Copper-dependent depolymerization of lignin in the presence of fungal metabolite, pyridine

Degradation of Methylene Blue with a Cu(II)-Quinoline Complex Immobilized on a Silica Support as a Photo-Fenton-Like Catalyst

A Cu(II)-quinoline complex immobilized on a silica support was prepared to enhance the degradation of dyes. Mesoporous silica functionalized with this Cu(II) complex was turned into a photo-Fenton-like catalyst. Various techniques were used to characterize the resulting material, and the catalytic activity was determined by the degradation of methylene blue (MB) under UV light irradiation. The Cu(II) ion was successfully coordinated to the quinoline ligand on a silica support. The dye degradation investigation has shown that 95% of the dye was degraded in 2.5 h. The active radical species involved in the reaction were OH^• and O₂ ^•-, suggesting that a peroxo complex intermediate might be formed during degradation processes.

Peroxisomes Implicated in the Biosynthesis of Siderophores and Biotin, Cell Wall Integrity, Autophagy, and Response to Hydrogen Peroxide in the Citrus Pathogenic Fungus Alternaria alternata

Little is known about the roles of peroxisomes in the necrotrophic fungal plant pathogens. In the present study, a Pex6 gene encoding an ATPase-associated protein was characterized by analysis of functional mutations in the tangerine pathotype of Alternaria alternata, which produces a host-selective toxin. Peroxisomes were observed in fungal cells by expressing a mCherry fluorescent protein tagging with conserved tripeptides serine-lysing-leucine and transmission electron microscopy. The results indicated that Pex6 plays no roles in peroxisomal biogenesis but impacts protein import into peroxisomes. The number of peroxisomes was affected by nutritional conditions and H₂O₂, and their degradation was mediated by an autophagy-related machinery termed pexophagy. Pex6 was shown to be required for the formation of Woronin bodies, the biosynthesis of biotin, siderophores, and toxin, the uptake and accumulation of H₂O₂, growth, and virulence, as well as the Slt2 MAP kinase-mediated maintenance of cell wall integrity. Adding biotin, oleate, and iron in combination fully restored the growth of the pex6-deficient mutant (Δpex6), but failed to restore Δpex6 virulence to citrus. Adding purified toxin could only partially restore Δpex6 virulence even in the presence of biotin, oleate, and iron. Sensitivity assays revealed that Pex6 plays no roles in resistance to H₂O₂ and superoxide, but plays a negative role in resistance to 2-chloro-5-hydroxypyridine (a hydroxyl radical-generating compound), eosin Y and rose Bengal (singlet oxygen-generating compounds), and 2,3,5-triiodobenzoic acid (an auxin transport inhibitor). The diverse functions of Pex6 underscore the importance of peroxisomes in physiology, pathogenesis, and development in A. alternata.

Recent advances in Cu-Fenton systems for the treatment of industrial wastewaters: Role of Cu complexes and Cu composites

Cu-based Fenton systems have been recognized as a promising suite of technologies for the treatment of industrial wastewaters due to their high catalytic oxidation capacity. Rapid progress regarding Cu Fenton systems has been made not only in fundamental mechanistic aspects of these systems but also with regard to applications over the past decade. Based on available literature, this review synthesizes the recent advances regarding both the understanding and applications of Cu-based Fenton processes for industrial wastewater treatment. Cu-based catalysts that are essential to the effectiveness of use of Cu Fenton reactions for oxidation of target species are mainly classified into two types: (i) Cu complexes with organic or inorganic ligands, and (ii) Cu composites with inorganic materials. Performance of the Cu-based catalysts for the removal of organic pollutants in industrial wastewaters are reviewed, with the key operating parameters illustrated. Furthermore, the roles of Cu complexes and composites in both homogeneous and heterogeneous Cu-Fenton systems are critically examined with particular focus on the mechanisms involved. Perspectives and future efforts needed for Cu-based Fenton systems using Cu complexes and composites for industrial wastewater treatment are presented.

Enhanced Cu(II)-mediated fenton-like oxidation of antimicrobials in bicarbonate aqueous solution: Kinetics, mechanism and toxicity evaluation

Increasing attention has been attracted in developing new technologies to remove chlorofene (CF) and dichlorofene (DCF), which were active agents in antimicrobials for general cleaning and disinfecting. This study investigated the significant influences of bicarbonate (HCO₃^-) on the degradation of CF and DCF in the Cu(II)-mediated Fenton-like system Cu²⁺/H₂O₂. Our results indicate that HCO₃^- may play a dual role to act 1) as a ligand to stabilize Cu(II), forming soluble [Cu^II(HCO₃^-)(S)]⁺ species to catalyze H₂O₂ producing hydroxyl radical (OH) and superoxide ion (O₂^-) and 2) as a OH scavenger. Furthermore, the reaction kinetics, mechanisms, and intermediates of CF and DCF were assessed. The apparent rate constants of CF and DCF were enhanced by a factor of 8.5 and 5.5, respectively, in the presence of HCO₃^- at the optimized concentration of 4 mM. Based on the intermediate identification and frontier electron densities (FEDs) calculations, the associated reaction pathways were tentatively proposed, including C-C scission, single or multiple hydroxylation, and coupling reaction. In addition, significant reduction in the aquatic toxicity of CF and DCF was observed after treatment with Cu²⁺/H₂O₂-HCO₃^- system, evaluated by Ecological Structure Activity Relationships (ECOSAR) program. These findings provide new insights into Cu(II)-mediated reactions to better understand the environmental fate of organic contaminants in carbonate-rich waters.

Free radical behaviours during methylene blue degradation in the Fe2+/H2O2 system

Behaviours of the free radicals during the methylene blue (MB) oxidation process in the Fe²⁺/H₂O₂ system were studied to reveal the reason for the low utilization efficiency of H₂O₂. The roles of O2-∙ , ∙OH and HO2∙ radicals were proven to be different in the MB oxidation process. The results showed that O2-∙ radicals had a strong ability to oxidize MB; however, they were not the main active substances for MB degradation due to the low concentration in the traditional Fe²⁺/H₂O₂ system. HO2∙ radicals could not oxidize MB. ∙OH radicals were the main active substances for MB oxidation. In the short initial stage, the utilization efficiency of H₂O₂ was high, because the generation rate of ∙OH was much higher than that of HO2∙ . More ∙OH radicals were involved in the MB oxidation reaction. In the long deceleration stage (after the short initial stage), a large amount of H₂O₂ was consumed, but the amount of oxidized MB was very small. Most of the ∙OH radicals were consumed via the rapid useless reaction between ∙OH and HO2∙ in this stage, resulting in the serious useless consumption of H₂O₂. It is a feasible method to improve the utilization efficiency of H₂O₂ by adding suitable additives into the Fe²⁺/H₂O₂ system to weaken the useless reaction between ∙OH and HO2∙ .

A Major Facilitator Superfamily Transporter Regulated by the Stress-Responsive Transcription Factor Yap1 Is Required for Resistance to Fungicides, Xenobiotics, and Oxidants and Full Virulence in Alternaria alternata

Alternaria alternata relies on the ability to produce a host-selective toxin and to detoxify reactive oxygen species to successfully colonize the host. An A. alternata major facilitator superfamily transporter designated AaMFS54 was functionally characterized by analysis of loss- and gain-of-function mutations to better understand the factors required for fungal pathogenesis. AaMFS54 was originally identified from a wild-type expression library after being subtracted with that of a mutant impaired for the oxidative stress-responsive transcription regulator Yap1. AaMFS54 contains 14 transmembrane helixes. Fungal mutant lacking AaMFS54 produced fewer conidia and increased sensitivity to many potent oxidants (potassium superoxide and singlet-oxygen generating compounds), xenobiotics (2,3,5-triiodobenzoic acid and 2-chloro-5-hydroxypyridine), and fungicides (clotrimazole, fludioxonil, vinclozolin, and iprodione). AaMFS54 mutant induced necrotic lesion sizes similar to those induced by wild-type on leaves of susceptible citrus cultivars after point inoculation with spore suspensions. However, the mutant produced smaller colonies and less fluffy hyphae on the affected leaves. Virulence assays on citrus leaves inoculated by spraying with spores revealed that AaMFS54 mutant induced less severe lesions than wild-type, indicating the requirement of AaMFS54 in pathogenesis. All defective phenotypes were restored in a strain re-acquiring a functional copy of AaMFS54. Northern blotting analysis revealed that the expression of AaMFS54 was suppressed by xenobiotics. The current studies indicate that the Yap1-mediated transporter plays a role in resistance to toxic oxidants and fungicides in A. alternata. The relationships of MFS transporters with other regulatory components conferring stress resistance and A. alternata pathogenesis are also discussed.

A Major Facilitator Superfamily Transporter-Mediated Resistance to Oxidative Stress and Fungicides Requires Yap1, Skn7, and MAP Kinases in the Citrus Fungal Pathogen Alternaria alternata

Major Facilitator Superfamily (MFS) transporters play an important role in multidrug resistance in fungi. We report an AaMFS19 gene encoding a MFS transporter required for cellular resistance to oxidative stress and fungicides in the phytopathogenic fungus Alternaria alternata. AaMFS19, containing 12 transmembrane domains, displays activity toward a broad range of substrates. Fungal mutants lacking AaMFS19 display profound hypersensitivities to cumyl hydroperoxide, potassium superoxide, many singlet oxygen-generating compounds (eosin Y, rose Bengal, hematoporphyrin, methylene blue, and cercosporin), and the cell wall biosynthesis inhibitor, Congo red. AaMFS19 mutants also increase sensitivity to copper ions, clotrimazole, fludioxonil, and kocide fungicides, 2-chloro-5-hydroxypyridine (CHP), and 2,3,5-triiodobenzoic acid (TIBA). AaMFS19 mutants induce smaller necrotic lesions on leaves of a susceptible citrus cultivar. All observed phenotypes in the mutant are restored by introducing and expressing a wild-type copy of AaMFS19. The wild-type strain of A. alternata treated with either CHP or TIBA reduces radial growth and formation and germination of conidia, increases hyphal branching, and results in decreased expression of the AaMFS19 gene. The expression of AaMFS19 is regulated by the Yap1 transcription activator, the Hog1 and Fus3 mitogen-activated protein (MAP) kinases, the ‘two component’ histidine kinase, and the Skn7 response regulator. Our results demonstrate that A. alternata confers resistance to different chemicals via a membrane-bound MFS transporter.

In situ synthesis and immobilization of a Cu(ii)–pyridyl complex on silica microspheres as a novel Fenton-like catalyst for RhB degradation at near-neutral pH

A Cu(ii)–pyridyl complex was in situ synthesized and immobilized onto silica microspheres as a highly effective Fenton-like catalyst at near-neutral pH.

Oxidation of disinfectants with Cl-substituted structure by a Fenton-like system Cu(2+)/H2O2 and analysis on their structure-reactivity relationship

As widely used chemicals intended to protect human being from infection of microorganisms, disinfectants are ubiquitous in the environment. Among them chlorine-substituted phenol is a basic structure in many disinfectant molecules. Removal of these pollutants from wastewater is of great concern. The oxidative degradation of antimicrobial agents such as triclosan, chlorofene, and dichlorofene by a Fenton-like system Cu(2+)/H2O2 was examined. Reaction conditions such as temperature, initial concentrations of H2O2 and Cu(2+), and pH were optimized using triclosan as a representative. The degradation kinetics of the above disinfectants followed pseudo-first-order kinetics under the investigated conditions. Fourteen chlorophenols (CPs) with different chlorine substitution were also studied to evaluate the influence of molecular structure on the degradation process in the Cu(2+)/H2O2 system. Fourteen structure-related parameters were calculated using Gaussian 09 program. A quantitative structure-activity relationship (QSAR) model was established using SPSS software with measured rate constant (k) as dependent variable and calculated molecular descriptors as independent variables. A three-parameter model including energy of HOMO (E homo), molar heat capacity at constant volume (Cv(θ)), and the most positive net charge of hydrogen atoms (qH(+)) was selected for k prediction, with correlation coefficient R(2) = 0.878. Analyses of the model demonstrated that the Cv(θ) was the most significant factor affecting the k of chlorophenols. Variance analysis and standard t-value test were used to validate the model.

Micronized Copper Wood Preservatives: Efficacy of Ion, Nano, and Bulk Copper against the Brown Rot Fungus Rhodonia placenta

Recently introduced micronized copper (MC) formulations, consisting of a nanosized fraction of basic copper (Cu) carbonate (CuCO3·Cu(OH)2) nanoparticles (NPs), were introduced to the market for wood protection. Cu NPs may presumably be more effective against wood-destroying fungi than bulk or ionic Cu compounds. In particular, Cu- tolerant wood-destroying fungi may not recognize NPs, which may penetrate into fungal cell walls and membranes and exert their impact. The objective of this study was to assess if MC wood preservative formulations have a superior efficacy against Cu-tolerant wood-destroying fungi due to nano effects than conventional Cu biocides. After screening a range of wood-destroying fungi for their resistance to Cu, we investigated fungal growth of the Cu-tolerant fungus Rhodonia placenta in solid and liquid media and on wood treated with MC azole (MCA). In liquid cultures we evaluated the fungal response to ion, nano and bulk Cu distinguishing the ionic and particle effects by means of the Cu2+ chelator ammonium tetrathiomolybdate (TTM) and measuring fungal biomass, oxalic acid production and laccase activity of R. placenta. Our results do not support the presence of particular nano effects of MCA against R. placenta that would account for an increased antifungal efficacy, but provide evidence that attribute the main effectiveness of MCA to azoles.

Design and synthesis of metal complexes of (2E)-2-[(2E)-3-phenylprop-2-en-1-ylidene]hydrazinecarbothioamide and their photocatalytic degradation of methylene blue

The photocatalytic degradation has been considered to be an efficient process for the degradation of organic pollutants, which are present in the effluents released by industries. The photocatalytic bleaching of cationic dye methylene blue was carried out spectrometrically on irradiation of UV light using Cu(II), Ni(II), and Co(II) complexes of (2E)-2-[(2E)-3-phenylprop-2-en-1-ylidene]hydrazinecarbothioamide (HL). The effects of pH and metal ion were studied on the efficiency of the reaction. Cu(II) complex shows better catalytic activity and the highest percentage degradation (~88.8%) of methylene blue was observed at pH 12. A tentative mechanism has also been proposed for the photocatalytic degradation of methylene blue.

Stress Response and Pathogenicity of the Necrotrophic Fungal Pathogen Alternaria alternata

The production of host-selective toxins by the necrotrophic fungus Alternaria alternata is essential for the pathogenesis. A. alternata infection in citrus leaves induces rapid lipid peroxidation, accumulation of hydrogen peroxide (H2O2), and cell death. The mechanisms by which A. alternata avoids killing by reactive oxygen species (ROS) after invasion have begun to be elucidated. The ability to coordinate of signaling pathways is essential for the detoxification of cellular stresses induced by ROS and for pathogenicity in A. alternata. A low level of H2O2, produced by the NADPH oxidase (NOX) complex, modulates ROS resistance and triggers conidiation partially via regulating the redox-responsive regulators (YAP1 and SKN7) and the mitogen-activated protein (MAP) kinase (HOG1) mediated pathways, which subsequently regulate the genes required for the biosynthesis of siderophore, an iron-chelating compound. Siderophore-mediated iron acquisition plays a key role in ROS detoxification because of the requirement of iron for the activities of antioxidants (e.g., catalase and SOD). Fungal strains impaired for the ROS-detoxifying system severely reduce the virulence on susceptible citrus cultivars. This paper summarizes the current state of knowledge of signaling pathways associated with cellular responses to multidrugs, oxidative and osmotic stress, and fungicides, as well as the pathogenicity/virulence in the tangerine pathotype of A. alternata.

The NADPH oxidase-mediated production of hydrogen peroxide (H(2)O(2)) and resistance to oxidative stress in the necrotrophic pathogen Alternaria alternata of citrus

It has become increasingly apparent that the production of reactive oxygen species (ROS) by the NADPH oxidase (Nox) complex is vital for cellular differentiation and signalling in fungi. We cloned and characterized an AaNoxA gene of the necrotrophic fungus Alternaria alternata, which encodes a polypeptide analogous to mammalian gp91(phox) and fungal Noxs implicated in the generation of ROS. Genetic analysis confirmed that AaNoxA is responsible for the production of ROS. Moreover, deletion of AaNoxA in A. alternata resulted in an elevated hypersensitivity to hydrogen peroxide (H(2)O(2)), menadione, potassium superoxide (KO(2)), diamide and many ROS-generating compounds. The results implicate the involvement of AaNoxA in cellular resistance to ROS stress. The impaired phenotypes strongly resemble those previously seen for the ap1 null mutant defective in a YAP1-like transcriptional regulator and for the hog1 mutant defective in a HOG1-like mitogen-activated protein (MAP) kinase. The noxA null mutant was also hypersensitive to Nox inhibitors, nitric oxide (NO(·)) donors and NO(·) synthase inhibitors, implying a role of AaNoxA in the NO(·) signalling pathway. Expression of AaNoxA was activated by H(2)O(2), menadione, KO(2), NO(·) donors and L-arginine (a substrate for NO(·) synthase). AaNoxA may be able to sense and respond to both ROS and nitric oxide. Moreover, AaNoxA is required for normal conidiation and full fungal virulence. AaNoxA promoted the expression of the AaAP1 and AaHOG1 genes in A. alternata. Inactivation of AaNoxA greatly reduced the transcriptional activation of AaAP1 in response to ROS stress. Thus, we conclude that the regulatory functions of AaNoxA conferring ROS resistance are modulated partially through the activation of the YAP1- and HOG1 MAP kinase-mediated signalling pathways.

The SLT2 mitogen-activated protein kinase-mediated signalling pathway governs conidiation, morphogenesis, fungal virulence and production of toxin and melanin in the tangerine pathotype of Alternaria alternata

Fungi respond and adapt to different environmental stimuli via signal transduction systems. We determined the function of a yeast SLT2 mitogen-activated protein (MAP) kinase homologue (AaSLT2) in Alternaria alternata, the fungal pathogen of citrus. Analysis of the loss-of-function mutant indicated that AaSLT2 is required for the production of a host-selective toxin, and is crucial for fungal pathogenicity. Moreover, the A. alternata slt2 mutants displayed hypersensitivity to cell wall-degrading enzymes and chemicals such as Calcofluor white and Congo red. This implicates an important role of AaSLT2 in the maintenance of cell wall integrity in A. alternata. The A. alternata slt2 mutants were also hypersensitive to a heteroaromatic compound, 2-chloro-5-hydroxypyridine, and a plant growth regulator, 2,3,5-triiodobenzoic acid. Developmentally, the AaSLT2 gene product was shown to be critical for conidial formation and hyphal elongation. Compared with the wild-type, the mutants produced fewer but slightly larger conidia with less transverse septae. The mutants also accumulated lower levels of melanin and chitin. Unlike the wild-type progenitor, the A. alternata slt2 mutants produced globose, swollen hyphae that did not elongate in a straight radial direction. All defective phenotypes in the mutant were restored by transformation and expression of a wild-type copy of AaSLT2 under the control of its endogenous promoter. This study highlights an important role of the AaSLT2 MAP kinase-mediated signalling pathway, regulating diverse physiological, developmental and pathological functions, in the tangerine pathotype of A. alternata.

Decolorization of ammonium lignosulfonate with H(2)O(2)/Cu(II) heterogeneous catalyst

The potential of ammonium lignosulfonate (ALS) decolorization and degradation in aqueous solution was studied in a heterogeneous system using hydrogen peroxide and a Cu (II)-chelating ion exchanger. This was based on acrylic copolymers functionalized with N,N dimethylamino propylamine (DMAPA) as a catalyst. In order to optimize the efficiency of the system, the influence of such process parameters like H(2)O(2) concentration, pH, contact time, temperature, ALS concentration and catalyst amount were evaluated. The apparent rate constant of decolorization calculated from the absorbance data indicates that the process profiles follow pseudo-first order kinetics. Lignosulfonate degradation was furthermore studied by FTIR spectroscopy, thermogravimetric analysis and determination in phenolic compounds. The catalyst stability and reusability have also been investigated. Our experimental results clearly indicate that, under optimum conditions, the ammonium lignosulfonate solutions exhibit a total bleaching associated with degradation and significant mineralization to CO(2).

Dye house wastewater treatment through advanced oxidation process using Cu-exchanged Y zeolite: a heterogeneous catalytic approach

Catalytic wet hydrogen peroxide oxidation of an anionic dye has been explored in this study. Copper(II) complex of NN'-ethylene bis(salicylidene-aminato) (salenH2) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by Fourier transforms infra red spectroscopy, X-ray powder diffractograms, Thermo-gravimetric and differential thermal analysis and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that complete removal of color has been obtained after a period of less than 1h at 60 degrees C, 0.175M H2O2 and 0.3g l(-1) catalyst. More than 95% dye removal has been achieved using this catalyst for commercial effluent. These studies indicate that copper salen complex encapsulated in zeolite framework is a potential heterogeneous catalyst for removal of color from wastewaters.

Biocatalytic ketone reduction—a powerful tool for the production of chiral alcohols—part II: whole-cell reductions

Enzymes are able to perform reactions under mild conditions, e.g., pH and temperature, with remarkable chemo-, regio-, and stereoselectivity. Due to this feature the number of biocatalysts used in organic synthesis has rapidly increased during the last decades, especially for the production of chiral compounds. The present review highlights biotechnological processes for the production of chiral alcohols by reducing prochiral ketones with whole cells. Microbial transformations feature different characteristics in comparison to isolated enzymes. Enzymes that are used in whole-cell biotransformations are often more stable due to the presence of their natural environment inside the cell. Because reductase-catalyzed reactions are dependent on cofactors, one major task in process development is to provide an effective method for regeneration of the consumed cofactors. Many whole-cell biocatalysts offer their internal cofactor regeneration that can be used by adding cosubstrates, glucose or, in the case of cyanobacteria, simply light. In this paper, various processes carried out on laboratory and industrial scales are presented. Thereby, attention is turned to process parameters, e.g., conversion, yield, enantiomeric excess, and process strategies, e.g., the application of biphasic systems. The biocatalytic production of chiral alcohols utilizing isolated enzymes is presented in part I of this review.

The use of hydroxyl-radical-generating systems for the treatment of olive mill wastewaters

Three hydroxyl-radical producing biomimetic systems, composed of CuII, hydrogen peroxide and pyridine, glucaric or succinic acid, were able to perform decolorization of olive mill wastewaters (OMW) >85 % within 3 d combined with a significant removal of total phenols (>75 %). The systems consisting of 50 mmol/L succinic acid, 5-10 mmol/L CuSO4 and 100 mmol/L H2O2 were the most effective at OMW treatment, and led to the reduction of phenol contents to <1 % along with high decolorization (>88 %) and acceptable values of chemical oxygen demand.

Copper-ligand complex for the decolorization of synthetic dyes

The reaction system containing Cu(II), hydrogen peroxide and D-arabinono-1,4-lactone was found to be effective in the decolorization and reduction of toxicity of azo, thiazine-, triphenylmethane- and anthraquinone-based synthetic dyes. More than 85% decolorization was obtained with 100ppm Acridine Orange, Azure B, Chicago Sky Blue 6B, Crystal Violet, Evans Blue, Poly B-411, Reactive Blue 2, Reactive Blue 5, and Remazol Brilliant Blue R incubated for 24h in the presence of 10mM CuSO(4), 20mM D-arabinono-1,4-lactone and 80 mM H(2)O(2). The rate of decolorization was not affected by pH in the range of 3-9. The rapid decolorization was accompanied by a fast decomposition of H(2)O(2) in the reaction mixture and by a fast production of hydroxyl radicals.

Decolorization of synthetic dyes using a copper complex with glucaric acid

Selected azo, acridine, triphenyl methane, anthraquinone and thiazine-based dyes were decolorized using a catalytic system consisting of Cu(II)/glucaric acid/H(2)O(2). More than 90% decolorization was obtained with 100 ppm Acridine Orange, Azure B, Chicago Sky Blue, Crystal Violet, Methyl Orange, Poly B-411, Reactive Black 5, Reactive Blue 2, and Remazol Brilliant Blue R within 24 h. Seventy to eighty percent decolorization was achieved within the first 6 h. The decolorizaton was not affected by pH. The involvement of hydroxyl radicals produced in the system in the decolorization of the dye molecules was confirmed by electron spin resonance study.

Chemical synthesis, iron redox interactions and charge transfer complex formation of alkylitaconic acids from Ceriporiopsis subvermispora

In 1999, we first reported that a white rot fungus, Ceriporiopsis subvermispora produced a series of novel alkylitaconic acids (ceriporic acids). In the present paper we synthesized the metabolite, 1-nonadecene-2,3-dicarboxylic acid (ceriporic acid B) by Grignard reaction to analyze chemical properties of the alkylitaconates. Mass spectrometer (MS) and nuclear magnetic resonance (NMR) spectra of the synthetic compound was identical to those of the fungal metabolite isolated. The dicarboxylic acid inhibited autoxidation of Fe(2+) to Fe(3+) as well as reduction of Fe(3+) to Fe(2+) by the strong natural reductants, cysteine, glutathione, and ascorbic acid. The formation of charge transfer complexes (CTCs) between 1-heptadecene-2,3-dicarboxylic acid and oxidized intermediates from phenolic substrates were also observed. Thus, we herein report that the new class of lipid-related metabolites produced by C. subvermispora are potential metabolites participating in the control of iron redox reactions and CTCs formation from oxidized lignin fragments.

Lignin degrading system of white-rot fungi and its exploitation for dye decolorization

With global attention and research now focused on looking for the abatement of pollution, white-rot fungi is one of the hopes of the future. The lignin-degrading ability of these fungi have been the focus of attention for many years and have been exploited for a wide array of human benefits. This review highlights the various enzymes produced by white-rot fungi for lignin degradation, namely laccases, peroxidases, aryl alcohol oxidase, glyoxal oxidase, and pyranose oxidase. Also discussed are the various radicals and low molecular weight compounds that are being produced by white-rot fungi and its role in lignin degradation. A brief summary on the developments in research of decolorization of dyes using white-rot fungi has been made.

Decolorization of synthetic dyes by the Fenton reagent and the Cu/pyridine/H2O2 system

Representative azo, triphenylmethane, heterocyclic and polymeric synthetic dyes have been decolorized by two biological non-ezymatic systems, copper/pyridine/H2O2 and the Fenton reagent. With the former system, intensive decolorization measured after 1 h was obtained with phenol red (89%), tropaeolin 00 (58%), Evans blue (95%), eosin yellowish (84%), and Poly B-411 (92%). The rate of decolorization was not affected by pH in the range of 3-9 and increased with increasing temperature. The use of the radical scavengers thiourea and superoxide dismutase showed that hydroxyl radicals rather than superoxide anions are involved in the reaction. Omission of pyridine led to a substantial decrease in the extent of decolorization (20-50% decolorization). The use of organic peroxide instead of H2O2 resulted in slightly slower decolorization, similar values of decolorization being obtained only after a 2-h incubation. Decolorization of the dyes by the Fenton reagent was also very effective but slower than that obtained with the first system. Except for phenol red and eosin yellowish, (decolorization 8% and 52%, respectively) the dyes were decolorized up to 99% after 1-day incubation.

Formation of acyl radical in lipid peroxidation of linoleic acid by manganese-dependent peroxidase from Ceriporiopsis subvermispora and Bjerkandera adusta

Lipid peroxidation by managanese peroxidase (MnP) is reported to decompose recalcitrant polycyclic aromatic hydrocabon (PAH) and nonphenolic lignin models. To elucidate the oxidative process, linoleic acid and 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid [13(S)-HPODE] were reacted with MnPs from Ceriporiopsis subvermispora and Bjerkandera adusta and the free radicals produced were analyzed by ESR. When the MnPs were reacted with 13(S)-HPODE in the presence of Mn(II), H2O2 and tert-nitrosobutane (t-NB), the ESR spectrum contained a sharp triplet of acyl radical (aN = 0.81 mT). Formation of acyl radical was also observed in the reactions of Mn(III)-tartrate with 13(S)-HPODE and with linoleic acid, but the latter reaction occurred explosively after an induction period of around 30 min. Reactions of MnP with linoleic acid in the presence of Mn(II), H2O2 and t-NB gave no spin adducts while addition of t-NB after preincubation of linoleic acid with MnP/Mn(II)/H2O2 for 2 h gave spin adducts of carbon-centered (aN = 1.53 mT, aH = 0.21 mT) and acyl (aN = 0.81 mT) radicals. In contrast to linoleic acid, methyl linoleate and oleic acid were not peroxidized by MnP and chelated Mn(III) within a few hours, indicating that structures containing both the 1,4-pentadienyl moiety and a free carboxyl group are necessary for inducing the peroxidation in a short reaction time. These results indicate that MnP-dependent lipid peroxidation is not initiated by direct abstraction of hydrogen from the bis-allylic position during turnover but proceeds by a Mn(III)-dependent hydrogen abstraction from enols and subsequent propagation reactions involving the formation of acyl radical from lipid hydroperoxide. This finding expands the role of chelated Mn(III) from a phenol oxidant to a strong generator of free radicals from lipids and lipid hydroperoxides in lignin biodegradation.

Extracellular lipid peroxidation of selective white-rot fungus, Ceriporiopsis subvermispora

Ceriporiopsis subvermispora is capable of decomposing lignin without penetration of enzymes into wood cell walls. To elucidate the mechanism of lignolysis at a site far from enzymes, peroxidation of low molecular mass compounds produced by this fungus was analyzed. C. subvermispora produced free 9,12-octadecadienoic, 9-octadecenoic, 11-octadecenoic, hexadecanoic and octadecanoic acids, predominantly at an early stage of cultivation on wood meal cultures. In prolonged cultivation period after 2 weeks, the amount of intact fatty acids decreased with increasing organic hydroperoxide and TBARS production. These results suggest that lignin degradation by C. subvermispora is related to extracellular lipid peroxidation.