Degradation mechanisms of benzo[a]pyrene and its accumulated metabolites by biodegradation combined with chemical oxidation

A high degradation extent of benzo[a]pyrene (BaP) should not be considered as the sole desirable criterion for the bioremediation of BaP-contaminated soils because some of its accumulated metabolites still have severe health risks to human. Two main metabolites of BaP, benzo[a]pyrene-1,6-quinone (BP1,6-quinone) and 3-hydroxybenzo[a]pyrene (3-OHBP) were identified by high performance liquid chromatography (HPLC) with standards. This study was the first time that degradation of both BaP and the two metabolites was carried out by chemical oxidation and biodegradation. Three main phases during the whole degradation process were proposed.

Hydrogen peroxide–zinc (H₂O₂–Zn), the fungus – Aspergillus niger and the bacteria – Zoogloea sp. played an important role in the different phases. The degradation parameters of the system were also optimized, and the results showed that the effect of degradation was the best when fungus–bacteria combined with H₂O₂–Zn, the concentration range of BaP in the cultures was 30–120 mg/l, the initial pH of the cultures was 6.0. However, as co-metabolites, phenanthrene significant inhibited the degradation of BaP. This combined degradation system compared with the conventional method of degradation by domestic fungus only, enhanced the degradation extent of BaP by more than 20% on the 12 d. The highest accumulation of BP1,6-quinone and 3-OHBP were reduced by nearly 10% in the degradation experiments, which further proved that the combined degradation system was more effective as far as joint toxicity of BaP and its metabolites are concerned.

Degradation of phenanthrene and pyrene in soil slurry reactors with immobilized bacteria Zoogloea sp.

The environmental fate of polycyclic aromatic hydrocarbons (PAHs) in soils is motivated by their wide distribution, high persistence, and potentially deleterious effect on human health. Polycyclic aromatic hydrocarbons constitute the largest group of environmental contaminants released in the environment. Therefore, the potential biodegradation of these compounds is of vital importance. A biocarrier suitable for the colonization by micro-organisms for the purpose of purifying soil contaminated by polycyclic aromatic hydrocarbons was developed. The optimized composition of the biocarrier was polyvinyl alcohol (PVA) 10%, sodium alginate (SA) 0.5%, and powdered activated carbon (PAC) 5%. There was no observable cytotoxicity of biocarriers on immobilized cells and a viable cell population of 1.86 × 10¹⁰ g^–1 was maintained for immobilized bacterium. Biocarriers made from chemical methods had a higher biodegradation but lower mechanical strengths. Immobilized bacterium Zoogloea sp. had an ideal capability of biodegradation for phenanthrene and pyrene over a relative wide concentration range. The study results showed that the biodegradation of phenanthrene and pyrene reached 87.0 and 75.4%, respectively, by using the optimal immobilized method of Zoogloea sp. cultivated in a sterilized soil. Immobilized Zoogloea sp. was found to be effective for biodegrading the soil contaminated with phenanthrene and pyrene. Even in "natural" (unsterilized) soil, the biodegradation of phenanthrene and pyrene using immobilized Zoogloea sp. reached 85.0 and 67.1%, respectively, after 168 h of cultivation, more than twice that achieved if the cells were not immobilized on the biocarrier. Therefore, the immobilization technology enhanced the competitive ability of introduced micro-organisms and represents an effective method for the biotreatment of soil contaminated with phenanthrene and pyrene.

Photochemical degradation of 2,4-D and atrazine in well-defined media

Atrazine and 2,4-D are common herbicides used for crop, lawn, and rangeland management. Photochemical degradation has been proposed as one safe and efficient remediation strategy for both 2,4-D and Atrazine. In the presence of iron(llI) and hydrogen peroxide these herbicides decay by both thermal and light induced oxidation. Past studies have focused primarily on sun light as an energy source. This work provides a mechanistic description of herbicide degradation incorporating intermediate degradation products produced in the dark and under well-defined light conditions.

Influence of chemical oxidant on degradation of benzo[a]pyrene metabolites by the bacterium-Zoogloea sp.

It is neither comprehensive nor appropriate that the bioremediation of a benzo[a]pyrene (BaP)-contaminated environment be assessed only by its high degradation extent because its metabolites' chemical structures are similar to the parent compound and maybe equally toxic. Therefore, further degradation of BaP metabolites is significant. Three methods, combining the Zoogloea sp. with potassium permanganate, combining the Zoogloea sp. with H₂O₂, Zoogloea sp. alone, were investigated to degrade cis-BP4,5-dihydrodiol and cis-BP7,8-dihydrodiol, which are the metabolites of BaP formed by bacterium-Zoogloea sp. Optimum parameters of degradation in the best method are that: of the three methods, coupling the Zoogloea sp. and KMnO₄ is the best; compared with cis-BP7,8-dihydrodiol, cis-BP4,5-dihydrodiol is the more liable to be accumulated in pure cultures; the degradation effect of the two metabolites is optimal when the initial concentration of KMnO₄ in the cultures is 0.05%; initial concentration of cis-BP4,5-dihydrodiol and cis-BP7,8-dihydrodiol is 4 mg L⁻¹, 8 mg L⁻¹, respectively; cometabolic substance is salicylic acid or sodium succinate. The degradation extent of cis-BP4,5-dihydrodiol and cis-BP7,8-dihydrodiol using combining the Zoogloea sp. and KMnO₄ reach 76.1% and 85.9% after 12 days of cultivation, respectively, which were more than twice compared with conventional method.

The reactivity of diorganotellurium oxides towards phenol and o-nitrophenol. Hypervalent and secondary bonding of four different product classes

The reaction of the diorganotellurium oxides R2TeO (R = Ph, p-MeOC6H4, p-Me2NC6H4) with phenol and o-nitrophenol produces diorganotellurium hydroxy phenolates, R2Te(OH)OPh (1, R = Ph; 2, R = p-MeOC6H4; 3, R = p-Me2NC6H4), diorganotellurium bis(phenolates) R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4), tetraorganoditelluroxane bis(o-nitrophenolates), (R′O)R2TeOTeR2(OR′) (7, R = p-MeOC6H4; 8, R = p-Me2NC6H4; R′ = o-NO2C6H4), and a hexaphenyltritelluroxane bis(o-nitrophenolate) (R′O)Ph2TeOTePh2OTePh2(OR′) (9, R′ = o-NO2C6H4), respectively. The redistribution reactions of R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4) with the corresponding diorganotellurium oxides R2TeO and diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) give rise to the formation of moisture sensitive tetraorganoditelluroxane bis(phenolates) (PhO)R2TeOTeR2(OPh) (10, R = Ph; 11, R = p-MeOC6H4; 12, R = p-Me2NC6H4) and diorganotellurium chloro phenolates, R2Te(Cl)OPh (13, R = Ph; 14, R = p-MeOC6H4; 15, R = p-Me2NC6H4), respectively. The reaction of the diorganotellurium oxides R2TeO with the corresponding diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) affords tetraorganoditelluroxane dichlorides ClR2TeOTeR2Cl (16, R = Ph; 17, R = p-MeOC6H4; 18, R = p-Me2NC6H4) as air-stable solid materials. The reactivity of 1–18 can be rationalized by the kinetic lability of the Te–O and Te–Cl bonds. Compounds 1–18 have been characterized by solution and solid-state 125Te NMR spectroscopy and 2, 4, 6, 7, 9, 17, and 18 have also been analyzed by X-ray crystallography.

Thermal degradation of natural rubber/ZNO nanocomposites

Nanoparticies have been widely used to enhance the properties of natural rubber (NR). In the present paper a novel nanocomposite was developed by blending nano-ZnO slurry with prevulcanized NR latex, and the thermal degradation process of pure NR and NR/ZnO nanocomposites with different nano-ZnO loading was studied with a Perkin Elemer TGA-7 thermogravimetric analyzer. The thermal degradation parameters of NR/ZnO (2 parts ZnO per hundred dlY rubber) at different heating rates (Bs) were studied. The results show that the thermal degradation of pure NR and NR/ZnO nanocomposites in nitrogen is a one-step reaction. The degradation temperatures of NR/ZnO nanocomposite increase with an increasing B. The peak height (R_p) on the differential thermogravimetric curve increases with the increase of B. The degradation rates are not affected significantly by B, and the average values of thermal degradation rate C_p and C_f are 44.42 % and 81.04 %, respectively. The thermal degradation kinetic parameters are calculated with Ozawa-Flynn-Wall method. The activation energy (E) and the frequency factor (A) vary with ecomposition degree, and can be divided into three phases corresponding to the volatilization of low-molecular-weight materials, the thermal degradation ofNR main chains and the decomposition of residual carbon.

The effect of estrogen on Akt signalling and protein synthesis in C2C12 mouse skeletal myotubes

The maintenance of skeletal muscle mass is a critical component of health in both chronic wasting diseases and aging. A considerable amount of progress has been made in the understanding of the signalling pathways that mediate skeletal muscle hypertrophy and atrophy. Akt is seen as a key molecular protein involved in the maintenance of skeletal muscle mass as it has the dual ability to positively influence protein syntheses and negatively regulate protein degradation in its active state (Glass, 2003). Potential mechanisms which may assist with maintaining skeletal muscle mass are the estrogen hormones. Estrogens increase the proliferation of mouse and rat myoblasts and can also attenuate immobilization-induced skeletal muscle atrophy in rats in vivo (Kahlert et al., 1997). No studies have investigated the effect of estrogens on the activation of skeletal muscle hypertrophy and atrophy signalling pathways. Estrogens may contribute to maintaining skeletal muscle mass via their activation of the Akt signalling pathways. Therefore, the aims of the present study were to determine if treatment of C2C12 myotubes with either 17β-estrodiol or estrone increases the activity of Akt and its downstream anabolic signalling proteins, GSK, p70s6k and 4E-BP1 and decreases its catabolic stimulating targets, FOXO, atrogin-1 and MuRF-1. A secondary aim was to determine if this was associated with an increased rate of protein synthesis.

C2C12 myotubes were incubated at 37°C in serum free DMEM without phenol red containing 10 000 units/ml penicillin, 10 000 μg/ml streptomycin, and 250μg/ml amphotericin B for 24h. Myotubes were then stimulated with 17-β estradiol (10nM) for 24h. Phosphorylated and total proteins for Akt, p70S6k, GSK3β, 4E-BP1, FOXO and atrogin-1 were measured using western blotting techniques. Atrogin-1 and MuRF1 mRNA levels were measured using real time-PCR. Protein synthesis rates were measured by incorporation of [3H]-tyrosine into the myotubes during the last hour of treatment.

Compared to control myotubes, treatment with 17β-estradiol increased the ratio of phosphorylated to total protein contents for Akt, GSK-3β and P70s6k by, 1.62, 1.53 and 2.2 fold, respectively (n=6 per group; p < 0.05). There was, however, no difference in the ratios of phosphorylated to total 4E-BP1 or Foxo3a or Atrogin-1 and MuRF1 mRNA. Protein synthesis rates remained unchanged.

This study demonstrates that in C2C12 mouse myotubes, 17β-estradiol treatment increases the phosphorylation of the hypertrophy signalling protein, Akt, and its downstream hypertrophy signalling targets, GSK-3β and P70s6k; no associated changes in protein synthesis were observed. Future studies should investigate the ability of 17β-estradiol to activate these proteins in a model of myotube catabolism and to determine if protein degradation is attenuated.

Partial purification and characterization of limonoate dehydrogenase from Rhodococcus fascians for the degradation of limonin

An extracellular limonoate dehydrogenase was purified 10-fold from a cell-free extract of Rhodococcus fascians by ammonium sulfate precipitation, dialysis, and ultrafiltration. This purified dehydrogenase catalyzed the
conversion of limonoate to 17-dehydrolimonoate. The enzyme showed optimum activity at pH 8.0 and 40oC, with K_m value of 0.9 µM, and requires Zn ions and sulfhydryl groups for catalytic action. The enzyme activity was inhibited by Hg²⁺ and NaN₃ ions. The degradation of limonin (66%) in Kinnow mandarin juice was successfully demonstrated with partially
purified limonoate dehydrogenase. With scale-up preparation of limonoate dehydrogenase, a successful debittering operation of fruit juices appears feasible.

Collapse of an avifauna : climate change appears to exacerbate habitat loss and degradation

Aim. We characterized changes in reporting rates and abundances of bird species over a period of severe rainfall deficiency and increasing average temperatures. We also measured flowering in eucalypts, which support large numbers of nectarivores characteristic of the region.

Location.  A 30,000-km2 region of northern Victoria, Australia, consisting of limited amounts of remnant native woodlands embedded in largely agricultural landscapes.

Methods. There were three sets of monitoring studies, pitched at regional  (survey programmes in 1995–97, 2004–05 and 2006–08), landscape (2002–03 and 2006–07) and site (1997–2008 continuously) scales. Bird survey techniques used a standard 2-ha, 20-min count method. We used Bayesian analyses of reporting rates to document statistically changes in the avifauna through time at each spatial scale.

Results. Bird populations in the largest remnants of native vegetation (up to 40,000 ha), some of which have been declared as national parks in the past decade, experienced similar declines to those in heavily cleared andscapes. All categories of birds (guilds based on foraging substrate, diet, nest site; relative mobility; geographical distributions) were affected similarly. We detected virtually no bird breeding in the latest survey periods. Eucalypt flowering has declined significantly over the past 12 years of drought.

Main conclusions. Declines in the largest woodland remnants commensurate with those in cleared landscapes suggest that reserve systems may not be relied upon to sustain species under climate change. We attribute population declines to low breeding success due to reduced food. Resilience of bird populations in this woodland system might be increased by active management to enhance habitat quality in existing vegetation and restoration of woodland in the more fertile parts of landscapes.

Studies on the photochemical stability of organo phosphorus insecticides for textile mothproofing

The light stability of 0,0-diethyl-0-(4-ethylthiophenyl)phosphorothioate, a parent structure of a new class of fibre-reactive organophosphorus insectproofing agents for use on wool textiles was extensively examined. The rate of degradation of 0,0-diethyl-0-(4-ethylthiophenyl)phosphoro-thioate in polar and non-polar solution and on wool upon irradiation by simulated sunlight was investigated using high performance liquid chromatography.. The major photodegradation products in each case were correlated with the HPLC retention times of synthetically prepared compounds. The main product formed was the sulphoxide, 0,0-diethyl-O-(4-ethylsulphinylphenyl)phosphorothioate, whose insecticidal activity against the major textile pests was shown to be similar to that of the parent compound. In polar solution a polar product which could not be identified was formed. Both 4-ethylsulphinylphenol and 4-ethyIsulphony1-phenol were found on wool but not in solution. The effect of various ultraviolet stabilizers on the rate of photodegradation of 0,0-diethyl-0-(4-ethylthiophenyl)phosphorothioate was also examined. Ultraviolet absorbers of the 2-hydroxybenzophenone and 2-hydroxybenzotriazole classes conferred the best protection in each case. However, on wool typical wool dyes applied at conventional levels were also effective.