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1.
Gene ; 893: 147927, 2024 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-38374023

RESUMO

Recent semi-targeted metabolomics studies have highlighted a number of metabolites in wheat that associate with leaf rust resistance genes and/or rust infection. Here, we report the structural characterization of a novel glycosylated and partially saturated apocarotenoid, reminiscent of a reduced form of mycorradicin, (6E,8E,10E)-4,9-dimethyl-12-oxo-12-((3,4,5-trihydroxy-6-(2-hydroxyethoxy)tetrahydro-2H-pyran-2-yl)methoxy)-3-((3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)dodeca-6,8,10-trienoic acid, isolated from Triticum aestivum L. (Poaceae) variety 'Thatcher' (Tc) flag leaves. While its accumulation was not associated with any of Lr34, Lr67 or Lr22a resistance genes, infection of Tc with leaf rust was found to deplete it, consistent with the idea of this metabolite being a glycosylated-storage form of an apocarotenoid of possible relevance to plant defense. A comparative analysis of wheat transcriptomic changes shows modulation of terpenoid, carotenoid, UDP-glycosyltransferase and glycosylase -related gene expression profiles, consistent with anticipated biosynthesis and degradation mechanisms. However, details of the exact nature of the relevant pathways remain to be validated in the future. Together these findings highlight another example of the breadth of unique metabolites underlying plant host-fungal pathogen interactions.


Assuntos
Basidiomycota , Triticum , Triticum/genética , Triticum/microbiologia , Resistência à Doença/genética , Plantas , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Piranos
2.
Bioresour Technol ; 387: 129595, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37541546

RESUMO

Despite known metabolic versatility of Burkholderia spp., sugar metabolism and end-product synthesis patterns in Burkholderia thailandensis have been poorly characterized. This work has demonstrated that B. thailandensis is capable of simultaneously uptaking glucose and xylose and accumulating up to 64% of its dry mass as poly(3-hydroxyalkanoate) (PHA) biopolymers, resulting in a PHA titer of up to 3.8 g L-1 in shake flasks. Rhamnolipids - mainly (68-75%) in the form of Rha-Rha-C14-C14 - were produced concomitantly with a titer typically in the range of 0.2-0.4 g L-1. Gluconic and xylonic acids were also detected in titers of up to 5.3 g L-1, and while gluconic acid appeared to be back consumed, xylonic acid formed as a major end product. This first example of co-production of three products from mixed sugars using B. thailandensis paves the way for improving biorefinery economics.


Assuntos
Burkholderia , Açúcares , Açúcares/metabolismo , Burkholderia/metabolismo , Glucose/metabolismo
3.
N Biotechnol ; 77: 40-49, 2023 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-37390901

RESUMO

Glucose and xylose are fermentable sugars readily available from lignocellulosic biomass, and are a sustainable carbon substrate supporting industrial biotechnology. Three strains were assessed in this work - Paraburkholderia sacchari, Hydrogenophaga pseudoflava, and Bacillus megaterium - for their ability to uptake both C5 and C6 sugars contained in a hardwood hydrolysate produced via a thermomechanical pulping-based process with concomitant production of poly(3-hydroxyalkanoate) (PHA) biopolymers. In batch conditions, B. megaterium showed poor growth after 12 h, minimal uptake of xylose throughout the cultivation, and accumulated a maximum of only 25 % of the dry biomass as PHA. The other strains simultaneously utilized both sugars, although glucose uptake was faster than xylose. From hardwood hydrolysate, P. sacchari accumulated 57 % of its biomass as PHA within 24 h, whereas H. pseudoflava achieved an intracellular PHA content of 84 % by 72 h. The molecular weight of the PHA synthesized by H. pseudoflava (520.2 kDa) was higher than that of P. sacchari (265.5 kDa). When the medium was supplemented with propionic acid, the latter was rapidly consumed by both strains and incorporated as 3-hydroxyvalerate subunits into the polymer, demonstrating the potential for production of polymers with improved properties and value. H. pseudoflava incorporated 3-hydroxyvalerate subunits with at least a 3-fold higher yield, and produced polymers with higher 3-hydroxyvalerate content than P. sacchari. Overall, this work has shown that H. pseudoflava can be an excellent candidate for bioconversion of lignocellulosic sugars to PHA polymers or copolymers as part of an integrated biorefinery.


Assuntos
Poli-Hidroxialcanoatos , Açúcares , Poliésteres/química , Xilose , Hidrólise
4.
Front Cell Infect Microbiol ; 13: 1287418, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38239502

RESUMO

Introduction: The fungal G protein-coupled receptors Ste2 and Ste3 are vital in mediating directional hyphal growth of the agricultural pathogen Fusarium graminearum towards wheat plants. This chemotropism is induced by a catalytic product of peroxidases secreted by the wheat. Currently, the identity of this product, and the substrate it is generated from, are not known. Methods and results: We provide evidence that a peroxidase substrate is derived from F. graminearum conidia and report a simple method to extract and purify the FgSte2-activating ligand for analyses by mass spectrometry. The mass spectra arising from t he ligand extract are characteristic of a 400 Da carbohydrate moiety. Consistent with this type of molecule, glycosidase treatment of F. graminearum conidia prior to peroxidase treatment significantly reduced the amount of ligand extracted. Interestingly, availability of the peroxidase substrate appears to depend on the presence of both FgSte2 and FgSte3, as knockout of one or the other reduces the chemotropism-inducing effect of the extracts. Conclusions: While further characterization is necessary, identification of the F. graminearum-derived peroxidase substrate and the FgSte2-activating ligand will unearth deeper insights into the intricate mechanisms that underlie fungal pathogenesis in cereal crops, unveiling novel avenues for inhibitory interventions.


Assuntos
Fusarium , Peroxidase , Ligantes , Peroxidases/farmacologia , Doenças das Plantas/microbiologia
5.
Phytochemistry ; 178: 112456, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32692663

RESUMO

The gene Lr34res is one of the most long-lasting sources of quantitative fungal resistance in wheat. It is shown to be effective against leaf, stem, and stripe rusts, as well as powdery mildew and spot blotch. Recent biochemical characterizations of the encoded ABC transporter have outlined a number of allocrites, including phospholipids and abscisic acid, consistent with the established general promiscuity of ABC transporters, but ultimately leaving its mechanism of rust resistance unclear. Working with flag leaves of Triticum aestivum L. variety 'Thatcher' (Tc) and a near-isogenic line of 'Thatcher' into which the Lr34res allele was introgressed (Tc+Lr34res; RL6058), a comparative semi-targeted metabolomics analysis of flavonoid-rich extracts revealed virtually identical profiles with the exception of one metabolite accumulating in Tc+Lr34res, which was not present at comparable levels in Tc. Structural characterization of the purified metabolite revealed a phenylpropanoid diglyceride structure, 1-O-p-coumaroyl-3-O-feruloylglycerol (CFG). Additional profiling of CFG across a collection of near-isogenic lines and representative Lr34 haplotypes highlighted a broad association between the presence of Lr34res and elevated accumulations of CFG. Depletion of CFG upon infection, juxtaposed to its relatively lower anti-fungal activity, suggests CFG may serve as a storage form of the more potent anti-microbial hydroxycinnamic acids that are accessed during defense responses. Altogether these findings suggest a role for the encoded LR34res ABC transporter in modifying the accumulation of CFG, leading to increased accumulation of anti-fungal metabolites, essentially priming the wheat plant for defense.


Assuntos
Ascomicetos , Basidiomycota , Diglicerídeos , Resistência à Doença , Doenças das Plantas , Triticum
6.
Biochem Cell Biol ; 94(5): 459-470, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27565003

RESUMO

For almost a century, the wheat Lr34 gene has conferred durable resistance against fungal rust diseases. While sequence homology predicts a putative ATP binding cassette transporter, the molecules that are transported (allocrites) by the encoded LR34 variants, and any associated mechanism of resistance, remain enigmatic. Here, the in vitro transport characteristics of 2 naturally occurring Lr34 variants (that differ in their ability to mediate disease resistance; Lr34sus and Lr34res) are investigated. Initially, a method to express and purify recombinant LR34Sus and LR34Res pseudo half-molecules from Saccharomyces cerevisiae, is described. Subsequently, a semi-targeted chlorophyll catabolite (CC) extraction from Lr34res-expressing wheat plants was performed based on previous reports highlighting increased accumulation of CCs in Lr34res-expressing flag leaves. Following partial biochemical characterization, this extract was applied to an LR34 in vitro proteoliposome transport assay. Mass spectroscopic analyses of transported metabolites revealed that LR34Sus imported a wheat metabolite of 618 Da and that the LR34Res transporter did not. While the identity of the LR34Sus transported metabolite remains to be confirmed and any allocrites of LR34Res remain to be detected, this work demonstrates that these variants have different allocrite preferences, a finding that may be relevant to the mechanism of disease resistance.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Imunidade Inata/imunologia , Doenças das Plantas/imunologia , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Triticum/metabolismo , Transportadores de Cassetes de Ligação de ATP/genética , Clorofila/metabolismo , Doenças das Plantas/microbiologia , Folhas de Planta/genética , Folhas de Planta/imunologia , Proteínas de Plantas/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Triticum/genética , Triticum/imunologia
7.
Bioresour Technol ; 104: 775-82, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22154584

RESUMO

Presently lignin is used as fuel but recent interests in biomaterials encourage the use of this polymer as a renewable feedstock in manufacturing. The present study was undertaken to explore the potential applicability of microwaves to isolate lignin from agricultural residues. A central composite design (CCD) was used to optimize the processing conditions for the microwave (MW)-assisted extraction of lignin from triticale straw. Maximal lignin yield (91%) was found when using 92% EtOH, 0.64 N H(2)SO(4), and 148 °C. The yield and chemical structure of MW-extracted lignin were compared to those of lignin extracted with conventional heating. Under similar conditions, MW irradiation led to higher lignin yields, lignins of lower sugar content, and lignins of smaller molecular weights. Except for these differences the lignins resulting from both types of heating exhibited comparable chemical structures. The present findings should provide a clean source of lignin for potential testing in manufacturing of biomaterials.


Assuntos
Grão Comestível/química , Grão Comestível/efeitos da radiação , Lignina/isolamento & purificação , Lignina/efeitos da radiação , Modelos Químicos , Componentes Aéreos da Planta/química , Componentes Aéreos da Planta/efeitos da radiação , Simulação por Computador , Relação Dose-Resposta à Radiação , Lignina/química , Micro-Ondas , Doses de Radiação
8.
J Environ Monit ; 13(8): 2304-11, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21734991

RESUMO

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a widely used explosive that is present in soils at a number of military sites, including training and testing ranges. Because of its relatively weak adsorption to soil, RDX frequently migrates through the unsaturated zone and causes groundwater contamination. In the environment, RDX can transform to produce mono-, di-, and tri-nitroso derivatives (MNX, DNX, and TNX) and the ring cleavage products methylenedinitramine (MEDINA) and 4-nitro-2,4-diazabutanal (NDAB). The present study was undertaken to analyze RDX and its products in groundwater samples taken from various US military sites. The stability of some of the common transformation intermediates of RDX, including the nitroso derivatives, NDAB and MEDINA, under typical conditions in a groundwater aquifer is not well understood, and appropriate preservation methods for these compounds have not been established. Therefore, we studied the inherent stability of these compounds in deionized water and in groundwater, and evaluated various preservation techniques, including adjustment of pH, temperature, and salinity. NDAB and nitroso derivatives were stable under typical ambient environmental conditions, but MEDINA was highly unstable. The addition of sea salts (10% w/v) was found to stabilize MEDINA when the samples were stored at 4 °C. Using appropriate preservation techniques, we detected nitroso derivatives and NDAB, but no MEDINA, at some of the sites investigated. Stabilizing RDX intermediate products in field samples to allow detection is important because the presence of any of these chemicals can indicate past contamination by RDX and provide insight into the occurrence of in situ natural attenuation.


Assuntos
Monitoramento Ambiental , Substâncias Explosivas/análise , Solo/análise , Triazinas/análise , Poluentes Químicos da Água/análise , Água/análise , Estados Unidos
9.
Environ Toxicol Chem ; 29(4): 998-1005, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20821531

RESUMO

The uptake of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from soil by the earthworm Eisenia andrei was examined by using the equilibrium partitioning (EqP) theory and a three-compartment model including soil (S), interstitial water (IW), and earthworms (E). The RDX concentrations were measured using U.S. Environmental Protection Agency (U.S. EPA) Method 8330A and high-performance liquid chromatography (HPLC). The S-IW studies were conducted using four natural soils with contrasting physicochemical properties that were hypothesized to affect the bioavailability of RDX. Each soil was amended with nominal RDX concentrations ranging from 1 to 10,000 mg/kg. The HPLC analysis showed that the IW extracted from soil was saturated with RDX at 80 mg/kg or greater soil concentrations. The calculated S-IW coefficient (K(p)) values for RDX ranged from 0.4 to 1.8 ml/g soil, depending on the soil type, and were influenced by the organic matter content. In the IW-E studies, earthworms were exposed to nonlethal RDX concentrations in aqueous media. The uptake of RDX by the earthworms correlated well (r(2) = 0.99) with the dissolved RDX concentrations. For the E-S studies, earthworms were exposed to RDX-amended soils used in the S-IW studies. The bioconcentration factors (BCF; ratios of E-to-IW RDX concentrations) were relatively constant ( approximately 5) up to 80 mg/kg soil RDX concentrations, which encompass the RDX saturation limit in the interstitial water of the tested soils. At this concentration range, the RDX uptake from interstitial water was likely dominated by passive diffusion and could be used as an indicator of bioavailability. Other mechanisms may be involved at greater RDX soil concentrations.


Assuntos
Substâncias Explosivas/farmacocinética , Oligoquetos/metabolismo , Poluentes do Solo/farmacocinética , Triazinas/farmacocinética , Poluentes Químicos da Água/farmacocinética , Animais , Disponibilidade Biológica , Poluentes do Solo/análise , Poluentes Químicos da Água/análise
10.
J Hazard Mater ; 174(1-3): 281-8, 2010 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-19815337

RESUMO

GIM (Greener Insensitive Material) is a new explosive formulation made of HMX (51.5%), TNT (40.7%), and a binder, ETPE (7.8%), which is currently investigated by the Canadian Department of National Defense for a wider use by the Army. In the present study, dissolution of GIM in water was measured and compared to the dissolution of octol (HMX/TNT: 70/30). Although the presence of ETPE did not prevent completely TNT and HMX from dissolving, GIM appeared to dissolve more slowly than octol. The ETPE was shown to prevent the formulation particles from collapsing and to retard the dissolution of both TNT and HMX by limiting their exposure to water. In both octol and GIM, the dissolution rate of the particles was governed by the compound(s) that are slower to dissolve, i.e. HMX in octol, and HMX and ETPE in GIM. A model based on Fick's diffusion law allowed fitting well the dissolution data of octol but was less appropriate to fit the data of GIM likely due to a physical rearrangement of the solid upon dissolution. The present findings demonstrate that ETPE in GIM decreases the risks of explosives leakage from particles of the new formulation and should facilitate the collecting of non-exploded GIM particles in training sites.


Assuntos
Azocinas/química , Substâncias Explosivas , Trinitrotolueno/química , Cinética , Solubilidade
11.
Environ Pollut ; 157(1): 77-85, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18801604

RESUMO

Hexanitrohexaazaisowurtzitane (CL-20) is an emerging explosive that may replace the currently used explosives such as RDX and HMX, but little is known about its fate in soil. The present study was conducted to determine degradation products of CL-20 in two sandy soils under abiotic and biotic anaerobic conditions. Biotic degradation was prevalent in the slightly acidic VT soil, which contained a greater organic C content, while the slightly alkaline SAC soil favored hydrolysis. CL-20 degradation was accompanied by the formation of formate, glyoxal, nitrite, ammonium, and nitrous oxide. Biotic degradation of CL-20 occurred through the formation of its denitrohydrogenated derivative (m/z 393 Da) while hydrolysis occurred through the formation of a ring cleavage product (m/z 156 Da) that was tentatively identified as CH(2)=N-C(=N-NO(2))-CH=N-CHO or its isomer N(NO(2))=CH-CH=N-CO-CH=NH. Due to their chemical specificity, these two intermediates may be considered as markers of in situ attenuation of CL-20 in soil.


Assuntos
Compostos Aza/análise , Substâncias Explosivas/análise , Compostos Heterocíclicos/análise , Poluentes do Solo/análise , Solo/análise , Compostos Aza/química , Biodegradação Ambiental , Monitoramento Ambiental/métodos , Substâncias Explosivas/química , Compostos Heterocíclicos/química , Dióxido de Silício , Microbiologia do Solo , Poluentes do Solo/química
12.
J Environ Qual ; 37(3): 858-64, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18453407

RESUMO

Sinking of military ships, dumping of munitions during the two World Wars, and military training have resulted in the undersea deposition of numerous unexploded ordnances (UXOs). Leaching of energetic compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from these UXOs may cause adverse ecological effects so that the long-term fate of these chemicals in the sea should be known. The present study assesses the contribution of alkaline hydrolysis into the natural attenuation of RDX and HMX in coastal waters. Alkaline hydrolysis rates were shown to be unaffected by the presence of sodium chloride, the most common component in marine waters. Kinetic parameters (E(a), ln A, k(2)) quantified for the alkaline hydrolysis of RDX and HMX in deionized water (30-50 degrees C, pH 10-12) agreed relatively well with abiotic degradation rates determined in sterilized natural coastal waters (50 and 60 degrees C, variable salinity) even if the latter were generally slightly faster than the former. Furthermore, similar products (HCHO, NO(2)(-), O(2)NNHCH(2)NHCHO) were obtained on alkaline hydrolysis in deionized water and abiotic degradation in coastal waters. These two findings suggested that degradation of nitramines in sterilized natural coastal waters, away from light, was mainly governed by alkaline hydrolysis. Kinetic calculations using the present parameters showed that alkaline hydrolysis of RDX and HMX in marine waters at 10 degrees C would respectively take 112 +/- 10 and 2408 +/- 217 yr to be completed (99.0%). We concluded that under natural conditions hydrolysis should not contribute significantly to the natural attenuation of HMX in coastal waters whereas it could play an active role in the natural attenuation of RDX.


Assuntos
Azocinas/química , Triazinas/química , Poluentes Químicos da Água/química , Cinética , Água do Mar
13.
Chemosphere ; 70(5): 791-9, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17765284

RESUMO

Dinitrotoluenes (DNTs) are widely used in the manufacturing of explosives and propellants hence causing contamination of several terrestrial and aquatic environments. The present study describes biotransformation of 2,4-DNT and 2,6-DNT in marine sediment sampled from a shipwreck site near Halifax Harbour. Incubation of either 2,4-DNT or 2,6-DNT in anaerobic sediment slurries (10% w/v) at 10 degrees C led to the reduction of both DNTs to their corresponding diaminotoluene (2,4-DAT and 2,6-DAT) via the intermediary formation of their monoamine derivatives (ANTs). The production of diaminotoluene was enhanced in the presence of lactate for both DNT isomers. Using [(14)C]-2,4-DNT less than 1% mineralization was observed as determined by liberated (14)CO(2). Sorption of DNTs, ANTs, and DATs was thus investigated to learn of their fate in marine sediments. Under anaerobic conditions, sorption followed the order: DNTs (K(d)=8.3-11.7lkg(-1))>ANTs (K(d)=4.5-7.0lkg(-1))>DATs (K(d)=3.8-4.5lkg(-1)). Incubation of 2,4-DAT in aerobic sediment led to rapid disappearance from the aqueous phase. LC/MS analysis of the aqueous phase and the acetone sediment extract showed the formation of azo- and hydrazo-dimers and trimers, as well as unidentified polymers. Experiments with radiolabelled 2,4-DAT showed a mass balance distributed as follows: 22% in the aqueous phase, 24% in acetone extracts, and 50% irreversibly bound to sediment. We concluded that DNT in anoxic marine sediment can undergo in situ natural attenuation by reduction to DAT followed by oxidative coupling to hydrazo-oligomers or irreversible binding to sediment.


Assuntos
Dinitrobenzenos/metabolismo , Sedimentos Geológicos/microbiologia , Poluentes Químicos da Água/metabolismo , Aerobiose , Anaerobiose , Biodegradação Ambiental , Biotransformação , Sedimentos Geológicos/química , Isomerismo , Medição de Risco , Temperatura , Fatores de Tempo
14.
Environ Sci Technol ; 41(15): 5376-82, 2007 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-17822105

RESUMO

The present study was initiated to determine the capacity of sulfide minerals (pyrite FeS2 and chalcopyrite CuFeS2) to delay the migration of inorganic selenium species in geological formations. Interactions between Se(IV) and Se(-II) and synthetic and natural sulfide minerals were investigated under anoxic conditions using the batch method. Significant sorption of selenium occurred under acidic conditions. Analysis of the solids after Se sorption using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) demonstrated the presence of reduced selenium species on the metallic sulfide surfaces, thus suggesting an oxido-reduction process coupled with sorption. Selenium reduction occurred concomitantly with the oxidation of pyritic sulfur, whereas metallic species (Fe, Cu) were not involved in the redox process. Formation of ferroselite (FeSe2) was postulated to take place on the synthetic solid while surface complexation or ionic exchange processes were more likely on the natural solids.


Assuntos
Metais/química , Selênio/química , Sulfetos/química , Adsorção , Concentração de Íons de Hidrogênio , Ferro , Oxirredução , Selenito de Sódio , Análise Espectral , Propriedades de Superfície , Termodinâmica
15.
J Chromatogr A ; 1154(1-2): 34-41, 2007 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-17462661

RESUMO

Biopolymers such as poly(hydroxyalkanoates) (PHAs) have received much attention due to their physico-chemical properties, biodegradability, and biocompatibility that make them good candidates for industrial and medical applications. Produced by some microorganisms PHAs accumulate within the cells of these organisms. The optimization of microbial processes to produce PHAs at a lower cost requires rapid and accurate techniques for quantification of the biopolymer in biomass. The present study describes a method based on solid-phase microextraction (SPME) coupled to gas chromatography (GC) for the determination of poly(3-hydroxybutyrate) (PHB) in Alcaligenes latus cells. First PHB was depolymerized by either methanolic or hydrolytic digestion into methyl 3-hydroxybutyrate (Me-3-HB) or crotonic acid (CA), respectively. The resulting analytes were then subjected to analysis by headspace SPME/GC with flame ionization detection (FID). The two depolymerization/SPME/GC-FID methods were optimized and applied to the analysis of PHB in bacterial biomass harvested from a fermentation process that uses A. latus. Results were compared with those obtained using GC-FID analysis of MeOH/CHCl(3) digested samples. Excellent agreement was found between the three methods but the two SPME-based methods were environmentally friendly and easier to perform.


Assuntos
Bactérias/química , Cromatografia Gasosa/métodos , Hidroxibutiratos/análise , Poliésteres/análise , Microextração em Fase Sólida/métodos , Alcaligenes/química , Clorofórmio , Cromatografia Gasosa-Espectrometria de Massas/métodos , Metanol , Reprodutibilidade dos Testes
16.
J Colloid Interface Sci ; 303(1): 25-31, 2006 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-16899253

RESUMO

Compounds containing copper are likely candidates to delay iodide migration in environmental media through the formation of sparingly soluble phases. Preliminary experiments showed that iodide was neither sorbed onto chalcopyrite nor by a binary system pyrite/copper(II), although significant amounts of copper were present at the pyrite surface. In the present study, spectroscopic studies (XPS, XANES and EXAFS) were thus performed to determine the nature of sorbed copper species. Although introduced as Cu(II), copper was mainly present at the oxidation state (I) on the pyrite surface suggesting a heterogeneous reduction process. Moreover, copper appeared tetrahedrally coordinated to two sulfur and two oxygen atoms onto the pyrite surface, a chemical environment, which seemingly stabilized the metal and made it unreactive towards iodide.

17.
J Colloid Interface Sci ; 293(1): 27-35, 2006 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-16111692

RESUMO

Understanding sorption processes is fundamental for the prediction of radionuclide migration in the surroundings of a deep geological disposal of high-level nuclear wastes. Pyrite (FeS2) is a mineral phase often present as inclusions in temperate soils. Moreover, it constitutes an indirect corrosion product of steel, a containment material that is candidate to confine radionuclides in deep geological disposals. The present study was thus initiated to determine the capacity of pyrite to immobilize Sr(II) and Eu(III). An air oxidized pyrite and a freshly acid-washed (non-oxidized) pyrite were used in background electrolytes of varying reducing-oxidizing ability (NaCl, NH3OHCl, and NaClO4) to study the sorption of both cationic species. The sorptive capacity of pyrite appeared directly correlated to the oxidation of the surface. Non-oxidized pyrite had nearly no affinity for the studied cations whereas Sr(II) and Eu(III) species were significantly retained by oxidized pyrite surface. Using the surface complexation theory, sorption mechanisms were modeled with the Fiteql v3.2 and the Jchess 2.0 codes. Sorption of both Sr and Eu was well fitted, assuming hydroxylated species as the major surface species. This study demonstrates that not only the components of a barrier but also the redox conditions and specifications should be well characterized to predict transport of contaminants in the surrounding of a nuclear wastes disposal.

18.
Chemosphere ; 63(1): 175-81, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16112713

RESUMO

In previous studies, we found that the emerging energetic chemical, CL-20 (C6H6N12O12, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), can be degraded following its initial denitration using both aerobic and anaerobic bacteria. The C and N mass balances were not determined due to the absence of labeled starting compounds. The present study describes the degradation of the emerging contaminant by Phanerochaete chrysosporium using ring-labeled [15N]-CL-20 and [14C]-CL-20. Ligninolytic cultures degraded CL-20 with the release of nitrous oxide (N2O) in amounts corresponding to 45% of the nitrogen content of CL-20. When ring-labeled [15N]-CL-20 was used, both 14N14NO and 15N14NO were observed, likely produced from -NO2 and N-NO2, respectively. The incubation of uniformly labeled [14C]-CL-20 with fungi led to the production of 14CO2 (> 80%). Another ligninolytic fungus, Irpex lacteus, was also able to degrade CL-20, but as for P. chrysosporium, no early intermediates were observed. When CL-20 was incubated with manganese peroxidase (MnP), we detected an intermediate with a [M-H]- mass ion at 345 Da (or 351 and 349 Da when using ring-labeled and nitro-labeled [15N]-CL-20, respectively) matching a molecular formula of C6H6N10O8. The intermediate was thus tentatively identified as a doubly denitrated CL-20 product. The concomitant release of nitrite ions (NO2-) with CL-20 degradation by MnP also supported the occurrence of an initial denitration prior to cleavage and decomposition.


Assuntos
Compostos Aza/metabolismo , Compostos Heterocíclicos/metabolismo , Phanerochaete/metabolismo , Poluentes do Solo/metabolismo , Compostos de Anilina/metabolismo , Biodegradação Ambiental , Radioisótopos de Carbono/química , Cátions , Cromatografia Gasosa-Espectrometria de Massas , Nitritos/metabolismo , Nitrobenzenos/metabolismo , Óxido Nitroso/metabolismo , Peroxidases/metabolismo , Fatores de Tempo
19.
J Ind Microbiol Biotechnol ; 32(6): 261-7, 2005 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15915354

RESUMO

Undersea deposition of unexploded ordnance (UXO) constitutes a potential source of contamination of marine environments by hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The goal of the present study was to determine microbial degradation of RDX and HMX in a tropical marine sediment sampled from a coastal UXO field in the region of Oahu Island in Hawaii. Sediment mixed cultures growing in marine broth 2216 (21 degrees C) anaerobically mineralized 69% or 57% (CO2, 25 days) of the total carbon of [UL-14 C]-RDX (100 microM) or [UL-14 C]-HMX (10 microM), respectively. As detected by PCR-DGGE, members of gamma-proteobacteria (Halomonas), sulfate-reducing delta-proteobacteria (Desulfovibrio), firmicutes (Clostridium), and fusobacterium appeared to be dominant in RDX-enrichment and/or HMX-enrichment cultures. Among 22 sediment bacterial isolates screened for RDX and HMX biodegradation activity under anaerobic conditions, 5 were positive for RDX and identified as Halomonas (HAW-OC4), Marinobacter (HAW-OC1), Pseudoalteromonas (HAW-OC2 and OC5) and Bacillus (HAW-OC6) by their 16S rRNA genes. Sediment bacteria degraded RDX to N2O and HCHO via the intermediary formation of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and methylenedinitramine. The present findings demonstrate that cyclic nitramine contaminants are likely to be degraded upon release from UXO into tropical marine sediment.


Assuntos
Bactérias/metabolismo , Triazinas/metabolismo , Trinitrotolueno/metabolismo , Poluentes Químicos da Água/metabolismo , Azocinas/química , Azocinas/metabolismo , Biodegradação Ambiental , Biotecnologia , Havaí , Compostos Heterocíclicos com 1 Anel/química , Compostos Heterocíclicos com 1 Anel/metabolismo , Biologia Marinha , Minerais/metabolismo , Água do Mar/microbiologia , Triazinas/química , Trinitrotolueno/química
20.
J Chromatogr A ; 1066(1-2): 177-87, 2005 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-15794569

RESUMO

Gas chromatography with electron capture detection (GC-ECD) is a highly explosive-sensitive analytical technique. However, its application to the analysis of sediment extracts is hampered by the presence of numerous endogenous interferences. In the present study, solid-phase microextraction (SPME) was used both as a purification technique for sediment extracts and as an extraction technique for water samples prior to analysis by GC-ECD. SPME/GC-ECD coupling was optimized and applied to the trace analysis of nine explosives including nitroaromatics and RDX in real seawater and marine sediment samples. Addition of a high concentration of salt (30%, w/v) in the aqueous medium and use of a carbowax/divinylbenzene (CW/DVB) coating led to optimal extraction efficiencies. Method detection limits (MDLs) ranged from 0.05 to 0.81 microg/L in water and from 1 to 9 microg/kg in dry sediment. Except for RDX, spike recoveries in seawater were satisfactory (89-147%) when samples were fortified at 2 microg/L of each analyte. Spike recoveries from dry sediment fortified at 10 microg/kg of each analyte gave lower recoveries but these could also be due to degradation in the matrix. With a smaller volume of aqueous sample required compared to solid-phase extraction (SPE), SPME is an attractive method for the analysis of limited volumes of sediment pore-water. Moreover, the use of SPME eliminated interferences present in sediment extracts thus allowing the detection of the target analytes that were otherwise difficult to detect by direct injection.


Assuntos
Cromatografia Gasosa/métodos , Sedimentos Geológicos/química , Água do Mar/química , Acetonitrilas , Adsorção , Substâncias para a Guerra Química/química , Explosões , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Cloreto de Sódio/análise , Solubilidade
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