Volume 13 Issue 1

A delignification pretreatment is important for enhancing lignocellulose biodegradation. Alkali pretreatment is a promising approach. Fiber morphology, alkaline nitrobenzene oxidation, and ozonation were used to characterize the wheat straw modified by mild alkali pretreatment (2% sodium hydroxide (NaOH) at 121 °C for 30 min), and for studying the advantageous performance by Pycnoporus sanguineus NFZH-1 in the aspects of lignin and carbohydrate biodegradation. The results indicated a powerful and selective delignification in the mild alkali pretreatment process. The relative contents of the G unit and the T form both decreased with mild alkali pretreatment. Meanwhile, epicuticular wax removal and increased porosity was observed in the fibrous tissue of alkali-treated wheat straw. Thus, the biodegradation of the Klason lignin in alkali-treated wheat straw was clearly enhanced and reached 41.4% during the following 10 days of fermentation with P. sanguineus NFZH-1. In addition, the modification of fiber tissue with a mild alkali pretreatment enhanced the biodegradation of xylan. The biodegradation of the chemical constituents of the wheat straw was enhanced by the effective modification with a mild alkali pretreatment. The enhanced biodegradation will be helpful for improving the efficiency of straw return.

Scots pine and Norway spruce, the most used commercial wood species in Europe, were thermally treated under industrial conditions by steam (Thermowood®) and vacuum (Termovuoto). Matched boards were treated, and the alterations in chemistry, color, mass loss, mechanical properties, and durability were compared. In treatments at identical temperature and duration, Thermowood® and the thermo-vacuum process caused similar mass loss in both wood species. The thermal treatments showed minor effects on the released acetic acid during the thermal degradation of polysaccharides. The equilibrium moisture content correlated well with the mass loss and confirmed indirectly the similarity of the two processes. The chemical composition and durability of the two groups of treated wood were similar. In conclusion, Thermowood® and thermo-vacuum treatments according to Termovuoto technology both produce similar final products with regard to chemical composition, physical-mechanical properties, and durability, with some differences in the appearance.

Nanostarch has a small particle size and large surface area compared with traditional modified starch. In this study, nanostarch was prepared by dual screw extrusion and was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray diffraction (XRD). The nanostarch was studied as a coating adhesive in surface coating of lightweight coated paper. The crystallinity of nanostarch granules was decreased by dual screw extrusion, and its average particle size was about 100 nm. The results showed that for the paper coating formula of styrene butadiene latex and an ordinary oxidized coating starch ratio of 9:5, all ordinary oxidized coating starch and part of the styrene butadiene latex can be replaced by nanostarch. When 5 parts of ordinary oxidized coating starch and 4 parts of styrene butadiene latex were replaced by 6.5 parts nanostarch, the water retention property of nanostarch coating was increased by 64.0%, and its viscosity was decreased by 11.0%. The IGT printing surface strength of lightweight coated paper by the nanostarch coating was increased by 11.6%, and the glossiness of coated paper was increased by 7.2%. These results show that nanostarch surface coatings have good prospects for application in papermaking.

Methacryloyl chloride was grafted onto lignocresol to increase the acyl content of lignocresol and to enhance the interfacial compatibility of lignocresol and polylactic acid. The physical and mechanical properties of the modified lignocresol sample were studied. The methacryloyl-modified lignocresol was characterized by infrared spectroscopy (IR), ultraviolet-visible (UV) spectroscopy, and gel permeation chromatography (GPC). Unmodified and modified lignocresol samples were used to prepare composite films with polylactic acid, and its tensile strengths and elongations at breaks were analyzed after film formation. Thermal stabilities were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicated that methacryloyl group was successfully grafted onto lignocresol, and that the optimum dosage of methacryloyl chloride required was 0.5 mL per 0.5 g of lignocresol. When unmodified lignocresol was added to polylactic acid, the tensile strength gradually decreased as the amount of lignocresol increased. However, the composite films prepared from the methacryloyl-modified lignocresol exhibited a slower decline in tensile strength and displayed an increased elongation at break. The optimum mechanical properties were found using a 10% blend of modified lignocresol with polylactic acid.

Biofuel is an important alternative source of fuel, as many countries are looking to decrease their dependence on fossil fuels. One of the critical steps in biofuel production is the conversion of lignocelluloses to fermentable sugars, and there is need for cheaper and more efficient enzymatic strategies. Consequently, lignocellulase genes from various organisms have been explored. Termites possess varied sets of efficient micro-scale lignocellulose degrading systems. In this study, bacteria that degraded cellulose and xylan were isolated from termite gastrointestinal tract. The isolate was identified as Cellulomonas sp. by 16S rRNA gene sequencing. The bacterial enzymes cellulase and xylanase showed the highest activity at 50 °C and pH 8.0. The agricultural substrates were hydrolyzed by cellulases and xylanases, and more sugar was released from corn stover (18.903+0.65 mM/L) than from rice straw or cotton stalk. After direct hydrolysis and fermentation of agricultural substrates, ethanol (0.425+0.035 g/L) and lactate (0.772+0.075 g/L) were the major end products. Thus, termite gut bacteria can efficiently hydrolyze hemicellulose and cellulose, and these bacteria also have the potential to convert these fermentable sugars into valuable secondary metabolites.

The effect of a fire-retardant treatment on some physical properties, including dimensional stability, hygroscopicity, and surface color variation of Sugi (Cryptomeria japonica), Korean Pine (Pinus koraiensis), and Hinoki (Chamaecyparis obtusa) were investigated in this study. These softwoods were subjected to vacuum-pressure and impregnated with a developed fire-retardant chemical. The results showed that the radial and tangential swelling of 1% moisture content (MC) increment were lower for all three wood species compared with the control specimen after the fire-retardant treatment, despite higher equilibrium moisture content (EMC) at 75% relative humidity (RH) and 90% RH at 40 °C. Meanwhile, the bulk coefficient after water immersion decreased for all specimens after the treatment, which indicated higher dimensional stability. However, the fire-retardant treatment proved a shift in surface color to darkness.

The surface quality of silicone resin coating on the veneer surface was evaluated. Silicone resins of various types (weakly, moderately, strongly hydrophobic, and hydrophilic resins) were applied on veneer and cured. The quality of the coatings was assessed according to the impact resistance of the surface and the resistance to cold liquids (acetic acid, citric acid, ethanol, sodium carbonate, sodium chloride, cleaner SAVO). The gloss value of silicone coatings on the veneer surface was determined from the aesthetic qualities. Radially sliced beech, oak, walnut, and ash veneers were tested. Veneer surface roughness was measured before and after modification with the silicone resins. The results obtained show that after modification by silicone resins, the surface roughness of the veneers was not significantly different from that of resin-free veneers. Impact resistance testing showed that intrusions on veneer surfaces with silicone coatings were free of cracks visible to the naked eye. Surface resistance to cold liquids on the surfaces with silicone coatings was lower if compared to that of commonly used coatings. In some cases, the surfaces showed strong damage, mostly without changing the structure of the coating, after only 10 min exposure to cold liquid. The gloss value of silicone coatings on wood veneers was graded as matte to semi-gloss.

Refining is a critical step in the manufacturing of medium-density fiberboard (MDF). To ensure fiber quality and control of the energy consumption during refining, proper production parameters, such as feeding screw revolution speed (SR), accumulated chip height (CH), opening ratio of the discharge valve (OV), and content of Chinese poplar (CP), are vital. These parameters were monitored and recorded in an MDF mill to investigate the relationships between the parameters and the fiber quality and energy consumption. In this study, fuzzy models of the fiber quality and the energy consumption during refining were established based on subtractive clustering and an adaptive neuro-fuzzy inference system (ANFIS). The fiber quality and energy consumption models demonstrated high prediction accuracy because their predictive mean relative errors were as low as 4.14% and 6.72%, respectively. The errors of fiber quality were optimized using the simulated annealing method, and the input parameters were obtained. Based on the energy consumption model, the minimum energy consumption was 41.51 kWh/t, on the premise of the minimum requirement of fiber quality. This study can be a guideline for MDF production management to improve fiberboard quality and reduce energy consumption.

Oven-dry wood density variations are reported for European ash (Fraxinus excelsior L.) and English oak (Quercus robur L.) trees growing in floodplain mixed forests in South Moravia, Czech Republic. Two sites with different water regime conditions were selected along the Dyje (site A) and the Morava (site B) Rivers. In total, 20 dominant, healthy trees were chosen to determine the tree-ring structure and the oven-dry wood density (ρ0) along the radius of the stem cross section. The tree-ring width followed the common trend of a general decline as the trees aged. After removing the age influence, significant differences were observed in the tree-ring structure, recorded several years after water regime treatments. The European ash and the English oak ρ0 were found to be 677.3 kg∙m-3 and 618.2 kg∙m-3, respectively, significantly differing between the sites, for both species. High variability of ρ0 was also noticed along the stem radius in both species and sites.

As consumer demand for more fuel-efficient vehicles increases, automakers are looking for innovative ways to reduce the weight of vehicles. Many automotive-grade plastics contain traditional reinforcing fillers, such as glass or talc, to improve the mechanical properties of the material. By replacing these high-density fillers with natural fibers, the material and corresponding weight can be reduced, which results in an improvement of the vehicle fuel economy. The objective of this study was to investigate the use of blue-agave bagasse fibers, which was sourced from tequila manufacturing waste, as a reinforcing agent in polypropylene composites. The effects of the fiber processing method, fiber loading level, and addition of a compatibilizer (polypropylene-grafted maleic anhydride) on the composite properties were determined. Samples were produced via twin-screw extrusion and injection molding. The resulting mechanical properties and morphology of the fracture surfaces were investigated. The fiber processing method (Agave C vs. Agave R) did not significantly affect the composite properties. Higher loading levels of fiber reduced both the elongation at break and impact strength, but increased the stiffness of the agave composites. The compatibilizer increased the fiber matrix adhesion, but reduced impact strength because the polymer matrix was softened.