Photoelectrochemical assay for DNA hydroxymethylation determination based on the inhibited photoactivity of black TiO2 nanosphere by ZnO.

A photoelectrochemical method was proposed for DNA hydroxymethylation determination using black TiO2 (B-TiO2) nanosphere as photoactive material and ZnO as photoactivity inhibitor. After hydroxymethylated DNA (5hmC-DNA) was captured on the probe modified B-TiO2/ITO electrode surface through hybridization, a glycosyl can be then transferred from uridine diphosphoglucose to 5hmC-DNA and formed a covalent structure with -CH2OH in the presence of T4 ß-glucosyltransferase (ß-GT). Afterwards, based on a series of covalent reaction, amino functionalized ZnO nanoparticles are further immobilized to the surface of the electrode. Due to the capacity to expend the irradiation light and the photogenerated electron of electron donor, the modified ZnO nanoparticles can result in a decreased photocurrent. The developed method shows wide linear ranges from 0.05-200 nM for hydroxymethylated DNA and 1-220 unit·mL-1 for T4-ß-glucosyltransferase. The corresponding determination limits were 0.013 nM and 0.24 unit·mL-1, respectively. The enzyme activity inhibited by 4-phenylimidazole was evaluated. This photoelectrochemical method shows high specificity for 5hmC-DNA (compared to 5fC, 5mC, m6A, control) and ß-GT (compared to ß-AGT, UGT2B7), and shows excellent stability for testing 5hmC (RSD = 2.75%). Graphical abstractSchematic representation of photoelectrochemical method for DNA hydroxymethylation and ß-glucosyltransferase detection based on the glycosylation reaction of -CH2OH in 5-hydroxymethylcytosine and the inhibition activity of ZnO to the photoactivity of black TiO2 nanospheres.

Application of Rice Grain Husk Derived Biochar in Ameliorating Toxicity Impacts of Cu and Zn on Growth, Physiology and Enzymatic Functioning of Wheat Seedlings.

Livestock and poultry manure containing high levels of copper and zinc have led to contamination of farmland and products which could have an impact on human health. Biochar is an inexpensive and efficient heavy metal absorbent. In the present study, we have used biochar to mitigate the effects of heavy metals on the growth of wheat seedlings. The study showed that the effects of heavy metals on wheat seedlings growth were mitigated by increasing exposure to biochar. Compared to the control group, the germination potential, germination rate, germination index and vigor index of wheat seedlings with supplemented biochar increased significantly. Moreover, the specific activity of catalase, peroxidase, superoxide dismutase decreased and chlorophyll contents increased, which promote wheat growth and suggests that the addition of biochar could reduce the effects of heavy metals on wheat seedlings.

Preparation, characterization, and removal of nitrate from water using vacant polyoxometalate/TiO2 composites.

Due to the rapid development of industry and agriculture, nitrate pollution in groundwater has been continuously increasing. NO3-N is a chemically stable nitrogen species and is quite difficult to remove. In this study, using heteropoly silicotungstate K8[α-SiW11O39] and Cu2+ as the active components, SiW11 and Cu2+ were loaded onto TiO2 by a sol-gel method to prepare a composite photocatalyst SiW11/TiO2/Cu. The photocatalytic reduction of dissolved NO3-N was subsequently performed using SiW11/TiO2/Cu under UV irradiation, and the influence of different experimental parameters on the photocatalytic performance was investigated. The mechanism of NO3-N reduction by the composite catalyst was also investigated. Free radicals existing within the system were detected by ESR spectroscopy, and the results indicated that CO2- anion free-radicals were generated by the reaction of photogenerated holes and formic acid (HCOOH). At a SiW11/TiO2/Cu dose of 1.2 g L-1 and in the presence of HCOOH as a hole scavenger, the proposed composite catalytically reduced NO3-N anddemonstrated significantadvantages in terms of its photocatalytic activity in comparison with pure TiO2. In particular, the removal efficiency of NO3-N and the selectivity of nitrogen achieved a maximum of 96% and 77%, respectively.

Characterization of TiO2 and an as-prepared TiO2/SiO2 composite and their photocatalytic performance for the reduction of low-concentration N-NO3- in water.

Excessive N-NO3- water pollution has become a widespread and serious problem that threatens human and ecosystem health. Here, a TiO2/SiO2 composite photocatalyst was prepared via the sol-gel/hydrothermal method. TiO2 and TiO2/SiO2 were characterized by X-ray diffraction (XRD), UV-Vis differential reflectance spectroscopy (DRS), Fourier infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Afterward, the photocatalytic performance of TiO2 and TiO2/SiO2 to reduce low nitrate concentrations (30 mgN L-1) under UV light was evaluated and the effects of different factors on this process were investigated, after which the reaction conditions were optimized. Removal rates of up to 99.93% were achieved at a hole scavenger (formic acid) concentration of 0.6 mL L-1, a CO2 flow rate of 0.1 m3 h-1, and a TiO2 concentration of 0.9 g L-1. In contrast, TiO2/SiO2 at a 1.4 g L-1 concentration and a TiO2 load rate of 40% achieved a removal rate of 83.48%, but with more than 98% of nitrogen generation rate. NO2- and NH4+ were the minor products, whereas N2 was the main product.

Synthesis of polyoxometalates (POM)/TiO2/Cu and removal of nitrate nitrogen in water by photocatalysis.

Nitrate nitrogen is one of the vital issues needed to be addressed in the water purification process utilizing groundwater as a drinking water source. In this study, a sandwich-type polyoxometalate Na [α-SiW9O34] has been synthesized and SiW9/TiO2/Cu composite has been prepared by sol-gel method. Samples have been characterized by XRD, BET, FTIR, SEM, ED-Mapping, UV-Vis, XPS. The catalytic reduction of nitrate was performed in the presence of SiW9/TiO2/Cu composite as photocatalyst. The effects of catalyst loading, initial nitrate concentration, sandwich-type polyoxometalate loading, dissolved O2, and concentration of formic acid on nitrate removal have been investigated. The results showed that the prepared composite catalyst had better photocatalytic activity than the TiO2. 76.53% of nitrate removal with 82.09% of N2 selectivity was obtained under the following conditions: catalyst dosage 0.8 g/L, initial nitrate concentration of 30 mg/L, SiW9/Cu loading percentage of 10%, 30 mmol/L of formic acid, in presence of N2, and 6 h reaction time.

[Effect of environmental factors on bacterial community in Lake Dongping sediment].

OBJECTIVE: In order to investigate the effect of environmental factors on the bacterial composition of Lake Dongping sediment. METHODS: We set six sampling points in Lake Dongping and sampled once in July and once October. Terminal Restriction Fragment Length Polymorphism (T-RFLP) method was used to analyze the bacterial diversity. Ammonium nitrogen (NH4(+)-N) , nitrate nitrogen (NO3(-)-N) , total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC) and water depth were measured. RESULTS: T-RFLP profiles showed high similarity among samples. However, bacterial diversity indices were significant difference in various samples. The richness, diversity, and evenness in samples which were collected in dry season (October) were generally higher than those in wet season (July), and the bacterial species dominance was higher in wet season than that in dry season. Principal Component Analysis showed that the structure of bacterial communities in sample 2B was marked different from the other samples. The results of Canonical Correspondence Analysis suggested that the abundance of 558 bp T-RF was negatively correlated with NH4(+)-N, NO3(-)-N, TN, TP and TOC, but positively correlated with TOC/TN and the water depth; the abundance of 64.5, 164, 509, and 543 bp T-RFs were positively correlated with NH4(+)-N, NO3(-)-N, TN, TOC, TOC/TN and the water depth. The dominant bacteria in Lake Dongping sediments were Firmicutes and Proteobacteria. CONCLUSION: Environmental factors affect bacterial diversity of Lake Dongping sediments, although affect less on indigenous bacteria.

Removal of nitrate nitrogen from water by phosphotungstate-supported TiO2 photocatalytic method.

Nitrate nitrogen in water, especially in groundwater, is a major problem in the current drinking water environment. In this study, copper- and nickel-modified phosphotungstate catalysts supported on TiO2 were prepared by the sol-gel solvothermal method, and photocatalytic reduction by phosphotungstate was used to remove nitrate nitrogen in water under ultraviolet irradiation. The maximum removal rate was 59.60% with 0.8 g/L Cu-H3PW12O40/TiO2, 90 mg/L nitrate nitrogen, and 60 min reaction time. For Ni-H3PW12O40/TiO2, the maximum removal rate of nitrate nitrogen was 54.58%, achieved with a catalyst concentration of 0.8 g/L, nitrate nitrogen concentration of 120 mg/L, and reaction time of 30 min. Both catalysts could remove nitrate nitrogen from water under the condition of photocatalysis.

Effects of an external magnetic field on microbial functional genes and metabolism of activated sludge based on metagenomic sequencing.

This study explored the effect of 70-mT magnetic field on wastewater treatment capacity for activated sludge in long-term laboratory-scale experiments. Metagenomic sequencing were conducted based on Illumina HiSeq 2000 platform after DNA extraction of the activated sludge. Then the effect of the magnetic field on the microbial unigene and metabolic pathways in activated sludge was investigated. As a result, higher pollutant removal was observed at 70 mT, with which the elimination of total nitrogen (TN) was the most effective. Functional genes annotated based on eggNOG database showed that unigenes related to information storage and processing were enhanced by the magnetic field. For CAZy classification, category such as glycosyl transferases was more abundant in the reactor with magnetic field, which has been shown to promote the entire energy supply pathway. Additionally, in the KEGG categories, unigenes related to signaling molecules and interaction were significantly inhibited. Through the enrichment analysis of the nitrogen metabolism pathway, the magnetic field inhibited anabolic nitrate reduction by significantly inhibiting enzymes such as [EC:1.7.7.2], [EC:1.7.7.1], [EC:3.5.5.1], [EC:1.4.1.2] and [EC:4.2.1.1], which are related to the improvement of the denitrification ability. This study can provide insight for future research on the response mechanism of activated sludge to magnetic fields.

Preparation and characterization of a copper phosphotungstate/titanium dioxide (Cu-H3PW12O40/TiO2) composite and the photocatalytic oxidation of high-concentration ammonia nitrogen.

Currently, the majority of wastewater with a high concentration of ammonia nitrogen (NH4+/NH3) is treated using biological methods, which have poor biodegradability and low removal efficiency. In this paper, a composite photocatalyst of copper phosphotungstate/titanium dioxide (Cu-H3PW12O40/TiO2) was prepared by sol-gel hydrothermal synthesis, and the composite catalyst was characterized by X-ray diffraction (XRD), UV-vis-diffuse reflectance spectroscopy (UV-VIS-DRS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS)、scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The photocatalytic oxidation of a high-concentration NH4+/NH3 solution was carried out under ultraviolet (UV) light to explore the effects of different influencing factors on the photocatalytic effect and to optimize the reaction conditions. The prepared composite catalyst exhibited higher photocatalytic activity than that of TiO2. When the initial concentration of the solution was 300 mg·L-1, the initial pH was 11, the catalyst concentration was 1.5 g·L-1, the loading level of Cu-H3PW12O40 was 40%, and the aeration rate was 1.5 L·min-1, the removal rate of NH4+/NH3 by the composite photocatalyst could reach >80%. Very little NO2- and NO3- were produced, and N2 was the main product.

Preparation of highly-conductive pyrogenic carbon-supported zero-valent iron for enhanced Cr(â ¥) reduction.

In this work, electron transfer (ET) moiety of PC was ascertained in chromate (Cr(Ⅵ)) reduction by zero-valent iron supported by pyrogenic carbon (PC) (ZVI/PC) prepared by pyrolysis of hematite (α-Fe2O3)-treated pinewood. X-ray diffraction analysis suggested successive phase transformation of α-Fe2O3→magnetite (Fe3O4)→wustite (FeO)→ZVI (Feo). Raman spectra and Brunauer-Emmett-Teller analysis revealed that ZVI/PC is characterized with more ordered graphitic carbon and greater surface area than pristine PC. Maximal Cr(Ⅵ) removal capacity (pH = 3) as predicted by Langmuir isotherm model were 5.78, 36.12 and 8.39 g kg-1 for PC, ZVI/PC and ZVI, respectively. ZVI/PC maintained significantly greater Cr(Ⅵ) removal capacity than ZVI and PC at pH 3-9, but Cr(Ⅵ) removal dropped rapidly to 6.78 g kg-1 at pH 4 and above. X-ray photoelectron spectroscopy and successive desorption of Cr-laden ZVI/PC and ZVI showed trivalent Cr was the dominant species, suggesting reduction was an important mechanism for Cr(Ⅵ) detoxification. Electrochemical analysis demonstrated that ZVI/PC exhibited greater Tafel corrosion rate and ET quantity, with lower electrical resistance. Besides, Cr(Ⅵ) reduction showed reversal trend with electrical resistance of ZVI/PC. To conclude, ET capacity was closely associated with electrical conductivity of ZVI/PC due to intensified conductive graphitic carbon structure of PC at higher pyrogenic temperatures.

[Treatment Efficiency and Microbial Community Diversity in a Magnetic Field Enhanced Sequencing Batch Reactor (SBR)].

The application of SBR reactors is becoming more common and in order to further improve the efficiency of their treatment it has been proposed to add a magnetic field to SBR systems. The effects of different magnetic fields on the degradation efficiency of conventional pollutants in an SBR was studied. MiSeq high-throughput sequencing techniques were used to analyze the diversity of microbial communities in activated sludge under magnetic field conditions. These results show that the addition of a magnetic field improves the performance of a SBR system to an extent and magnetic induction effects are most obvious at 7×10-2 T. This is identified through a significant effect on the removal efficiency of total nitrogen and an increase in the denitrification rate from 65.69% to 85.98%. It also significantly improves the activity of sludge dehydrogenase and has a positive effect on the removal of various pollutants. The diversity of microbial communities in activated sludge under different magnetic field intensities shows a greater microbial abundance and diversity in the active sludge. The bacterial domain in the experimental SBR includes 14 phyla, which are mainly Proteobacteria (25.3%-61.5%), Bacteroidetes (18.6%-46.2%), Actonobacteria (5.3%-47.2%), and Acidobacteria (0.4%-4.0%). Important denitrification bacteria such as Rhodoblastus, Paracoccus of α-Proteobacteria, Alicycliphilus, Comamonas, Xenophilus, Acidovorax, Dechloromonas, Thauera of ß-Proteobacteria, Desulfovibrio of δ-Proteobacteria and Planctomycetes, etc. at a moderate magnetic induction of 7×10-2 T have a high abundance and there is an internal relationship between this and an increase in denitrification efficiency. Polyphosphate-accumulating organisms (PAOs) such as Acinetobacter, Pseudomonas, Propionicimonas, etc., are present at higher levels under these conditions and follow the same trends as for the phosphorus removal rates. There is a correlation between bacterial community structure changes and sewage treatment efficiency in activated sludge. Applied magnetic fields have a positive effect on sewage treatment by changing the microbial community structure.