BioResources, Volume 2, Issue 4
NOTE: Each current issue of BioResources continues to build as new articles are approved.
The three main types of chemical components in wood are cellulose, hemicellulose, and lignin. These three components have rather different physical and chemical characteristics. In some respects, the three types of materials can be described as “incompatible.” However, most of the biomass existing on the planet depends on their successful interactions. It can be useful to think of wood as being a natural composite structure. Concepts related to composites also are useful as we envision possible new and improved uses of wood-derived materials. PDF
Handsheets produced from corn stalks and wheat straw soda AQ pulps were recycled in the lab. Pulping of corn stalks resulted in a low pulp yield, low bonding strength, and low recyclability. Conversely, wheat straw fiber had a better yield, very good tensile properties, and showed a considerably better response to recycling. The tensile index of wheat straw fibers retained 67% of its original value after four cycles. It could be shown that recycling caused only small changes in chemical compo-sition, but that the crystallinity index increased considerably. To be able to understand the behavior of wheat straw fiber as part of a commercial papermaking furnish, a paper containing 20% wheat straw fiber was produced on a 24 inch pilot paper machine and was recycled using a handsheet mold with white water return. Chemical analysis of the control (no wheat fiber) and the wheat-containing paper demonstrated slightly higher xylan content for the wheat-containing material. Recyclability increased slightly with addition of wheat fibers to a commercial furnish. PDF
Zhu, J. Y., Scott, C. T., Gleisner, R., Mann, D., Dykstra, D. P., Quinn, G. H., and Edwards, L. L. (2007). "Mill demonstration of TMP production from forest thinnings: Pulp quality, refining energy, and handsheet properties," BioRes. 2(4), 544-559.
High-value, large-volume utilization of forest thinning materials from U.S. National Forests is a potentially important contributor to sustainable forest health. This study demonstrated the utilization of wood chips produced from thinnings for the production of thermomechanical pulp (TMP). Both whole-log chips (primarily from small-diameter logs, tops, and reject logs) and sawmill “residue” chips from a HewsawTM system (Mäntyharju, Finland) were evaluated. The residue chips produced in this study were substituted for a TMP mill’s standard residue chips up to about 50%. The whole-log chips were substituted for the mill’s whole-log chips up to about 30%. The results show that substitution of chips produced from forest thinnings reduced refining energy in all trials. Pulp quality was maintained throughout all trials. PDF
Sodium aluminosilicate has been precipitated in-situ as filler on hardwood bleached kraft pulp fibers using papermaker’s alum and sodium silicate. The filler was produced in two ways, first in the absence of the fibers and second in the presence of fibers, i.e. in-situ precipitation of filler. The filler produced in absence of fiber was then added to the pulp slurry. Various pulp and paper properties were compared for direct loading of market filler, fresh filler loading, and filler prepared in-situ with fibers. In-situ precipitation technology provided paper with significant improvements in various properties of paper as compared to fillers directly added to the stock. Bulk and stiffness of the handsheets prepared with in-situ precipitation were much higher as compared to those of sheets prepared with fillers directly added to the pulp. There was no appreciable increase in brightness and whiteness of paper with in-situ precipitation, as an appreciable proportion of filler was precipitated inside the fibers. In-situ filler loaded pulps showed a higher filler retention value as compared to directly filler loaded pulps, as a high dose of retention aid was needed with the fillers directly added to the stock. PDF
Shulga, G., Betkers, T., Shakels, V., Neiberte, B., Verovkins, A., Brovkina, J., Belous, O., Ambrazaintene, D., and Žukauskaite, A. (2007). "Effect of the modification of lignocellulosic materials with a lignin-polymer complex on their mulching properties," BioRes. 2(4), 572-582.
The lignosulphonate/polymer complex, in which the macromolecules of both components are linked together by physico-chemical bonds, has been applied as a new effective lignin-based soil conditioner (LSC). lt has an adhesive affinity both for mineral soil particles and the organic surface of lignocellulosic mulch. The modification of the mulch particles with aqueous solutions of the developed conditioner by means of impreg-nation makes it possible not only to anchor mulch to sandy soil and, thereby, to diminish significantly the evaporation from the soil surface, but also, due to mulch biodegradation, to enrich soil with the main nutrient elements and to create favourable conditions for plant growth. The effect of the mulch modification is determined by the complex composition and depends on its content in the aqueous solution and the application rate. PDF
Conditions for obtaining microcrystalline cellulose (MCC) by the thermocatalytic method from hardwood (birch, aspen) and softwood (pine) bleached sulphate pulp have been developed. After thermocatalytic treatment, cellulose polymerization degree has decreased to the so-called levelling-off degree of polymerization (LODP), which, in the case of birch, aspen and pine wood pulp, made up 450, 370 and 250 units, respectively. After grinding the destructed pulp in a ball mill, MCC powder samples were obtained with particles, the major part of which had sizes of 2-20 mm. in terms of physico-chemical indices investigated in this work, the obtained samples conform to the pharmacopoeia requirements. Dispersing the destructed pulp in water medium, at a sufficiently high cellulose concentration (³ 8%), MCC gel samples were prepared, with rheological properties typical for liquid crystalline polymers. The indices of the obtained hardwood and softwood MCC were compared. PDF
Langer, V., Lundquist, K., and Parkås, J. (2007). "The stereochemistry and conformation of lignin as judged by X-ray crystallographic investigations of lignin model compounds: Arylglycerol beta-guaiacyl ethers," BioRes. 2(4), 590-597.
The conformations of a variety of crystalline lignin models representing different diastereomeric forms of structural elements in lignin of the arylglycerol b-guaiacyl ether type have been studied using X-ray crystallography. Based on X-ray crystallographic data, sequences of units attached to each other by b-guaiacyl ether linkages were constructed. The appearance of the resulting oligomers shows that stereoisomerism can be expected to influence the shape of the lignin molecules to a great extent. The constructed oligomers provide an idea about the contribution to the complexity of lignins by stereochemistry alone. It is proposed that structural differences, together with conformational variations, are the main reasons for the broadness of the signals in NMR spectra of lignins. PDF
Manganese peroxidase (MnP) and lignin peroxidase (LiP) are two major peroxidases involved in lignin biodegradation. The cDNA mnp1 encoding a kind of MnPs, and cDNA clg5 encoding a kind of LiPs were fused to one cDNA mnp1- clg5 (rmc15) by over-lap PCR technology in this research. Then the recombinant cDNA rmc15 was cloned into a vector pTrcHisB to construct its efficient expression plasmid pTHmc15 in Escherichia coli. The E. coli transformed by pTHmc15 was induced by isopropyl-b-D-thiogalactoside. The expressed protein was analyzed by SDS-PAGE, and a new one was observed with a molecular weight of about 77KD. Enzyme activities of MnP and LiP could not be observed in the unfolded fused protein. However, the enzyme activity of MnP was detected in the recombinant protein after it was refolded and activated by Ca2+ and heme, while the activity of LiP was not detected. These results show that the enzyme activity of the protein at N-terminal was not affected, but at C-terminal it was affected in the fusion protein of ligninolytic enzymes. Therefore, it is unfeasible to construct the gene of bifunctional ligninolytic enzyme with the fusion of the cDNA mnp1 encoding MnP and cDNA clg5 encoding LiP. PDF
It is well established that the glass transition temperature (Tg) is a sensitive measure of cure in neat thermosets. As cure advances, network mobility declines and the Tg rises in a systematic fashion. This study sought to determine if such a relationship exists for polymeric isocyanate adhesives (pMDI) cured in the presence of wood. Yellow-poplar (Liriodendron tulipifera) specimens were impregnated with neat pMDI and then isothermally cured for various periods in two different differential scanning calorimeters (DSCs). After this isothermal cure period, the Tg and residual heat of cure were determined. These thermal scans were performed using either constant (conventional) or modulated (MDSC) heating rates. For both methods, the degree of resin cure varied significantly under identical isothermal curing conditions; nevertheless a strong relationship was found between the degree of resin cure and the associated Tg. While the conventional DSC method yielded slightly improved sensitivity and reproducibility, results from both methods compared favorably. PDF
da Silva, T. A., Mocchiutti, P., Zanuttini, M. A., and Ramos, L. P. (2007). "Chemical characterization of pulp components in unbleached softwood kraft fibers recycled with the assistance of laccase/HBT system," BioRes. 2(4), 616-629.
Oxidative treatments, without and with assistance of a Laccase-Mediator System (LMS), were characterized in relation to their effects on the chemical composition and strength properties of the fibrous fraction of an unbleached recycled softwood kraft pulp. The LMS, composed of a Trametes hirsuta laccase extract and 1-hydroxybenzotriazole (HBT), was applied on the fibrous fraction of a recycled pulp at low consistency under continuous stirring and oxygen bubbling. Control treatments adding neither the enzyme nor the mediator were also considered. The LMS treatment caused a partial reversion of the detrimental effects of hornification. A considerable increase in the amount of carbonyl groups on the lignin structure was observed as a result of the enzyme treatment. The amount of extractives in ethanol:toluene also increased after the enzymatic treatment, and the dioxane-soluble kraft lignin underwent a noticeable decrease in its apparent molecular mass. This latter effect was readily attributed to the hydrolysis of aryl-ether bonds that survived the severity employed in the pulping process. These observations were useful to explain why LMS-recycled fibers produce handsheets with 9.4% better tensile strength than the control pulps. PDF
Many natural dyes, for example carminic acid, are soluble in water. We present a simple strategy to naturalize synthetic azadyes through their linkage with lactose to induce their water solubility. The dyeing process of textile fibres then becomes possible in water without additives such as surfactants and mordants, which result in products that are difficult to eliminate. Glyco-azadyes (GADs) we are presenting here are obtained through a diether linker to bond the azadye and the sugar. Tinctorial tests were carried out with fabrics containing wool, polyester, cotton, nylon, and acetate. GADs were found to be multipurpose and capable of dyeing many fabrics efficiently under mild conditions. PDF
Saarimaa, V. J., Pranovich, A. V., Sundberg, A. C., and Holmbom, B. R. (2007). "isolation of pectic acids from bleached TMP water and aggregation of model and TMP pectic acids by calcium," BioRes. 2(4), 638-651.
Pectins are important structural elements in spruce fibres. Alkaline peroxide bleaching of spruce thermomechanical pulp (TMP) causes degradation and demethylation of pectins, yielding high-charge-density pectic acids. The pectic acids in fibres contribute strongly to the negative fibre charge, and the dissolved pectic acids increase the cationic demand of bleached TMP water. In this study, a method to isolate pectic acids from peroxide-bleached TMP pulp water is presented. The pectic acids were isolated and purified in good yield using a polyacrylate resin to remove lignin, a cellulose filter to remove galactoglucomannans (GGM), and an anion exchange resin to separate pectic acids from neutral carbohydrates. Salts and residual low-molar-mass carbohydrates were further removed from the isolated pectic acids by dialysis. The isolated pectic acids (>80% purity) had a low molar mass and a wide polydispersity (5.9 kDa, MW/MN 3.3). The aggregation and precipitation of the isolated pectic acids, as well as citrus fruit pectic acids with well-defined molar masses, by Ca2+-ions were studied. The molar mass of pectic acids was a key factor determining the precipitation of Ca2+-pectates. Pectic acids below 6 kDa were not precipitated by Ca2+, while higher molar masses led first to partial and then to complete precipitation. The precipitated Ca2+-pectates may impair paper machine runnability and paper quality. PDF
Model surfaces of alkyl ketene dimer (AKD) and alkenyl succinic anhyd-ride (ASA) were prepared by casting and spin-coating methods. The surface chemical composition and surface topography were investigated by XPS, ellipsometry, AFM and contact angle studies. Spin-coating resulted in layered structure of AKD and ASA surfaces; the molecular layer thickness of both AKD and ASA was found to be ca. 2.5 nm. To achieve a covering surface layer, an average thickness of ca. 35 nm was required. The rms roughness of the created surfaces was 1 - 6 nm. Colloidal probe adhesion measurements were performed to verify that the roughness was in a range suitable for these measurements. The high reactivity of ASA with water generated stability problems with the ASA layers and it has to be recognized that surface force measurements with ASA in aqueous environment are very difficult, if not impossible. How-ever, surfaces created in this way were found to be useful in providing explanations of earlier ASA adhesion studies. The contact angle measurements on ASA layers also indicated that it might be possible to asses the hydrolysis rate issues through a set of similar measurements. PDF
In this paper multifactor non-linear dependencies of cutting forces from several machining parameters for low density wood of Liriodendron tulipifera Linn., known as Yellow Poplar, and Cordia alliodora Ruiz. & Pav., known as laurel blanco wood or capa prieto, were evaluated from experimental matrices. In the analyzed relations there was evidence for several strong interactions, which have been graphically illustrated and discussed. PDF
Modification of chemithermomechanical pulp (CTMP) by fungal treatment was investigated. Eucalyptus CTMP was treated with three different types of white-rot fungi, namely, Phanerochaete chrysosporium (P.c-1767), Trametes hirsute 19-6 (T.h-19-6), and Trametes hirsute19-6w (T.h-19-6w), under a stationary culture condition. Pulp total weight loss, lignin loss, and cellulose loss were determined to compare the different enzymes secreted by the three fungal strains. Pulp physical strengths, optical properties, and bleachability after the fungal treatment were investigated to compare the effect of fungal treatment on the pulp quality improvement. The results show that lignin reduction by both T.h-19-6 and T.h-19-6 (w) was about twice as much as that by P.c-1767. However, the selectivity of T.h-19-6 (w) towards lignin over cellulose was only 0.82, while that of T.h-19-6 was as high as 4.43. After T.h-19-6 treatment, pulp tensile, tear, and internal bonding strength increased by about 27%, 38%, and 40%, respectively. PDF
An experimental study was conducted to determine the abrasive wear behaviour of different weight percentage bamboo powder filled polyester composites under the multipass mode. The effect of bamboo powder concentration and sliding distance on the weight loss of composites has been analyzed. Worn surface have been analyzed to observe the mechanism of wear. The weight loss depends on bamboo powder concentration. The weight loss decreases with the increase of sliding distance. Samples having 20 weight percentage (wt%) of bamboo powder show the maximum weight loss during abrasion. PDF
The composition and properties of the products of fast pyrolysis of hardwood, obtained in a two-chamber (drying and pyrolytic) ablation type reactor in the temperature range 450-600ºС, were investigated. It has been found that, upon the additional drying of wood at 200ºС and subsequent pyrolysis, the quality of bio-oil is improved owing to the decrease in the amount of water and acids. It has been shown that the increase of the drying temperature to 240ºС decreases the yield of the main product. Optimum parameters of the drying conditions and the temperature of the pyrolysis of wood, at which the bio-oil yield exceeds 60% and its calorific value makes up 17-20 МJ/kg, have been determined. PDF
This article reviews developments in the technology for ethanol production from lignocellulosic materials by “enzymatic” processes. Several methods of pretreatment of lignocelluloses are discussed, where the crystalline structure of lignocelluloses is opened up, making them more accessible to the cellulase enzymes. The characteristics of these enzymes and important factors in enzymatic hydrolysis of the cellulose and hemicellulose to cellobiose, glucose, and other sugars are discussed. Different strategies are then described for enzymatic hydrolysis and fermentation, including separate enzymatic hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), non-isothermal simultaneous saccharification and fermentation (NSSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP). Furthermore, the by-products in ethanol from lignocellulosic materials, wastewater treatment, commercial status, and energy production and integration are reviewed. PDF
Both reversible and irreversible changes take place as cellulosic fibers are manufactured into paper products one or more times. This review considers both physical and chemical changes. It is proposed that by understanding these changes one can make better use of cellulosic fibers at various stages of their life cycles, achieving a broad range of paper performance characteristics. Some of the changes that occur as a result of recycling are inherent to the fibers themselves. Other changes may result from the presence of various contaminants associated with the fibers as a result of manufacturing processes and uses. The former category includes an expected loss of swelling ability and decreased wet-flexibility, especially after kraft fibers are dried. The latter category includes effects of inks, de-inking agents, stickies, and additives used during previous cycles of papermaking. PDF
The occurrence of cracks and loss of mechanical properties are major problems in wood drying, and careful control of drying conditions is necessary in order to avoid this form of defects. Wood drying at different temperatures, especially high temperatures, has gained much interest in the last several decades. Some solutions for minimizing drying defects, such as cracks and decrease of mechanical properties due to the increase of drying rates, decrease of drying time and thus cost, must be acknowledged and understood. The present review tries to summarize the influence of temperature during kiln drying on the mechanical properties of wood and on the occurrence of cracks. PDF