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Three enzyme preparations based on the cellulase complex of Penicillium verruculosum and three Trichoderma reesei-based enzyme cocktails were used for evaluating the enzymatic convertibility of cel ...

A combined pretreatment of sugarcane bagasse with glycerol and sulfuric acid was investigated based on a central composite rotatable experimental design. The following factors were varied: temperature (150–199°C), time (0.69–2.3 h), H2SO4 concentration (0.0–1.1%), and glycerol concentration (55.4–79.6%). Xylans and lignin were considerably solubilized during pretreatment. Xylan solubilization, ranging between 6% and 94%, increased significantly with the increase of temperature, time, and H2SO4 concentration and dropped with the increase of glycerol amount. Glycerol restricted the solubilization and full hydrolysis of xylans and the degradation of xylose. Lignin solubilization (20.6–49.4%) increased with the increase of all the experimental factors. Cellulose recovery, which was generally high, increased with the increasing of glycerol concentration and declined at high levels of the other factors. Recoveries above 97% were achieved at low H2SO4 concentration and high glycerol load, whereas the lowest value (83.4%) was achieved in the longest-lasting experiment. The models based on the experimental results predicted the maximal lignin solubilization at 187.7°C, 2.3 h, 79.6% glycerol, and 0.64% H2SO4, whereas the highest yield of enzymatic hydrolysis can be expected at 194.1°C, 1.67 h, 79.6% glycerol, and 1.1% H2SO4. The optimal conditions were confirmed in control experiments. The synergistic effect of sulfuric acid and glycerol on the enzymatic hydrolysis of cellulose was demonstrated.

In steam pretreatment the defibration is usually achieved by an explosion at the end of the treatment, but can also be carried out in a subsequent refiner step. A steam explosion and a steam refining unit were compared by using the same raw material and pretreatment conditions, i.e. temperature and time. Smaller particle size was needed for the steam explosion unit to obtain homogenous slurries without considerable amounts of solid chips. A higher amount of volatiles could be condensed from the vapour phase after steam refining. The results from enzymatic hydrolysis showed no significant differences. It could be shown that, beside the chemical changes in the cell wall, the decrease of the particle size is the decisive factor to enhance the enzymatic accessibility while the explosion effect is not required.

In this study, correlations between the charge density of adsorbed cationic xylans and the mechanical properties of selected pulps are discussed. Hand-sheet experiments were carried out using birch sulfate pulp and spruce sulfite pulp after the adsorption of 2-hydroxypropyl-trimethylammonium-4-O-methylglucuronoxylans (HPMAGXs) with different molar degrees of substitution (MS) in the range of 0.06–0.19. The charge density of the HPMAGX in water was determined by polyelectrolyte titration. Properties such as the tensile and burst index increased after HPMAGX addition and showed an optimum depending on the MS, which was 0.1 for both pulps. Other properties like the tear-index or the specific volume changed depending on the pulp. Beating experiments were also performed and showed an increasing tensile index of birch kraft pulp in the range of 53.7 to 85.7 N m g−1 for a beating time of 10 min. The adsorption of HPMAGXs with different MS onto thiol-based self-assembled monolayers (SAMs) on gold and regenerated cellulose surfaces were studied using surface plasmon resonance (SPR). Electrostatic interactions were found to be the most important factors affecting HPMAGX adsorption, and a strong correlation between HPMAGX adsorption onto carboxyl-terminated SAMs (SAM-COOH) and paper strength when HPMAGX was used as a papermaking additive was observed.

Arabinoxylans from corn cob and oat spelt were studied in sorption experiments onto bleached and unbleached softwood kraft pulp. The corn cob (CC) xylans were produced by steam extraction (SE-CC) and alkaline extraction (NaOH-CC), while the oat spelt xylan (NaOH-OS) was obtained by alkaline extraction. Both alkaline extracted xylans exhibited a high degree of polymerization (DP) (230–240), whereas the steam extraction induced a significant degradation resulting in DPs around 36. Investigation of the xylan addition mode revealed that adding xylan before beating of pulp is most effective for increasing the beating degree and the strength properties. The tensile and burst indices are improved by xylan addition over the whole range of beating degrees. In contrast to that, the tear strength is increased significantly for unbeaten pulps but declines after beating, compared to the reference. Xylan sorption rates are increased with prolonged beating. Highest sorption rates are observed for the NaOH-OS (12–32%) and lowest for the SE-CC xylan (6.6–14%). In general, the alkaline extracted xylans have a better performance, most likely as a result of their higher molar masses.

Different paper-grade pulps were extracted with nitren, NaOH and KOH in order to produce dissolving pulps and polymeric xylan. The yield and structure of the isolated nitren and alkali xylans were investigated by carbohydrate analysis, HPSEC and 1H-NMR spectroscopy. In addition the effect of washing stages on the residual nickel content of the nitren xylans was investigated. By nitren extraction up to 98% of the xylan could be extracted out of the fully bleached eucalyptus and birch kraft pulps. The nitren extracted kraft xylans had DP values between 95 (birch) and 111 (eucalyptus). At most 5 mol% of the xylose units were substituted. In the case of pulps with low mannan content only marginally differences between the nitren and alkaline (KOH, NaOH) extractions occurred. The extraction of the relatively “mannnan rich” pulps of this study like softwood kraft and beech sulfite pulps revealed that the dissolution effect regarding mannans increased in the following order: nitren

Angesichts hoher Olpreise und der sich abzeichnenden globalen Klimaveranderungen erscheinen biotechnisch hergestellte Energietrager als vielversprechende Zukunftsoption. Mit seinen Jahresproduktionsmengen von 2 Mio t Biodiesel, 560.000 t Bioethanol und seinen 2.700 Biogasanlagen befindet sich Deutschland in Sachen Bioenergie in der vorderen Halfte der Industrienationen. Vorgestellt werden die Moglichkeiten, die die weise Biotechnologie zur Herstellung von Energietragern bietet. In view of the high price of oil and the emerging global climate changes, biotechnologically produced energy sources appear to be a promising option for the future. Of the industrial nations, Germany with annual production figures of 2 m tons of biodiesel, 560,000 tons of bioethanol and some 2,700 biogas plants is in the upper half of the bioenergy rankings. Here, the potential of industrial biotechnology for energy production is presented in detail.

Boiling processes in veneer industry generate large amounts of process water replete with dissolved wood extractives. In the present study the chemical composition of boiling waters from 18 industrially treated wood species were investigated. Contamination levels of the boiling waters varied within a wide range depending on the different extractive contents of the processed wood species and operational conditions. Boiling wood species with high extractives content, heated over several days at temperatures above 80 °C, generate highly loaded waste waters with chemical oxygen demands (CODs) of up to 7000 mg l-1. The determination of the elemental composition, using optical emission spectrometry (ICP-OES), showed iron contents of up to 10 mg l-1. Phenolic compounds were in a range of 40 to 900 mg l-1. Flavonoid compounds and phenolic acids were identified in the boiling waters by liquid chromatography (RP-HPLC-UV). The results confirm the need for water treatment facilities to establish a recycling process and to avoid discolourations of the wood by accumulated wood extractives.

The topochemical distribution of accessory compounds responsible for wood colouration during heartwood formation and processing of black cherry (Prunus serotina) is restricted to the axial and ray parenchyma cells. (+)-Catechin, taxifolin, aromadendrin, eriodictyol, naringenin, 4′-methoxynaringenin and prunin were identified in acetone/water extracts. However, the colour of wood after extraction is still reddish-brown, indicating that the coloured material is polymeric (cross-linked, condensed). It was demonstrated that (+)-catechin plays a pivotal role in the development of heartwood colour. Its concentration at the sapwood/heartwood boundary decreases, presumably due to the formation of non-soluble polymeric proanthocyanidins. Heat treatment of heartwood during veneer production intensifies the reddish-brown heartwood colour, probably by promoting the polymerisation of (+)-catechin and other flavonoid monomers.

Xylans were selectively removed from paper-grade pulps by nitren extraction to produce dissolving pulps. Extraction parameters were optimised for a birch kraft pulp regarding time, temperature, liquor/pulp ratio, and total nitren charge. Furthermore, the applicability of the method was investigated for two other kraft pulps obtained from eucalyptus and mixed softwood, and for one beech sulfite pulp. Extracted pulps were characterised regarding their carbohydrate content and Cuen viscosity. The nitren charge was a decisive factor for xylan removal and pulp purity. The combination of a high nitren concentration and low liquor/pulp ratio was most effective for xylan removal. However, a high liquor/pulp ratio with a lower nitren concentration proved to be more selective and minimised cellulose degradation as well. Glucomannans were almost insoluble under the extraction conditions investigated. Therefore, softwood pulps were not suitable for the upgrading of chemical pulps to dissolving pulps by nitren extraction. On the other hand, hardwood pulps obtained by kraft and sulfite processes contained 96–97% cellulose after nitren extraction.

Technical cellulose-2.5-acetates (CA 2.5) were characterized regarding their carbohydrate composition in comparison to the raw material. The association of the CA 2.5 samples in acetone was studied by size exclusion chromatography (SEC) using various acetone grades and styrene divinylbenzene copolymer columns. In HPLC grade acetone with and without addition of 1% water up to three different pre-humps eluted in front of the main fraction of the polymer. The evaluation of the main peak by light scattering measurements resulted in high molar masses indicating that for these technical CA 2.5 samples even the main fraction is not dissolved without association. No pre-humps or association phenomena were observed after addition of 1 ppm LiBr to HPLC grade acetone or with p.a. grade acetone. In addition pre-hump enriched and pre-hump free fractions were isolated by fractionated precipitation. The carbohydrate composition of these fractions was determined and correlated with their association pattern in SEC investigations.

The gene encoding the branching enzyme (BE) from the thermoalkaliphilic, anaerobic bacterium Anaerobranca gottschalkii was fused with a twin arginine translocation protein secretory-pathway-dependent signal sequence from Escherichia coli and expressed in Staphylococcus carnosus. The secreted BE was purified using hydrophobic interaction and gel filtration chromatography. The monomeric enzyme (72 kDa) shows maximal activity at 50 degrees C and pH 7.0. With amylose the BE displays high transglycosylation and extremely low hydrolytic activity. The conversion of amylose and linear dextrins was analysed by applying high-performance anion exchange chromatography and quantitative size-exclusion chromatography. Amylose (10(4)-4 x 10(7) g/mol) was converted to a major extent to products displaying molecular masses of 10(4)-4 x 10(5) g/mol, indicating that the enzyme could be applicable for the production of starch or dextrins with narrow molecular mass distributions. The majority of the transferred oligosaccharides, determined after enzymatic hydrolysis of the newly synthesized alpha-1,6 linkages, ranged between 10(3) and 10(4) g/mol, which corresponds to a degree of polymerisation (DP) of 6-60. The minimal donor chain length is DP 16. Furthermore, the obtained results support the hypotheses of a random endocleavage mechanism of BE and the occurrence of interchain branching.

Two different approaches for the isolation of xylan from hemicellulose-rich sources have been investigated: Alkaline extraction from roller-mill pretreated oat spelts and Nitren extraction of birch kraft pulp. For xylan recovery from oat spelts the experiments included extraction with 5% NaOH at 90 °C, followed by precipitation in methanol or 2-propanol without neutralisation in order to facilitate NaOH recovery. A subsequent peroxide bleaching yielded a product of approximately 90% ISO brightness. The work on Nitren extraction of birch kraft pulp included the optimisation of the extraction process with regard to the Nitren charge. Nitren was much more specific in xylan extraction compared to Cuen, and up to 90% of the xylan content of the birch kraft pulp could be removed. It turned out that dried pulps were superior for this process compared to never-dried pulps, since substantial cellulose proportions in never-dried pulps were also mobilised by Nitren treatment. The properties of the recovered xylans from both processes were compared with regard to molar mass and substitution. It could be demonstrated that more or less intact arabinoxylans with molar masses of 30,000 g/mol could be obtained from oat spelts. The arabinoxylans contained 8-10 mol-% arabinofuranose and 2 mol-% 4-O-methyl-glucuronic acid substituents. Nitren extraction of a birch kraft pulp yielded xylans of 9,400 and 11,200 g/mol. Only traces of 4-0-methyl-glucuronic- and hexenuronic acid substituents could be found.

Due to over-exploitation in the past, native conifer species in many tropical countries are hardly available anymore for wood utilization. In the last decades Costa Rica has undertaken considerable efforts to study the silvicultural characteristics of the native species of the family Podocarpaceae, in particular Podocarpus oleifolius var. macrostachyus (Parl.) Buchholz and Gray, in order to evaluate its suitability for cultivation in mixed plantations with preference for native species. However, sufficient information on the structural, chemical and physical characteristics of the wood of this species are not available. This investigation reports on selected wood characteristics of old-growth trees from the Cordillera de Talamanca (approximately 2,700 m a.s.l.), Costa Rica. Tracheids occupy 93% of total volume; average tracheid length is 4 mm, wall thickness ranges 2.5–4.5 (–6.5) μm throughout the annual increment. Lignin content is between 33.6 and 34.7% excluding any lignin-like compounds. Cellular UV microspectrophotometry reveals that the compound middle lamella (CML) and S2 layer are characterized by a higher absorbance than is commonly observed in e.g. Pinaceae, and with a distinct gradient from S1 to S3. The carbohydrate (cellulose and hemicelluloses) composition reflects the typical proportions as found in other conifers. A low content of organic extractives explains the only moderate (white rot) to low (brown rot) natural durability of the heartwood against wood destroying fungi. The wood density (12% mc) ranges 0.5–0.68 g cm-³; compression strength (44±2.38 MPa) and corresponding modulus of elasticity (8,600±1,720 MPa) indicate good elastomechanical properties. Accordingly, the wood is recommended for multiple indoor enduses. For exterior applications, effective protective measures and/or preservative treatment are required.

Endoglucanases were used as a selective tool to determine the substituent distribution along the chains of partially substituted cellulose acetates. Unsubstituted segments are intensively fragmented while highly substituted segments are only slightly degraded or not affected at all. Two different procedures were developed to perform a preparative separation of the fragments by size exclusion chromatography. One system is based on a direct separation of the fragmentation products using pyridine : water (9 : 1) as an eluent. The isolated fragments can be analysed regarding to their DS values by ATR/FTIR spectroscopy or by hydrolysis and HPLC. The second system is based on deutero-acetylation of endoglucanase fragmented samples. The complete acetylation of all OH groups enables a chromatographic separation in chloroform. Afterwards the isolated fragments can be analysed regarding to their partial DS values by 1H-NMR spectroscopy.

This paper introduces Multi-Application Purpose SAR (MAPSAR). A new Synthetic Aperture Radar (SAR) mission for earth observation. MAPSAR is the result of a joint pre-phase A study conducted by INPE and DLR targeting a mission for assessment, management and monitoring of natural resources. The applicability of the sensor system was investigated for cartography, forestry, geology, geomorphology, hydrology, agriculture, disaster management, oceanography, urban studies and security. An L-band SAR, based on INPE's multi-mission platform (MMP), has been chosen as payload of the satellite. The key component of the SAR instrument is the SAR antenna, which is designed as an elliptical parabolic reflector antenna. L-band (high spatial resolution, quad-pol) has been selected for the SAR sensor as optimum frequency accounting for the majority of Brazilian and German user requirements. At the moment, the pre-phase A has been concluded and the phase A is planned to start in early 2003.

The supermolecular structure of dissolving pulps produced from hardwood by the organosolv processes Acetosolv, Formacell, and Milox was characterized by physical methods (TEM, WAXS, SAXS, NMR) and compared with conventional Sulfite and standard commercial dissolving pulps. The suitability of the pulps for the NMMO technology was tested by spinning fibres and blowing films, whose structural and mechanical properties have also been determined. With TEM it was shown that the TCF-bleached organosolv pulps have only the primary (Formacell), the primary and S1 (Milox), or mainly the S1 (Acetosolv) layers exposed to the surface, whereas Sulfite pulping exposes the S2 cell wall layer. Especially for Milox and Acetosolv Eucalyptus wood pulps, a reduced degree of crystallinity was found, both with WAXS and NMR. The SAXS results indicate a lower pore intersection length for the new pulps as compared to conventional pulps. Unbleached organosolv pulps show a lower crystallinity, very low pore intersection lengths, and an average crystallite shape different from their bleached counterparts. The dissolution behaviour in NMMO and the processability of the bleached organosolv pulps was satisfactory so far. Fibres and films could be produced with structural and mechanical properties comparable with conventional Sulfite and standard commercial dissolving pulp products. However, unbleached organosolv pulps did not meet the requirements of the NMMO process.

New acidic organosolv pulping processes, such as Acetosolv, Formacell and Milox, promise to have superior potential in terms of purification selectivity and specific investment costs. Consequently, a thorough investigation of these new acidic pulping processes in comparison to state-of-the-art acidic magnesium sulfite technology was conducted. The impact of pulping and bleaching parameters on the physical and chemical characteristics was studied to compare process efficiency and selectivity for each type of pulp made from Eucalypt wood. In addition to a detailed analysis of the chemical composition and physical properties on a molecular and supramolecular level, the TCF-bleached dissolving pulps were tested for their applicability in viscose fiber production. The influence of pulp properties as determined by standard and advanced analytical methods on process performance and selected fiber properties is emphasized.

Four methyl cellulose samples in the degree of substitution range from 0.5 to 2.0 were characterised by combination of different analytical methods. Samples were analysed regarding their partial degree of substitution by hydrolysis and anion exchange chromatography with pulsed amperometric detection. For calibration of the chromatographic system, standard substances were isolated by preparative HPLC and their structure was confirmed by 13C-NMR spectroscopy. For two methyl cellulose samples per-acetylation and 13C-NMR with inverse gated decoupling was carried out for comparison with the chromatographic analysis. Endoglucanase fragmentation of methyl celluloses was performed and water-soluble and insoluble fractions were analysed separately. A preparative size exclusion chromatography system for enzymatic-degraded water-soluble methyl cellulose was developed and the molar masses of the individual fractions were examined by analytical size exclusion chromatography. By combination of endoglucanase fragmentation, preparative chromatography, hydrolysis and anion exchange chromatography an approach for the analysis of the substitutent distribution along the polymeric chain of water-soluble methyl cellulose could be established.

Eight cellulose acetate samples with degree of substitution (DS) in the range from 0.4 to 2.7 were characterised regarding their DS, substituent distribution in the anhydroglucose units, molar mass distribution and intrinsic viscosity. Samples were intensively hydrolyzed with a purified endoglucanase and the degradation monitored by analytical size exclusion chromatography (SEC). A preparative SEC system using pyridine:water was developed, suitable for the analysis of samples over a wide range of DS. Two methods were established to determine the DS in milligram scale for further analysis of isolated fragments. For cellulose acetate samples with DS 0.4, 0.7 and 1.2 endoglucanase fragmentation followed by preparative chromatography and analysis of isolated fragments was performed. The procedure was suitable to determine differences in the substituent distribution along the polymeric chain of cellulose acetates susceptible to endoglucanase hydrolysis.

Cellulose acetate (CA) was found to be a substrate of several acetyl xylan esterases (AXE). Eight AXE from different carbohydrate esterase (CE) families were tested on their activity against CA with a degree of substitution of 0.7 and 1.4. The classification of the AXEs into CE families according to their structure by hydrophobic cluster analysis followed clearly their activity against CA. Within the same CE family similar, and between the CE families different deacetylation behaviours could be observed. Furthermore, each esterase family showed a distinct regioselective mode of action. The CE 1 family enzymes regioselectively cleaved the substituents in C2- and C3-position, while CE 5 family enzymes only cleaved the acetyl groups in C2-position. CE 4 family enzymes seemed to interact only with the substituents in C3-position. Evidence was found that the deacetylation reaction of the CE 1 family enzymes proceeded faster in C2- than in C3-position of CA. The enzymes were able to cleave acetyl groups from fully substituted anhydroglucose units.

Summary The topochemical distribution of phenolic extractives in steamed and kiln-dried beechwood with discolourations was investigated on a cellular level by using scanning UV microspectrophotometry (UMSP). For the chemical characterisation of accessory compounds, acetone and methanol extracts of the discoloured beechwood were separated by accelerated solvent extraction (ASE) and analysed with high performance liquid chromatography (HPLC). The UV microscopic investigations reveal that the accessory compounds responsible for the discolouration of beechwood are mainly restricted to the longitudinal and ray parenchyma cells and the lumen of vessels. The detected extractives are characterised by high UV absorbance values and an absorbance maximum in a wavelength range between 280 and 290 nm. The separation of the acetone and methanol extracts of discoloured beechwood shows the presence of different low molecular phenols such as catechin and 2,6-dimethoxybenzochinon, which are transformed into high condensation compounds during steaming and kiln-drying.

Two cellulose acetates (CA) were regioselectively deacetylated by action of a pure Aspergillus niger acetylesterase from the carbohydrate esterase family 1. The action of acetyl esterase along the polymeric chain was monitored by a new enzyme-aided method. CA with and without esterase modification was hydrolysed with a pure endoglucanase. The fragments were deutero-acetylated and separated by preparative SEC in CHCl3. The partial degree of substitution of the individual fragments was determined by 1H-NMR spectroscopy. The investigation confirmed the uniform regioselective and regular deacetylation along the polysaccharide chain. The partial substitution in C2 seemed to be of major importance for the enzyme's mode of action.

A purified acetyl esterase (AE), isolated from a commercial enzyme preparation, released acetic acid from water-soluble and water-insoluble cellulose acetates (CAs), native and chemically acetylated xylan as well as acetylated starch. The AE specifically cleaved off the acetyl substituents from the C2- and C3-positions from CAs of DS

Summary Eucalyptus globulus wood samples were delignified in two-stage treatments carried out in media made up of formic acid, water and hydrogen peroxide under selected operational conditions. The pulps were subjected to Totally Chlorine Free (TCF) bleaching sequences. Alkaline treatments, oxygen delignification, ozone stages and treatments with peroxyacids were assayed in order to reach the target values for dissolving pulps. Under the best conditions, a fully bleached pulp (91.6% ISO brightness) with SCAN viscosity of 649 ml/g and favourable molar mass distribution was obtained.

Four xylan samples from different origin were investigated, using a multi-detector, size exclusion, chromatographic system with two chromatographic column sets and mobile phases differing in the DMSO:water ratio. Molar mass distribution could be analysed best using a mobile phase of DMSO:water (90:10) with addition of 0.05 M LiBr, a system offering good solubilisation of the polymers and a proper chromatographic separation. SEC analysis in aqueous systems provided information on solubility and aggregation of xylans. A comparison of UV- and RI-signals in different systems gave further information on lignin impurities, which in some cases were involved in aggregation phenomena. Both analytical systems were applied to study the enzymatic fragmentation of xylans. Combining the information derived from the two systems can differentiate between the enzymatic degradation of the well-dissolved and the associated polymer fractions.

Summary FTIR spectroscopy was used to estimate monosaccharide content in Eucalyptus globulus wood, using the natural variability of the species for calibration and validation of the method . A total of 38 samples from 9 year old trees from provenance trials was used. The composition ranged for glucose from 43.2% to 59.5%, for xylose from 9.4% to 17.8%, for galactose from 0.5% to 5.4%, for mannose from 0% to 2.8%, and for rhamnose from 0.3% to 0.8%, based on extractive-free dry wood. The multivariate analysis gave in general, better results with increased R2, lower SEC and SEP errors, although the univariate method also gave good fits with high coefficient of determination (R2) based on remaining data once outliers were removed. FTIR techniques may be used in large scale breeding programmes to measure wood monosaccharide composition with considerably less effort and in shorter time than wet-lab methods, once a reliable calibration has been made for the species.

A screening of commercial enzyme preparations for the capability ofcellulose acetate (CA) deacetylation revealed that such enzyme activity ismore common than could be anticipated. Enzyme-aided deacetylation of celluloseacetate was clearly a function of the degree of substitution (DS). Celluloseacetates up to a DS of 1.4 were deacetylated by a large number of enzyme mixes.Interestingly, none of the investigated enzyme preparations had the capabilityfor complete cellulose acetate deacetylation. Definitely most hydrolasepreparations investigated in our study deacetylated cellulose acetate with nopreference for a certain position, as could be confirmed by NMR spectroscopy.However, one acetyl esterase had a clear preference for the C2- andC3-positions, leaving the acetyl substituents at the C6-position intact.

An approach is presented for the quantitative analysis of the substituent distribution in carboxymethyl cellulose (CMC). Standard substances have been isolated by preparative HPLC and characterised by 13C-NMR spectroscopy. The availability of these reference substances enabled a quantitative HPLC determination of glucose and its seven carboxymethyl derivatives by anion exchange chromatography and pulsed amperometric detection. A comparison of sulphuric acid and perchloric acid hydrolysis for conventional CMC samples gave higher yields for perchloric acid. The yield of the eight CMC building units decreased with increasing DS for both hydrolysis methods. Results were different, when samples from new synthesis concepts were investigated. While CMCs from induced phase separation showed increasing hydrolysis yields up to a DS of 1.9 regioselectively substituted 2,3-O-CMC gave lower yields with increasing DS. For 2,3-O-CMC samples sulphuric acid proved to be the superior hydrolysis medium.

Four carboxymethyl cellulose samples derived from the synthesis concept of “reaction in reactive microstructures” were characterised in detail by combination of different analytical techniques. Fractionation of one of the samples according to water-solubility into four fractions revealed that a non-statistical distribution of the substituents occurred for all fractions. Endoglucanase fragmentation of three samples was performed followed by analytical and preparative SEC. The multi-detected analytical SEC proved samples of high degree of substitution up to 1.9 to be intensively degraded, supporting the proposed block-like substitution pattern. The detailed investigation of soluble fragmentation products by preparative SEC, hydrolysis and anion exchange chromatography with pulsed amperometric detection revealed that all samples contain fragments of much higher DS values than the average DS of the starting material. On the other hand, high quantities of degradation products of low DS or almost no substitution occurred. Therefore, a structure can be proposed with segments of very high DS alternating with areas of limited substitution. The result clearly showed that the high substituted fragments were dominated by 2,3,6-tri-O-CMG.

Summary In the present study, the biological, chemical and mechanical wood properties of “Wulstholz” as a response to mechanical stress of spruce trees (Picea abies [L.] Karst.) were investigated. “Wulstholz” is formed locally on the compression side of overstressed tree trunks after slip planes were initiated. It is characterized by an increased xylem production leading to bulges. The S2-layers of “Wulstholz”-tracheids are thicker than the corresponding cell wall layers in normal wood, and the cell lumen diameter is significantly reduced. The tracheid length decreases gradually from an average of 4 mm to 2.5 mm compared to normal wood, and the tracheids conspicuously are shifted against each other longitudinally. “Wulstholz” contains a higher concentration of lignin than normal wood, whereas the concentration of glucose in the hydrolysates is reduced. The hemicelluloses-concentration, particularly the mannose-content, is significantly higher compared to normal wood. The compression strength and the modulus of elasticity, despite a higher density, are significantly reduced in “Wulstholz” in comparison to normal wood. But due to the specific anatomical and chemical properties, “Wulstholz”-tracheids can be deformed and compressed considerably without fracturing. The investigations demonstrate that “Wulstholz” can restabilize wind-exposed trees.

The determination of the molecular structure of 2,3-O-carboxymethyl cellulose (2,3-O-CMC), prepared via 6-O-(4-monomethoxy)triphenylmethyl cellulose, was carried out in detail by means of enzymatic and chemical methods. The 2,3-O-CMCs had degrees of substitution (DS) in the range of 0.5–1.2 showing a narrow molar mass distribution as revealed by SEC. As a result of an endoglucanase treatment, an intensive depolymerization of the samples occurred which was more pronounced for 2,3-O-CMC with comparatively low DS. All degraded samples could be separated into 18 fractions by preparative SEC and the proportion of each individual repeat unit was analysed by anion exchange chromatography (AEC) following complete hydrolytic chain degradation. The results indicated a homogeneous distribution of the functional groups within the polymer chain. Moreover, it became obvious that a preferred carboxymethylation of O-2 compared with O-3 occurred and that a preferred functionalization of already carboxymethylated units occurred as the reaction progressed. AEC with pulsed amperometric detection, which was used to separate and analyse the differently functionalized repeating units as well as glucose, had to be calibrated. Therefore, a method to determine the response factors of the individual carboxymethylated glucose units was developed using 13C NMR spectroscopic measurements (inverse gated decoupling) of depolymerised 2,3-O-CMC.

Two conventionally prepared carboxymethylcelluloses (CMCs) with differing degrees of substitution (DS: 0.6 and 1.2) were fragmented by endoglucanase treatment until no further degradation was possible. This treatment brought about a decisive improvement in the water solubility of the polymers. The degraded samples were separated into 18 fractions by size exclusion chromatography (SEC). The quality of the preparative SEC was monitored by analytical SEC equipped with a multiple detector system. After acidic hydrolysis of each individual fraction, the carboxymethyl derivatives of the anhydroglucose units were determined by anion exchange chromatography and pulsed amperometric detection. The accessibility of endoglucanase action was clearly a function of the degree of substitution (DS). As the DS increased the efficiency of the enzyme became more limited. It could also be demonstrated that the polysaccharide chain of both CMC samples included some regions that were highly substituted and some other regions of low substitution.

SUMMARY: Sodium carboxymethylcellulose (NaCMC) with varying degrees of substitution (DS) was investigated with different analytical methods in order to characterize the functional group distribution. The following methods were tested and adapted: high-resolution 13 C NMR spectroscopy in the solid state ( 13 C CP/ MAS NMR) and 13 C NMR spectroscopy on solutions of NaCMC samples with a reduced molar mass. Partial degradation was accomplished by ultrasonic means and with the enzyme endoglucanase. Combining the two techniques resulted in the greatest reduction in molar mass and hence in the best spectral resolution. Analysis of the NaCMC fragments following ultrasonic and/or endoglucanase degradation also reveals another interesting experimental finding. It appears that ultrasonic degradation is favored at unsubstituted areas near the center of the chain. These methods were compared with the following already familiar techniques of analysis: titrimetric techniques; 13 C and 1 H NMR spectroscopy as well as HPLC on completely hydrolysed solutions (hydrolysis with perchloric acid, trifluoroacetic acid and sulfuric acid). All of the methods characterize the samples as a series with increasing DS, the values of which range from 0.9 to 2.4. Methods that permit analysis of the partial degree of substitution produced the distribution x 2 A x6 A x3. Therefore, they are in principle suited for determining the functionalization pattern of the NaCMC samples relative to one another. The most suitable method can therefore be selected according to the objectives and the apparatus available. However, the measured values do exhibit considerable spread, variances of approx. 20%, thus, place restrictions on using the values of DS or xi in absolute comparisons beyond these methods.

Three types of sprucewood chemical pulps, which differed in their characteristics, were treated with two xylanases and two mannanases of fungal and bacterial origin. The effect of the enzymes was measured in terms of a range of chemical and physical pulp properties, in order to obtain a clearer understanding of the reaction of hemicellulases on pulps. The amount of carbohydrates dissolved by the enzymes seems to be dependent on the size of the enzyme, the accessible surface area of the pulp, and topochemical substrate restrictions. Xylanases released more carbohydrates compared to mannanases. There was a synergistic effect observed with combined treatments using xylanases and mannanases. Using different techniques it could be shown that internal structural changes in the pulp fibres occurred in addition to the well-known surface modifications

Drei chromatographische Methoden, namlich die Boratkomplex-Anionenaustauschchromatographie, die Anionenaustausch-chromatographie in NaOH-Medium und die Hochleistungsdunnschichtchromatographie werden am Beispiel saurer Hydrolysate von Buchenholz, Fichtenholz und Chinaschilf auf ihre Eignung zur Quantifizierung der funf Holzzucker Galactose, Glucose, Mannose, Arabinose und Xylose uberpruft.

The major α-glucuronidase of T. reesei Rut C-30 was purified by chromatographic methods. The molecular and hydrolytic properties of the purified enzyme were studied. The enzyme had a molecular weight of 91,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and a pI of 5.0–6.2 as determined by chromatofocusing. The pH optimum was pH 4.5–6.0 and the enzyme was stable for 24 h at 40°C at pH 4.8–5.5. The purified α-glucuronidase preferred low-molecular-weight xylooligomers as substrate. The enzyme seemed to act almost exclusively on the bond between the terminal xylose at the nonreducing end of a xylose chain and the methyl glucuronic acid attached to it. Minor activity against long-chain glucuronoxylan was also detected. A significant enhancing effect of α-glucuronidase on the hydrolysis of glucuronoxylan by pure xylanases was observed.

Steam refining was investigated as a pretreatment for enzymatic hydrolysis of poplar wood from a short rotation plantation. The experiments were carried out without debarking to use an economically realistic raw material. Steam refining conditions were varied in the range of 3–30 min and 170–220°C, according to a factorial design created with the software JMP from SAS Institute Inc., Cary, NC, USA. Predicted steaming conditions for highest glucose and xylose yields after enzymatic hydrolysis were at 210°C and 15 min. Control tests under the optimized conditions verified the predicted results. Further pretreatments without bark showed that the enzymes were not significantly inhibited by the bark. The yield of glucose and xylose was 61.9% of theoretical for the experiments with the whole raw material, whereas the yield for the experiments without bark was 63.6%. Alkaline extraction of lignin from the fibers before enzymatic hydrolysis resulted in an increase of glucose yields from mild pretreated fibers and a decrease for severe pretreated fibers. The extracted lignin had a high content of xylose of up to 14% after very mild pretreatments. On the other hand, molecular weights of the extracted lignin increased substantially after pretreatments with a severity factor above 4. Hence, alkaline extraction of the lignin seems only attractive in a narrow range of steaming conditions.

No abstract available

Rice hulls are potential low-cost feedstocks for fuel ethanol production in many countries. Most of the relevant publications are devoted to homogenous (high quality) hulls generated in industrial mills. On the other hand, small-scale mills give rise to hulls containing grain fragments and bran. In the present work, the dilute-acid pretreatment of such heterogeneous rice hulls was investigated based on a central composite rotatable experimental design. The variables were: temperature (140–210°C), biomass load (5–20%), and sulfuric acid concentration (0.5–1.5% based on reaction mixture). A total of 16 experimental runs were carried out, including a 23-plan, two replicates at the central point and six star points. Low temperatures were found to be favorable for the hydrolysis of xylan and of the easily hydrolyzable glucan fraction. High glucose formation (up to 15.3% of the raw material dry weight), attributable to starch hydrolysis, was detected in the hydrolysates obtained under the least severe pretreatment conditions. Several models were developed for predicting the effect of the operational conditions on the yield of pretreated solids, xylan and glucan conversion upon pretreatment, and on enzymatic convertibility of cellulose. The pretreatment temperature exerted the most significant effect on the conversion of the polysaccharides. Optimum results were predicted for the conversion of easily-hydrolyzable glucan in the material pretreated at 140.7°C, and for the enzymatic saccharification of cellulose in the material pretreated at 169°C. These results are interpreted that a two-step acid hydrolysis may be the best pretreatment strategy for heterogeneous rice hulls produced in small mills.

Soluble oligosaccharide carbohydrates from the partial enzymatic hydrolysis of pulp were degraded to monosaccharides by enzymatic hydrolysis using a complete mixture of cellulolytic and hemicellulolytic enzymes and subsequently analysed by HPLC. With this method it was possible to obtain a quantitative estimate of both the 5- and 6-carbon sugars comprising the soluble oligosaccharides.

A low-molecular-weight endo-β-1,4- d -xylanase (endo-β-1,4- d -xylan xylanohydrolase; E.C. 3.2.1.8) isolated from solid-state cultures of Myrothecium verrucaria has M r and pI values of 15,900 and 4.35, respectively, and a carbohydrate content of 11% (w/w). The enzyme is most active at pH 5.5 and 45°C, and has a half-life of 16 min at pH 5, 50°C. It catalyzes the hydrolysis of various β-1,4-linked and mixed (1,3; 1,4)-linked β-glucans, but kinetic parameters showed it to be primarily a xylanase. Inhibition studies suggested the possible involvement of arginine, cysteine, histidine, tryptophan, and a carboxylate(s) in binding or catalysis. The pattern of products of hydrolysis of various xylans and of xylopentaose clearly demonstrated the purified enzyme to be an endo-β-1,4-xylan xylanohydrolase (E.C. 3.2.1.8).

Two endo-β-1,4-xylan xylanohydrolases (EC 3.2.1.8), XynA and XynB, from solid-state cultures ofPenicillium capsulatum, were purified to apparent homogeneity as judged by electrophoresis and isoelectric focusing. Each is a single subunit glycoprotein. XynA containing 97 mol carbohydrate·mol−1 protein, while XynB contains 63 mol·mol−1.M r and pI values are 28 500, 5.0–5.2 (XynA) and 29 500, 5.0–5.2 (XynB), respectively. Both enzymes are most active at pH 4 and 47–48°C, and have half-lives of 32 min (XynA) and 13 min (XynB) at pH 4, 60°C. Each form catalyzed the hydrolysis of a variety of xylans, albeit with different degrees of efficiency. In addition, XynB catalyzed extensive degradation of barley β-glucan, CM-cellulose and, to a lesser extent, lichenan, but kinetic parameters indicate that it is primarily a xylanase. The products of hydrolysis of various xylans and xylopentaose differed for each enzyme and ranged from xylose to xyloheptaose depending on the substrate used. Each enzyme is endo-acting and has transferase as well as direct hydrolase activity. Inactivation byN-bromosuccinimide indicated the possible involvement of tryptophan in binding and/or catalysis.

The two main xylanases produced by Trichoderma reesei were purified to electrophoretic homogeneity by ion-exchange and gel chromatography. The enzymes had isoelectric points of 9.0 and 5.5 and their molecular masses were 20 and 19 kDa, respectively. The purified xylanases were most probably distinct gene products, as they were also serologically dissimilar and had different proteolytic cleavage patterns. The pI 9.0 xylanase tolerated higher pH values and temperatures than the pI 5.5 xylanase. Both enzymes clearly preferred polymeric substrates to xylo-oligosaccharides. The substrate preference for polymeric xylans decreased with decreasing substitution (decreasing solubility). The apparent Km values for different xylans varied from 3.0 to 6.8 mg ml-1 for the pI 9.0 xylanase and from 14.8 to 22.3 mg ml-1 for the pI 5.5 xylanase. The pI 9.0 xylanase also showed transxylosidase activity with xylotetraose and xyloheptaose as substrates.

Xylan-degrading enzyme activities were isolated from crude extracts of solid-state cultures of Aspergillus fumigatus Fresenius (Xyl I, Xyl III, Xyl IV and Xyl V) and Humicola grisea var. thermoidea (Xyl II) by chromatographic procedures. The pattern of hydrolysis of different xylans and pulps varied from traces of xylose to xylooligomers. The products formed suggest an endo-type enzyme mode of action. Some enzymes showed debranching and transglycosidase activities.

Simultaneous hydrolysis of acetyl-4-O-methylglucuronoxylan by xylanase and acetyl xylan esterase leads to the highest recoveries of acetic acid, xylobrise, and xylotriese. Treatment with xylanase prior to deacetylation leads to a broad spectrum of neutral and uronic acid-substituted xylooligomers, whereas deacetylation followed by xylanase hydrolysis results in the liberation of fewer but more uniform xylan fragments, with xylobiose as the main neutral degradation product and (4-O-methylglucuronosyl) xylotriose as the main acidic product.

On etudie l'effet de la temperature de traitement a la vapeur (de 170° a 210°C) sur la subsistance de groupes lateraux acetyl- et 4-O-methyl-glucuronosyle dans le xylane du bois de bouleau.

Production of extracellular esterase cleaving phenolic sidegroups from xylan was investigated using strains of Aspergillus. The activity levels produced were unrelated to the ferulic acid content of the lignocellulosic raw material in the cultivation medium. No correlation between the production of feruloyl esterase, acetyl xylan esterase and acetyl esterase activities was observed either. An esterase produced by Aspergillus oryzae was purified to electrophoretic homogeneity. The enzyme was an acidic monomeric protein having an isoelectric point of 3.6 and a molecular mass of 30 kDa. It was most active in the pH-range from 4.5 to 6.0 and was stable at temperatures up to 45°C. The esterase had a wide substrate specificity, liberating ferulic, p-coumaric and acetic acids from steam-extracted wheat straw fragments and acetic acid from acetylated xylo-oligomers and α-naphthyl acetate. The enzyme acted in synergism with other xylanolytic enzymes, which was reflected in increased production of phenolic acids from wheat straw xylo-oligosaccharides in the presence of xylanases of Trichoderma reesei.

Different paper grade pulps were extracted with nitren in order to produce dissolving pulps and polymeric xylan. The yield and molecular structure of the extracted pulps were investigated by carbohydrate analysis and HPSEC combined with fluorescence labelling in order to additionally monitor the carbonyl and carboxyl group profiles of the pulps. The supramolecular structure of selected pulps were further studied by solid state C-13-CP/MAS-NMR and wide-angle X-ray scattering (WAXS). These supramolecular data of nitren extracted pulps were compared to samples extracted with NaOH and a conventional dissolving pulp in order to classify the properties of nitren extracted pulps. Nitren extraction results in selective xylan removal without noticeable degradation or oxidation of the cellulose fraction. The resulting dissolving pulps have high molar masses, a narrow molar mass distribution and the typical contents of carbonyl and carboxyl groups. The supramolecular structure of cellulose is less affected by nitren compared to strong NaOH, and the resultant dissolving pulps still have the cellulose I structure.

Two previously purified esterases of Trichoderma reesei were used to study the deacetylation of polymeric, oligomeric and dimeric acetylated xylan fragments. For the first time nearly complete enzymatic deacetylation of polymeric xylan with purified acetyl xylan esterase was demonstrated, resulting in precipitation of the remaining polymer structure. The esterases had very different substrate specifities, one having a preference for high molecular weight substrates and the other showing high activity only towards acetyl xylobiose. The latter enzyme was also regioselective, cleaving off the acetyl substituent only from the C-3 position of the xylopyranose ring. The highest xylose yield from acetylated xylan was obtained by the synergistic action of xylanase, \-xylosidase and acetyl xylan esterase.