Arsenic inhibits induction of cytochrome P450 1A1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin in human hepatoma cells

The aim of this study was to examine the arsenic effect on activation of aryl hydrocarbon receptor (AhR)-mediated gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in human hepatoma cells. The human hepatoma Huh7 cells were treated with sodium arsenite (NaAsO2) from 0.5 to 20 microM for 24 h. Our data revealed that NaAsO2 < or = 10 microM caused no significant cytotoxic effect on Huh7 cells (p>0.05). We also established a dioxin-responsive element (DRE)-mediated Chemical Activated LUciferase eXpression (CALUX) cell line, Huh7-DRE-Luc, by stable transfection of Huh7 with a DRE-driven firefly luciferase reporter plasmid (4xDRE-TATA-Luc). Treatments of Huh7-DRE-Luc and Huh7 with NaAsO2 attenuated the 2,3,7,8-TCDD-induced DRE-CALUX and cytochrome P450 1A1 (CYP1A1) activations, respectively, in a dose-dependent manner. We found that the calculated CALUX-toxic equivalent (TEQ) levels induced by cotreatment of NaAsO2 > or = 3.0 microM and 10 nM 2,3,7,8-TCDD were significantly lower than that induced by 2,3,7,8-TCDD alone (p<0.05). In the present study, we demonstrated that arsenic not only inhibited the TCDD-induced CYP1A1 activation but also interfered with DRE-CALUX bioassay in human hepatoma cells. Our finding also suggests that extensive cleanup of sample for removal of any possible interfering factor is critical to guarantee the accuracy of dioxin-TEQ levels using DRE-CALUX bioassay.     

Development of bioreactor system for treatment of dioxin-contaminated soil using Pseudallescheria boydii

We developed a conceptual feasible design of bioreactor system for treatment of dioxin-contaminated soils that uses the dioxin-degrading fungus Pseudallescheria boydii (P. boydii) we had isolated. The dioxin-degradation conditions in bioreactor treatment was established by clarifying the inhibiting factors for the growth of P. boydii using both real contaminated and laboratory prepared soils mixed with fly ash. In addition, ethanol extraction process as post-treatment methods for the remaining dioxins, and the sterilization conditions of P. boydii, i.e., a weakly pathogenic fungus, in the residue was investigated. The better growth conditions of P. boydii were found to be chloride ion concentration of less than 10 g/L and a pH of less than 9. Under these conditions, 7310 pg-TEQ/g of the soil was treated to 2860 pg-TEQ/g by the bioreactor process, and the dioxin concentration was further decreased to 580 pg-TEQ/g by ethanol extraction, resulting to total removal ratio of 92%. Furthermore, development of an effective sterilization method for living P. boydii in the residue increased the applicability of our bioreactor system for practical use in dioxin-contaminated sites.     

The biodegradation pathway of triethylamine and its biodegradation by immobilized Arthrobacter protophormiae cells

A bacterial strain named R4 was isolated from a wastewater treatment pool containing triethylamine (TEA) as the sole source of carbon and nitrogen. Strain R4 was identified as Arthrobacter protophormiae based on 16S rRNA gene sequence analysis and morphological and physiological properties. The optimal pH, temperature and concentration of NaCl for TEA degradation by strain R4 were 7.0, 30°C and 0.5%, respectively. Strain R4 could completely degrade 100 mg l(-1) TEA to ammonia in 32 h, and could also effectively degrade diethylamine (DEA) and ethylamine (EA) to ammonia. The degradation of TEA was strongly inhibited by some metal ions (Cu(2+), Mn(2+), Zn(2+), Co(2+), Ni(2+) and Ag(+)) (1.0mM). Addition of either SO(4)(2-) or NH(4)(+) reduced the degradation efficiency of TEA by strain R4 to a certain extent. The inhibition became significant when the concentration of SO(4)(2-) and NH(4)(+) reached to 11 mM and 30 mM, respectively. Cell-free extracts prepared from cells grown in TEA exhibited TEA monooxygenase, DEA monooxygenase and EA monooxygenase activity. Here, we propose the metabolic pathway of TEA degradation in strain R4. The efficiency of TEA removal by immobilized cells of strain R4 was found to be equivalent to that of free cells. In addition, the immobilized cells could be reused without reduction in their ability to degrade TEA.     

Enzymatic degradation of anthracene by the white rot fungus Phanerochaete chrysosporium immobilized on sugarcane bagasse

Bagasse is a by-product of sugar milling and important fuel resource for that industry. It is a fibrous, low density material with a very wide range of particle sizes and high moisture content. The goal of this study is the development of a system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) produced by Phanerochaete chrysosporium for the degradation of polycyclic aromatic hydrocarbons (PAHs), of which anthracene was selected as an example. The white rot fungus P. chrysosporium immobilized on bagasse was grown in both stationary and agitated cultures (rotary shaker, 80rpm) using nitrogen limited growth medium to study the ability of the fungus to degrade anthracene in aqueous media. Production of MnP occurred simultaneously in nitrogen limited culture medium with the added MnSO4 at 40ppm. The MnP activity was at relatively high level (76Ul(-1)) and in this condition, the residual anthracene concentration was 16%.     

Treatment of metal cyanide bearing wastewater by simultaneous adsorption and biodegradation (SAB)

This paper presents process review and comparative study of biodegradation and adsorption alone with simultaneous adsorption and biodegradation (SAB) process using Pseudomonas fluorescens. Ferrocyanide solution was used for all studies with initial CN(-) concentrations of 50, 100, 200 and 300mg/L, and initial pH of 6. Pseudomonas fluorescens used ferrocyanide as sole source of nitrogen and biodegradation efficiency was observed as 96.4, 94.1, 86.2 and 69.3%, respectively after 60h of agitation. Whereas in adsorption process with granular activated carbon (GAC) as adsorbent, CN(-) removal efficiency was found to be 85.6, 80.1, 70.2 and 50.2%, respectively. But in SAB process the removal efficiency could be more than 70% for all concentrations only at 36h of agitation and achieved removal efficiency of 99.9% for 50 and 100mgCN(-)/L. It was found that SAB process is more effective than biodegradation and adsorption alone.     

Degradation of polycyclic aromatic hydrocarbons by the Chilean white-rot fungus Anthracophyllum discolor

The degradation of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) in Kirk medium by Anthracophyllum discolor, a white-rot fungus isolated from the forest of southern Chile, was evaluated. In addition, the removal efficiency of three-, four- and five-ring PAHs in contaminated soil bioaugmented with A. discolor in the absence and presence of indigenous soil microorganisms was investigated. Production of lignin-degrading enzymes and PAH mineralization in the soil were also determined. A. discolor was able to degrade PAHs in Kirk medium with the highest removal occurring in a PAH mixture, suggesting synergistic effects between PAHs or possible cometabolism. A high removal capability for phenanthrene (62%), anthracene (73%), fluoranthene (54%), pyrene (60%) and benzo(a)pyrene (75%) was observed in autoclaved soil inoculated with A. discolor in the absence of indigenous microorganisms, associated with the production of manganese peroxidase (MnP). The metabolites found in the PAH degradation were anthraquinone, phthalic acid, 4-hydroxy-9-fluorenone, 9-fluorenone and 4,5-dihydropyrene. A. discolor was able to mineralize 9% of the phenanthrene. In non-autoclaved soil, the inoculation with A. discolor did not improve the removal efficiency of PAHs. Suitable conditions must be found to promote a successful fungal bioaugmentation in non-autoclaved soils.     

Combined effects of external mass transfer and biodegradation rates on removal of phenol by immobilized Ralstonia eutropha in a packed bed reactor

Biodegradation of phenol by calcium-alginate immobilized Ralstonia eutropha was carried out in a batch stirred and a packed bed reactor. In the batch system studies, the effect of initial phenol concentration on biodegradation was investigated at 30 degrees C and pH 7 while in the continuous system studies, the effects of flow rate and inlet phenol concentration on biodegradation were tested at the same temperature and pH. The observed biodegradation rate constant was calculated at different flow rates with the assumption of first-order biodegradation kinetics. Various external mass transfer correlations were evaluated and a new correlation of the type JD=K(NRe)(-(n-1)) was developed with the values of K=1.34 and n=0.65. The intrinsic first-order biodegradation rate constants and the external mass transfer coefficients were calculated then the combined effects of these rates on the observed first-order biodegradation rate constants were also investigated.     

Biological synthesis of silver nanoparticles using the fungus Aspergillus flavus

The fungus, Aspergillus flavus when challenged with silver nitrate solution accumulated silver nanoparticles on the surface of its cell wall in 72 h. These nanoparticles dislodged by ultrasonication showed an absorption peak at 420 nm in UV-visible spectrum corresponding to the plasmon resonance of silver nanoparticles. The transmission electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodisperse silver nanoparticles (average particle size: 8.92 ± 1.61 nm) by the fungus. X-ray diffraction spectrum of the nanoparticles confirmed the formation of metallic silver. The Fourier transform infrared spectroscopy confirmed the presence of protein as the stabilizing agent surrounding the silver nanoparticles. These protein-stabilized silver nanoparticles produced a characteristic emission peak at 553 nm when excited at 420 nm in photoluminescence spectrum. The use of fungus for silver nanoparticles synthesis offers the benefits of eco-friendliness and amenability for large-scale production.     

Effect of the loading rate on mode I interlaminar fracture toughness of laminated composites

The objective of the present study is to determine the influence of the loading rate on the critical energy release rate G_Ic of fibre-reinforced epoxy laminates. In order to perform pure mode I loading at higher opening velocities, a new test device is developed. The approach is based on a symmetrical opening displacement applied to a DCB specimen. In the data reduction, the influence of the kinetic energy has to be taken into account. The results obtained on the unidirectional carbon-epoxy laminate T300/914 at crack opening rates up to 1.6 m/s show a slight effect of the loading rate on G_Ic.     

Effects of component size, geometry, microstructure and aging on the embrittling behavior of creep crack growth correlated by the Q parameter

The driving force for creep crack growth is dominated by local elastic-plastic stress in the creep damage zone around a crack tip, temperature and microstructure. In previous work, C^∗, C_t, load line displacement rate dδ/dt and Q^∗ parameters have been proposed as formulations of creep crack growth rate (CCGR). Furthermore, using parameters mentioned above, the construction of the algorithm of predictive law for creep crack growth life is necessary for life assessment procedures. The aim of this paper is to identify the effects of component size, geometry, microstructure, aging and weldment on the embrittling behavior of creep crack growth and incorporate these effects in a predictive law, using the Q^∗ parameter. It was found that for specimen size (width and thickness) and of material softening due to aging the values of the activation energy were the same whereas for grain size change and structural brittleness, which affected crack tip multi-axial stress state the values for the activation energy for CCGR differ.     

Effect of mycorrhizal fungi on the phytoextraction of weathered p,p-DDE by Cucurbita pepo

Field experiments were conducted to assess the impact of inoculation with mycorrhizal fungi on the accumulation of weathered p,p'-DDE from soil by three cultivars of zucchini (Cucurbita pepo spp. pepo cv Costata Romanesco, Goldrush, Raven). Three commercially available mycorrhizal products (BioVam, Myco-Vam, INVAM) were inoculated into the root system of the zucchini seedlings at planting. In agreement with our previous findings, plants not inoculated with fungi accumulated large but variable amounts of contaminant, with root bioconcentration factors (BCFs, ratio of p,p'-DDE, on a dry weight basis, in the root to that in the soil) ranging from 10 to 48 and stem BCFs ranging from 5.5 to 11. The total amount of contaminant phytoextracted during the 62 day growing season ranged from 0.72-2.9%. The effect of fungal inoculation on the release of weathered p,p'-DDE from soil and on the subsequent uptake of the parent compound by zucchini appeared to vary at the cultivar level. For Goldrush, fungal inoculation generally decreased tissue BCFs but because of slightly larger biomass, did not significantly impact the percent contaminant phytoextracted. Alternatively, for Costata, BioVam and Myco-Vam generally enhanced p,p'-DDE accumulation from soil, and increased the amount of contaminant phytoextracted by up to 34%. For Raven, BioVam reduced contaminant uptake whereas Myco-Vam and INVAM increased contaminant phytoextraction by 53 and 60%, respectively. The data show that fungal inoculation may significantly increase the remedial potential of C. pepo ssp. pepo. The apparent cultivar specific response to mycorrhizal inoculation is unexpected and the subject of ongoing investigation.     

Removal of Cu(II) and Pb(II) by Pithophora oedogonia: sorption, desorption and repeated use of the biomass

Maximum sorption of Cu(II) and Pb(II) by dried filamentous green alga Pithophora oedogonia occurred at pH 4.5 and 5.0, respectively. Chemical pretreatment could not appreciably enhance the metal sorption ability of the biomass. HCl and EDTA desorbed 92-96% of the sorbed metal from the metal-loaded biomass. Sorption and desorption of both the test metals were very rapid attaining an equilibrium within 15 min. The time course data of both the processes fitted well to the pseudo-first and the pseudo-second-order Lagergren kinetic models with r2> or =0.979. The isotherm equilibrium of Cu(II) and Pb(II) followed the Redlich-Peterson and Sips model very well with r2> or =0.991. The sorption of Cu(II) and Pb(II) at varying biomass doses could be well defined by linear and hyperbolic decrease, respectively. The regenerated biomass of Pithophora has better reusability for Pb(II) than for Cu(II). A good mechanical strength of Pithophora biomass was apparent as only 10-15% loss of biomass occurred at the end of the fifth cycle.     

Impact of the Se evaporation rate on the microstructure and texture of Cu(In,Ga)Se2 thin films for solar cells

Coevaporated Cu(In,Ga)Se₂ layers on Mo-coated soda-lime glass substrates were produced by a three-stage process using various Se overpressure conditions during the three stages. Cross-sections of these samples were analyzed by electron backscatter diffraction (EBSD) in a scanning electron microscope in order to reveal the microstructures in the Cu(In,Ga)Se₂ layers. In addition, the preferential orientations of these Cu(In,Ga)Se₂ layers were studied by plan-view EBSD measurements. It was found that Cu(In,Ga)Se₂ exhibits a texture in 110 orientation for Se/(Cu + In + Ga) atomic flux ratios R which are sufficiently large (≥ 4). In one Cu(In,Ga)Se₂ layer produced with approximately R = 4, a large density of (near) Σ3 (twin) boundaries were detected which are oriented preferentially perpendicular to the substrate. By comparison of the local textures of neighboring grains and the theoretically possible changes in orientation by twinning, it is possible to retrace how the twinning occurred.     

Multivariate analysis of anionic, cationic and nonionic textile surfactant degradation with the H(2)O(2)/UV-C process by using the capabilities of response surface methodology

Anionic, cationic and nonionic surfactants being frequently employed in the textile preparation process were subjected to H(2)O(2)/UV-C treatment. As a consequence of the considerable number of parameters affecting the H(2)O(2)/UV-C process, an experimental design methodology was used to mathematically describe and optimize the single and combined influences of the critical process variables treatment time, initial H(2)O(2)concentration and chemical oxygen demand (COD) on parent pollutant (surfactant) as well as organic carbon (COD and total organic carbon (TOC)) removal efficiencies. Multivariate analysis was based on two different photochemical treatment targets; (i) full oxidation/complete treatment of the surfactants or, alternatively, (ii) partial oxidation/pretreatment of the surfactants to comply with the legislative discharge requirements. According to the established polynomial regression models, the process independent variables "treatment time" (exerting a positive effect) and "initial COD content" (exerting a negative effect) played more significant roles in surfactant photodegradation than the process variable "initial H(2)O(2) concentration" under the studied experimental conditions.