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Introduction. The oil palm (Elaeis guineensis Jacq.) in the Peruvian Amazon has an installed production area of 72,861 ha, whose fruit processing generates solid residues such as the stalk and dry mesocarp. Objective. To determine the physicochemical characteristics of the residual biomass, stalk, and fruit fiber from palm oil extraction in the Peruvian Amazon, for its potential use in the elaboration of biodegradable materials. Materials and methods. During August to October 2020, 19.39 t/day of stalk and 13.05 t/day of oil palm fruit fiber were collected in Pucallpa, Neshuya District, Peru. Solubility analyzes in hot water and moisture were determined using the American standard test (American Society for Testing and Materials). The solubility in soda was obtained using the Technical Association of the Pulp and Paper Industry standard method. High performance liquid chromatography (HPLC) and refractive index (RI) detector were used to determine cellulose, hemicellulose, and lignin. Results. The physical properties of moisture (%) and solubility in soda (%) showed no differences between stalk and fiber. Both stalk and the fiber showed solubility in hot water, with values lower than 17 %. The chemical properties of the fiber were higher than those in the stalk, based on the percentage of cellulose, hemicellulose, and lignin. Conclusions. The physical and chemical results of oil palm stalk and fruit fiber would allow the development of appropriate technological processes for their conversion to biological products., Introducción. La palma aceitera (Elaeis guineensis Jacq.) en la Amazonia peruana tiene un área instalada en producción de 72 861 ha, cuyo procesamiento del fruto genera residuos sólidos como el escobajo y el mesocarpio secos. Objetivo. Determinar las características fisicoquímicas de la biomasa residual, escobajo y fibra del fruto, de la extracción de aceite de palma en la Amazonia peruana, para su potencial uso en la elaboración de materiales biodegradables. Materiales y métodos. Durante agosto a octubre del 2020, se recolectaron 19,39 t/día de escobajo y 13,05 t/día de fibra del fruto de la palma aceitera en Pucallpa, Distrito de Neshuya, Perú. Los análisis de solubilidad en agua caliente y humedad se determinaron mediante la prueba estándar americana (American Society for Testing and Materials). La solubilidad en soda, se obtuvo mediante el estándar de Technical Association of the Pulp and Paper Industry. Para la determinación de la celulosa, hemicelulosa y lignina, se empleó la cromatografía líquida de alta resolución (HPLC) y detector de índice de refracción (RI). Resultados. Las propiedades físicas de humedad (%) y solubilidad en soda (%) no presentaron diferencias entre el escobajo y la fibra. El escobajo y la fibra presentaron solubilidad en agua caliente con valores inferiores al 17 %. Las propiedades químicas en la fibra fueron mayores que en el escobajo, en base al porcentaje de celulosa, hemicelulosa y lignina. Conclusiones. Los resultados físicos y químicos del escobajo y de la fibra del fruto de palma aceitera, permitirían el desarrollo de procesos tecnológicos adecuados para su conversión a productos biológicos.

Lignin has gained interest in academia as a rawmaterial for advancedmaterials such as thermosets. Attractive features include its natural and technical abundances, its structural compositions, distribution of functionalities and most importantly its origin from renewable sources, i.e. lignocellulosic biomass. In this chapter, we will focus on lignin-based thermosets, specifically reviewing the recent strategies for such applications in polyurethanes, phenol-formaldehyde resins and epoxy thermosets. In these contexts, the advantages and competitiveness of lignin over conventional petrol-based will be discussed based on comparisons with benchmark properties. The chapter emphasizes the unique polymer chemistries adopted by different researchers, the effects of the chemical and physical properties of lignin on both reactivities during synthesis and thermomechanical properties of materials. Furthermore, the direct use of lignin in the unmodified state is contrasted with the use of selectively modified lignins in these polymer systems. The use of multifunctional lignin oligomers as raw material is also contrasted with the use of lignin platform monomers obtained through de-polymerization approaches. Finally, the challenges of lignin or monomers thereof, as a raw material in these applications are discussed to direct the future outlook of this research area., QC 20220209

[Abstract] Class III plant peroxidases (Prxs) are involved in the oxidative polymerization of lignins. Zinnia elegans Jacq. Basic peroxidase (ZePrx) has been previously characterized as capable of catalyzing this reaction in vitro and the role in lignin biosynthesis of several of its Arabidopsis thaliana homologous has been previously confirmed. In the present work, ZePrx was overexpressed in Nicotiana tabacum to further characterize its function in planta with particular attention to its involvement in lignin biosynthesis. Since Prxs are known to alter ROS levels by using them as electron acceptor or producing them in their catalytic activity, the impact of this overexpression in redox homeostasis was studied by analyzing the metabolites and enzymes of the ascorbate-glutathione cycle. In relation to the modification induced by ZePrx overexpression in lignin composition and cellular metabolism, the carbohydrate composition of the cell wall as well as overall gene expression through RNA-Seq were analyzed. The obtained results indicate that the overexpression of ZePrx caused an increase in syringyl lignin in cell wall stems, suggesting that ZePrx is relevant for the oxidation of sinapyl alcohol during lignin biosynthesis, coherently with its S-peroxidase nature. The increase in the glucose content of the cell wall and the reduction of the expression of several genes involved in secondary cell wall biosynthesis suggests the occurrence of a possible compensatory response to maintain cell wall properties. The perturbation of cellular redox homeostasis occurring as a consequence of ZePrx overexpression was kept under control by an increase in APX activity and a reduction in ascorbate redox state. In conclusion, our results confirm the role of ZePrx in lignin biosynthesis and highlight that its activity alters cellular pathways putatively aimed at maintaining redox homeostasis.

Lignins have polyphenolic structures, making them candidates to replace phenols and polyphenols in polymers. Lignins are highly recalcitrant, making their refining challenging, requiring harsh temperatures and pressures. Lignins could be partially modified under milder conditions for their use in biopolymers. The main purpose of this research was to upgrade Indulin AT, a kraft pine lignin, to enhance its properties. The first part of this thesis dealt with formic acid aided pressurized hot water extraction (FAPHWE) of hemicelluloses from birch hardwood as the first step in separating the components of a lignocellulosic feedstock (LCF). More than half of the hemicelluloses were extracted as hydrolysis products, while keeping the cellulose hydrolysis products in the extract under 5% and the lignin under 3%. In the second part of this work, a method to determine the amount of phenolic hydroxyl groups (OHph) in lignins was assessed. The Δε IDUS method was found to be useful for comparing the OHph of pine kraft and birch milox lignins, albeit not as precise as carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR). The third part of this thesis explored the tuning of the molar mass (MM) and OHph of Indulin AT by aqueous ethanol fractionation. The results showed that a higher water content favored the extraction of fractions with low MM and low OHph. A high ethanol content favored the extraction of fractions with medium MM and high OHph. A 50–60 wt% ethanol content allowed for near complete solubilization of Indulin AT, which could be beneficial for a single-phase chemical reaction. The fourth part of this research dealt with the depolymerization of Indulin AT in an ethanol-water solvent with formic acid as hydrogen donor. The properties of interest were MM, polydispersity (PDI), OHph, and formaldehyde uptake capability (FUC). The results of the reaction were affected predominantly by temperature. Higher temperatures led to lower MM and PDI, and higher, Tiivistelmä Ligniini on rakenteeltaan polyfenoli, mikä tekee siitä mahdollisen fenolien korvaajan polyfenolien valmistuksessa. Ligniinin rakenne on hyvin kestävä, mikä tekee sen jalostuksesta haastavaa vaatien usein korkean lämpötilan ja paineen käyttöä. Tästä huolimatta ligniiniä voidaan tietyssä määrin muokata miedommissa olosuhteissa, mikä lisää sen käyttökelpoisuutta biopolymeerien raaka-aineena. Tämän tutkimuksen tarkoitus oli jalostaa Indulin AT -kraft ligniiniä siten, että sen ominaisuudet paranevat. Aluksi väitöstyössä tarkasteltiin puun hemiselluloosan muurahaishappokatalysoidun kuumavesiuutton soveltuvuutta lignoselluloosaraaka-aineiden fraktioinnin ensimmäiseksi vaiheeksi. Yli puolet hemiselluloosasta voitiin uuttaa monosakkarideiksi samalla, kun selluloosasta uuttui alle 5 % ja ligniinistä alle 3 %. Seuraavaksi arvioitiin fenolisten hydroksyyliryhmien määritysmenetelmää. Δε IDUS metodin havaittiin olevan hyödyllinen ainakin sulfaattimenetelmän havupuuligniinien ja Milox-prosessin koivuligniininäytteiden vertailussa, vaikkakaan se ei ole yhtä tarkka kuin ydinmagneettiseen resonanssispektroskopiaan (NMR) perustuva analyysi. Tämän jälkeen tutkittiin mahdollisuuksia tuottaa etanoli-vesiliuosfraktioinnilla jakeita, joissa ligniinillä on haluttu molekyylikoko ja fenolisten hydroksyyliryhmien pitoisuus. Tulokset näyttivät, että korkea vesipitoisuus suosii pienen molekyylikoon ja matalan OHph -pitoisuuden sisältäviä jakeiden uuttumista. Korkea etanolipitoisuus suosii keskikokoisen molekyylikoon jaetta, jossa ligniinillä on korkea OHph -pitoisuus. 50–60 m-% etanolipitoisuudessa Indulin AT liukenee lähes täydellisesti, mikä voi olla edullista kemiallisten reaktioiden toteuttamiseen yhdessä faasissa. Lopuksi tutkimuksessa tarkasteltiin ligniinin osittaista depolymerisointia etanoli-vesiliottimessa muurahaishapon toimiessa vetylähteenä. Tarkasteltavat tuotteen ominaisuudet olivat molekyylikoko, polydispersiteetti, fenolisten hydroksyyliryhmien määrä ja formalde

A grass soda technical lignin (PB1000) underwent a process combining solvent fractionation and treatment with an ionic liquid (IL), and a comprehensive investigation of the structural modifications was performed by using high-performance size-exclusion chromatography, 31P NMR spectroscopy, thioacidolysis, and GC–MS. Three fractions with distinct reactivity were recovered from successive ethyl acetate (EA), butanone, and methanol extractions. In parallel, a fraction deprived of EA extractives was obtained. The samples were treated with methyl imidazolium bromide ([HMIM]Br) by using either conventional heating or microwave irradiation. The treatment allowed us to solubilize 28 % of the EA-insoluble fraction and yielded additional free phenols in all the fractions, as a consequence of depolymerization and demethylation. The gain of the combined process in terms of antioxidant properties was demonstrated through 2,2-diphenyl-1-picrylhydrazyl (DPPH.) radical-scavenging tests. Integrating further IL safety-related data and environmental considerations, this study paves the way for the sustainable production of phenolic oligomers competing with commercial antioxidants.

We conducted an in situ decomposition experiment to better understand how habitat nutrient content controls aquatic plant decomposition and, more precisely, to determine the relative importance of the wetland conditions in decomposition, and the intrinsic degradability of plant tissues. We collected the green leaves of three aquatic plant species with contrasting plant strategies from three wetlands of differing nutrient contents, and allowed them to decompose in seven wetlands along a nutrient gradient. The plant mass loss was higher for competitive and ruderal species collected in nutrient richer wetlands as well as when they were led to decompose in nutrient richer wetlands. Plant water content correlated with mass loss for the competitive and ruderal species, which may explain the increase in mass loss with increasing nutrient content in the collection wetlands. Litter decomposition rate may be enhanced by wetland eutrophication, because of both the modification of wetland decomposition conditions and by changes in plant tissue quality.

Lignins were isolated from spruce, wheat straw and eucalyptus by using the milled wood lignin (MWL) method. Functional groups and compositional analyses were assessed via 2D NMR and 31P to realize their effect on enzyme binding. Films of the lignins were fabricated and ellipsometry, atomic force microscopy and water contact angle measurements were used for their characterization and to reveal the changes upon enzyme adsorption. Moreover, lignin thin films were deposited on quartz crystal microgravimetry (QCM) and surface plasmon (SPR) resonance sensors and used to gain further insights into the lignin-cellulase interactions. For this purpose, a commercial multicomponent enzyme system and a monocomponent Trichoderma reesei exoglucanase (CBH-I) were considered. Strong enzyme adsorption was observed on the various lignins but compared to the multicomponent cellulases, CBH-I displayed lower surface affinity and higher binding reversibility. This resolved prevalent questions related to the affinity of this enzyme with lignin. Remarkably, a strong correlation between enzyme binding and the S/G ratio was found for the lignins, which presented a similar hydroxyl group content (31P NMR): higher protein affinity was determined on isolated spruce lignin (99% G units) while the lowest adsorption occurred on isolated eucalyptus lignin (70% S units). The effect of electrostatic interactions in enzyme adsorption was investigated by SPR, which clearly indicated that the screening of charges allowed more extensive protein adsorption. Overall, this work furthers our understanding of lignin-cellulase interactions relevant to biomass that has been subjected to no or little pretreatment and highlights the widely contrasting effects of the nature of lignin, which gives guidance to improve lignocellulosic saccharification and related processes

During the last decade, many efforts have been made in pulp and paper industry to construct more effective, sustainable and environmentally friendly pulp bleaching sequences. In this work, enzymatic (laccase-mediator system, L), non-oxidative chemical (urea, U) and mechanical (PFI refining, R) treatments have been conducted, alone or in a combination, on unbleached eucalyptus kraft pulps to evaluate their bleaching effects and thus the further potential as additional treatment(s) on a conventional bleaching process. The pulps obtained were characterized in terms of kappa number, hexenuronic acid content, brightness and viscosity. Moreover, the lignin-carbohydrates complexes (LCCs) were fractionated and characterized concerning lignin content and carbohydrate composition and for 1HNMR and thioacidolysis-GC and -SEC analysis. It has been found that the effect of the L treatment was limited at delignification by a kappa number reduction of 0.8 units. The effects of the U treatment included delignification (1.4 kappa units), HexA removal (3 mol/g) and pulp brightening (3.4 ISO units). The refining darkened the pulp (3 ISO units) while the subsequent L or U treatment could bleached more than without the R stage. The delignification extent by all the treatments could be noticed also from the isolation yields of the LCC1 (glucan-lignin) fraction. Thioacidolysis-SEC analysis revealed the darkening mechanism of the R treatment and the delignification mechanisms of L and U treatment, showing that the L treatment removed more effectively the condensed parts of the lignin located at LCC2 (xylan-lignin) fraction., QC 20140829

Amination of lignin conducted simply by Mannich reaction is an important mean for lignin structural and value upgradation. However, there is a lack of powerful analysis for quantification of the amine groups introduced and at the meantime for supplement of structural information about e.g. binding positions and side reactions etc. Various types of NMR analysis have thus been performed for the analysis of Mannich reaction products from lignin model, 4-hydroxy-3-methoxyacetophenone (HMAP), and from industrial spruce Kraft lignin. As revealed by NMRs, the reaction was very selective at C-5 position of guaiacyl lignin units and complete under acidic conditions with 11-fold amounts of reagents of piperidine (PIP) or dimethylamine (DMA) and formaldehyde over HMAP. No side reactions took place at the aromatic structure. For industrial lignin, 13.5 (by PIP) and 15 (by DMA) nitrogen atoms were introduced per 100 aromatic rings. Using other analytical methods, the aminated lignin was found with higher molecular weights, reaching Mp of 5.06kDa from the original 3.92kDa by DMA modification, and with a sharp increased solubility especially in acetic acid aqueous solution, 31.2 mg/ml after DMA modification. A preceding phenolation of the lignin resulted in a 70% increase of available aromatic rings and an introduction of 56 amine groups over 100 original aromatic rings after Mannich reaction by using DMA, which caused increases of molecular weights to 5.11kDa (Mp) and of solubility in acetic acid aqueous solution up to 77.2 mg/mL. Potential applications of these modified lignins of high values include many applications in different fields such as surfactant chemicals, polycationic materials and slow released fertilizers etc., QC 20140901

Lignin, the second most abundant component after cellulose in biomass, has been examined in this study as a fuel for a direct conversion into electricity using direct carbon fuel cell (DCFC). Two different types of industrial lignins were investigated: lignosulphonate (LS) and kraft lignin (KL), either directly in their commercial forms, after their blending with commercial active carbon (AC) or after alternation of their structures by a pH adjustment to pH 10. It has been found that the open circuit voltage (OCV) of the DCFC could reach around 0.7 V in most of the trials. Addition of active carbon increased the maximum current density from 43∼57 to 85∼101 mA/cm 2. The pH adjustment not only increased the maximum current density but also reduced the differences between the two types of lignins, resulting in an OCV of 0.680-0.699 V and a maximum current density of 74∼79 mA/cm 2 from both lignins. Typical power density was 12 (for KL +AC) and 24 mW cm -2 (for LS +AC). It has been concluded that a direct lignin fuel cell is feasible and the lignin hydrophilicity is critical for the cell performance., QC 20140923

Enzyme catalyzed oxidative polymerization of technical bagasse lignin and low-molecular-weight ultra-filtered kraft pulp lignin (UFL) were studied in methanol-water solution. Lignin was dissolved in methanol-water solution at pH 13 in steam heated autoclave at 130°C for 2h. The polymerization reaction was conducted at 40°C with a commercial laccase under oxygen saturation. The weight-average molecular weight (Mw) of original macromonomer and polymerized lignin were characterized with alkaline size exclusion Chromatograph (SEC) system. Enzyme treatment increased the molecular weight of both technical bagasse lignin and ultra-filtered lignin up to 20 times. The reaction time and the enzyme dosage were studied to obtain the maximal molecular weight., QC 20140903

The bleaching efficiency of the final D stage in the D 0(EP) D 1D 2 bleaching sequence was investigated focusing on the effect of pH in relation to the bleaching history of pulp samples. The pulps used were unbleached kraft Eucalyptus grandis pulps with a kappa number of 14.8, and the same pulp oxygen-delignified to kappa numbers 12 and 9.8. The samples were bleached according to the D 0(EP)D 1 sequence to a brightness of about 86% ISO and then submitted to the final D 2 stage under identical conditions. The target final brightness was 90.5% ISO. Changes in the kappa number, brightness, viscosity and contents of hexenuronic acid (HexA), 4-O-methylglucuronic acid and the total amount of carboxylic acid groups in pulps were monitored during the bleaching sequence. The target brightness in the D 2 stage was achieved for all pulps, but this required a different final pH for individual samples, indicating dissimilarities between chromophore types in them. In general, brightness increased as the pH increased from 3 to 6. The optimal value with respect to pulp viscosity was between pH 3 and 5. Despite unlike conditions applied in previous bleaching stages, the samples after the D 1 stage revealed similar residual lignin contents as shown by kappa number analysis. The content of hexenuronic acid in the samples was, however, found to vary broadly in the range from 2 to 26 mmol/kg. Conductometric titration showed different amounts of carboxylic (COOH) groups in pulps after the D 1 stage, of which HexA accounted for only a minor part. Since the content of 4-O-methylglucuronic acid groups was similar for all samples, the difference in the amount of COOH groups was mainly associated with oxidation of the residual lignin. Some of the charges might also originate from oxidized cellulose. It was concluded that the variations in the fiber charge result from the different bleaching conditions applied prior to the D 1 stage., QC 20140908

Autohydrolysis using water is a promising method to extract hemicelluloses from wood prior to pulping in order to make co-products such as ethanol and acetic acid besides pulp. Many studies have been carried out on the kinetics and mechanism of autohydrolysis using batch reactors. The present study was performed in a continuous mixed flow reactor where the wood chips are retained in a basket inside the reactor. This reactor is well suited to determine intrinsic kinetics of hemicellulose dissolution because the dissolved products are rapidly removed from the reactor, thus minimizing further hydrolysis and degradation of the hemicelluloses in solution. The xylan removal rate follows an S-shaped behavior. GPC analysis of the continuously removed extract shows that the dissolved xylan oligomers have a DP smaller than about 25. Lignin-free xylan oligomers and cellulose oligomers are the major components dissolved in the initial stage of autohydrolysis, while xylan covalently bound to lignin (i.e. an LCC) is the major component removed during the later stage of autohydrolysis. The molecular weight of the dissolved components decreases with time in the second stage. The kinetics of xylan removal are explained in terms of a mechanism based on recent knowledge of the ultrastructure of the cell fibre wall., QC 20120207

Extraction of hemicelluloses from wood prior to pulping is being pursued to generate more value-added products, while still producing high quality pulp from the pre-extracted wood. For a better understanding of the factors limiting selective extraction, enzymatic hydrolysis in combination with size exclusion chromatography (SEC) was applied to milled wood and hydrothermally treated wood. Complete dissolution was achieved in a lithium chloride/dimethylacetamide solvent system after mild ball-milling of a Southern Hardwood Mixture (SHM), of SHM extracted using auto-hydrolysis, and of enzyme-treated SHM. SEC tests showed that severe degradation of wood polymers occurred after a milling time of 3 hours. The SEC data also confirmed the presence of lignin-carbohydrate complexes. Based on the results, it is suggested that linkages between lignin and polysaccharides may play an important role in limiting extraction of hemicelluloses., QC 20120201

Lignin is one of the most predominant biopolymers present in plants. Together with cellulose and hemicelluloses, lignin builds up the cell wall in an arrangement which is regulated on the nano-scale and results in lignin-carbohydrate network structures. The molecular complexity of lignin renders all isolation and identification processes difficult and, consequently, many structural questions still remain. This chapter reviews the present knowledge about the formation of lignin in plants, its presence in different types of plants as well as several different approaches taken to reveal the chemical structure, is summarized. Furthermore, this chapter briefly discusses the chemical changes introduced in lignin as the result of different types of delignification processes, such as kraft and sulfite pulping and steam explosion, is included., QC 20140923

The chemical structure of milled-wood lignins from Eucalyptus globulus, E. nitens, E. maidenii, E. grandis, and E. dunnii was investigated. The lignins were characterized by analytical pyrolysis, thioacidolysis, and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units. E. globulus lignin had the highest syringyl content. The heteronuclear single quantum correlation (HSQC) NMR spectra yielded information about relative abundances of inter-unit linkages in the whole polymer. All the lignins showed a predominance of beta-O-4' ether linkages (66-72% of total side-chains), followed by beta-beta' resinol-type linkages (16-19%) and lower amounts of beta-5' phenylcoumarin-type (3-7%) and beta-1' spirodienone-type linkages (1-4%). The analysis of desulfurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds, and the type of units ( syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, 93-94% of the total beta-beta' dimers included two syringyl units indicating that most of the beta-beta' substructures identified in the HSQC spectra were of the syringaresinol type. Moreover, three isomers of a major trimeric compound were found which were tentatively identified as arising from a beta-beta' syringaresinol substructure attached to a guaiacyl unit through a 4-O-5' linkage., QC 20100525

The rapid expansion of bioethanol production will, in addition to fermentation of sugar and starch sources, also involve a conversion of lignocellulosic materials. In addition to carbohydrates, this will result in large amounts of lignin which can be used as process fuel but also serve as a feedstock for chemicals. Modern kraft mills constitute a second source of lignin since the energy balance is such that a partial outtake of lignin can be permitted. Irrespective of source, technical lignins must be upgraded, e.g. by purification in order to acquire properties which make them suitable as feedstock in value-added products., QC 20150602

Spirodienone structures have been detected in spruce, birch, and kenaf lignin isolates. NMR signals corresponding to guaiacyl and syringyl spirodienones were fully identified and assigned based on C-13, QUAT, HSQC, HSQC-TOCSY, and HMBC NMR data. Spruce lignin contains spirodienone structures of the guaiacyl type. Syringyl spirodienones dominate in kenaf and birch lignins. Each type of spirodienone was found to be present in two different stereoisomeric forms, with one of the isomers being more prevalent. Signal integrations indicate that about three spirodienones per 100 phenylpropanoid units are present in the spruce and birch lignins and about four in the kenaf lignin., QC 20100525

The gelatinous layer (G-layer) formed on the lumen wall in early- and latewood fibres of poplar and birch tension wood was characterised using a novel molecular marker specific for crystalline cellulose in conjunction with fluorescence and FE-SEM microscopy. Crystalline cellulose was localised using a cloned Cel7A cellulose-binding module (CBM1(HjCel7A)) from the fungus Hypocrea jecorina conjugated directly to FITC/TRITC or indirectly via a secondary antibody conjugated to FITC for fluorescence microscopy or to gold/silver for FE-SEM. With the CBM1(HjCel7A) conjugate, the G-layer was clearly distinguished from other secondary cell-wall layers as a bright green layer visible in fibres of tension wood in fluorescence microscopy. FEM-SEM images revealed the supramolecular architecture of the G-layer of poplar wood, which consists of well-defined, often concentrically orientated, cellulose aggregates of the order of 30-40 nm. The cellulose aggregates typically have a microfibril angle of almost 0 degrees. Studies on cellulose marked with CBM1(HjCel7A) followed by Au labelling and Ag enhancement complemented the fluorescence observations. The studies demonstrate the usefulness of this novel molecular marker for crystalline cellulose in situ, which was previously difficult to localise. Further proof of distinct cellulose aggregates was observed., QC 20100525

Lignin-carbohydrate complexes and their relationship to pulp bleachability and unbleached pulp brightness were studied in four birch kraft pulps produced at high and low hydroxide ion and sodium ion concentrations, using size-exclusion chromatography (SEC). About 75-80%of the lignin was found to be associated with carbohydrates, a larger part with hemicelluloses and a smaller part with cellulose. Easily bleached pulps, produced under high [OH-] or low [Na+] conditions, had more lignin associated with cellulose than their counterparts. Furthermore, a high [OH-] gave a residual lignin that was significantly more accessible in the residual lignin isolation, and where the inaccessible lignin was bonded to carbohydrates. Colour differences of pulps caused by variations in the cooking conditions, as studied in the SEC system, were associated with all the lignin, irrespective of whether it was associated with hemicelluloses or cellulose., QC 20100525

The successive retardation of lignin dissolution towards the end of a kraft pulping process can be explained by the predominance of biphenyl and biphenyl ether structures being present in the lignin. As a possible mode of formation of such structures during the cook, a one-electron transfer reaction involving elemental sulfur/polysulfide has been suggested. Consequently, reactions between dissolved phenolic lignin fragments and pulp lignin might give rise to the formation of stable biphenyl (or biphenyl ether/thioether) structures. In order to find further support for such reactions, kraft pulps (isolated lignins) and the corresponding black liquor lignins were subjected to analysis using thioacidolysis in combination with GC-MS as well as quantitative 1D and 2D NMR techniques. The results obtained so far support the hypothesis that radical coupling reactions may play an essential role for the presence of residual lignin in kraft pulps., QC 20141202

In this study different dissolved wood components (DWC) in the industrial black liquor and their effect on the delignification during the kraft cook has been investigated. The cooking were performed on softwood as well as hardwood to se different effects on the delignification rates. Different wood model components as well as treated black liquor components were added to the kraft cooking liquor. The results show that the phenolic groups in the black liquor lignin has a positive effect on the delignifiacation rate. It was also shown that surfactant had a positive effect on the delignification rate in systems with low amount of DWC. Furthermore, it was shown that a black liquor with a low amount of lignin i.e. mostly carbohydrates had a positive effect on the delignification rate. Cellulose and hemicellulos, on the other hand, did not seem to have any effect on the delignification rate., QC 20141202

The changes observed in the research projects of the Nordic Pulp and Paper Research Journal (NPPRJ) during the last two decades, are discussed. One of the research project implied that the same sorption which was used to measure isolation and degraded hemicellulose during 1960s, is studied by enzymatic peeling of the outer layers of the fiber surface. It was also observed that the smaller fractions having a greater influence on the delignification rate is largely because of their higher phenolic content. During the last two decades, the research focus in the pulp and paper field has been increasingly on the development of new products and their end use., QC 20141202

Recent discoveries have shown the presence of reduced lignin structures in softwood lignin, such as dihydroconiferyl alcohol and secoisolariciresinol. During lignin polymerization, the oxidative radical coupling of monolignols generates quinone methides as intermediates. Several reduction agents were tested on a quinone methide model. The products were analyzed by GC-MS and 1H, 13C, DEPT and HSQC NMR techniques were used to confirm the structure of the reduced quinone methide. An uncatalyzed reduction of this quinone methide model was achieved with β-NADH, a biologically significant reducing agent, demonstrating that the formation of reduced lignin structures is not necessarily biologically controlled., QC 20141203

Isolated residual lignin from art oxygen-bleached kraft pulp was subjected to oxidation with alkaline hydrogen peroxide under different time and temperature conditions in both the absence and presence of stabilizing agents and transition metal ions. The resulting lignin samples were analyzed by UV/VIS and FTIR spectroscopy. The analyses demonstrate the occurrence at a temperature as low as 50 degreesC: of a rapid but limited elimination of chromophoric groups, resulting in the formation of carboxyl groups. The presence of DTPA and magnesium ions stabilizes the hydrogen peroxide towards decomposition and the chromophore elimination is improved. At a higher oxidation temperature, 80 degreesC, the effect of added stabilizer(s) is particularly pronounced. Addition of transition metal ions resulted in a rapid decomposition of hydrogen peroxide and the introduction of new chromophoric groups., QC 20100525

Residual lignin was isolated from an oxygen-bleached softwood kraft pulp and subjected to oxidation with alkaline hydrogen peroxide in order to study how the degradation of the lignin is influenced by parameters such as time, temperature, addition of stabilizing agents and metal ions. The oxidized lignin samples were analyzed with respect to carboxyl and phenolic hydroxyl content. It was found that the peroxide treatment resulted in a rapid increase in the amount of carboxyl groups, presumably due to the elimination of chromophoric groups. Phenolic hydroxyl groups in the lignin required a higher temperature to be oxidized and this led to the formation of more carboxyl groups. The presence of DTPA and/or Mg (II) stabilized the hydrogen peroxide against decomposition and suppressed the degradation of phenolic groups, while the carboxyl groups remained the same. The addition of transition metal ions to the reaction system resulted in a rapid decomposition of hydrogen peroxide but also in a rapid formation of carboxyl groups and a degradation of the lignin., QC 20100525

The purpose of this investigation was primarily td investigate how variations in cooking conditions in the kraft pulping of softwood influence the subsequent bleaching, and secondly to study the relationship between the bleaching response and the chemical structure of the pulp. The cooking variables studied were hydroxide ion concentration, hydrogen sulfide ion concentration and cooking temperature. The pulps had the same kappa number after the cook, about 20, and were oxygen delignified to about kappa number 8 before bleaching. The influence of the cooking variables on the TCF-bleachability was studied in an AZQP*- and in a QPQP*-sequence (A=acid treatment, Z=ozone stage, Q=chelating agent stage, P*=peroxide stage with the addition of magnesium ions). All three cooking variables studied influenced the TCF-bleachability, but to different extents. The bleachability was improved by increased temperature for low chemical charges, but not at higher chemical charges. When [HS-] was increased the QPQP*-bleachability was improved but the AZQP*-bleachability was not affected. When [HO-] was varied a bleachability maximum was seen for the intermediate hydroxide ion concentration. The content of hexenuronic acid in the pulp after cooking could be reduced by using high initial [HO-], low initial [HS-] and a long cooking time. A high content of beta-O-4 structures in the unbleached residual lignin was found to contribute to a better bleachability of the pulp. However, the phenolic hydroxyl content could not be related to the bleaching response., QC 20100701

The structural significance of a kappa number has been studied by quantifying the permanganate consumption of various isolated pine, birch and poplar lignins, of lignin model compounds and of carbohydrate and other aliphatic compounds under kappa number measurement conditions. It was found that the average permanganate consumption for the different lignins was 11-12 equivalents per phenylpropane unit. This value is in accordance with the addition of permanganate ion to all three double bonds in the aromatic rings regardless of whether these are phenolic or non-phenolic or whether they belong to a guaiacyl or a syringyl unit. It was further found that permanganate can be consumed by other types of oxidizable structures like aliphatic double bonds, aldehyde groups and alpha-keto-carboxylic acid groups. For unbleached kraft pulp samples, the combined consumption of permanganate by lignin and hexenuronic acid groups from xylan was found to be fairly close to the measured kappa number. The small discrepancies found indicate, however, that other types of structures may contribute to the kappa number., QC 20100521

Curie-point pyrolysis-gas chromatography-mass spectrometry was applied to study the chemical structure of sound and fungus degraded, industrial and synthetic lignins. Pyrolysis products reflected in some detail the structural units present in the lignin polymer. Thus, sound spruce lignin yielded trans-isoeugenol coniferaldehyde and trans-coniferyl alcohol as major pyrolysis products. Biodegraded lignin yielded oxidized units, including vanillin, acetoguaiacone, methyl vanillate, propioguaiacone, vanilloyl methyl ketone and vanillic acid as major products. Kraft lignin also showed evidence of oxidation, although not as much as the biodegraded lignin. Major products from this industrial lignin were guaiacol, methylguaiacol, vinylguaiacol and homovanillic acid. Results indicated that synthetic lignin duplicates fairly well the structure of natural lignin. However, coniferylaldehyde and trans-coniferyl alcohol were the dominant products only from the synthetic lignin, indicating the presence of large amounts of coniferyl alcohol and coniferylaldehyde end groups.

Pyrolysis-gas chromatography-mass spectrometry studies of soil fulvic and humic acids were made. The high boiling point compounds produced by pyrolysis were separated in a column packed with Chromosorb AW DMCS 80-100 mesh coated with 10% FFAP. Humic acids with a high nitrogen content yielded a complex variety of protein derivatives, such as alkylpyridines, alkylpyrroles, alkylbenzonitriles, indoles, piperidines, pyrazines, and pyrrolidones. Humic acids with low N content yielded a smaller number of heterocyclic nitrogen compounds. Lignin derivatives were also identified, but the amount varied in different samples. Furanes were not as prominent as protein and lignin fragments. Acid hydrolysis released proteins, polysaccharides, and lignins, which could be considered as companion materials of a humic "core". The majority of the pyrolysis compounds from the residue after hydrolysis were identified as alkylbenzenes, alkylnaphthalenes, phenols, benzofuranes, indenes, and fluorenes. Alkanes and alkenes were noted in trace amounts. Pyrolysis behavior of fulvic acids differed from that of humic acids. They produced poorly resolved pyrograms with smaller number and a lower intensity of peaks, from which only furfurals, phenols, benzofuranes, and naphthalenes could be identified.