Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Research news : pulping and bleaching activities
    Keijsers, E.R.P. - \ 2008
    pulpbereiding - papier - bleking - vezels - karton - wetenschappelijk onderzoek - pulping - paper - bleaching - fibres - paperboard - scientific research
    Agrotechnology & Food Sciences Group is an organisation for fundamental and applied scientific research. The research department Fibre and Paper Technology is actively involved in pulping and bleaching research with a wide range of raw materials, including wood, non- wood and recycled fibres.
    Biotechnological application of enzymes for making paper pulp from green jute/kenaf
    Snijder, M.H.B. ; Lips, S.J.J. ; Maas, R.H.W. ; Kamp, R.G.M. op den; Valk, H.C.P.M. van der; Jong, E. de - \ 2004
    Wageningen : Agrotechnology & Food Innovations (Rapport 93)
    papier - pulpbereiding - jute - kenaf - productieprocessen - biotechnologie - voorbehandeling - enzymen - biobased economy - paper - pulping - production processes - biotechnology - pretreatment - enzymes
    The objectives of the tasks of Agrotechnology & Food Innovation (formerly ATO) in the project are: to determine at laboratory level the best conditions for producing high-yield pulps from whole jute for utilisation in wood containing papers; to test the potential of using recommended enzyme recipes in both extruder and refiner processes in terms of pulp quality, chemicals and energy consumption, brightness and production cost; to evaluate the potential of a micro-biological pre-treatment with selected strains of fungi; to establish process conditions for pilot confirmatory trials.
    Alkaline hemp woody core pulping : impregnation characteristics, kinetic modelling and papermaking qualities
    Groot, B. de - \ 1998
    Agricultural University. Promotor(en): K. van 't Riet; J.E.G. van Dam. - S.l. : S.n. - ISBN 9789054858898 - 97
    hennep - plantenvezels - papier - pulpbereiding - hemp - plant fibres - paper - pulping

    The aim of this thesis is to elucidate alkaline processing of hemp woody core, supporting the development and optimization of an efficient and non-polluting pulping process. This study has been a constituent of an integral programme to study fibre hemp.

    It is known that the outer part of the fibre hemp stem can be used for textile and specialty paper purposes. The inner part consists of hemp woody core, which resembles hardwood and might be processed similarly for paper pulp. Literature data and prefeasibility studies show that alkaline processes can be used to produce hemp woody core pulp for papermaking.

    Alkaline processes, based on sodium hydroxide (NaOH) are used for many wood and non-wood species. The most important process is the kraft process, but alternative NaOH based processes for pulp production have been investigated too. The currently developed alkaline process for high yield hardwood pulping may also be implemented for hemp woody core.

    Pulp mixes for papermaking can vary, depending on the available fibre sources. The technological developments and the growing market outlet for hardwood fibres increase the possibilities to use hemp woody core for papermaking.

    In chapter 2 swelling of hemp woody core chips after alkaline (peroxide) impregnation at 70 °C has been studied, as is practised in alkaline peroxide mechanical pulping (APMP) processes. Swelling of hemp woody core chips has been examined in relation to pulp yield and chemical composition of the chips after impregnation.

    In contrast to wood chips, maximum swelling is attained at 70 °C without chemical treatment, possibly as the result of relatively high porosity of hemp woody core cell walls.

    Alkaline swelling at 70 °C correlates with the xylan:lignin ratio. Swelling at ambient temperature shows some correlation with acidic group content.

    Apparent pore size distributions have been examined, using 1H NMR spin-spin relaxation. Several apparent pore size distributions can be distinguished within each sample. Elevated temperature, NaOH and peroxide addition influence the apparent pore size distribution and the total pore volume in different ways.

    Addition of peroxide results in remark-able increase of the apparent pore sizes. This emphasizes its importance, not only as bleaching chemical in the APMP process, but also promoting fibre flexibility.

    Alkaline delignification of hemp woody core is studied in chapter 3. Shavings of hemp woody core were delignified isothermally at several temperatures with 1M NaOH in a flow-through reactor. From literature data and from experimental data reported in this chapter, it appears that the initial delignification stage is completed before customary reaction temperatures are reached. Consequently, modelling of alkaline delignification kinetics can be restricted to the bulk and residual delignification stages. This can be described with two simultaneous first order reactions: L/L0 = a2 exp (-k2t) + a3 exp (-k3t), with ki = Ai exp -Eai/(RT).

    This equation has been solved integrally, calculating a2, a3, Ea2, Ea3, A2 and A3 for the best fit for the experimental data, resulting in an accurate description of the delignification reactions. This kinetic model has also been applied on literature data, supporting its validity for alkaline delignification kinetics in general.

    This model is also used in chapter 4, to describe the kinetics of alkaline delignification in more detail, and to describe the degradation of xylan and cellulose. Shavings of hemp woody core were impregnated at room temperature with various NaOH concentra-tions (0.25-2.0M) and delignified isothermally at various reaction temperatures (150-180 °C) in a flow-through reactor.

    Extraction and degradation of xylan from hemp woody core strongly depends on NaOH concentration. Consequently, to attain a certain lignin content, lower NaOH concentrations result in higher pulp yields. Extended pulping diminishes the differences in pulp yields, due to further xylan degradation.

    The kinetics of lignin, xylan and cellulose degradation are modelled as a function of reaction time, temperature and NaOH concentration. The combined models resulted in a pulp yield model for hemp woody core, suitable for process optimization purposes. Degradation kinetics of perennial wood can be modelled similarly, which was illustrated using literature data on spruce and poplar.

    In chapter 5 strength and surface properties of test sheets, produced from alkaline hemp woody core pulp were examined. The development of bulk and tear with beating are similar as found for straw pulp; maximum tear strength is attained without beating. Burst and tensile strength, scattering and opacity develop similarly as for hardwood pulps, with less mechanical energy needed. Tear strength is not affected by pulp yield or composition, whereas lower tensile and burst strength are found with decreased yield and lower xylan content.

    As the paper strength and surface properties of hemp woody core pulp are comparable with those for hardwood and straw pulps, it is conceivable that similar amounts of alkaline hemp woody core pulp can be used in pulp mixes for printing paper grades.

    The polymerization degree (DP) of hemp woody core pulps has been related to the paper strength properties, and modelled as function of pulping conditions and time.

    The influence of NaOH concentration on depolymerization and cellulose degradation is much stronger than reported in literature for other pulps. This may be related to the low density of hemp woody core, preventing diffusion effects. Finally, crystallinity has been examined and related to cellulose degradation of alkaline hemp woody core pulp.

    In chapter 6 the results and conclusions are discussed. It is emphasised that hemp woody core has a lower density than hardwood or softwood. It is suggested that this is the cause for maximal swelling without NaOH addition, the found xylan and yield losses with NaOH impregnation, and the strong dependency of cellulose degradation and depolymerisation on NaOH concentration.

    In general, it was confirmed that hemp woody core can be delignified similarly as hardwood. The modelling techniques used have been proved to be generally applicable on degradation and depolymerisation kinetics, not only for hemp woody core, but also for hardwood and softwood species. The paper characteristics are comparable both to hardwood and to straw pulp characteristics.

    Physiological roles and metabolism of fungal aryl alcohols
    Jong, E. de - \ 1993
    Agricultural University. Promotor(en): J.A.M. de Bont, co-promotor(en): M.M.G.R. Bol; J.A. Field. - S.l. : De Jong - ISBN 9789054851943 - 224
    enzymen - bosbouw - pulpbereiding - biodegradatie - oxidoreductasen - peroxidasen - katalase - basidiomycotina - scheurvorming - decompositie - degradatie - lignine - chemische verbindingen - enzymes - forestry - pulping - biodegradation - oxidoreductases - peroxidases - catalase - basidiomycotina - cracking - decomposition - degradation - lignin - chemical compounds

    The major structural elements of wood and other vascular tissues are cellulose, hemicellulose and generally 20-30% lignin. Lignin gives the plant strength, it serves as a barrier against microbial attack and it acts as a water impermeable seal across cell walls of the xylem tissue. However, the presence of lignin has practical drawbacks for some of the applications of lignocellulosic materials. First, lignin has to be removed for the production of high quality pulps. Second, lignin reduces the digestibility of lignocellulosic materials. High quality pulps can be produced with chemical methods, however the abundant use of chemicals and energy, and the formation of an enormous waste stream has led scientists to investigate the possibilities of biodelignification. White-rot fungi give the most rapid and extensive degradation and have become subject of intensive research. Results obtained with the model organism Phanerochaete chrysosporium and other strains have revealed that lignin biodegradation is an extracellular, oxidative and non-specific process. This unique biodegradative potential has been considered for broader applications such as waste water treatment and the degradation of xenobiotic compounds. The research described in this thesis concentrates on the function of aryl alcohols in fungal physiology.

    Aryl alcohols In the physiology of white-rot fungi. White-rot fungi have a versatile machinery of enzymes, including peroxidases and oxidases, which work in harmony with secondary aryl alcohol metabolites to degrade the recalcitrant, aromatic biopolymer lignin. In chapter 2 literature concerning the important physiological roles of aryl (veratryl, anisyl and chlorinated anisyl) alcohols in the ligninolytic enzyme system has been reviewed. Their functions include stabilization of lignin peroxidase, charge-transfer reactions and as substrate for oxidases generating extracellular H 2 O 2 .

    The experimental research described in this thesis was initiated to evaluate the possibilities of white-rot fungi in the biopulping of hemp stem wood. Sixty-seven basidiomycetes were isolated and screened for high peroxidative activity (chapter 3). Several of the new isolates were promising manganese peroxidase-producing white-rot fungi. Enzyme assays indicated that for the production of H 2 O 2 either extracellular glyoxal or aryl alcohol oxidase were present. In contrast, lignin peroxidase was only detected in P. chrysosporium , despite attempts to induce this enzyme in other strains with oxygen and oxygen/veratryl alcohol additions. A highly significant correlation was found between two ligninolytic indicators: ethene formation from α-keto-γ- methylthiolbutyric acid and the decolorization of a polymeric dye, Poly R-478. Three of the new isolates had significantly higher Poly R decolorizing activities compared to P. chrysosporium .

    One of the best Poly R decolorizing strains, Bjerkandera sp. BOS55 was selected for further characterization. A novel enzyme activity (manganese independent peroxidase) was detected in the extracellular fluid of Bjerkandera sp. BOS55 (chapter 4). The purified enzyme could oxidize several compounds like phenol red, 2,6-dimethoxyphenol (DMP), Poly R-478, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and guaiacol with H 2 O 2 as an electron acceptor. In contrast, veratryl alcohol was not a substrate. This enzyme also had the capacity to oxidize DMP in the absence of H 2 O 2 . Bjerkandera sp. BOS55 also produced de novo several aromatic metabolites. Besides veratryl alcohol and veratraldehyde, compounds which are known to be involved in the ligninolytic system of several other white-rot fungi (chapter 2), other metabolites were formed. These included anisaldehyde, 3-chloro-anisaldehyde, 3,5-dichloro-anisaldehyde and small amounts of the corresponding anisyl, 3-chloro-anisyl and 3,5-dichloro-anisyl alcohol (chapters 5 and 6). This was the first report of de novo biosynthesis of simple chlorinated aromatic compounds by a white-rot fungus. These unexpected findings led us investigate the physiological role(s) of the denovo biosynthesized chlorinated anisyl alcohols (chapter 6). All metabolites were produced simultaneously with the extracellular ligninolytic enzymes. The monoand dichlorinated anisyl alcohols appeared to be excellent substrates for the extracellular aryl alcohol oxidases. The formed aldehydes were readily recycled via reduction by washed fungal mycelium, thus creating an extracellular H 2 O 2 production system regulated by intracellular enzymes. Lignin peroxidase does not oxidize the chlorinated anisyl alcohols both in the absence and in the presence of veratryl alcohol. It was therefore concluded that the chlorinated anisyl alcohols are well protected against the fungus's own aggressive ligninolytic enzymes. The relative amounts of veratryl alcohol and the chlorinated anisyl alcohols differ significantly depending on the growth conditions, indicating that the production of veratryl alcohol and the (chlorinated) anisyl metabolites are independently regulated.

    It was concluded that the chlorinated anisyl metabolites, biosynthesized by the white-rot fungus Bjerkandera sp. BOS55, are purposeful for ecologically significant processes such as lignin degradation. These results made us speculate if a significant biogenesis of chlorinated aromatics by fungi occurs in natural environments (chapter 7). Many common wood- and forest litter-degrading fungi were indeed detected that produced chlorinated anisyl metabolites (CAM). These compounds, which are structurally related to xenobiotic chloroaromatics, were present in the environment and occur at high concentrations of approximately 75 mg CAM kg -1wood or litter. The ubiquity among common fungi to produce large amounts of chlorinated aromatic compounds in the environment leads to the conclusion that these kind of compounds can no longer be considered to originate from anthropogenic sources only.

    Degradation of aryl alcohols by fungi. In chapter 2 the anabolic and catabolic routes of aryl alcohols by white-rot fungi has been reviewed. These fungi can not use veratryl alcohol as sole source of carbon and energy. However, several bacteria, yeasts and fungi were selectively isolated from paper mill waste water that grew on veratryl alcohol (chapter 8). Penicilliumsimplicissimum was selected for the characterization of the veratryl alcohol degradation route. P. simplicissimum oxidized veratryl alcohol via a NAD(P) +-dependent veratryl alcohol dehydrogenase to veratraldehyde which was further oxidized to veratric acid in a NAD(P) +-dependent reaction. Veratric acid-grown cells contained NAD(P)H-dependent O -demethylase activity for veratrate, vanillate and isovanillate. Ring-cleavage of protocatechuate was by a protocatechuate 3,4-dioxygenase. An interesting aspect of P. simplicissimum is the production of vanillyl alcohol oxidase with covalently bound FAD (chapter 9). The intracellular enzyme was purified 32-fold. SDS-PAGE of the purified enzyme revealed a single fluorescent band of 65 Kda. Gel filtration and sedimentation-velocity experiments indicated that the purified enzyme exists in solution as an octamer, containing 1 molecule flavin/subunit. The covalently bound prosthetic group of the enzyme was identified as 8α-(N 3-histidyl)FAD from pH dependent fluorescence quenching (p Ka = 4.85) and no decrease in fluorescence upon reduction with sodium borohydride. The enzyme showed a narrow and rather peculiar substrate specificity. In addition to vanillyl alcohol and 4-hydroxybenzyl alcohol, eugenol and chavicol are substrates for the enzyme (chapter 10). The formed products, coniferyl and coumaryl alcohol are the natural precursors of lignin in plants. This reaction has a potential application to produce coniferyl alcohol and subsequent synthetic lignin (DHP) from the inexpensive precursor eugenol.

    The role of natural wood constituents on the anaerobic treatability of forest industry wastewaters
    Sierra - Alvarez, R. - \ 1990
    Agricultural University. Promotor(en): G. Lettinga. - S.l. : Sierra-Alvarez - 128
    bosbouw - houtpulp - pulpbereiding - afvalwaterbehandeling - waterzuivering - anaërobe behandeling - pulp- en papierwarenindustrie - chemische behandeling - forestry - wood pulp - pulping - waste water treatment - water treatment - anaerobic treatment - pulp and paper industry - chemical treatment

    Anaerobic treatment has been shown to be an efficient and energy conserving method for treating various types of readily biodegradable non-inhibitory forest industry wastewaters. However, the high toxicity of paper mill effluents derived from chemical wood processing operations has hampered the wide spread application of anaerobic treatment in the forest industry.

    This dissertation describes research on the anaerobic treatment of inhibitory wastewaters from the forest industry. The main objective was to determine the role of natural woodderived organic constituents on the methanogenic toxicity of these wastewaters.

    Lignocellulosic feedstocks were pulped by processes commonly applied in the forest industry, namely thermomechanical (TMP) and alkaline pulping processes, to determine which factors are responsible for the extraction of toxic substances. Batch anaerobic biodegradability and methanogenic toxicity assay results indicated that the pulping conditions applied had a significant effect on the anaerobic treatability of the resulting wastewaters. TMP effluents were highly biodegradable and non-inhibitory. Soda pulping liquors contain important fractions of recalcitrant organic matter and exerted severe toxicity. Wood resin constituents were shown to be the major inhibitors present in pulping wastewaters. Wood resin is composed of fatty constituents which are poorly soluble in water at neutral to acid pH values. The increased solubility of resin at high pH values, indicates that the contact of alkali with wood contributes strongly to producing toxic wastewaters by extracting resinous compounds. The alkali promotes lignin solubilization and thereby also contributes to a lowered biodegradability of the wastewater.

    Compounds representative of the major wood resin constituents were assayed for methanogenic toxicity. The high toxicity of a variety of resin compounds including volatile terpenes, resin acids and apolar phenols was demonstrated. Concentrations causing 50% inhibition ranged from 20 to 330 mg/l.

    Aside from the resinous wood constituents, lignin derived compounds are also potential sources of toxicity in pulping wastewaters. The methanogenic toxicity of lignin mixtures isolated from paper mill effluents was determined. Experiments with ultrafiltered lignins revealed that the toxicity of various wastewater lignins originated from the low molecular weight (MW) fraction. Studies with selected low MW lignin model compounds showed that their inhibitory activity was related to the functional groups on the aromatic ring. Compounds with aldehyde groups or apolar substituents were highly toxic; whereas, those with carboxylic groups were distinctly less toxic.

    The effect of chemical structure on the methanogenic toxicity of aromatic compounds was investigated. Some basic structure- toxicity relationships were evident. In general, the toxicity increased with increasing the length of aliphatic side-chains and increasing the number of alkyl or chlorine groups. On the other hand, the toxicity decreased as polar 'functional groups were introduced on the alkylic side chains. The partition coefficient n-octanol/water, an indicator of hydrophobicity, was observed to be positively correlated with the methanogenic inhibition. The results indicate that hydrophobicity is an important factor contributing to the high toxicity of numerous aromatic compounds. Therefore, highly hydrophobic compounds such as resin constituents, apolar lignin derivatives and chlorinated aromatics and are the primary suspect toxicants in forest industry effluents.

    The susceptibility of important organic toxins in forest industry effluents to anaerobic biodegradation was assessed. The results indicated that anaerobic treatment technologies have a limited capacity to mineralize natural wood toxins. Although the degradation of a lignin derivative, guaiacol, and long chain fatty acids was demonstrated, other important wood toxins such as volatile terpenes and resin acids were persistent.

    Finally, the treatability of TMP and soda pulping effluents was evaluated in lab-scale upward-flow anaerobic sludge blanket (UASB) reactors. TMP wastewaters were found highly suitable for anaerobic treatment. Despite the inhibitory character of soda pulping liquors, anaerobic systems were feasible for removing the biodegradable COD if, prior to biological treatment, the wastewaters were diluted to subtoxic levels or detoxified by pretreatment with the adsorbent Amberlite-XAD-2.

    Populierehout, een grondstof
    Zwan, R.P. van der - \ 1987
    Populier 24 (1987)3. - ISSN 0166-7491 - p. 53 - 57.
    chemische behandeling - bosbouw - pulp- en papierwarenindustrie - pulpbereiding - bomen - chemical treatment - forestry - pulp and paper industry - pulping - trees
    Het artikel geeft een overzicht van populierehout. Aan de orde komen de anatomie en chemie en de toepassingen in de vorm van vezel, plaatmaterialen en massiefhout. Het besluit met een beschouwing over de gebruiksmogelijkheden in de toekomst. Dit artikel is een uitgebreide samenvattingen van een rapport dat is aangeboden aan de NPC (Nationale Populieren Commissie). Het rapport past in een groter onderzoeksproject inzake inlands hout met bijzondere aandacht voor populieren
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