Study on mechanism of removal of sudden Tetracycline by compound modified biological sand filtration process.

The removal of tetracycline from the sewage plant effluents through advanced treatment methods is key to controlling tetracycline levels in the water environment. In this study, modified quartz sands (QS) were used in a biological sand filter to remove tetracycline. The modified QS, with different surface characteristics, were prepared using glass etching technology combined with subsequent chemical modification methods, including hydroxylation treatment, metal ion modification, and amino modification. The adsorption efficiency of hydroxylated QS was higher than that of metal ion modified and amino modified QS, with adsorption efficiencies of 20.4331 mg/kg, 12.8736 mg/kg, and 10.1737 mg/kg, respectively. Results indicated that QS primarily reduce tetracycline through adsorption. Adsorption on ordinary QS fit the pseudo-first-order kinetic model, while adsorption on other modified QS and biofilm-coated QS fit the pseudo-second-order kinetics model. Biodegradation was identified as another mechanism for tetracycline reduction, which fit the zero-order kinetic model. Pseudomonas alcaligenes and unclassified Pseudomonas accounted for 96.6% of the total tetracycline-degrading bacteria. This study elucidates the effectiveness and mechanisms of five types of QS in treating tetracycline from sewage plant effluents. It provides a novel method for tetracycline reduction in real-world wastewater scenarios.

Adsorption performance of Ni(II) by KOH-modified biochar derived from different microalgae species.

Microalgae biochar is potential adsorbents to remove heavy metals from wastewater due to abundant functional groups, high porosity and wide sources, but performance is not fully developed since it depends on microalgae species attributing to distinct morphology and biomass compositions. Here, two microalgae species Chlorella Pyrenoidosa and Scenedesmus Obliquus were used for biochar preparation via KOH-modification, biochar properties and their influences on Ni(II) adsorption were investigated. Ni(II) adsorption performances responding to biochar properties and operating conditions were upgraded via progressive optimization and response surface methodology. Together, adsorption isotherms and kinetics were analyzed to obtain significant factors for Ni(II) removal. As results, 100 % of Ni(II) removal was achieved under 100 mg/L initial Ni(II) concentration as pH was higher than the biochar zero-charge point of 6.87 with low biochar dosage (0.5 g/L), which provides an efficient approach for heavy metal removal from wastewater with microalgae biochar.

Stability and bioactivity evaluation of black pepper essential oil nanoemulsion.

Black pepper essential oil has the same disadvantages as other plant essential oils, such as volatilization, high sensitivity to light and heat and poor water solubility, which leads to great limitations in application. This study improved the stability and antibacterial properties of black pepper essential oil (BPEO) based on a nano-emulsification process. Tween 80 was selected as the emulsifier to prepare the BPEO nanoemulsion. Gas chromatograph - mass spectrometer (GC-MS) was used to analyze the composition of BPEO, of which d-limonene was the main component (37.41%). After emulsification, black pepper nanoemulsion was obtained (droplet size was 11.8 nm). The water solubility and stability of the emulsions at 25 °C were also improved with decreasing particle size. Antimicrobial properties of plant pathogens (Colletotrichum gloeosporioides, Botryodiplodia theobromae) and foodborne pathogens (Staphylococcus aureus, Escherichia coli) were evaluated by disk diffusion and other techniques for determining minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). With 12.5 mg mL-1 MIC and 25 mg mL-1 MBC, BPEO inhibited the growth of two tested plant pathogens and two foodborne pathogens. Essential oils (EO) were encapsulated in a nanoemulsion system to enhance the bacteriostatic effect of essential oils and reduce MIC and MBC concentrations. After emulsification, the biological activity (antimicrobial and antioxidant) of the BPEO nanoemulsion was considerably improved, nano-emulsification had certain significance for the study of EOs.

Abnormal chilling injury of postharvest papaya is associated with the antioxidant response.

Generally, the lower the temperature and/or the longer the duration of low temperature, the more serious chilling injury (CI) symptom appears in fruit. However, our previous study showed that the higher storage temperature (6°C) resulted in a more serious CI in papaya fruit compared to that stored at 1°C, which could be viewed as an abnormal CI behavior. This study investigated the antioxidant responses that existed in abnormal CI behavior of papaya fruit. Compared to 6°C, antioxidant enzyme activities of papaya fruit which was stored at 1°C were maintained at a higher level while the circulatory metabolism of the ascorbate-glutathione cycle (AsA-GSH) was more vigorous in papaya fruit, as indicated by higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) activities and higher AsA and GSH levels, which could reduce the superoxide anion (·O2 - ) production rate and the hydrogen peroxide (H2 O2 ) content. Suppressed reactive oxygen species (ROS) generation in papaya fruit at 1°C resulted in reduced membrane permeability and malondialdehyde (MDA) accumulation when compared to that at 6°C, thus the development of CI was restricted during storage at 1°C. This study deepened the understanding of differential antioxidant responses during cold storage at 1°C and 6°C in papaya fruit and provided a theoretical basis for further study on the mechanism of the abnormal CI behavior in papaya fruit. PRACTICAL APPLICATIONS: Low-temperature storage is one of the most effective methods to preserve fruit and vegetable products. While, inappropriate low temperature could induce CI, and the damage caused by CI is often more serious than estimated. Therefore, it is necessary to study the physiological and biochemical characteristics of different postharvest fruits and vegetables to prolong storage period, improve storage quality and reduce the loss of products. This study analyzed the antioxidant reaction in abnormal CI behavior of papaya, which could contribute to the further study on the mechanism of CI in papaya fruit and provide theoretical basis for the development of preservation technology of papaya fruit.

Abnormal behavior of chilling injury in postharvest papaya fruit is associated with sugar metabolism.

In the most chilling-sensitive fruits and vegetables, usually, the lower the storage temperature, the more serious the symptoms of chilling injury (CI). As one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. Such abnormal CI phenomenon has not received enough attention and its mechanism is not clear. The present study investigated the difference of CI severity and sugar metabolism in papaya fruits when stored between 1℃ and 6℃. The results showed that CI index in papaya fruits preserved at 1°C was markedly lower than that in fruit at 6°C, which was accompanied by higher content of glucose, fructose, and sucrose. In addition, compared to 6°C, 1°C promoted higher activities of sucrose synthase, sucrose-phosphate synthase, and neutral invertase, but lowered acid invertase activity. RT-qPCR analysis showed that 1°C upregulated the CpSPS expression and downregulated the CpAI expression when compared to 6°C. The present results indicate that higher chilling tolerance in papaya fruit at 1°C could be attributed to more accumulation of sucrose and reducing sugars in relation to more advantageous sugar metabolism. These results provided a basis for explaining the abnormal behavior of papaya fruits in response to varying low temperatures. PRACTICAL APPLICATION: For most chilling-sensitive fruits and vegetables, in the range of temperatures that induce chilling injury (CI), the lower storage temperature may lead to more severe CI. However, as one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. The reason for this abnormal CI symptom in papaya fruits is that 1°C storage can regulated enzyme activities and changes in gene expression related to sugar metabolism, which could result in more accumulation of sucrose and slower degradation of hexose and contribute to alleviation of CI. Our results provided a basis for explaining the abnormal behavior of papaya fruit in response to varying low temperatures.

Surface Ligand Environment Boosts the Electrocatalytic Hydrodechlorination Reaction on Palladium Nanoparticles.

We present an enhanced catalytic efficiency of palladium (Pd) nanoparticles (NPs) for the electrocatalytic hydrodechlorination (EHDC) reaction by incorporating the tetraethylammonium chloride (TEAC) ligand into the surface of NPs. Both experimental and theoretical analyses reveal that the surface-adsorbed TEAC is converted to molecular amine (primarily triethylamine) under reductive potentials, forming a strong ligand-Pd interaction that is beneficial to the EHDC kinetics. Using the EHDC of 2,4-dichlorophenol (2,4-DCP), a dominant persistent pollutant identified by the U.S. Environmental Protection Agency, as an example, the Pd/amine composite delivers a mass activity of 2.32 min-1 gPd-1 and a specific activity of 0.16 min-1 cm-2 at -0.75 V versus Ag/AgCl, outperforming Pd and most of the previously reported catalysts. The mechanistic study reveals that the amine ligand offers three functions: the H+-pumping effect, the electronic effect, and the steric effect, providing a favorable environment for the generation of reactive hydrogen radicals (H*) for hydrogenolysis of the C-Cl bond. It also weakens the adsorption strength of EHDC products, alleviating their poisoning on Pd. Investigation into the intermediate products of EHDC on Pd/amine and the biological safety of the 2,4-DCP-contaminated water after EHDC treatment demonstrates that EHDC on Pd/amine is environmentally benign for halogenated organic pollutant abatement. This work suggests that the tuning of NP catalysis using facile ligand post-treatment may lead to new strategies to improve EHDC for environmental remediation applications.

Effects of ZnO nanoparticles on aerobic denitrifying bacteria Enterobacter cloacae strain HNR.

The aerobic denitrification process is a promising and cost-effective alternative to the conventional nitrogen removal process. Widely used ZnO nanoparticles (NPs) will inevitably reach wastewater treatment plants, and cause adverse impacts on aerobic denitrification and nitrogen removal. Therefore, a full understanding of the responses and adaption of aerobic denitrifiers to ZnO NPs is essential to develop effective strategies to reduce adverse effects on wastewater treatment. In this study, the responses and adaption to ZnO NPs were investigated of a wild type strain (WT) and a resistant type strain (Re) of aerobic denitrifying bacteria Enterobacter cloacae strain HNR. When exposed to 0.75 mM ZnO NPs, the nitrate removal efficiency of Re was 11.2% higher than that of WT. To prevent ZnO NPs entering cells by adsorption, the production of extracellular polymeric substances (EPS) of WT and Re strains increased 13.2% and 43.9%, respectively. The upregulations of amino sugar and carbohydrate-related metabolism contributed to the increase of EPS production, and the increased nitrogen metabolism contributed to higher activities of nitrate and nitrite reductases. Interestingly, cationic antimicrobial peptide resistance contributed to resist Zn (II) released by ZnO NPs, and many antioxidative stress-related metabolism pathways were upregulated to resist the oxidative stress resulting from ZnO NPs. These findings will guide efforts to improve the aerobic denitrification process in an environment polluted by NPs, and promote the application of aerobic denitrification technologies.

Seasonal variations of carbonic anhydrase activity in Chongqing urban section of Jialing River and its influencing factors.

Carbonic anhydrase (CA) is an enzyme in algal carbon-utilization that plays an important role in the formation of algal blooms. A year-long monitoring program in the shore area of Chongqing Urban Section of the Jialing River (JR) was launched to determine the variations in carbonic anhydrase activity (CAA) and its change mechanism in the hydro-fluctuation belt of the tributaries in the Three Gorges Reservoir (TGR) area. The variations in basic water quality parameters, different carbon forms, and CAA were investigated from November 2013 to October 2014. Results showed that the mean CAA value in JR was 0.67 ± 0.31 EU/106 cells. CAA was high during the flood stage, low during the impounding stage, and peaked on April 3, 2014 during the discharging stage. No significant difference was observed in the CAA of different sampling sites in JR. However, a significant difference was observed between the CAA of JR and that of the Yangtze River. Correlation analyses showed that water temperature, pH, algal cell density, and dissoluble organic carbon were positively correlated with CAA, whereas CO2 and dissoluble inorganic carbon were negatively correlated with CAA. A model for CAA and related parameters was built through principal component regression. The equation was expressed as follows: CAA = 0.116T + 0.00746Cells+0.0156pH-0.0157CO2-0.0150DIC+0.0135DOC+0.565. Results revealed that CAA in JR was controlled by multiple factors, which could be used for CAA monitoring. The model demonstrated a potential value in controlling algal blooms.

Significance of different carbon forms and carbonic anhydrase activity in monitoring and prediction of algal blooms in the urban section of Jialing River, Chongqing, China.

The Three Gorges Dam is one of the largest hydroelectric power plants worldwide; its reservoir was preliminarily impounded in 2003 and finally impounded to 175 m in 2012. The impoundment caused some environmental problems, such as algal blooms. Carbonic anhydrase (CA) is an important biocatalyst in the carbon utilization by algae and plays an important role in algal blooms. CA has received considerable attention for its role in red tides in oceans, but less investigation has been focused on its role in algal blooms in fresh water. In this study, the seasonal variation of water quality parameters, different carbon forms, carbonic anhydrase activity (CAA), and the algal cell density of four sampling sites in the urban section of the Jialing River were investigated from November 1, 2013 to October 31, 2014. Results indicated that CAA exhibited a positive correlation with dissoluble organic carbon (DOC), pH, and temperature, but a negative correlation with CO2 and dissoluble inorganic carbon (DIC). Algal cell density exhibited a positive correlation with flow velocity (V), pH, particulate organic carbon (POC), and CAA, a negative correlation with CO2, and a negative partial correlation with DIC. The relationship between CAA and algal cell density for the entire year can be described as cells = 23.278CAA - 42.666POC + 139.547pH - 1057.106. The algal bloom prediction model for the key control period can be described as cells = -45.895CAA + 776.103V- 29.523DOC + 14.219PIC + 35.060POC + 19.181 (2 weeks in advance) and cells = 69.200CAA + 203.213V + 4.184CO2 + 38.911DOC + 40.770POC - 189.567 (4 weeks in advance). The findings in this study demonstrate that the carbon utilization by algae is conducted by CA and provide a new method of monitoring algal cell density and predicting algal blooms.

Control of osteoblast cells adhesion and spreading by microcontact printing of extracellular matrix protein patterns.

In this study, we report a simple method for creating extracellular matrix (ECM) protein patterns to control osteoblast cell adhesion and spreading. The fibronectin patterns are directly produced on polystyrene (PS) surfaces by microcontact printing (µCP). Confocal laser scanning microscopy (CLSM) images show that protein patterns are successfully fabricated on PS surfaces. Newborn rat osteoblast cells are then seeded on these protein patterns and cultured for 4 days. The results demonstrate that osteoblast cells preferentially adhere and grow on the protein areas. The pattern dimensions have significant influences on cell behaviors, including cell adhesion, spreading, distribution, and growth direction. Therefore, it is possible to control the cell morphology and even cell function by carefully designing the pattern shapes and sizes. The present study suggests that the ECM protein patterns can be used to modify biomaterials' surfaces and spatially control the morphologies of osteoblast cells. We believe that our work could find applications for creating patterned bioactive surfaces to control cell adhesion, spreading and cell function. It may be helpful for the development of novel implantable biomaterials, such as artificial bone implants, where control of interfacial biological interactions between implants and cells would be preferable.

[Effects of extracellular matrix protein micropatterns on osteoblast cell adhesion and spreading].

The main purpose of the present study was to investigate the cell behaviors of rat primary osteoblast cells on extracellular matrix (ECM) protein micropatterns. For this purpose, a series of fibronectin micropatterns with different shapes and varying dimensions were created on polystyrene (PS) surfaces by microcontact printing. The results of confocal laser scanning microscopy (CLSM) images indicated that excellent micropatterns were successfully obtained. These protein patterns were stable during the cell culture. The cell experiments suggested that the osteoblast cells preferentially attached onto protein-functionalized areas and displayed different cell shape and spreading behavior on different protein micropatterns. The protein micropatterns can significantly influence the cell adhesion, spreading, alignment and orientation and so on. Therefore, this work can be used to modify biomaterial surfaces, especially that of bone-implant biomaterials, to effectively control cell behavior. It further contributes to clarify the interfacial biological behaviors between biomaterials and osteoblast and can provide the cues for development of bone implantable materials which is able to modulate osteoblast cell growth behavior.

Enhancing the antibacterial activity of biomimetic HA coatings by incorporation of norvancomycin.

BACKGROUND: Bacterial infections associated with the use of biomaterials remain a great challenge for orthopedic surgery. The main purpose of the work discussed in this paper was to improve the antibacterial activity of a biomimetic calcium phosphate (CP) coating widely used in orthopedic biomaterials by incorporation of norvancomycin in the biomimetic process. METHODS: CP coating and CP coating containing norvancomycin were produced on a titanium alloy (Ti6Al4V) surface by a biomimetic process. The morphology, surface crystal structure, and concentrations of elements in the coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), respectively. The amount of norvancomycin and its release were investigated by UV-visible spectroscopy. MTT was used to investigate cell behavior. The morphology of adhered bacteria was observed by SEM. Antibacterial activity was expressed as inhibition zone by using Staphylococcus aureus (ATCC 25923) as model bacteria. RESULTS: Results from SEM, EDX, and XRD revealed formation of a hydroxyapatite (HA) coating. The amount of antibiotic in the CP coating increased with increasing concentration of norvancomycin in the coating solution, followed by a plateau when the concentration of norvancomycin in the coating solution reached 600 mg/l. Approximately 2.16 µg norvancomycin per mg coating was co-precipitated with the CP layer onto titanium alloy discs when 600 mg/l norvancomycin coating solution was applied. The norvancomycin had a fast release profile followed by slow release. The MTT test of osteoblast cell cultures suggested that coatings containing norvancomycin did not cause any cytotoxicity compared with the CP coating and control titanium plate. The antibacterial activity test showed that the norvancomycin released from the coatings inhibited the growth of Staphylococcus aureus; more bacteria were found on the CP coating than on the norvancomycin-loaded coating. CONCLUSIONS: A norvancomycin-loaded HA-like coating was successfully obtained on titanium surfaces. The norvancomycin incorporated had no negative effects on osteoblast cell behavior. The released norvancomycin results in excellent antibacterial activity of Ca-P coatings. Therefore, incorporation of norvancomycin can enhance antibacterial activity and the norvancomycin-loaded CP coating can be used to inhibit post-surgical infections in orthopaedics.