Research Articles

Some pretreatments that swell and/or open the structure of wood fibers could increase the effectiveness of a biobleaching process, allowing for an industrial application. To this end, a chemical pretreatment (urea, U), a physical pretreatment (refining, R), and their combinations (RU and UR) were optimized to evaluate and compare their enhancement of the LE biobleaching sequence (laccase-mediator treatment plus alkali extraction). The urea pretreatment before biobleaching (ULE) provided the highest delignification (37.5%) and the highest increase in brightness (6.1 points % ISO). As expected, adding a refining process before or after the urea pretreatment increased paper strength. However, when the refining was applied after the urea pretreatment (URLE), the delignification was higher than that obtained after RULE. Thus, URLE provided a similar Kappa number and an increase of 97%, 149%, and 98% in the tensile, tear, and burst indexes, respectively, compared with ULE treatment, but it had a reduction of 2.8 points (% ISO) in brightness, caused by the action of refining. Therefore, depending on the final use of the paper (which can require high optical properties or high strength), either ULE or URLE would be the optimal sequence.

This study was carried out to determine the thickness swelling of three-layered hybrid particleboard composed of sawdust and Acacia mangium under two different testing conditions. The experimental particleboards, composed of mixed sawdust and Acacia mangium, were fabricated with different resin contents and densities within the face and back (both composed of sawdust) and the core (composed of Acacia mangium particles). Particleboards consisting of only Acacia mangium particles were used as the control. Three different resin ratios (8:10:8, 10:10:10, and 12:10:12) were tested in combination with three different board densities (500, 600, and 700 kg/m3). Urea formaldehyde (UF), with the addition of wax, was used as a binder. The thickness swelling was evaluated using two tests: water immersion, and change in relative humidity, specifically between 10 and 90%, in accordance with the ASTM D 3502-76 (ASTM 1999) standard. The results indicated that there were significant interactions between the resin contents and the densities, which had an impact on the percentage of thickness swelling of the mixed sawdust-Acacia mangium composites in both test conditions.

This study focuses on the use of demountable furniture joints in combination with 38-mm-thick honeycomb panels. These fittings were incorporated into L-shaped corner joints and then tested to determine their bending moment capacity. Overall, seven combinations of demountable fittings were tested. These groups of connectors consisted of solution non-glued, partly-glued connectors, and fully-glued connectors. All of the connectors were positioned in the test samples as they are commonly located in furniture construction. The highest capacities were obtained with glued connectors, followed by partly glued and then non-glued connectors. The difference in capacity between the inside and outside positions was insignificant for the non-glued and fully-glued connectors. A large difference between connectors in different positions was found for the partly glued connectors and for the second type of unglued connectors. The modes of failure were analyzed for each connector, and the possibilities for use in construction are described.

Poplar (Populuseuramericanacv.) is one of the most important fast-growing tree species in China, but so far its utilization has been limited to nonstructural wood-based panels. The objective of this work was to develop a good understanding of how to improve the mechanical properties of poplar laminated veneer lumber (LVL) with carbon fiber reinforced polymer (CFRP). A theoretical model was successfully developed to predict the bending modulus of elasticity (MOE) of LVL reinforced by CFRP. To validate the model, two different configurations of LVL were made in the laboratory: LVL reinforced with a single layer of CFRP on one side (LVL-SR) and LVL reinforced with a single layer of CFRP on each side (LVL-DR). It was found that the model prediction of the LVL MOE agreed well with the experimental results. LVL reinforced with CFRP had a greater MOE and modulus of rupture (MOR) than the control LVL. The MOE of the LVL-SR and LVL-DR increased by 40% and 67%, respectively.

Corn stover was pretreated with liquid hot water (LHW) to enhance its enzymatic hydrolysis and L-lactic fermentation. The cellulose conversion rate and L-lactic acid concentration were used to evaluate LHW pretreatment performance. Results showed that the optimum conditions for the LHW pretreatment of corn stover are a reaction temperature of 190 °C for 20 min and a solid-to-liquid ratio of 1:10. The cellulase loading was 30 filter paper units per gram of oven-dried, water-insoluble solid. These conditions resulted in 92.3% conversion of cellulose to glucose. Sequential hydrolysis and fermentation using pretreated water-insoluble solid (WIS) produced an L-lactic acid concentration of 45 g/L. This study indicated that LHW pretreatment of corn stover is a suitable method for achieving high cellulose conversion and L-lactic acid concentration.

The phenylpropanoid pathway serves as a rich source of metabolites in plants. It is required for the biosynthesis of lignin and acts as a starting point for the production of many other important compounds involved in growth and development. Phenylalanine ammonia-lyase (PAL) catalyzes the first step of the phenylpropanoid pathway. PAL gene expression changes during the growth and development of plants as it regulates the synthesis of lignin and other phenylpropanoid compounds. The gene expression of sugarcane (Saccharum officinarum L.) PAL (SoPAL) was analyzed using quantitative real-time PCR (qPCR) and the comparative ΔΔCt method in different tissues during different developmental stages. The results showed that SoPAL was expressed in all tissues and developmental stages. SoPAL mRNA levels were increased from germination to tillering stages, except in the sheath, and from tillering to grand growth stages in the leaf and stem. PAL expression decreased from the grand growth to maturation stages in all tissues except the sheath. The highest expression of SoPAL occurred in the stem during the grand growth stage, while its lowest expression occurred in the leaf during germination (p<0.05). In conclusion, PAL, as a rate-limiting enzyme of the phenylpropanoid pathway, displays critical roles in the development of sugarcane, particularly in lignified tissues.

Chitosan was used as a sizing promoter to improve the sizing performance of ASA emulsion stabilized by montmorillonite. It was found that chitosan with low molecular weight significantly improved the sizing performance of ASA emulsion without inducing the flocculation of the ASA droplets when the amount was less than 0.125% based on ASA. Confocal fluorescence microscopy revealed the formation of chitosan shell around the ASA droplet. Adding ammonia into the emulsion induced desorption of chitosan from the ASA droplet surface and the ammonolysis of ASA. The former reduced the ASA emulsion stability, while the latter resulted in the secondary emulsification of ASA-water system. Meanwhile, the presence of ammonia was demonstrated to be detrimental to the sizing performance of the ASA emulsion. The hydrolysis resistance of the ASA emulsion was higher when chitosan was present.

A phenol-formaldehyde (PF) resin treatment of OPTL with various concentrations of finely ground palm shell, together abbreviated PF-FGPS, has been used to improve termite resistance. Termite resistance was evaluated in two ways, in a laboratory test and in a field test that lasted 3 months. A feeding arena sample was prepared for the first experiment so that the responses of the subterranean termite (Coptotermes curvignathus (Holmgren)) and the drywood termite (Cryptotermes cynocephalus (Light)) to the laboratory test could be observed for 4 weeks and 12 weeks, respectively. In general, the PF-FGPS led to greater termite resistance than did the control (dried OPTL and rubberwood), and the resistance of the samples to the subterranean termite C. curvignathus was classified as moderate when the samples were treated with OPS meal. Meanwhile, the resistance of the samples to the drywood termite C. cynocephalus was classified as moderate when samples were treated with OPS meal concentrations of 0, 1, and 3%. The samples treated with 5% OPS meal were classified as resistant. In the field test, samples impregnated with OPS meal at levels of 3%, 5%, and 10% were classified as resistant, while those impregnated with OPS meal at levels of 0 and 1% were classified as moderately resistant to attack by the subterranean termite.

Continuous and batch tests were conducted to evaluate fermentative biohydrogen production from starch wastewater via a mesophillic up-flow anaerobic staged reactor (UASR). The effects of organic loading rate (OLR) and food to micro-organisms ratio (F/M) on hydrogen yield (HY) and hydrogen production rate (HPR) were investigated. The bioreactor was continuously operated at a constant hydraulic retention time (HRT) of 6.7 h. The optimal OLR and F/M ratios were 54 g-COD/L.d and 1.4 g-COD/g-VSS.d, respectively. The maximum HY and HPR were 1.87 mol-H2/mol-glucose and 246 mmol-H2/L.d, respectively. Batch experimental results indicated that the optimal initial cultivation pH ranged from 5.5 to 6.5 with a hydrogen potential (P) of 1435-1420 mL-H2, while the initial substrate concentration of 20 g-starch/L showed a maximum HPR (Rm) of 300 mL-H2/h. Zero, 1st and 2nd order kinetic studies were used to develop a model of the experimental data. The 2nd order model adequately fitted with the experimental results (R2>0.97) better than those for a zero- or a 1st order kinetic reaction.

Sixty-two fungal isolates were screened for lignin peroxidase production. The most potent isolates for lignin peroxidase production were identified using the DNA sequence of the internal transcribed spacer (ITS) region of Phanerochaete chrysosporium and Pleurotus ostreatus. The pretreatment of rice straw with P. chrysosporium, Pl. ostreatus, or lignin peroxidase for use in the biopulping process was studied. Great variations in the loss of pulp yield and kappa number were recorded with different fungal and enzyme treatments. Pretreatment of rice straw with P. chrysosporium for 25 days resulted in a substantial decrease in pulp yield (by 9.1%) and kappa number (by 25.6%). Losses of pulp yield and kappa number were considerably lower with lignin peroxidase treatment (3.7 and 14.1%, respectively). However, the pretreatment of rice straw with the Pl. ostreatus isolate caused moderate pulp yield losses (5.8%) and preferential lignin degradation (kappa number losses of 34.6%). This indicated that the Pl. ostreatus isolate might be superior to both the isolate of P. chrysosporium and lignin peroxidase for use in the biopulping process or other processes in which preferential lignin degradation is desired.