Volume 65, Issue 5

The aim of the present work is the process integration and the optimization of the enzymatic hydrolysis of wood and the following fermentation of the products to ethanol. The substrate is a fiber fraction obtained by organosolv pre-treatment of beech wood. For the ethanol production, a co-fermentation by two different yeasts ( Saccharomyces cerevisiae and Pachysolen tannophilus ) was carried out to convert glucose as well as xylose. Two approaches has been followed: 1. A two step process, in which the hydrolysis of the fiber fraction and the fermentation to product are separated from each other. 2. A process, in which the hydrolysis and the fermentation are carried out in one single process step as simultaneous saccharification and fermentation (SSF). Following the first approach, a yield of about 0.15 g ethanol per gram substrate can be reached. Based on the SSF, one process step can be saved, and additionally, the gained yield can be raised up to 0.3 g ethanol per gram substrate.

Scots pine ( Pinus sylvestris L.) heartwood samples were measured with electrical impedance spectroscopy (EIS) at frequency range 1 Hz–10 MHz in green and relative humidity (RH) 65% conditioned moisture content (MC) after oven-drying. Complex impedance parameters were studied in relation to the density, moisture, resin acid and stilbene contents. The measurements were conducted in tangential (T) and longitudinal (L) directions with 36 samples in each analysis. For green MC, there were significant correlations between impedance phase angle and contents of stilbenes and resin acids at frequencies below 400 Hz. For the resin acid content, the strongest correlation with phase-angle T was -0.45 (P<0.01) at 100 Hz. Impedance magnitude correlated significantly with MC throughout the frequency range, e.g., at 10 kHz, r was -0.71 (P<0.001) for L-direction. In moisture conditioned state, the correlation between stilbenes and T-measured phase angle was strongest at 250 Hz, (r=-0.56, P<0.001). Equivalent circuit model of two ZARC-Cole elements in series was fitted for the measurements in green MC. Several model parameters correlated with MC (e.g., R 1, L r=-0.64, P<0.001), but only one parameter correlated weakly with stilbene content (R 2, T r=0.35, P<0.05). The study shows that EIS has a potential for independent determination of resin acid or stilbene contents and MC for green pine heartwood.

The object of this study was to elucidate the relationship between the chemical structure of purified condensed tannin polymers from tree species and their radical scavenging characteristics. By means of 13 C-NMR spectrometry and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), four kinds of proanthocyanidins were identified: prorobinetinidins, profisetinidins, procyanidins, and prodelphinidins. The tannins were submitted to radical scavenging assays with DPPH and galvinoxyl radicals and from the time-course of the reactions was concluded: 1) Tannins with pyrogallol type B-ring scavenge radicals in the beginning faster than those with catechol type B-ring. 2) Tannins with catechol type B-ring needs more time to scavenge the same amount of radicals as those with pyrogallol type B-ring. 3) The IC 50 values of tannins with catechol type B-ring decrease after longer reaction times with the galvinoxyl radical. 4) Radical scavenging with DPPH radical proceeds faster than that for the galvinoxyl radical.

Two-step hydrolysis of nipa ( Nypa fruticans ) frond, one of the monocotyledonous angiosperms, was studied in a semi-flow hot-compressed water treatment at 230°C/10 MPa/15 min (first stage) and 270°C/10 MPa/30 min (second stage). In the first stage, hemicelluloses such as O -acetyl-4- O -methylglucuronoarabinoxylan and pectin and para-crystalline cellulose were selectively hydrolyzed, as well as lignin, which was partially decomposed. In the second stage, hydrolysis of crystalline cellulose and some additional decomposition of lignin were observed. In addition, inorganic constituents and free sugars, composed mainly of glucose, fructose, and sucrose, were recovered in cold water (20°C/10 MPa/30 min) prior to these 2 stages. In total, 97.3% of oven-dried nipa frond sample could be solubilized into cold and hot-compressed water. The degradation products in the water-soluble portion were primarily recovered as various saccharides (hydrolyzed moieties of the polyoses), which were later dehydrated, fragmented and isomerized partly. The residual (2.7%) is composed mainly of lignin associated with 0.4% of Si. A decomposition pathway is proposed for O -acetyl-4- O -methylglucuronoarabinoxylan as the major hemicellulose based on its various hydrolyzed products.

Effect of acetic acid (AcOH) addition on chemical conversion of Japanese beech ( Fagus crenata ), as a hardwood, and Japanese cedar ( Cryptomeria japonica ), as a softwood, was investigated in the course of treatment in a semi-flow reactor with hot-compressed water (H-CW). One-step treatment of Japanese beech was preliminarily performed to examine the effect of AcOH concentrations on the decomposition behavior at 150–290°C/10 MPa/30 min. Based on the obtained results, two-step semi-flow H-CW treatment with 1 wt% AcOH at 210°C/10 MPa/15 min (1st stage) and 260°C/10 MPa/15 min (2nd stage) was thus selected as the most appropriate treatment and a comparative study of the two woods was accordingly conducted. The differences in decomposition behavior observed between the two woods clearly proved that the addition of AcOH played an important role in enhancing the hydrolysis and decomposition of cell wall components in Japanese cedar due to the lesser amount of acetyl residue in softwood hemicelluloses and its lignin structure.

The extracellular aromatic peroxygenase of the agaric fungus Agrocybe aegerita catalyzed the H 2 O 2 -dependent cleavage of non-phenolic arylglycerol- β -aryl ethers ( β -O-4 ethers). For instance 1-(3,4-dimethoxyphenyl)-2-(2-methoxy-phenoxy)propane-1,3-diol, a recalcitrant dimeric lignin model compound that represents the major non-phenolic substructure in lignin, was selectively O -demethylated at the para -methoxy group to give formaldehyde and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol. The phenol moiety of the latter compound was then enzymatically oxidized into phenoxy radicals and a quinoid cation, which initiated the autocatalytic cleavage of the dimer and the formation of monomers such as 2-methoxy-1,4-benzoquinone and phenoxyl-substituted propionic acid. The introduction of 18 O from H 2 18 O 2 and H 2 18 O at different positions into the pro-ducts provided information about the routes of ether cleavage. Studies with a 14 C-labeled lignin model dimer showed that more than 70% of the intermediates formed were further coupled to form polymers with molecular masses above 10 kDa. The results indicate that fungal aromatic peroxygenases may be involved in the bioconversion of methoxylated plant ingredients originating from lignin or other sources.

Separation of vessel elements and fibers was carried out for Eucalyptus kraft and recycled pulp as raw materials. A new separation method is presented. The surface morphology, surface chemical characteristics and chemistry of individual vessel elements were studied using field emission scanning electron microscopy (FE-SEM), microbeam X-ray photo-electron spectroscopy (μ-XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). By FE-SEM it could be seen that vessel elements in recycled pulp were almost intact or only partly broken via the pits. They were also detected on the surface of newsprint paper. The chemical composition of vessel element surfaces was similar to that of fibers. The surface coverage by lignin in vessels showed scattered results by μ-XPS. However, normalized lignin peak intensities of ToF-SIMS indicated that vessels had lower surface lignin counts than fibers. Vessel elements in recycled pulp were rich in phthalates and other hydrocarbons originating probably from printing ink and paper chemicals. Fillers, sizes, and other paper chemicals were not completely removed from the recycled vessel surfaces during the de-inking.

Neosinocalamus affinis Keng is widely grown in south-western China for pulp and paper production. Rapid assessment of the chemical properties of N. affinis is necessary for both bamboo breeding and industrial utilization. This study was performed to investigate the abilities of Fourier transform near-infrared spectroscopy in the diffuse reflectance mode (FT-NIR-DR) and Fourier transform infrared attenuated total reflectance (FT-IR-ATR) spectroscopy to predict the contents of holocellulose, α-cellulose, Klason lignin, and NaOH extractives in N. affinis . Partial least squares regression models based on the raw and preprocessed spectra, including multiplicative scatter correction (MSC) and Savitzky-Golay 1st and 2nd derivative spectra, were developed for the chemical components of bamboo. The NIR-based calibrations displayed better performance than those using FT-IR-ATR spectra. The best calibrations developed by both methods for properties all had satisfactory correlations, with coefficient of determination (R 2 c ) values ranging from 0.81 (Klason lignin by FT-IR and MSC) to 0.98 (α-cellulose by FT-NIR and 2nd derivative), and root mean standard error of calibration between 0.50 and 1.47%. When applied to prediction sets, the correlations were good, with R 2 p above 0.68. The results demonstrate that both spectroscopic methods, combined with chemometric strategies, could rapidly predict the chemical composition of bamboo.

Soda lignin was converted into sulfonated lignin by oxidation, hydroxymethylation, and sulfonation assisted by microwave irradiation. Oxidation and hydroxymethylation under these circumstances led to lignins with much higher reactivity toward subsequent sulfonation, and the sulfonation degree could be elevated up to 2.75 mmol g -1 . A suitable microwave irradiation time is beneficial to obtain oxidized lignin with small molecular size, but the irradiation time must be selected adequately. Under optimal conditions, the sulfonated lignin exhibits a good dispersive effect to TiO 2 suspension. Compared to conventional water bath heating, microwave irradiation not only increases the sulfonation degree of lignin, but also sharply shortens the reaction time.

As one of the three main components in woody biomass, lignin is an abundant but underused renewable raw material and carbon source. Owing to its aromatic structure and large availability as a by-product of pulping, its conversion into chemicals is highly attractive. In the present work, the oxidation of a softwood kraft lignin in acidic media was investigated in the presence of a homogeneous catalyst. The objective was to find a cheap but efficient catalyst for the depolymerization of kraft lignin into aromatic monomers. Different transition metal salts were screened and compared to phosphomolybdic acid, which was investigated in previous studies, and to experiments in sulfuric acid without additional catalyst. Vanillin and methyl vanillate were the main monomeric products detected by gas chromatography/mass spectrometry but their formation was only slightly increased by using transition metal salts (up to 6.28 wt% yield). However, the presence of iron or copper chloride resulted in fast formation kinetics and significant amounts of other monomeric products. In addition, an efficient fragmentation of the lignin molecule from a weight-average molecular weight of 3500 g mol -1 down to 500 g mol -1 was observed by size-exclusion chromatography. The enhanced incorporation of oxygen into the reaction products in the presence of those catalysts was proven by Fourier transform infrared spectroscopy and the influence of the catalyst concentration was studied.

The white rot fungus Physisporinus vitreus is currently tested for several biotechnological applications such as permeability improvement of refractory wood species or the optimization of the acoustic properties of wood for violins. The enzymatic activity of P. vitreus results in the degradation of pit membranes and simultaneous alterations of the tracheid cell wall structure in wood of Norway spruce [ Picea abies (L.) Karst]. By this means, selective delignification and simultaneous degradation occur in the latewood tracheids at short incubation times. To study the delignification of individual cell wall layers in latewood tracheids, cellular UV-microspectrophotometry was applied to wood of Norway spruce that had been incubated for between 3 and 9 weeks. By means of this technique, the progressing delignification was demonstrated in the latewood tracheid secondary walls. Moreover, local delignification in close proximity to hyphal tunneling, cavities, and notches was evident. Additionally, the mechanical changes were measured (a) at the macroscopic level by Brinell hardness test and (b) at the cellular level by nanoindentation. Brinell hardness was significantly reduced with increasing incubation time which was attributed to the partial delignification. Unlike Brinell tests, results from nanoindentation tests did not show a clear effect of fungal activity because of the material heterogeneity and the high spatial resolution of this technique. The present study provides methodological approaches for the investigation of wood-fungus interactions and contributes to a better understanding of the characteristics of wood decay at the subcellular level caused by the white rot fungus P. vitreus . Moreover, it establishes the basis for a subsequent chemical analysis, for which the results will be the topic of a second paper in this series.

The biotechnological application of the white rot fungus Physisporinus vitreus named “bioincising” is currently being investigated for permeability improvement of Norway spruce ( Picea abies (L.) Karst.) wood. During short-term (<9 weeks) incubation, fungal activity induces degradation of pit membranes and a simultaneous alteration of the tracheid cell wall structure. In Part 1 of this article series, the occurrence of selective delignification and simultaneous degradation was shown by UV-microspectrophotometry (UMSP). Moreover, significant reduction of Brinell hardness was recorded after 7 and 9 weeks incubation. For a better understanding of the chemical alterations in the wood constituents and the corresponding changes of mechanical properties due to fungal activity, we applied microtensile tests on thin strips that were prepared from the surface of incubated Norway spruce wood. Indications for the occurrence of selective delignification and simultaneous degradation were evident. Determination of lignin content and carbohydrate analysis by borate anion exchange chromatography confirmed the results. The present study verifies the findings from Part 1 of this article series and from previously conducted microscopic investigations. Now, the degradation characteristics of P. vitreus are established and the bioincising process can be further optimized with higher reliability.

The critical stress intensity factor of mode I ( K Ic ) obtained by compact tension (CT) tests of wood and medium-density fiberboard (MDF) was experimentally and numerically analyzed. A double cantilever beam (DCB) test was also conducted and the results were compared with those of the CT tests. Similar to the results of single-edge-notched bending (SENB) and single-edge-notched tension (SENT) tests previously conducted, the value of K Ic was obtained properly from the CT test when an additional crack length was taken into account.

The main objective of this study was to evaluate the effect of oxalic acid (OA) wood chips pretreatment prior to refining, which is done to reduce energy used during the refining process. Selected mechanical and physical performances of medium-density fiberboard (MDF) – internal bonding (IB), modulus of elasticity (MOE), modulus of rupture (MOR), water absorption (WA) and thickness swelling (TS) – made from this OA-pretreated wood were tested and the effect of the OA treatment on carbohydrates investigated. The results showed that the OA treatment significantly reduced refining energy usage, and improved MDF dimensional stability and lightness. However, the OA treatment had a negative effect on the internal bonding strength of MDF panels. The amount of extracted carbohydrates was dramatically increased, up to 24 times, by the OA pretreatment. Carbohydrates extracted from wood chips could be a potential sustainable resource for biofuel or bio-based chemicals. This paper is a contribution to the so-called “value prior to pulping (VPP)” concept.

The objective of this study was to investigate how a stress wave travels in a standing tree as it is introduced into the tree trunk through a mechanical impact. A series of stress wave time-of-flight (TOF) data were obtained from three freshly-cut red pine ( Pinus resinosa Ait.) logs by means of a two-probe stress wave timer. Two-dimensional (2D) and three-dimensional (3D) stress wave contour maps were constructed based on the experimental data using a commercial software. These stress wave contour maps represent the wave fronts in a time sequence, illustrating the flow of stress wave energy within a log. The analysis of TOF data and wave fronts indicates that stress wave propagation in standing trees is affected by tree diameter, travel distance, and internal wood conditions (wood properties and structural defects). When a stress wave is introduced into a tree trunk from a point source, it initially propagates in the impact direction as a 3D wave. Then the flow of the stress wave energy gradually changes towards the longitudinal directions. As the diameter-to-distance ratio reaches 0.1 or below, the wave begins to travel as a quasi 1D wave.

Ring-porous hardwoods such as oak are in high demand for furniture-making, cooperage, flooring, and construction. However, evaluating the quality of such timber is difficult and time consuming, and simpler tests are required. Models for predicting as many mechanical properties as possible, based on easier-to-determine mechanical tests, may help. In this study, the hardness, modulus of elasticity, bending, compression, and impact bending strength parallel to grain were tested on defect-free laths obtained from a sample of 42 oak trees. The relationships between the variables were investigated. Three models that relate the resistance to axial compression with bending strength and stiffness (R 2 >0.55; P<0.01) are proposed for defect-free oak timber. Selection of models mainly depended on the bias, which was highly variable among the models tested. The prediction models proposed in the international standard EN 384:2004 for structural dimension timber are not suitable for small clear wood specimens, especially in very elastic woods. The relative independence of hardness and impact bending strength as regards the other mechanical properties is also demonstrated.

Near infrared spectroscopy coupled with multivariate data analysis has been used to predict the specific gravity, modulus of rupture, modulus of elasticity, and fiber stress at elastic limit in bending tests on radial and tangential strip wood samples obtained from five-year-old Eucalyptus tereticornis. Moisture content of samples was 6–21% for bending test and 7–16% for specific gravity. Partial least squares regression calibrations were developed for each wood property. Calibrations had good relationships between values measured in laboratory and NIR predicted values obtained from small clear samples. The coefficient of determination (R 2 ) for calibration ranged from 0.76 to 0.83 and for prediction (R p 2 ) it was between 0.58 and 0.77. Both radial and tangential faces are equally suited for calibration (for radial face R 2 was 0.77–0.83 and for tangential it was 0.76–0.83). Standard errors of predictions were slightly higher compared to standard error of calibration.

The present study examined the effect of morphological variability of incrusted pit membranes (PMs) on efficiency of transverse compression to improve liquid uptake. The heartwoods of four conifers were investigated, and the deformations and ruptures of incrusted PMs were evaluated after subjecting them to several treatments such as transverse compression, ethanol-benzene extraction, and combination of extraction and compression. (1) The PMs in Cunninghamia lanceolata Hook, formed a brittle surface that was easily broken by compression, and the wood showed improved liquid uptake; (2) In Cryptomeria japonica D. Don, additional margo gaps were exposed after extraction resulting in substantial liquid uptake; and (3) in Larix leptolepis Gordon and Pseudotsuga menziesii Franco, tori strongly stuck to the pit aperture, preventing any increase in liquid uptake despite all types of treatment. Moreover, the pit borders in C. lanceolata and C. japonica deformed like a viscoelastic body, whereas those in L. leptolepis and P. menziesii displayed irregular deformations during compression. These results demonstrate the influence of the unique morphology of the incrusted PM on the efficiency of liquid uptake enforced by transverse compression.

No abstract available

No abstract available