OTC at pH 7.8. The photochemical effect of OTC that is exposed to BLIA and VLIA on the deactivation of Escherichia coli (E. coli) is studied. The deactivation of E. coli has an insignificant effect on treatment with OTC alone. OTC is relatively unstable under BLIA and VLIA illumination in an alkaline solution, and OTC has been shown to inactivate E. coli by generating reactive oxygen species (ROS). Less anionic superoxide radicals (O2•-) are generated from OTC that is treated with BLIA than that from VLIA treatment, so OTC is more efficient in inactivating E. coli under VLIA. Inactivation of reduction rates of 0.51 and 3.65 logs in E. coli are achieved using 0.1 mM OTC under BLIA for 120 min and VLIA for 30 min, respectively, under the same illumination intensity (20 W/m2). Two photolytic products of OTC (PPOs) are produced when OTC is exposed to BLIA and VLIA, with molecular ions at m/z 447 and 431, molecular formulae C21H22N2O9 and C21H22N2O8, and masses of 446.44 and 430.44 g/mol, respectively. The results show that when exposed to VLIA, OTC exhibits enhanced inactivation of E. coli, suggesting that the photochemical treatment of OTC is a potential supplement in a hygienic process.

Bioguided Fractionation of Local Plants against Matrix Metalloproteinase9 and Its Cytotoxicity against Breast Cancer Cell Models: In Silico and In Vitro Study (Part II).

In our previous work, the partitions (1 mg/mL) of Ageratum conyzoides (AC) aerial parts and Ixora coccinea (IC) leaves showed inhibitions of 94% and 96%, respectively, whereas their fractions showed IC50 43 and 116 µg/mL, respectively, toward Matrix Metalloproteinase9 (MMP9), an enzyme that catalyzes a proteolysis of extracellular matrix. In this present study, we performed IC50 determinations for AC n-hexane, IC n-hexane, and IC ethylacetate partitions, followed by the cytotoxicity study of individual partitions against MDA-MB-231, 4T1, T47D, MCF7, and Vero cell lines. Successive fractionations from AC n-hexane and IC ethylacetate partitions led to the isolation of two compounds, oxytetracycline (OTC) and dioctyl phthalate (DOP). The result showed that AC n-hexane, IC n-hexane, and IC ethylacetate partitions inhibit MMP9 with their respective IC50 as follows: 246.1 µg/mL, 5.66 µg/mL, and 2.75 × 10-2 µg/mL. Toward MDA-MB-231, 4T1, T47D, and MCF7, AC n-hexane demonstrated IC50 2.05, 265, 109.70, and 2.11 µg/mL, respectively, whereas IC ethylacetate showed IC50 1.92, 57.5, 371.5, and 2.01 µg/mL, respectively. The inhibitions toward MMP9 by OTC were indicated by its IC50 18.69 µM, whereas DOP was inactive. A molecular docking study suggested that OTC prefers to bind to PEX9 rather than its catalytic domain. Against 4T1, OTC showed inhibition with IC50 414.20 µM. In conclusion, this study furtherly supports the previous finding that AC and IC are two herbals with potential to be developed as triple-negative anti-breast cancer agents.

Effects of protein-protein interface disruptors at the ligand of the glucocorticoid-induced tumor necrosis factor receptor-related gene (GITR).

The tumor necrosis factor (TNF) superfamily (TNFSF) includes about thirty structurally related receptors (TNFSFRs) and about twenty protein ligands that bind to one or more of these receptors. Receptors of the tumor necrosis factor (TNF) superfamily (TNFSFRs) are pharmacological targets for treatment of inflammatory and autoimmune diseases. Currently, drugs targeting TNFSFR signaling are biological drugs (monoclonal antibodies, decoy receptors) aimed at binding and sequestering TNFSFR ligands. The glucocorticoid-induced tumor necrosis factor receptor-related gene (GITR) signaling is involved in a series of inflammatory and autoimmune diseases, such as rheumatoid arthritis and Crohn's disease. Our study aimed at repurposing FDA approved small molecules as protein-protein disruptors at the GITR ligand (GITRL) trimer, in order to inhibit the binding of GITRL to its receptor (GITR). A structure based molecular modeling approach was carried out to identify, through high throughput virtual screening, GITRL monomer-monomer disruptors. We used a database of ~8,000 FDA approved drugs, and after virtual screening, we focused on two hit compounds, minocycline and oxytetracycline. These two compounds were tested for their capability to modulate IL-17, IL-21 and RORγT expression in T lymphocytes, isolated from wild-type and GITR knock-out (GITR-/-) mice. Minocycline showed immunomodulatory effects specific to GITR activation and could represent a novel pharmacological tool to treat inflammatory diseases.

Multidimensional assembly of oxygen vacancy-rich amorphous TiO2-BiOBr-sepiolite composite for rapid elimination of formaldehyde and oxytetracycline under visible light.

Herein, a novel oxygen vacancy-rich amorphous TiO2-BiOBr-sepiolite composite was synthesized through a facile one-pot solvothermal method. Under visible light, it exhibited enhanced adsorption and photocatalytic removal activity towards gaseous formaldehyde, whose reaction rate constant is nearly 11.75, 3.44, 1.69, 2.18 and 6.27 times higher than those of amorphous TiO2, BiOBr, TiO2-BiOBr, oxygen vacancy-poor composite and P25, respectively. Moreover, it also displayed significantly improved photodegradation performance towards oxytetracycline under visible light. The improved photocatalytic activity is mainly ascribed to the synergy between the ternary heterogeneous structure and introduced oxygen vacancy, leading to the superior adsorption performance, extended visible-light adsorption scope and faster carriers' separation rate. The photogenerated holes are the dominant active species during the reaction process. Additionally, a plausible photocatalytic degradation pathway for oxytetracycline was also proposed. In general, this work provides a viable strategy of visible-light-driven photocatalyst for practical environmental remediation of indoor volatile organic compounds (VOCs) and pharmaceuticals and personal care products (PPCPs).

Biologically safe colloidal suspensions of naked iron oxide nanoparticles for in situ antibiotic suppression.

A category of naked maghemite nanoparticles (γ-Fe2O3), named surface active maghemite nanoparticles (SAMNs), is characterized by biological safety, high water colloidal stability and a surface chemistry permitting the binding of ligands. In the present study, the interaction between SAMNs and an antibiotic displaying chelating properties (oxytetracycline, OxyTC) was extensively structurally and magnetically characterized. OxyTC emerged as an ideal probe for providing insights into the colloidal properties of SAMNs. At the same time, SAMNs turned out as an elective tool for water remediation from OxyTC. Therefore, a dilute colloidal suspension of SAMNs was used for the removal of OxyTC in large volume tanks where, to simulate a real in situ application, a population of zebrafish (Danio rerio) was introduced. Interestingly, SAMNs led to the complete removal of the drug without any sign of toxicity for the animal model. Moreover, OxyTC immobilized on SAMNs surface resulted safe for sensitive Escherichia coli bacteria strain. Thus, SAMNs were able to recover the drug and to suppress its antibiotic activity envisaging their feasibility as competitive option for water remediation from OxyTC in more nature related scenarios. The present contribution stimulates the use of novel smart colloidal materials to cope with complex environmental issues.

Construction of Ce-MOF@COF hybrid nanostructure: Label-free aptasensor for the ultrasensitive detection of oxytetracycline residues in aqueous solution environments.

Porous organic framework (COF) nanomaterials have drawn increasing attention and showed promising potential in the applications of various fields. Nevertheless, its applications in biosensing or biomedical fields are still in the early stage. In this work, we designed and synthesized a series of nanohybrids of COF and Ce-based metal organic framework (Ce-MOF) for the first time as label-free bioplatforms for a sensitive electrochemical aptasensor to detect oxytetracycline (OTC). A novel kinds of Ce-MOF@COF hybrids were prepared by adding different dosages of COF, into the preparation system of Ce-MOF, for which COF was synthesized using melamine and cyanutic acidmonomers through polycondensation (represented by MCA). Basic characterizations revealed that Ce-MOF@MCA nanohybrids not only remained their orignal crystal and chemical structure and features, such as different Ce species containing in Ce-MOF (Ce3+ and Ce4+), various functional amino-groups of MCA, and individual frameworks, but also showed a large specific surface area and interpenetrated morphologies. As a result, the Ce-MOF@MCA hybrid with high content of MCA exhibited high bioaffinity toward the OTC-targeted aptamer, further leading to the incremental detection effect for OTC detection. Among different hybrid-based aptasensors, the Ce-MOF@MCA-based one with an MCA dosage of 500 mg exhibited the lowest limit of detection at 17.4 fg mL-1 within a wider linearity of the OTC concentration within 0.1-0.5 ng mL-1. Additionally, the fabricated aptasensor displayed excellent analytical performance with great reproducibility, high selectivity and stability, and acceptable applicability for detecting OTC in various aqueous solutions, including milk, wastewater, and urine samples. This new Ce-MOF@MCA hybrid will become an excellent aptasensors platform for detecting various analytes, such as antibiotics, heavy metal ions, or cancer markers, and it have shown the promissing application potentials in the fields of biomedicine, food safety and environmental monitoring.

Evaluation of antibiotic oxytetracycline removal in water using a gas phase dielectric barrier discharge plasma.

Degradation of oxytetracycline (OTC), a primary member of antibiotics in water, was performed by a gas phase dielectric barrier discharge (GPDBD) plasma reactor. The influences of operation conditions including applied voltages, air bubbling rates, initial OTC concentrations and initial pH values on OTC abatement were investigated respectively. The results showed that the decontamination process can be fitted by first order kinetics, and the removal ratio and rate were affected obviously by those parameters. After 20 min of discharge treatment, approximately 93.4% of OTC was removed under the experimental conditions: applied voltage of 7.5 kV, air flow rate of 1.0 L/min, initial OTC concentration of 100 mg/L, and initial pH of 5.0. In addition, TOC and COD removal efficiency reached 43.0% and 73.7% at the original pH 9.3, respectively. Furthermore, the amounts of hydrogen peroxide and ozone in aqueous were quantitatively measured to evaluate their roles during antibiotic removal, and the main function of hydroxyl radicals was demonstrated by the radicals scavenger test. At last, the analyses of UV-Vis spectra and HPLC-MS were employed to study the OTC elimination mechanism, and the possible decomposition pathway was proposed based on the speculated intermediates.

Performance of bimetallic nanoscale zero-valent iron particles for removal of oxytetracycline.

In this study, bimetallic nanoscale zero-valent iron particles (nZVI), including copper/nanoscale zero-valent iron particles (Cu/nZVI) and nickel/nanoscale zero-valent iron particles (Ni/nZVI), were synthesized by one-step liquid-phase reduction and applied for oxytetracycline (OTC) removal. The effects of contact time and initial pH on the removal efficiency were studied. The as-prepared nanoscale particles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Finally, the degradation mechanisms of OTC utilizing the as-prepared nanoparticles were investigated by using X-ray photoelectron spectroscopy (XPS) and mass spectrometry (MS). Cu/nZVI presented remarkable ability for OTC degradation and removed 71.44% of OTC (100mg/L) in 4hr, while only 62.34% and 31.05% of OTC was degraded by Ni/nZVI and nZVI respectively. XPS and MS analysis suggested that OTC was broken down to form small molecules by ·OH radicals generated from the corrosion of Fe0. Cu/nZVI and Ni/nZVI have been proved to have potential as materials for application in OTC removal because of their significant degradation ability toward OTC.

Oil shale powders and their interactions with ciprofloxacin, ofloxacin, and oxytetracycline antibiotics.

The interaction of oil shale, as a widespread sedimentary rock, with common antibiotics ofloxacine, oxytetracycline, and ciprofloxacine was studied. The selected Moroccan deposit and its thermally treated forms were fully characterized from a chemical and structural point of view, indicating the prevalence of quartz as a mineral component together with aluminum- and iron-rich phase that are converted into Al-doped iron oxide phases upon heating. The presence of 4 wt% organics was also detected, which was removed at 550 °C without significant loss of specific surface area. The pseudo-second-order kinetic model and Langmuir equation were found the most adequate to reproduce the kinetics and isothermal sorption experiments. These analyses enlighten the contribution of the organic matter on antibiotic retention as well as the key role of hydrophobic interactions on the molecule-mineral surface interactions. Our results emphasize the possible contribution of raw oil shale in the accumulation of antibiotics in soils and suggest that thermally treated oil shell powders can constitute cheap mineral sorbents for environmental cleaning.

Nanocrystalline TiO2 Composite Films for the Photodegradation of Formaldehyde and Oxytetracycline under Visible Light Irradiation.

In order to effectively photodegradate organic pollutants, ZnO composite and Co-B codoped TiO2 films were successfully deposited on glass substrates via a modified sol-gel method and a controllable dip-coating technique. Combining with UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL) analyses, the multi-modification could not only extend the optical response of TiO2 to visible light region but also decrease the recombination rate of electron-hole pairs. XRD results revealed that the multi-modified TiO2 film had an anatase-brookite biphase heterostructure. FE-SEM results indicated that the multi-modified TiO2 film without cracks was composed of smaller round-like nanoparticles compared to pure TiO2. BET surface area results showed that the specific surface area of pure TiO2 and the multi-modified TiO2 sample was 47.8 and 115.8 m²/g, respectively. By degradation of formaldehyde and oxytetracycline, experimental results showed that the multi-modified TiO2 film had excellent photodegradation performance under visible light irradiation.

Simultaneous removal of structurally different pesticides in a biomixture: Detoxification and effect of oxytetracycline.

The biopurification systems (BPS) used for the treatment of pesticide-containing wastewater must present a versatile degrading ability, in order to remove different active ingredients according to the crop protection programs. This work aimed to assay the simultaneous removal of several pesticides (combinations of herbicides/insecticides/fungicides, or insecticides/fungicides) in a biomixture used in a BPS over a period of 115 d, and in the presence of oxytetracycline (OTC), an antibiotic of agricultural use that could be present in wastewater from agricultural pesticide application practices. The biomixture was able to mostly remove the herbicides during the treatment (removal rates: atrazine ≈ linuron > ametryn), and suffered no inhibition by OTC (only slightly for ametryn). Two fungicides (carbendazim and metalaxyl) were removed, nonetheless, in the systems containing only fungicides and insecticides, a clear increase in their half-lives was obtained in the treatments containing OTC. The neonicotinoid insecticides (imidacloprid and thiamethoxam) and the triazole fungicides (tebuconazole and triadimenol) were not significantly eliminated in the biomixture. Globally, the total removal of active ingredients ranged from 40.9% to 61.2% depending on the system, following the pattern: herbicides > fungicides > insecticides. The ecotoxicological analysis of the process revealed no detoxification towards the microcrustacean Daphnia magna, but a significant decay in the phytotoxicity towards Lactuca sativa in some cases, according to seed germination tests; in this case, OTC proved to be partially responsible for the phytotoxicity. The patterns of pesticide removal and detoxification provide inputs for the improvement of BPS use and their relevance as devices for wastewater treatment according to specific pesticide application programs.

Association efficiency of three ionic forms of oxytetracycline to cationic and anionic oil-in-water nanoemulsions analyzed by diafiltration.

The association efficiency of oxytetracycline (OTC) to pharmaceutical available, ionic oil-in-water nanoemulsions is studied. Theoretical mathematical developments allowed us to differentiate by diafiltration (DF) between thermodynamically and kinetically controlled binding of the drug to the nanoemulsions, and relate these important magnitudes to the association efficiency. The nanoemulsions have been prepared by the solvent displacement technique in the presence of cationic and anionic surfactants. The resulting nanoemulsions were stable at 4°C and 25°C for 60 days, have a size of ∼ 200 nm, showing polydispersity indexes ranging between 0.11 and 0.23, and present zeta potentials ranging between -90 and +60 mV, depending on the charge of the surfactants used. The zeta potential of the nanoemulsions influenced the interaction with OTC, having three ionic forms at different pH, namely, cationic, zwitterionic, and anionic. DF proved to be a powerful tool for the quantification of the drug association efficiency, achieving values up to 84%. Furthermore, this technique allowed obtaining different values of the drug fractions reversibly bound (11%-57%) and irreversibly bound (10%-40%) to the nanoemulsions depending on the surfactants used and pH. These findings may be useful for the development of new drug delivery systems, and as routine assays in academia and pharmaceutical industries.

The environment of professional practice and Burnout in nurses in primary healthcare / O ambiente da prática profissional e Burnout em enfermeiros na atenção básica / El ambiente de la práctica profesional y el síndrome de burnout en enfermeros en la atención básica

OBJECTIVES: to assess how nurses perceive autonomy, control over the environment, the professional relationship between nurses and physicians and the organizational support and correlate them with burnout, satisfaction at work, quality of work and the intention to quit work in primary healthcare. METHOD: cross-sectional and correlation study, using a sample of 198 nurses. The tools used were the Nursing Work Index Revised, Maslach Burnout Inventory and a form to characterize the nurses. To analyze the data, descriptive statistics were applied and Spearman's correlation coefficient was used. RESULTS: the nurses assessed that the environment is partially favorable for: autonomy, professional relationship and organizational support and that the control over this environment is limited. Significant correlations were evidenced between the Nursing Work Index Revised, Maslach Burnout Inventory and the variables: satisfaction at work, quality of care and the intent to quit the job. CONCLUSION: the nurses' perceptions regarding the environment of practice are correlated with burnout, satisfaction at work, quality of care and the intent to quit the job. This study provides support for the restructuring of work processes in the primary health care environment and for communication among the health service management, human resources and occupational health areas. .

OBJETIVOS: avaliar percepções dos enfermeiros sobre autonomia, controle sobre o ambiente, relação profissional entre enfermeiro e médico e suporte organizacional e correlacioná-las com Burnout, satisfação no trabalho, qualidade do cuidado e intenção de deixar o trabalho, na atenção básica. MÉTODO: estudo transversal e correlacional, com amostra de 198 enfermeiros. Foram utilizados o Nursing Work Index Revised, o Inventário de Burnout de Maslach e uma ficha de caracterização do enfermeiro. Para análise dos dados, foi realizada estatística descritiva e utilizado o coeficiente de correlação de Spearman. RESULTADOS: os enfermeiros avaliaram que o ambiente é parcialmente favorável para: autonomia, relação profissional e suporte organizacional e que há pouco controle sobre o mesmo. Evidenciaram-se correlações significativas entre o Nursing Work Index Revised, o Inventário de Burnout de Maslach e as variáveis: satisfação no trabalho, qualidade de cuidado e intenção de deixar o trabalho. CONCLUSÃO: percepções dos enfermeiros acerca do ambiente da prática correlacionam-se com Burnout, satisfação no trabalho, qualidade do cuidado e intenção de deixar o trabalho. Este estudo fornece subsídios para reestruturação de processos de trabalho no ambiente da atenção básica e para comunicação entre as áreas de gestão de serviços de saúde, recursos humanos e saúde do trabalhador. .

OBJETIVOS: evaluar percepciones de los enfermeros sobre autonomía, control sobre el ambiente, relación profesional entre enfermero y médico y soporte organizacional y correlacionarlas con el síndrome de burnout, la satisfacción en el trabajo, la calidad del cuidado y la intención de dejar el trabajo, en la atención básica. MÉTODO: estudio transversal y de correlación, con muestra de 198 enfermeros. Fueron utilizados el Nursing Work Index Revised, el Inventario de Burnout de Maslach y una ficha de caracterización del enfermero. El análisis de los datos fue realizado con estadística descriptiva y se utilizó el coeficiente de correlación de Spearman. RESULTADOS: los enfermeros evaluaron que el ambiente es parcialmente favorable para: autonomía, relación profesional y soporte organizacional y que existe poco control sobre el mismo. Se evidenciaron correlaciones significativas entre el Nursing Work Index Revised, el Inventario de Burnout de Maslach y las variables: satisfacción en el trabajo, calidad del cuidado e intención de dejar el trabajo. CONCLUSIÓN: las percepciones de los enfermeros acerca del ambiente de la práctica se correlacionan con burnout, satisfacción en el trabajo, calidad del cuidado e intención de dejar el trabajo. Este estudio ofrece subsidios para la reestructuración de procesos de trabajo en el ambiente de la atención básica y para comunicación entre las áreas de administración de servicios de salud, recursos humanos y salud del trabajador. .

Transferability of oxytetracycline (OTC) from feed to carp muscle and evaluation of the antibiotic effects on antioxidant systems in liver and kidney.

Oxytetracycline (OTC) is employed in fish farms to contest or prevent bacterial infections. We simulated an OTC treatment at therapeutic level (75 mg kg(-1)) and at higher doses (150, 300 mg kg(-1)) for 10 days. A withdrawal period of 10 days was considered for treated carp, carrying out the same chemical and biochemical analyses (total glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase and malondialdehyde). The aim was to obtain data related to the carryover in muscle and on variations in the antioxidant indicators in liver and kidney. The OTC residual levels in muscle showed a dose-response relationship. After 10 days of treatment at the recommended dose (75 mg kg(-1)), the mean value in muscle was 295 µg kg(-1). After 10 withdrawal days, residues in all treated groups were not entirely eliminated by fish. Residues of recommended 75 mg kg(-1) OTC dose were lower than the maximum permitted by EEC regulation: 100 µg kg(-1). Disturbance in the antioxidant systems in liver and kidney was recorded in (150, 300 mg kg(-1)) carp, as well as during the withdrawal period. A lowered superoxide dismutase activity and higher levels of catalase, glutathione peroxidase, glutathione reductase and glutathione were evaluated in liver, while in kidney only higher malondialdehyde and glutathione S-transferase concentrations were recorded for 300 mg kg(-1) dose. The therapeutic OTC dose exerted lower effects, and only in liver, enhancement of GPx and GR activities was recorded. After the withdrawal period, altered antioxidant responses in tissues were restored for all three OTC doses.

Removal of tetracycline and oxytetracycline by microscale zerovalent iron and formation of transformation products.

The main objective of this study was to determine the removal mechanism of tetracycline (TC) and oxytetracycline (OTC) by microscale zerovalent iron (mZVI) and the formation of transformation products during their removal studies. Solution pH, iron dose, and reaction temperature were studied with a batch experimental series in order to evaluate the removal efficiency of TC and OTC and the adsorption kinetics. The results showed that pH was a key factor in removing both tetracycline compounds, although increasing the temperature and iron dose enhanced their removal efficiency. The optimal pH was similarly found as 3 for both tetracycline and oxytetracycline. The kinetics of adsorption fitted the pseudo-second-order model perfectly. The adsorption data was interpreted by the Langmuir model with the maximum adsorption capacity of 23.98 and 34.01 mg g(-1) (60 °C) of TC and OTC on mZVI, respectively. The main transformation product was 4-epi-tetracycline for TC which quickly sorbed onto mZVI within 15 min. ß-Apo-OTC and α-Apo-OTC were found as OTC transformation products. The removal mechanism of TC and OTC using mZVI surface was due to the adsorption rather than the degradation process.

Photocatalytic degradation of agricultural antibiotics using a UV-LED light source.

With a view to developing a UV-LED photocatalytic reactor for small and remote water systems, the degradation of three representative agriculturally produced contaminants, two antibiotics and an endocrine disruptor hormone, was evaluated in a bench 365 nm LED photoreactor using a slurry of the well-known Degussa P25® (TiO2) as photocatalyst. Use of an additional electron capture additives O2 and H2O2 was also assessed. Loss of the parent organic compounds was tracked by HPLC or UV absorbance and mineralization, where feasible, was studied with TOC analysis with conventional instrumentation. In all cases, degradation is significant with moderate light dose. Lab data suggest log reduction with light delivery less than 2.2 kWhr per cubic meter light delivery.

Alternative sigma factor over-expression enables heterologous expression of a type II polyketide biosynthetic pathway in Escherichia coli.

BACKGROUND: Heterologous expression of bacterial biosynthetic gene clusters is currently an indispensable tool for characterizing biosynthetic pathways. Development of an effective, general heterologous expression system that can be applied to bioprospecting from metagenomic DNA will enable the discovery of a wealth of new natural products. METHODOLOGY: We have developed a new Escherichia coli-based heterologous expression system for polyketide biosynthetic gene clusters. We have demonstrated the over-expression of the alternative sigma factor σ(54) directly and positively regulates heterologous expression of the oxytetracycline biosynthetic gene cluster in E. coli. Bioinformatics analysis indicates that σ(54) promoters are present in nearly 70% of polyketide and non-ribosomal peptide biosynthetic pathways. CONCLUSIONS: We have demonstrated a new mechanism for heterologous expression of the oxytetracycline polyketide biosynthetic pathway, where high-level pleiotropic sigma factors from the heterologous host directly and positively regulate transcription of the non-native biosynthetic gene cluster. Our bioinformatics analysis is consistent with the hypothesis that heterologous expression mediated by the alternative sigma factor σ(54) may be a viable method for the production of additional polyketide products.

The interaction of polysaccharide from Auricularia polytricha with quantum dots and the protection of plasmid DNA from damage.

As a kind of folk medicine, edible mushrooms are known to be of medicinal characteristics, for example antitumor activity. However, the mechanism is not clear. In this study, the fluorescence (FL) spectroscopy was used to study the binding reactions of polysaccharide extracted from Auricularia polytricha with quantum dots (QDs). The modified Stern-Volmer quenching constant at different temperatures and corresponding thermodynamic parameters were calculated (∆G < 0, ∆H < 0, and ∆S < 0). The results show that the quenching constant is inversely correlated with temperature. It indicates that the quenching mechanism is the static quenching in nature rather than dynamic quenching. The negative values of free energy (∆G < 0) suggest that the binding process is spontaneous; ∆H < 0 and ∆S < 0 suggest that the binding of polysaccharide to QDs is enthalpy-driven. QDs were found to damage the plasmid DNA according to atomic force microscopy images. DNA damage is the important factor to induce tumor. Many chemical substances can induce tumor, which has been proved by modern medical science. In the presence of polysaccharide from A. polytricha, however, DNA was protected from damage due to polysaccharide winding around QDs, which is the basis for the bioeffect of polysaccharides. This study helps to understand that antitumor activity of edible mushrooms is attributed to protection of DNA from damage in the presence of harmful substances.