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Emissions of trace gases (carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC)), and volatile organic compounds (VOCs) from combustion of European beech, Pyrenean oak and black poplar in a domestic woodstove and fireplace were studied. These woods are widely used as biofuel in residential combustion in Southern and mid-European countries. VOCs in the flue gases were collected in Tedlar bags, concentrated in sorbent tubes and analysed by thermal desorption-gas chromatography flame ionisation detection (GC FID). CO2 emissions ranged from 1415 +/- 136 to 1879 +/- 29 g kg(-1) (dry basis). The highest emission factors for CO and THC, 115.8 +/- 11.7 and 95.6 24.7 +/- 6.3 g kg(-1) (dry basis), respectively, were obtained during the combustion of black poplar in the fireplace. European beech presented the lowest CO and THC emission factors for both burning appliances. Significant differences in emissions of VOCs were observed among wood species burnt and combustion devices. In general the highest emission factors were obtained from the combustion of Pyrenean oak in the woodstove. Among the VOCs identified, benzene and related compounds were always the most abundant group, followed by oxygenated compounds and aliphatic hydrocarbons. The amount and the composition of emitted VOCs were strongly affected by the wood composition, the type of burning device and operating conditions. Emission data obtained in this work are useful for modelling the impact of residential wood combustion on air quality and tropospheric ozone formation. (C) 2013 Elsevier Ltd. All rights reserved.

The polyoxometalate (POM)-laccase catalytic system was applied for the first time to aerobic delignification of kraft pulps at moderate (40-60 degreesC) temperatures. Laccase was found to readily catalyze the re-oxidation of different kinds of polyoxometalates, including those, which cannot be re-oxidized by dioxygen even at high temperatures (PMo11V1, SiW11V1. etc.). This allows a sequence of catalytic redox cycles similar to that in the laccase-mediator system (LMS) where electrons are transferred from the substrate (lignin) via POM and laccase to oxygen. Results obtained showed that the POM-laccase system could decrease kappa number of eucalypt kraft pulp from 13.7 to 8.5 though the reaction rate is relatively slow. Among different POM used, SiW11V showed the best results. The effect of the process variables on the delignification was studied. The best results in delignification of eucalypt pulp were obtained at 60 degreesC, oxygen pressure of 5 bar, pH 6.3, SiW11V concentration of 4.2 mM and laccase concentration of 0.65 U/ml. The reaction temperature appears to be one of the crucial factors in the achievement of a delignification rate acceptable for practical application. (C) 2001 Elsevier Science B.V. All rights reserved.

Summary Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo7V5O40]8− (HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O2/HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO2 + ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O2/HPA-5 was estimated by electrochemical methods using various lignin model compounds.

The degradation reactions of cellulose under conditions of dioxygen oxidation in acidic aqueous and organic solvent–water medium in the presence of molybdovanadophosphate heteropolyanions of series [PMo(12−n)VnO40](3+n)− have been investigated. The medium acidity and the heteropolyanions action were found to be the factors causing cellulose chain scission by solvolytic and oxidative degradation reactions, respectively. The cellulose oxidative depolymerisation was associated mainly with the action of VO2+ ions released from heteropolyanions via their partial dissociation under acidic conditions. The scheme reflecting the main pathways of cellulose degradation in the reaction system dioxygen/heteropolyanions is proposed. The effect of the medium ionic strength on cellulose depolymerisation is discussed in the context of possibilities to minimise the negative action of medium acidity and of VO2+ ions on cellulose.

Summary The behaviour of lignin in wood delignification by oxygen in acidic media in the presence of the molybdovanadophosphate heteropolyanion [PMO7V5O40]8−as studied using wet chemistry methods, solid and liquid state 13C NMR spectroscopy. Lignin is oxidised by [PMO7V5O40]8− almost completely to carbon dioxide, with a minor yield of intermediate low-molecular weight aromatic products. The analysis of the reaction products shows that the lignin acidolysis and homolysis involving the oxygen participation in oxidation take place. The residual lignin in the wood residue is more “condensed” and richer in guaiacyl structural units than that in the initial wood. The analysis of “condensed” structures issued from permanganate oxidation of residual lignins suggests that these are formed predominantly by acid-catalysed reactions. The use of an organic solvent, such as ethanol, in the pulping solution favours the oxidative delignification, protecting the lignin against competing reactions (condensation).

The lignin oxidative degradation in the reaction system [PMo 7 V 5 O 40 ] 8− /O 2 has been studied using guaiacyl and syringyl β-aryl ether dimeric lignin model compounds. The oxidation has been monitored by GC/MS and ESI/MS. Although the free phenolic and non-phenolic model compounds were both degraded under aerobic oxidation with [PMo 7 V 5 O 40 ] 8− , the reaction mechanisms involved are different. Oxidation routes leading to the cleavage of β-O-4 bonds have been proposed.

Oxygen-organosolv lignins, isolated from spent liquors after delignification of wood in different acidic organic solvent–water media, were used as unmodified macromonomers in conjuction with an oligoethyleneoxide di-isocyanate. This led to crosslinked elastomeric polyurethanes which were thoroughly characterized. It was found that the nature of the organic solvent used for the organosolv pulping had an influence on the reactivity of the isolated lignins towards the di-isocyanate because of the variation in the amount of alcoholic groups caused by reactions with solvent molecules during the delignification.

The catalytic effect of molybdovanadophosphate heteropolyanions (HPAs) on the delignification of wood by oxygen has been investigated. The VO2+ ions produced via the dissociation of HPA in acidic conditions are suggested to have a much stronger catalytic effect on the oxidation of lignin than parent HPA. The influence on delignification of the pH, medium composition and the partial reduction of HPA prior to its use in catalysis are discussed in terms of the reaction mechanisms. Kinetic studies show that the catalyst diffusion in the wood tissue is the rate-limiting step of delignification, while the lignin oxidation rate is determined by the HPA/VO2+ catalytic oxidation step.

Arundo donax plants were manually separated into fractions of different morphological regions (internodes, nodes and foliage) at different stages of maturity and submitted to chemical composition studies. General chemical composition was determined by established methods. The polysaccharides were fractionated by successive extractions of holocellulose with aqueous KOH solutions. The sugar composition was determined by hydrolysis of polysaccharides followed by GC analysis of neutral sugars as alditol acetates and spectrophotometric determination of uronic acids. In situ lignins, milled wood lignins (MWL) and dioxane lignin were characterised by permanganate oxidation followed by GC and GC-MS analysis of the methylated oxidation products and by quantitative 13C NMR spectroscopy. The results of general chemical analysis evidenced the different relative abundance of holocellulose, lignin, proteins, extractives and ashes in internodes, nodes and foliage, at different stages of maturity. In internodes, nodes and foliage about 70–80% of hemicelluloses (21–30% o.d. material) were easily extracted with 5% KOH aqueous solutions. The analysis of hemicelluloses indicated that they are constituted mainly by arabinoglucuronoxylans with a xylose:arabinose:uronic acid ratio of 91–93:5–7:2 for internodes. The high content of xylose in Arundo donax stem (24–27% o.d. material) and the easy extraction of hemicelluloses opens new perspectives for the use of this reed as a source of pentosans. The results obtained by the permanganate oxidation method indicated that Arundo donax lignins are essentially H-G-type with approximate H:G:S proportions of (32–36):(59–61):(5–8) in internodes. The H units are constituted mainly by esterified p-coumaric acid. These results were confirmed by quantitative 13C NMR spectroscopy of isolated dioxane lignin. The quantity of condensed structures in in situ lignin decreases from the older to the younger parts of the stems and is much higher in nodes than internodes.

Spruce wood (Picea abies) has been subjected to delignification by oxygen under acidic conditions using different solvent media. The residual and removed lignins were submitted to permanganate oxidation and the products analyzed by GC and GC-MS. Results from the analysis of the residual lignins indicate that lignin “condensation” depends on the nature of oxidation medium. It was found that the addition of acetone to the aqueous liquor decreases both acid catalyzed and radical side reactions. Lignin “condensation” in water containing media is dominated by radical reactions. Results from the analysis of the lignin removed during oxygen delignification in an acetone/water medium indicate that significant amounts of “condensed” structures are present, which are relatively stable towards oxidation. The presence of diphenylmethane, diarylether and biphenyl type structures in the removed lignin was confirmed by CP-MAS 13C NMR spectroscopy.

The oxidation of α-(1 → 5)-L-arabinotriose (Ara3), an oligosaccharide structurally related to side chains of coffee arabinogalactans, was studied in reaction with hydroxyl radicals generated under conditions of Fenton reaction (Fe(2+)/H2O2). The acidic and neutral oxidation products were separated by ligand exchange/size-exclusion chromatography, subsequently identified by electrospray ionisation mass spectrometry (ESI-MS) and structurally characterised by tandem MS (ESI-MS/MS). In acidic fraction were identified several oxidation products containing an acidic residue at the corresponding reducing end of Ara3, namely arabinonic acid, and erythronic, glyceric and glycolic acids formed by oxidative scission of the furanose ring. In neutral fractions were identified derivatives containing keto, hydroxy and hydroperoxy moieties, as well as derivatives resulting from the ring scission at the reducing end of Ara3. In both acidic and neutral fractions, beyond the trisaccharide derivatives, the corresponding di- and monosaccharide derivatives were identified indicating the occurrence of oxidative depolymerisation. The structural characterisation of these oxidation products by ESI-MS/MS allowed the differentiation of isobaric and isomeric species of acidic and neutral character. The species identified in this study may help in detection of roasting products associated with the free radical-mediated oxidation of coffee arabinogalactans.

An approach for the integrated utilization of grape skins from white grape pomaces has been proposed. This consists of consecutive or simultaneous extraction of grape skins with neutral organic solvent and water under reflux. Organic extract is a valuable raw material for the isolation of oleanolic acid. The aqueous extract (ca 50%, w/w) is composed of essentially hexoses and suitable for the high yield (till 51%) bioethanol production at a maximum specific cell growth rate (mu(max)) of 0.29 h(-1). The remained extracted grape skins are the complex of structural polysaccharides embedded into cutinous matrix. Extracted grape skins were shown to be a prospective raw material for the production of low-density boards (d

Cellulose/silica derived hybrids materials (CSH), functionalized with aluminium, calcium, and propylammonium ions, were tested for their possible use in the removal of arsenic from aqueous solutions with controlled compositions to levels lower than 10 μg As/L. CSH were synthesized by sol-gel method using bleached pulp, as source of cellulose fiber, and tetraethoxysilane (TEOS) as main silica precursor. The silica network, made in situ, contained various anchored cations such as propylammonium (CSH-PA), aluminium (CSH-Al) and, calcium (CSH-Ca). Thin films or mesoparticles of silica were deposited on cellulose fibers as shown by SEM and XRD. These hybrid materials were immersed in controlled ionic strength aqueous solutions with arsenic concentrations lower than 0.2 mg As/L. The best performance was shown by CSH-PA that was able to remove a maximum of 20 % of the total arsenic concentration.

Hardwood and softwood lignins obtained from industrial sulphite and kraft and laboratory oxygen-organosolv pulping processes were employed in co-polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol). The obtained lignin-based polyurethanes were doped with 0.72 w/w% of multiwall carbon nanotubes (MWCNTs) with the aim of increasing their electrical conductivity to the levels suitable for sensor applications. Effects of the polymer doping with MWCNTs were assessed using electrical impedance (EIS) and UV-Resonance Raman (UV-RR) spectroscopy. Potentiometric sensors were prepared by drop casting of liquid polymer on the surface of carbon glass or platinum electrodes. Lignin-based sensors displayed a very low or no sensitivity to all alkali, alkali-earth and transition metal cations ions except Cr(VI) at pH 2. Response to Cr(VI) values of 39, 50 and 53 mV pX(-1) for the sensors based on kraft, organosolv and lignosulphonate lignins, respectively, were observed. Redox sensitivity values close to the theoretical values of 20 and 21 mV pX(-1) for organosolv and lignosulphonate based sensors respectively were detected in the Cr(III)/Cr(VI) solutions while a very low response was observed in the solutions containing Fe(CN)(6)(3-)/(4-). Conducting composite lignin-based polyurethanes doped with MWCNTs were suggested as being promising materials for Cr(VI)-sensitive potentiometric sensors.

Different morphological regions of Hibiscus cannabinus plants grown in Portugal were submitted to chemical composition studies. General chemical composition was determined by established methods. The polysaccharides were fractionated by successive extractions of holocellulose with aqueous KOH solutions. The sugar composition was determined by hydrolysis of polysaccharides followed by gas chromatography (GC) analysis of neutral sugars and spectrophotometric determination of uronic acids. In situ lignins and milled wood lignins (MWL) were characterised by permanganate oxidation followed by GC and GC-MS (mass spectrometry) analysis of the methylated oxidation products. The results of general chemical analysis have evidenced the different relative abundance of holocellulose, lignin, proteins, extractives and ashes in bark, core and foliage, at different stages of maturity. About 70–80% of the core hemicelluloses (about 20% o.d. material) was easily extracted with 5% KOH aqueous solutions against 60–70% (about 15% o.d. material) for the hemicelluloses of the bark. This hemicellulose fraction was composed mainly by glucuronoxylans with high content of uronic acids (xylose: uronic acid: 3–5: 1 for bark and 5–10: 1 for core). The hemicellulose fraction extracted with 24% KOH aqueous solutions was composed mainly by glucuronoxylans (80–90%) and glucomannans (10–15%). The results obtained by the permanganate oxidation method indicated that kenaf lignins are H-G-S type with approximate H: G: S molar proportions of (9–13): (55–60): (27–34) in bark and (14–20): (57)-(74): (12–23) in core, which evidences a high content of H and G units and a relatively low content of S units when compared with traditional dicotyledons. The relative proportion of H, G and S units as well as the structural features of lignins depends on the stage of maturity and on the morphological region of the plant. Kenaf lignins present a lower degree of condensation when compared with traditional wood lignins.

The structural characterization of unknown oligosaccharides remains a big challenge since a large number of isomeric structures are possible even for disaccharides. In this work, electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) was used for the differentiation of isomeric pentose disaccharides, α-(1 → 5)-L-arabinobiose (Ara(2)) and β-(1 → 4)-D-xylobiose (Xyl(2)).ESI-MS/MS spectra of [M + Li](+) and [M + Na](+) ions of Ara(2) and Xyl(2), as well as these precursor ions of (18)O-labelled disaccharides, were acquired using two mass spectrometers equipped with different analyzers: LIT (linear ion trap) and Q-TOF (quadrupole time-of-flight).Product ions observed in MS/MS spectra arise from the cleavage at the nonreducing side of the glycosidic bond (Y(1)(+)) and from cross-ring cleavages (0,1)A(2)(+), (0,2)A(2)(+), and (0,3)A(2)(+) at the reducing residue. Statistically significant differences were observed between the relative abundance of specific product ions, when comparing both disaccharides. These differences allowed discriminant models to be built and to propose a criterion using the relative abundances of selected ions capable of discriminating between the isomers for both adduct ions and spectrometers.Isomeric pentose disaccharides can be distinguished based on the fragmentation of both [M + Li](+) and [M + Na](+) ions and using different mass spectrometers. However, LIT instrument has a better discriminant power.

The world is facing a reduction of global fossil fuels resources, like petroleum, natural gas, or charcoal, while energy requirements are progressively growing up. Fossil fuels should be replaced, at least partially, by biofuels once the current fuel supply is suspected to be unsustainable in the foreseen future. In fact, the search for sustainable alternatives to produce fuel and chemicals from non-fossil feedstocks has attracted considerable interest around the world, to face the needs of energy supply and to response to climate change issues. Alternative resources of energy are being explored in order to reduce oil dependence and increase energy production by exploring of solar, wind, hydraulic and other natural phenomena. Besides these sources of energy, also biomass possesses a potential target for fuel and power production as well as for chemicals or materials feedstocks. Thus biomass can efficiently replace petroleum-based fuels for a long term. (Sanchez et al. 2008; AlvaradoMorales et al. 2009; Brehmer et al. 2009; Gonzalez-Garcia et al. 2009; Singhania et al. 2009; Mussatto et al. 2010; Sannigrahi et al. 2010). Many countries in Europe, North and South America and Asia are replacing fossil fuels by biomass-based fuels according to international regulations. One of the directives of European Union (2009/28/CE) imposes a quota of 10% for biofuels on all traffic fuel until 2020 (Rutz et al. 2008; Xavier et al. 2010). Also economic incentives for research on biofuels are being implemented all over the world. Bioethanol can be produced from different raw materials containing simple sugars, starch or more complex substrates as lignocellulosics. New methodologies for biofuels (e.g. ethanol and biodiesel) production have been developed in the last years, to achieve new and non cost-intensive technologies for bioconversion of lignocellulosic renewable resources. The most common renewable fuel is ethanol, which is produced from direct fermentation of sugars (e.g. from sucrose of sugarcane or sugar beet) or polysaccharides (e.g. starch from corn and wheat grains) (Gonzalez-Garcia et al. 2009; Mussatto et al. 2010). The selection of the best raw material is strongly dependent on the local conditions where feedstock is obtained. Evidently, ethanol in Brazil is produced from sugarcane, whereas, in North America or Europe the ethanol industry is based on starchy materials. Besides, energy considerations should be attained: not only the energy input required for ethanol production and the content in fermentable

Sulphite spent liquor (SSL) is a side product from acidic sulphite pulping of wood, which organic counterpart is composed mainly by lignosulphonates (LS) and sugars. The last are a prominent substrate for the bioprocessing although a previous purification step is necessary to eliminate microbial inhibitors. In this study a fractionation of hardwood SSL (HSSL) has been accomplished employing ion exchange resins in order to separate sugars fraction from concomitant inhibitors: LS, acetic acid, furan derivatives, phenolics, acetic acid and excess of inorganic salts. The fractionation of HSSL has been carried out using two fixed-bed ion exchangers in series (cationic+anionic). The first cation exchange column packed with Dowex 50WX2 resin was able to eliminate free cations and partially separate sugars from high molecular weight LS and furan derivatives. The second anion exchange column packed with Amberlite IRA-96 sorbed remaining LS, phenolics and acetic acid. Overall, the series arrangement under investigation has removed 99.99% of Mg(2+), 99.0% of Ca(2+), 99.6% of LS, and 100% of acetic acid, whereas the yield of recovered sugars was at least 72% of their total amount in HSSL.

The main structural polysaccharides of grape stalks are cellulose, heteroxylan, and glucan. Cellulose contributes 30.3% of grape stalk matter and has an unusually high degree of the crystallinity (75.4%). Among hemicelluloses, xylan was the most abundant one, contributing ∼12% to the weight. The heteroxylan was isolated from the corresponding peracetic holocellulose by DMSO extraction followed by precipitation in ethanol. The Mw of heteroxylan (19.0kDa) was assessed by size exclusion chromatography (SEC) and the structure was inferred by methanolysis and methylation linkage analysis, as well as 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The heteroxylan is a partially acetylated (DS=0.49) glucuronoxylan possessing the main backbone composed by β-(1→4)-linked d-xylopyranosyl units ramified with α-(1→2)-linked 4-O-methyl-α-d-glucuronosyl residues (MeGlcpA) at a molar ratio 25:1. The isolated heteroxylan contained concomitant β-glucan (ca. 15%), whose structure was elucidated by methylation linkage analysis and by NMR spectroscopy. The results obtained revealed mixed β-(1→3; 1→4)-d-glucan with a molar ratio of β-(1→3)- to β-(1→4)-linked glucopyranosyl units of 1:2. info:eu-repo/semantics/publishedVersion

Electrochemical impedance spectroscopy was applied to the study of conducting lignin-derived polymers to be used in all-solid-state potentiometric chemical sensors. Conducting polymers were produced by step-growth polymerization of modified eucalyptus kraft lignin with isocyanate and doped by multi-wall carbon nanotubes (MWCNTs). Lignin possesses ion-exchange properties due to the presence of a variety of functional groups, which makes it an attractive active substance for chemical sensing. Co-polymerization allows fixing lignin inside polymer matrix ensuring high stability of the resulting material. Doping of the lignin-based polyurethane with multi-wall carbon nanotubes (MWCNTs) was adopted as a mean to obtain electrically conductive system with low mass of filler. The direct current (DC) electrical conductivity and the dielectric properties of the conducting polymers have been evaluated at MWCNTs contents from 0 to 0.72% (wt.) at the frequencies between 40 Hz and 100 MHz in the temperature range −100 to 100 °C. The percolation model theory was used to describe DC and the low frequency behaviour, where the electrical conductivity and the dielectric constant were expressed by scaling laws near the threshold conduction. The lignin-based polyurethane presented low critical concentration of MWCNTs around 0.18 wt.%. The dielectric analysis was carried out using the modulus formalism and the dielectric relaxation behaviour was modelled using the Cole–Cole expression.

Kraft lignin (KL) from industrial pulping of E. globulus wood was subjected to the oxidative modification with the aim to produce sorbent mimicking humic matter for the bioremediation purposes. Lignin was oxidized by polyoxometalate Na(5)[PMo(10)V(2)O(40)] (POM), solely or in the presence of laccase, under pre-selected aerobic conditions (50-60°C, 1-2h, oxygen pressure 5 bar). The most pronounced lignin oxidation without its depolymerisation was observed in the reaction system POM/O(2). Modified lignins possessed increased amounts of COOH (up to 15 %) and CO (up to 500 %) groups, when compared to unmodified KL, and significantly higher molecular weights. Sorption capacity of KL before and after modification towards transition metals (cadmium (II) and mercury (II)) and triazine pesticide (atrazine) was assessed in batch experiments under equilibrium conditions. KL oxidation improved sorption capacity towards transition metals (up to 15 %) but not necessarily the uptake of atrazine that was higher for unmodified KL.

The chemical composition and the structure of macromolecular components of grape stalks from red grape pomaces have been evaluated. These are composed mainly of cellulose (30.3%), hemicelluloses (21.0%), lignin (17.4%), tannins (15.9%) and proteins (6.1%). Among hemicelluloses the xylan was the most abundant (ca. 12%). The parameters of cellulose unitary cell, average diameter of nanofibrils and the degree of crystallinity (75.4%) were assessed by X-ray scattering analysis. The xylan was partially acetylated glucuronoxylan (DS=0.49) possessing the Xylp:MeGlcpA ratio of 25:1. The lignin of grape stalks was suggested to be of HGS type with H:G:S molar proportion of 3:71:26 as revealed by analysis of nitrobenzene oxidation products. Among alkali soluble condensed tannins procyanidins prevailed over prodelphinidins. The abnormal response of grape stalks to kraft pulping, leading to poorly delignified fibrous material, was attributed to a particular lignin structure and it structural association with other macromolecular components of grape stalks. info:eu-repo/semantics/publishedVersion

The effect of high pressure (HP) pre-treatments on the subsequent enzymatic hydrolysis of cellulose from bleached kraft Eucalyptus globulus pulp by cellulase from Tricoderma viride was evaluated. Pressure pre-treatments of 300 and 400 MPa during 5–45 min, lead to both an increased rate and degree of hydrolysis, reaching values ranging from 1.5- to 1.9-fold, quantified by the formation of reducing sugars. Both the pressure and time under pressure influenced the enzymatic hydrosability of the cellulosic pulps, with the former being more important. The results indicate that the pressure pre-treatments promoted an increased accessibility of cellulose towards cellulase in the cell wall. The results obtained open promising possibilities, to contribute to overcome conventional limitations of enzymatic cellulose hydrolysis for the production of fermentable glucose, for the production of second generation bioethanol and chemicals by enhancement of both rate and yield of hydrolysis. The results are also of interest for the preparation of “pressure engineered” celullose with incremented tailored hydrolysis patterns.

The fermentation of reducing sugars from hardwood (eucalypt) spent sulphite liquor (HSSL) into ethanol by Pichia ( Scheffersomyces ) stipitis is hindered by concomitant inhibitors of microbial metabolism. The conditions for the HSSL biological treatment step by Paecilomyces variotii were evaluated and optimised. Two different strategies of reactor operation were compared using single batch (B) and sequential batch reactor (SBR). Biological treatment of HSSL in the SBR revealed the best results with respect to the removal of microbial inhibitors. Also, most of inhibitory compounds, acetic acid, gallic acid, pyrogallol, amongst others, were removed from HSSL by P. variotii before the ethanol fermentation. The bio-detoxified HSSL was subjected to a successful fermentation by P. stipitis , attaining a maximum ethanol concentration of 2.4 g L −1 with a yield of 0.24 g ethanol g sugars −1 .

Wheat straw was submitted to a pre-treatment by the basidiomycetous fungi Euc-1 and Irpex lacteus, aiming to improve the accessibility of cellulose towards enzymatic hydrolysis via previous selective bio-delignification. This allowed the increase of substrate saccharification nearly four and three times while applying the basidiomycetes Euc-1 and I. lacteus, respectively. The cellulose/lignin ratio increased from 2.7 in the untreated wheat straw to 5.9 and 4.6 after the bio-treatment by the basidiomycetes Euc-1 and I. lacteus, respectively, thus evidencing the highly selective lignin biodegradation. The enzymatic profile of both fungi upon bio-treatment of wheat straw have been assessed including laccase, manganese-dependent peroxidase, lignin peroxidase, carboxymethylcellulase, xylanase, avicelase and feruloyl esterase activities. The difference in efficiency and selectivity of delignification within the two fungi treatments was interpreted in terms of specific lignolytic enzyme profiles and moderate xylanase and cellulolytic activities.

Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, 41080-Seville, Spain and CICECO and University of Aveiro, Department of Chemistry,3810-193 Aveiro, Portugal E-mail address: gisela@irnase.csic.es (G. Marques), The heteroxylan from sisal (Agave sisalana), an O-acetyl-(4-O-methylglucurono)xylan with a molecular weight (Mw) of 18 kDa, was isolated by extraction of peracetic holocellulose with Me2SO and thoroughly characterized by wet chemistry, and NMR spectroscopy. The heteroxylan backbone is composed of (1→4)-linked β-D-xylopyranosyl units (Xylp) partially branched with terminal (1→2)-linked 4-O-methyl-α-D-glucuronosyl (MeGlcpA, 9%mol.) and a small proportion of α-D-glucuronosyl (GlcpA, This study has been supported by the Spanish Projects AGL2005-01748 and AGL2008-00709 and the EU BIORENEW project (NMP2-CT-2006-26456). We thank CELESA (Tortosa, Spain) for providing the samples. G.M. thanks the Spanish Ministry of Education for a FPI fellowship.

Dioxane lignins from two fractions of banana plant ‘Dwarf Cavendish’ stalk (floral stalk (DL FS ) and rachis (DL R )) were structurally characterized by a set of spectroscopic (Ultraviolet (UV), FTIR, solid- and liquid-state NMR) and chemical degradation (permanganate (PO) and nitrobenzene oxidation (NO)) techniques. Despite both lignins are of HGS-type, strong structural differences were observed between them. Thus, DL FS showed almost twice the abundance of H and G units and almost half of the abundance of S units when compared to DL R . DL R possessed significantly higher amount of β- O -4′ structures (0.32/C 6 against 0.12/C 6 ) and the molecular weight (5400 Da against 3750 Da) than those of DL FS . About 72% of the condensed structures in DL FS are of β-5 and 5–5′ types, whereas 4- O -5′-diaryl ether structures were the most abundant condensed structures in DL R . Most of H units in both lignins are terminal phenolic coumarates linked to lignin substructures by ester bonds. Both lignins are structurally associated with suberin-like components in cell wall tissues. Structural features of stalk lignin were discussed in terms of possible restrictions for the kraft pulping of integral stem material.

The heteroxylan from the hybrid Paulownia elongata / Paulownia fortunei is an O -acetyl-(4- O -methylglucurono)xylan with an acetylation degree (DS) of 0.59 and a molecular weight ( M w ) of 29 kDa. The heteroxylan backbone is composed by (1→4)-linked β- d -xylopyranosyl units (Xyl p ) partially ramified with terminal (1→2)-linked 4- O -methyl-α- d -glucuronosyl (MeGlc p A) and a small proportion of α- d -glucuronosyl (Glc p A) residues in a molar ratio of Xyl p :(MeGlc p A+Glc p A) of 20:1. Roughly half of the β- d -xylopyranosyl units in the backbone are acetylated: 3-O-acetylated (22 mol %), 2-O-acetylated (23 mol %) or 2,3-di-O-acetylated (7 mol %). ESI-MS and MALDI-MS studies of partially hydrolyzed heteroxylan revealed a random distribution of O -Ac and MeGlc p A within the backbone. However, the frequency of substitution with O -Ac along the backbone is not uniform and the molecular regions that did not contain MeGlc p A substituents possessed an acetylation degree significantly lower than the average DS of the xylan.

The chemical composition of the dichloromethane extracts of different morphological parts of banana plant “Dwarf Cavendish”, cultivated in Madeira Island (Portugal), were studied by gas chromatography–mass spectrometry. The five different morphological fractions in study have a similar qualitative chemical composition. Fatty acids and sterols are the major families present in the lipophilic extract of “Dwarf Cavendish”, representing ca. 33–66% and 12–43%, respectively, of the total amount of lipophilic components. Among all the identified compounds, campesterol, stigmasterol, sitosterol and fatty acids, such as palmitic, stearic, linoleic, linolenic, 22-hydroxydocosanoic, 24-hydroxytetracosanoic and 26-hydroxyhexacosanoic acids, were the major components found in all morphological zones. Other families of compounds, such as aromatic compounds, fatty alcohols and alkanes were also identified. The high increase of some components after alkaline hydrolysis, particularly, ferulic and fatty acids, indicates the presence of a considerable fraction of such components in esterified structures.

Dioxane lignin (DL) isolated from leaf sheaths of banana plant (Musa acuminata Colla var. cavendish) and in situ lignin were submitted to a comprehensive structural characterization employing spectroscopic (UV, FTIR, solid state 13C CP-MAS NMR, liquid state 13C and 1H NMR) and chemical degradation techniques (permanganate and nitrobenzene oxidation). Results obtained showed that banana plant leaf sheath lignin is of HGS type with a molar proportion of p-hydroxyphenyl (H)/guaiacyl (G)/syringyl (S) units of 12:25:63. Most of the H units in DL are terminal phenolic coumarates linked to other lignin substructures by benzyl and Cgamma-ester bonds in contrast to ferulates that are mainly ether linked to bulk lignin. It is proposed that banana plant leaf sheath lignin is chemically bonded to suberin-like components of cell tissues by ester linkages via essentially hydroxycinnamic acid residues. beta-O-4 structures (0.31/C6), the most abundant in DL, comprise mainly S units, whereas a significant proportion of G units is bonded by beta-5, 5-5', and 4-O-5' linkages contributing to ca. 80% of condensed structures in DL.

The wood of Acacia mangium, a prominent fast-growing plantation species used in the pulp-and-paper industry and, so far, poorly investigated for its chemical structure, was submitted to a detailed characterization of its main macromolecular components. Lignin (28% wood weight) isolated by mild acidolysis and characterized by permanganate oxidation, 1H and 13C NMR, and GPC, showed a very low content of syringylpropane-derived units (S:G:H of 48:49:3), a high degree of condensation, a low content of beta-O-4 ( approximately 0.40-0.43 per C6) structures, and a Mw of 2230. Glucuronoxylan (14% wood weight) isolated by alkaline (KOH) or by dimethyl sulfoxide extraction was characterized by methylation analysis, 1H NMR, and GPC. About 10% of the xylopyranose (Xylp) units constituting the linear backbone were substituted at O-2 with 4-O-methylglucuronic acid residues. Almost half of the Xylp units (45%) were O-2 (18%), O-3 (24%) or O-2,3 (3%) acetylated. X-ray diffraction analysis of cellulose (46% wood weight), isolated according to the Kurschner-Hoffer method, showed a degree of crystallinity of 67.6%.

A heteroxylan was isolated from Eucalyptus globulus wood by extraction of peracetic acid delignified holocellulose with dimethyl sulfoxide. Besides (1-->4)-linked beta-D-xylopyranosyl units of the backbone and short side chains of terminal (1-->2)-linked 4-O-methyl-alpha-D-glucuronosyl residues (MeGlcA) in a 1:10 molar ratio, this hemicellulose contained galactosyl and glucosyl units attached at O-2 of MeGlcA originating from rhamnoarabinogalactan and glucan backbones, respectively. About 30% of MeGlcA units were branched at O-2. The O-acetyl-(4-O-methylglucurono)xylan showed an acetylation degree of 0.61, as determined by 1H NMR spectroscopy, and a weight-average molecular weight (M(w)) of about 36 kDa (P=1.05) as revealed from size-exclusion chromatography (SEC) analysis. About half of the beta-D-xylopyranosyl units of the backbone were found as acetylated moieties at O-3 (34 mol%), O-2 (15 mol%) or O-2,3 (6 mol%). Practically, all beta-D-xylopyranosyl units linked at O-2 with MeGlcA residues were 3-O-acetylated (10 mol%).

Milled wood lignin (MWL) and dioxane lignin (DL) from different morphological regions (nodes and internodes) of Arundo donax reed were subjected to a comprehensive structural characterization by (13)C, (1)H NMR, FTIR, and UV spectroscopies and functional analysis. The permanganate and nitrobenzene oxidation methods were also applied to the in situ lignins. Both node and internode lignins are HGS-type lignins, with a significant amount of H units (including p-coumaric acid type structures). The S/G ratio (1.13-1.32), the weight-average molecular weight (20,400-24,500), the methoxyl group content (0.90-0.98), the phenolic hydroxyl group content (0.23-0.27), and the aliphatic hydroxyl group content (1.00-1.09) are not very different in the lignins from nodes and internodes. However, some structural differences between node and internode lignins were observed. The former has much more phenolic acids (p-coumaric and ferulic), 8.8% in node versus 1.2% in internode and less beta-O-4 (0. 32 and 0.49 per aromatic unit in node and internode, respectively). In situ node lignin is more condensed than internode lignin.

A synergistic effect of polyoxometalate and laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) has been observed in the aerobic oxidation of a hydrazonaphthalene type colorant. The considerable increase in the decolorization rate of Solophenyl Blue GL dye with the new catalytic system composed by laccase and heptamolybdopentovanadophosphate heteropolyanion, when compared with the treatment with enzyme or heteropolyanion alone, was tentatively explained by the redox mediation action of the heteropolyanion.

An unusual heteroxylan composed of galactosyl, 4- O -methyl-glucuronosyl and xylosyl residues with molar ratio 1:3:30 was isolated from the wood of Eucalyptus globulus Labill. The results of linkage analysis, supported by data of 1 H, 2D 1 H– 1 H COSY and 13 C NMR spectroscopy, revealed that the polysaccharide is a (2- O -α- d -galactopyranosyl-4- O -methyl-α- d -glucurono)- d -xylan with a (1→4)-linked β- d -xylopyranosyl backbone branched at O-2 by short side chains composed of terminal 4- O -methyl-α- d -glucuronic acid and of 4- O -methyl-α- d -glucuronic acid substituted at O-2 with α- d -galactose.

Redox reactions of Keggin-type polyoxometalates (POM), [PVxMo12−xO40](3+x)− (x = 1, 2), have been studied for the first time employing an array of potentiometric chemical sensors. Variations in the concentrations of vanadyl ions (VO2+) during the redox reactions of POMs were followed in the real-time. Differences in the vanadyl concentration profiles observed during re-oxidation of di- and mono-substituted POMs allow us to infer principally different re-oxidation mechanisms for these compounds. At the beginning of the oxidation of [PVIV2Mo10O40]7− under air an instant release of VO2+ (ca. 7%) from the coordination sphere of POM to the outside solution was detected. VO2+ concentration decreased rapidly while oxidation proceeded indicating return of vanadyl back to the coordination sphere of [PVV2Mo10O40]5−. This finding indicates the participation of VO2+ outside Keggin structure in the re-oxidation mechanism of di-substituted POM. No release of VO2+ was detected during re-oxidation of [PVIVMo11O40]5− by air oxygen in the presence of laccase (this POM is not oxidisable by air at low temperature and atmospheric pressure). Biocatalysis of [PVIVMo11O40]5− oxidation may include activation of the molecular oxygen by the prosthetic group of laccase thus allowing the oxidation of V(IV) inside the Keggin structure of POM, i.e., without vanadyl release into the outside solution.

A review on the use of polyoxometalates (POMs) and oxygen, for the delignification of lignocellulosic pulps is presented. Two main processes using POMs for the delignification of pulp have been investigated: an anaerobic process in which the POMs have been used, in aqueous solutions, as stoichiometric reagents for the oxidative degradation of residual lignin, with their re-oxidation by oxygen occurring in a subsequently separate stage; and an aerobic process in which the POMs were designed to perform as catalysts in the oxygen delignification. In the aerobic approach, the lignin oxidation and the reactivation of the POM take place in the same stage of the process. The feasibility of the catalytic system was shown by pilot plant experiments. Following the green chemistry goals, these processes are environmentally friendly approaches and may allow a significant decrease of chlorine-based chemical consumption by the pulp-and-paper industry. The use of the POMs together with laccase for the oxygen delignification of lignocellulosic pulps will also be considered. Final comments regarding the practical application of the POMs are pointed out.

Industrial hardwoods such as Eucalyptus species, Betula pendula, and Acacia mangium required different chemical charges during kraft pulping and presented distinct profiles of polysaccharides removal. The corresponding kraft pulps showed different chlorine dioxide consumption during bleaching. Woods and corresponding kraft pulps were characterized by chemical methods, 1 H and 13 C NMR spectroscopy, X-ray diffraction analysis, and gel permeation chromatography. The ease of lignin degradation and dissolution was essentially determined by differences in the proportion of syringyl and guaiacyl units and in the degree of condensation. The bleaching response was shown to be related also to the content of β-O-4 structures in the residual lignin. The relative stability of xylans during the pulping was suggested to be associated with differences in structure and molecular weight. The higher retention of Eucalyptus xylans was attributed essentially to their peculiar structure, including 0-2-substituted uronic acid groups linked to other cell wall polysaccharides.