Redox silencing of the Fenton reaction system by an alkylitaconic acid, ceriporic acid B produced by a selective lignin-degrading fungus, Ceriporiopsis subvermispora

The selective lignin-degrading fungus, Ceriporiopsis subvermispora secretes alkylitaconic acids (ceriporic acids) during wood decay. We reported that ceriporic acid B (hexadecylitaconic acid) was protective against the depolymerization of cellulose by the Fenton reaction. To understand the redox silencing effects, we analyzed the physicochemical and redox properties of itaconic, octylitaconic and hexadecylitaconic acids. The initial rate of HO production by the Fenton system with Fe(3+), H(2)O(2) and L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids by 0.04 and 0.16 of the reaction rate without chelators. ESR, O(2) uptake and the assay of Fe(2+) with BPS demonstrated that Fe(3+) reduction by L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids while the reaction of Fe(2+) with H(2)O(2) was not suppressed by the two alkylitaconic acids. Ligand exchange experiments with NTA demonstrated that Fe(3+) chelation by two carboxyl groups of alkylitaconic acids is a critical step in iron redox modulation. In stark contrast, the production of HO* and reduction of Fe(3+) were not suppressed by itaconic acid due to HO*--initiated degradation of the chelator. The strong redox silencing effects by a series of alkylitaconic acids have attracted interest in controlling microbial plant cell wall degradation and chemoprotection against cellular oxidative injury.     

Alkadienyl and alkenyl itaconic acids (ceriporic acids G and H) from the selective white-rot fungus Ceriporiopsis subvermispora: a new class of metabolites initiating ligninolytic lipid peroxidation

New ceriporic acids-alkadienyl and alkenyl itaconic acids having a bis-allyl (3-[(Z,Z)-hexadec-7,10-dienyl]-itaconic acid; ceriporic acid G) and a monoene (3-[(Z)-octadec-9-enyl]-itaconic acid; ceriporic acid H) structure in their side chains-were isolated from the cultures of the selective lignin-degrading fungus Ceriporiopsis subvermispora. The new metabolites ceriporic acid G and H were synthesized by a cross-aldol condensation and a Grignard substitution reaction, respectively. Ceriporic acid G triggered the manganese peroxidase (MnP)-catalyzed lipid peroxidation and decomposed a recalcitrant non-phenolic lignin substructure model compound. Except for simple fatty acids, this is the first report of a fungal metabolite that induced ligninolytic lipid peroxidation.     

Characteristics of black zones associated with delignified wood

Several white-rot fungi cause two micromorphologically distinct types of decay. White-rot fungi typically cause a simultaneous removal of all cell wall components in close proximity to fungal hyphae. This type of degradation results in erosion troughs and holes in the cell walls. In addition, a selective removal of lignin and hemicellulose can occur intermittently throughout the decayed wood. Selectively delignified wood can be characterized by the complete removal of middle lamellae, resulting in a defibration of cells and exposure of cellulosic macrofibrils within cell walls. A common observation of decay in the field is the association of dark zones with selectively delignified wood. Swollen hyphae containing pigmented materials were commonly associated with the dark zones in wood delignified byHeterobasidion annosum, Ganoderma applanatum, G. tsugae, Ischnoderma resinosum, Perenniporia medulla-panis, orDichomitus squalens. Dark zones examined using scanning electron microscopy in conjunction with energy dispersive X-ray analysis were found to contain high concentrations of manganese. Multielement analyses using inductively coupled plasma atomic emission spectrometry indicated approximately a 50-fold increase of Mn in black zones. Pigmented substances containing Mn were readily decolorized with acids. Since large concentrations of Mn were only found in selectively delignified wood, manganese may influence the selective degradation of lignin.     

Selective delignification of wood by white-rot fungi

The white-rot fungi,Cerrena unicolor, Ganoderma applanatum, G. tsugae,Ischnoderma resinosum, andPerenniporia medullapanis, caused two distinct types of decay. Large areas of decayed wood were selectively delignified and a typical white-rot causing a simultaneous removal of all cell wall components was present. Preferential lignin degradation was intermittently dispersed throughout the decayed wood. Scanning and transmission electron microscopy were used to identify the micromorphological and ultrastructural changes that occurred in the cells during degradation. In delignified areas the compound middle lamella was extensively degraded without substantial alteration of the secondary wall. The S₂ layer of the secondary wall was least affected. The loss of middle lamellae resulted in extensive defibration of the cells. Sulfuric acid lignin determinations indicated that 95–98% of the lignin was removed. Wood sugar analyses using high pressure liquid chromatography demonstrated that hemicelluloses were removed in preference to cellulose when lignin was degraded. The results suggest that a highly diffusible ligninolytic system was responsible for the selective degradation of the wood. In simultaneously white-rotted wood, all cell wall layers were progressively removed from the cell lumen toward the middle lamella, causing erosion troughs or holes to form. Large voids filled with fungal mycelia resulted from a coalition of degraded areas. Chemical analyses of white-rotted wood indicated lignin, cellulose, and hemicellulose were removed in approximately the same amounts. Degradation was confined to areas around fungal hyphae.     

Comparison of mechanical properties of heat treated beech wood cured under nitrogen or vacuum

Heat treated wood has been subjected to increasing interest during the last decade. This non biocidal treatment is an attractive alternative with a low environmental impact to improve decay resistance of low natural durability wood species. Nowadays, several types of heat treatment processes exist. These treatments differ mainly by the nature of the inert atmosphere used to avoid combustion of wood: nitrogen, steam pressure, oil or more recently vacuum. We have shown in a previous study that utilization of vacuum to perform thermal treatment instead of nitrogen allows to reduce considerably degradation of wood polysaccharrides. Indeed, it appears that for a similar 12% mass loss generated by thermal degradation, thermodegradation performed under vacuum allowed to reduce degradation of sugar constitutive of hemicelluloses and formation of recondensation products within the wood structure. These results may be explain by the effect of vacuum allowing removal of volatile degradation products like organic acids, aldehydes and furans limiting therefore acidic degradation of polysaccharides and recondensation of volatile by-products. Decay durability tests, performed against different brown and white rots fungi, have shown no significant differences for vacuum and nitrogen heat treated samples, all presenting an improved decay resistance.     

Investigations of the reasons for fungal durability of heat-treated beech wood

It is generally accepted that thermal treatment of wood by mild pyrolysis (retification or torrefaction) improves its durability to fungal degradation. However, this property has recently been questioned in the literature and definitely needs further investigation. The increase in durability conferred by thermal treatment is generally explained by four hypotheses: the low affinity of heat-treated wood to water; the generation of toxic compounds during heating; the chemical modification of the main wood polymers and the degradation of hemicelluloses. This study was undertaken to understand the reasons for durability of heat-treated beech wood. In order to confirm or not the above mentioned hypotheses, the durability of heat-treated beech wood towards Coriolus versicolor was evaluated according to different parameters like mass loss, wettability or chemical composition. The heat treatment was carried out in a temperature range of 20-280 °C under inert atmosphere for 10 different temperatures. The results show clearly an important correlation between the temperature of treatment and the fungal durability. At the same time, there was insufficient evidence to support the hypothesis of improved decay resistance due to generation of fungicidal compounds or due to the hydrophobic character of wood. Finally, the most plausible hypothesis to explain improvement of wood durability concerns its chemical modifications. Indeed, degradation of hemicellulose associated with other chemical modifications appearing during treatment could be the origin of improved durability. There is a good correlation between decay resistance and mass loss measurements which are directly correlated to hemicellulose degradation.     

The Identification of New Triterpenoids in Eucalyptus globulus Wood

Eight polyhydroxy triterpenoid acids, hederagenin, (4α)-23-hydroxybetulinic acid, maslinic acid, corosolic acid, arjunolic acid, asiatic acid, caulophyllogenin, and madecassic acid, with 2, 3, and 4 hydroxyl substituents, were identified and quantified in the dichloromethane extract of Eucalyptus globulus wood by comparing their GC-retention time and mass spectra with standards. Two other triterpenoid acids were tentatively identified by analyzing their mass spectra, as (2α)-2-hydroxybetulinic acid and (2α,4α)-2,23-dihydroxybetulinic acid, with 2 and 3 hydroxyl substituents. Two MS detectors were used, a quadrupole ion trap (QIT) and a quadrupole mass filter (QMF). The EI fragmentation pattern of the trimethylsilylated polyhydroxy structures of these triterpenoid acids is characterized by the sequential loss of the trimethylsilylated hydroxyl groups, most of them by the retro-Diels-Alder (rDA) opening of the C ring with a π-bond at C12-C13. The rDA C-ring opening produces ions at m/z 320 (or 318) and m/z 278 (or 277, 276, 366). Sequential losses of the hydroxyl groups produce ions with m/z from [M - 90] to [M - 90*y], where y is the number of hydroxyl substituents present (from 2 to 4). Moreover, specific cleavage in ring E was observed, passing from m/z 203 to m/z 133 and conducting other major fragments such as m/z 189.     

Use of wood elemental composition to predict heat treatment intensity and decay resistance of different softwood and hardwood species

Heat treatment is an attractive alternative to improve decay resistance of low natural durability wood species. Decay resistance is strongly correlated to thermal degradations of wood cell wall components. Some recent studies proposed the use of wood elemental composition as a valuable marker to predict final properties of the material. These results, initially obtained with pine, have been extended to different softwood and hardwood species to check validity of the method using equipment specially designed to measure mass losses during thermal treatment. Heat treatment was performed on two softwood species (pine and silver fir) and three hardwood species (poplar, beech and ash) at 230 °C under nitrogen for different times to reach mass losses of 5, 10 and 15%. Heat-treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta and the weight losses due to fungal degradation determined as well as initial wood elemental composition. Correlations between weight losses recorded after fungal exposure and elemental composition indicated that carbon content and O/C ratio can be used to predict wood durability conferred by heat treatment. Moreover, it was observed that for given curing conditions thermo-degradation patterns differed considerably according to the wood species. The sole analysis of wood physical properties like its density, thermal conductivity and diffusivity cannot allow explaining the observed differences, which should also depend on thermally activated chemical processes depending on wood chemical composition.     

Prediction of the decay resistance of heat treated wood on the basis of its elemental composition

The effect of heat treatment temperature on the elemental composition of Scots pine sapwood (Pinus sylvestris) has been investigated in the range of temperatures between 220 and 250 °C. The results revealed an important increase of carbon content, while oxygen content significantly decreases. Independently of the heat treatment temperature, elemental composition is strongly correlated with the mass losses due to thermal degradations. Carbon content as well as O/C ratio seem to represent valuable markers to estimate wood degradation after heat treatment. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta and the weight losses due to fungal degradation were determined. Correlations between weight losses recorded after fungal exposure and elemental composition indicated that carbon content or O/C ratio can be used to predict wood durability conferred by heat treatment allowing us to envisage the development of a proper method to evaluate the quality of heat treated wood and predict its durability. These results also confirm that chemical modifications of wood cell wall polymers are the main factors responsible for wood durability improvement against fungal decay after heat treatment.     

Identification of ω-oxocarboxylic acids as acetal esters in aerosols using capillary gas chromatography-mass spectrometry

An homologous series of ω,ω-dimethoxycarboxylic acid methyl esters (acetal esters) has been identified in the most polar methyl ester fraction separated from remote aerosol samples by liquid chromatography. These compounds were separated by silica gel column chromatography and their structures determined by capillary gas chromatography (GC) and GC—mass spectrometry with a synthesized standard. The acetal esters are originally present in the samples as ω-oxocarboxylic acids, which are derivatized to acetal esters during treatment with boron trifluoride in methanol. This method enables the determination of ω-oxocarboxylic acids in environmental samples as their acetal esters.     

Acidogenic Digestion of Pre-pulping Extracts for Production of Fuels and Bioproducts Via Carboxylate Platform Processing

Hemicellulose extracted from wood prior to processing the wood into paper or composite materials can be a resource for the production of biofuels or bioproducts. Mixed microbial cultures are capable of converting biomass into mixed carboxylic acids, which can be purified as products or converted to biofuels or other biochemicals. Mixed cultures are robust conversion systems and do not require added enzymes to hydrolyze biomass to sugars. We produced mixed carboxylic acids using mesophilic and thermophilic fermentation of raw, unconditioned green liquor and hot water hardwood extracts, as well as baseline sugar solutions. Daily samples were taken from the fermentations and analyzed for composition, pH, and gas volume. The extract digestions were capable of hydrolyzing oligomeric hemicellulose without supplemental enzymes and converting all types of released sugars. Lactic acid was prominent in lower pH systems and acetic acid, the main product at more neutral pH. Compared to thermophilic systems, mesophilic fermentations had higher hydrolysis conversion, carbohydrate conversion, acid yields, and selectivity for C₃–C₇ acids. Carbon balances on the wood extracts closed to within ±9%. Methane production in all cases was essentially zero.     

Fragmentation and sequencing of cyclic peptides by matrix-assisted laser desorption/ionization post-source decay mass spectrometry.

A series of synthetic cyclic decapeptides and other smaller cyclic peptides were analyzed using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The investigated compounds were cyclized in a head-to-tail manner and contained non-proteinaceous amino acids, such as D-phenylalanine, D,L-4-carboxyphenylalanine, epsilon-aminocaproic acid, and gamma-aminobutyric acid, and were synthesized in a program to develop inhibitors of pp60(c-src) (Src), a tyrosine kinase that is involved in signal transduction and growth regulation. Post-source decay (PSD) spectra of the cyclic peptides featured abundant sequence ions. Two preferential ring opening reactions were detected resulting in linear fragment ions with an N-terminus of proline and a C-terminus of glutamic acid, respectively. MALDI-PSD spectra even permitted de novo sequencing of some cyclic peptides. Systematic studies on cyclic peptides using this method of fragmentation have not been reported to date. This work presents an easy mass spectrometric method, MALDI-PSD, for the characterization and identification of cyclic peptides.     

Analysis of 1,2-diols of linoleic, alpha-linolenic and arachidonic acid by gas chromatography--mass spectrometry using cyclic alkyl boronic esters

Arachidonic acid is metabolized by hepatic and renal cortical microsomes in the presence of NADPH to vicinal dihydroxyeicosatrienoic acids as some of the major metabolites. Other polyunsaturated, long-chain fatty acids might be metabolized to vicinal dihydroxy acids (1,2-diols) in the same way. To facilitate identification of 1,2-diols in biological samples, a series of unsaturated 1,2-diols were synthesized from linoleic, alpha-linolenic and arachidonic acid and the electron-ionization mass spectra of cyclic methane- and n-butaneboronic ester derivatives and of trimethylsilyl (TMS) ether derivatives were compared. The TMS ether derivatives gave rise to weak molecular ions but prominent informative fragmentation ions were formed by alpha-cleavage as well as cleavage between the carbons with the TMS ethers. The TMS ether derivative of methyl 15,16-dihydroxy-9,12-octadecadienoate had a considerably larger carbon value than the other C18 diols, while the cyclic boronates were poorly separated on gas chromatography. The methane- and n-butaneboronic acid derivatives showed strong molecular ions and a characteristic but not very informative fragmentation, although the position of the hydroxyls could be deduced from one or two fragments formed by alpha-cleavage. Linoleic and alpha-linolenic acid are metabolized in the rabbit to many polar products by hepatic and renal cortical microsomes and NADPH. 12,13-Dihydroxy-9-octadecenoic acid and other metabolites of linoleic acid were identified by gas chromatography--mass spectrometry.     

Determination of resin acids in pulp mill EOP bleaching process effluent

Resin acids are tricyclic diterpenoids which are natural constituents of the wood from conifers. They are released from the wood during the manufacture of pulp and paper. These acids are very resistant to chemical degradation and survive the pulping and also the EOP bleaching process (EOP=alkaline extraction, oxygen and peroxide, the chemicals used in the bleaching process). Resin acids were extracted from alkaline medium using liquid–liquid extraction with t-butyl methyl ether and solid phase extraction with RP C18 adsorbent and a highly porous polystyrene-divinylbenzene polymer. After conversion of the acids to their pentafluorobenzyl esters, the extracts were analysed by GC/MS using a 25 m OV17 capillary column. Recovery values for single resin acids were determined by all three extraction methods. The solid phase extraction methods were applied to the analysis of the EOP effluent from a pulp mill bleaching process. 14 different resin acids and one resin acid methyl ester have been identified in the effluent. One of these was an oxo resin acid which might well be a product of the bleaching process.     

Beech (Fagus orientalis) wood modification through the incorporation of polystyrene-ricinoleic acid copolymer with Ag nanoparticles

Today, there is a growing interest in eco-friendly processes that are greatly needed as a result of the worldwide problem of environmental pollution. In this study, ricinoleic acid was autoxidized in the presence of silver nitrate in order to prepare ricinoleic acid macroperoxide initiator with silver nanoparticles (PriciAg). Beech (Fagus orientalis Lipsky) sapwood samples were impregnated with the solution of PriciAg under vacuum in a small-scale impregnation container. Thermal polymerization of styrene with PriciAg was carried out inside the Beech sapwood samples leading to wood composite material containing polystyrene-g-ricinoleic acid with silver nanoparticles (Ag NPs). The decay test of wood treated with AgNPs against white-rot (Trametes versicolor) fungus was then investigated. Insect resistance was performed with Trichoferus holosericeus Rossi. In addition, the leaching test was carried out according to the EN 84 standard and silver content in leached water measured by inductively coupled plasma (ICP) analysis (AWPA A7). Chemical characterization of the modified wood was characterized using FTIR-ATR technique. The nano silver obtained via environmentally friendly processes exhibited high potential activity against white rot fungus. In addition, the AgNPs showed a higher resistance to leaching because of the polystyrene, as demonstrated by the resistance of treated samples to decay compared with that of the control. Leached and unleached test samples indicated the same mass loss after decay tests. FTIR spectra showed that characteristic peak values of polystyrene and ricinoleic acid appeared at 2980 cm^?1and 1728 cm^?1, respectively in the impregnated wood.

Graphical abstract

     

Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry

Several triacylglycerol (TAG) molecular species, that contain two short-chain fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol backbone, were isolated from bovine udder by using solvent extraction and silica gel column chromatography. Their structures were identified by fast atom bombardment (FAB) tandem mass spectrometry (MS/MS), based on the information obtained from collision-induced dissociation (CID) spectra of sodium-adducted molecules ([M + Na](+)) of model TAG compounds which had been synthesized from glycerol and appropriate fatty acids. For each species, the relative positions of the three fatty acids on the glycerol backbone, as well as fatty acid composition and double-bond position in the fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FAB mass spectrum were mixtures of at least two components that have different fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatty acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position.     

A gas chromatographic study of the residual contents of a medieval sphero-conical vessel

Black deposit was discovered on the inner wall of a sphero-conical vessel found during archaeological excavations on the territory of the Volga Bulgars. Compounds from the deposit were extracted with organic solvents and studied by gas chromatography with flame ionization and mass spectrometry detectors. Abietic acid derivatives, including retene, present in the composition of soft wood turpentine were identified. The relatively high retene concentration in the remains of the spherocone and also the presence of other polycyclic aromatic hydrocarbons suggest the thermal version of their origin. Probably, the vessel was used as a part of alambik, which is an ancient distillation apparatus for the distillation of soft wood turpentine.     

“Osmiophilic particles”—a fungal agent with characteristic distribution in white-and brown-rotted wood

When pine wood decayed by white- and brown-rot fungi was observed in TEM after fixation and staining with glutaraldehyde/osmium tetroxide/ uranylacetate and embedding in Spurr’s ultralow viscosity resin electron dense particles, called “osmiophilic particles,” a typical distribution for the two decay types could be observed: in white-rotted wood the particles could be found in and around the hyphae and on the lumen surface of the wood cell wall, mostly aggregated to thick clusters. During the whole course of decay the wood cell walls were free of the particles, but they were present on the corroded surfaces. In brown-rotted wood the “osmiophilic particles” also could be found in and around the hyphae, but in contrast the particles were distributed over all the wood cell wall layers from the early to late stages of decay. The distribution of the “osmiophilic particles” coincides with the place where the major cell wall degradation takes place: in white-rot the cell walls are degraded from the lumen to the middle lamella; in brown-rot a depolymerization and degradation of the carbohydrates takes place all over the wood cell wall. Since the “osmiophilic particles” can be found where the degradation takes place, it can be concluded that they are causally connected with wood decay. The fact that they also were found in, and some of them also around, hyphae grown on malt-agar or Sabouraud-dextrose-agar proves that they are produced by the fungi and cannot be degradation products. The possibility that they could be preparative artifacts can be excluded because uncolonized wood was free of “osmiophilic particles.” Since the “osmiophilic particles” are produced by the fungi and can be found in places where wood is decaying, it can be further concluded that they are a fungal agent that is involved in wood degradation, probably fungal enzymes. The observation that the large “osmiophilic particles,” which may have a size of up to 20 nm, are composed of globular subunits of a diameter of 2—3 nm also speaks for their enzymatic nature. To find out which type of enzyme they might be, the white-rot fungusTrametes hirsuta was grown on wood pulp with 7% lignin, on delignified wood pulp containing cellulose and hemicellulose, and on filterpaper (pure cellulose). The hyphae on wood pulp containing 7% lignin were surrounded by thick sheaths of “osmiophilic particles,” whereas with the hyphae grown on delignified wood pulp and pure cellulose only a few particles could be found. This makes it clear that the production of the “osmiophilic particles” is induced by lignin.     

Identification of Abnormal Urinary Organic Acids in Inherited Metabolic Diseases by Gas Chromatography-Mass Spectrometry

A gas chromatography/mass spectrometry (GC/MS) coupled system has been established for the confirmatory identification of abnormal urinary organic acids in inherited metabolic diseases. Samples of patient urines were extracted with an organic solvent and trimethylsilylated (TMS). A mass spectra of gas chromatographically separated TMS derivatives can be obtained using the GC/MS coupled system with a single analytical run. Those compounds with close methylene units (e.g., 4-hydroxyphenylacetaic acid and phenylpyruvic acid) in the gas chromatograph can be identified by their specific mass spectra. The results indicate that this GC/MS system is a powerful method for identifying abnormal urinary organic acids. These acids can be identified by comparison with authentic mass spectra established in our laboratories or with mass spectra files from other sources or they can be directly identified by analysis of the mass spectrum. By using this system, we were able to make positive identification of several inherited metabolic diseases found in Chinese patients, including phenylketonuria, propionic acidemia, and methylmalonic aciduria. This GC/MS system is a powerful tool for the diagnosis of inherited metabolic diseases.     

On-line product analysis of pine wood pyrolysis using synchrotron vacuum ultraviolet photoionization mass spectrometry

The pyrolysis process of pine wood, a promising biofuel feedstock, has been studied with tunable synchrotron vacuum ultraviolet photoionization mass spectrometry. The mass spectra at different photon energies and temperatures as well as time-dependent profiles of several selected species during pine wood pyrolysis process were measured. Based on the relative contents of three lignin subunits, the data indicate that pine wood is typical of softwood. As pyrolysis temperature increased from 300 to 700 °C, some more details of pyrolysis chemistry were observed, including the decrease of oxygen content in high molecular weight species, the observation of high molecular weight products from cellulose chain and lignin polymer, and potential pyrolysis mechanisms for some key species. The formation of polycyclic aromatic hydrocarbons (PAHs) was also observed, as well as three series of pyrolysis products derived from PAHs with mass difference of 14 amu. The time-dependent profiles show that the earliest products are formed from lignin, followed by hemicellulose products, and then species from cellulose.