Research Articles

Coastal Bermuda grass (CBG) has been shown to have potential as a biomass feedstock for sugar production. In this study, the effectiveness of ozone pretreatment for CBG to improve the sugar recovery via enzyme hydrolysis was investigated. Raw CBG and autohydrolysis-treated CBG were pretreated with ozone at ozone consumption of 1.8 to 26.4 % (w/w) at room temperature. Lignin degradation and hemicellulose solubilization increased with increased ozone consumption. At 26.4% ozone consumption by weight on CBG the amount of lignin in the CBG was reduced by 34%. Autohydrolysis of CBG increased the reactivity of cellulose, hemicellulose, and lignin with ozone. The maximum total sugar recovery after enzymatic hydrolysis was 32% for a 14.0% consumption of ozone on raw CBG. For CBG samples pretreated with autohydrolysis followed by a 3.1% ozone consumption pretreatment the maximum total sugar recovery after enzyme hydrolysis was 40.1%. Autohydrolysis pretreatment followed by enzyme hydrolysis yielded a 36.4% sugar recovery, indicating that the application and benefits of ozone after autohydrolysis with the conditions studied herein are marginally better than autohydrolysis alone.

Considering the mild degradation strength and the fact that it may be an organic matter reserve for the soil, in the past years lignocellulosic materials have been used as fibrous raw materials in the manufacture of biodegradable nutritive pots for the seedling in vegetable containerized production. This paper analyses the behavior of the nutritive pots madefrom biodegradable composites for the vegetable seedling production process, focusing on their mechanical strength properties and biodegradability. It was found that the biodegradability of composite materials obtained from a mixture of secondary cellulosic fibers, peat, and additives, is strongly influenced by the presence or absence of the rhizosphere effect and the synergistic relations set in the culture substrate between the plant roots and microorganisms, which develop permanently the recycling and solubilization of mineral nutrients. The results showed that the presence in the substrate of some complex populations made by heterotrophic bacteria favors full degradation of the pulp and lignin contained in the substrate and pots composition. Therefore, unlike the reference sample (plant-free), cultivated versions exhibited an intense biodegradation on the account of rhizosphere effect.

Cellulose hydrogels with quaternary ammonium (QA) groups were prepared via the etherification and cross-linking reaction. The structure of the functional hydrogels with QA groups was confirmed with FT-IR. Differential scanning calorimeter (DSC) analysis indicated that there was a large amount of free water in the hydrogels. The hydrogels showed salt-sensitivity behavior, and they also exhibited a strong antibacterial activity toward Escherichia coli.

The durability of Scots pine heartwood has previously been shown to be affected by the industrial drying process of sawn lumber. The durability of heartwood from boards dried at temperatures between 20°C-110°C was studied by measuring the mass loss in a decay test with a brown rot fungus (Coniophora puteana), and the concentration of total phenolics was measured according to the Folin-Ciocalteu (FC) assay. The relation between mass loss and phenolics in dried heartwood showed a weaker negative correlation at lower levels of phenolics as compared to the strong relationship found in a study on heartwood from standing Scots pine trees. Mass loss in dried heartwood showed a weak negative correlation to density. Heating of extractives-rich green sawdust under moist conditions resulted in a reduction of phenolics with temperature up to 180 oC and with increasing time. The concentration of phenolics in heated, green sawdust was higher in extractives-rich pine heartwood than in heartwood with a normal extractives content.

Lignocellulosic fibers from green coconut fruit were treated with alkaline solution (NaOH 10%m/v) and then bleached with sodium chlorite (NaClO2) and acetic acid (CH3COOH). Alkali-treated and bleached fibers were mixed with high impact polystyrene (HIPS) and placed in an injector chamber in order to obtain specimens for tensile tests. Specimens of HIPS/alkali-treated and bleached coconut fiber composites were tested in tensile mode, and the fracture surfaces of the composites were analyzed by scanning electron microscopy. Untreated, alkali-treated, and bleached coconut fibers were analyzed by scanning electron microscopy and X-ray diffraction. Alkaline treatment was effective for removing the extractives and increasing the roughness of surfaces, while the bleaching treatment intensified the effect of alkaline treatment, while increasing the crystallinity index and surface energy of fibers. Results of tensile tests showed that the addition of 30% alkali-treated and bleached fibers reinforcing the HIPS matrix provided considerable changes in the mechanical properties of composites in comparison with the pure HIPS. On the other hand, chemical treatments were not totally effective for improving the adhesion between the fiber and matrix, as was observed in the analysis of the fracture surfaces of composites materials.

Oxygen delignification can be considered to be the most important part of TCF and ECF bleaching sequences because it allows for cleaner production of pulp. During the process, oxygen gets one electron from lignin in the alkaline condition to form some active oxygen species (AOS), including a superoxide anion radical (O2-•), which is crucial for lignin degradation without damage of carbohydrates. The reaction of O2-• on cellulolytic enzymatic lignin (CEL) from Masson pine was studied. The change in active hydroxyl content after reaction with O2-• was investigated using 31P-NMR. After reaction, the aliphatic hydroxyl and uncondensed type phenol hydroxyl contents decreased, but the content of carboxylic group increased in Masson pine lignin. Through the analysis with HSQC-2D13C-H technology, β-O-4 linkages could be cleaved by O2-•, but β-β and β-5 linkages were observed to be more stable; benzaldehyde and cinnamic aldehyde structures could be oxidized to carboxylic acids by O2-•. Guaiacyl units in lignin were more easily degraded than p-hydroxybenzene units.

In this study it was shown that the enzymatic removal of xylan from ECF-bleached birch kraft pulp enhances the water removal from the pulp, especially in the late stages of pulp drying. The effect of xylanase treatments on dewatering was clarified by using a moving belt former (MBF), a press simulator (MTS), and an IR-drying equipment, to simulate and to measure dewatering properties on wire, press and drying sections of a paper machine. The xylanase treatment slightly increased the pulp freeness indicating improved pulp drainage properties. At the moving belt former, however, no significant changes that would indicate enhanced dewatering in forming were observed. The xylanase treatments slightly enhanced the dewatering in wet pressing and furthermore, at the thermal drying the xylanase treatment had a positive effect on the dry solid content (DSC) development, and time to reach the 95% dry solids content was reduced by up to 15%. This was also confirmed by the decrease in the fiber saturation point (FSP) values and the amount of bulk water. Our results indicate that the xylanase treatment affected the water-binding xylan in the fiber cell wall, yielding enhanced dewatering properties, without deteriorating the pulp and paper properties.

Self-assembled multilayers were fabricated from lignosulfonate (LS) and poly(diallyldimethylammonium chloride) (PDAC), and the adsorption and desorption behaviors of LS on the LS/PDAC multilayers under different pH conditions were intensively investigated. Results showed that the adsorption and desorption behaviors were controlled by electrostatic attraction, hydrophobic interaction, and changes in the microstructure, which depended on solution pH. Lignosulfonates exist as colloids in solutions at low pH because of a hydrophobic interactions, and the LS colloids adsorbed on the PDAC layer because of electrostatic attraction. LS colloids started to disassociate at pH 3.5, resulting in an abrupt rise of the adsorption rate, a sharp decrease of the adsorbed amount, and a steep reduction in the surface roughness. Desorption behaviors of LS multilayers were related to the pH values of both LS dipping solution for self-assembly and the immersing solution for post-preparation treatment. Desorption of LS could be induced by a weakening of electrostatic attraction or hydrophobic interaction. A significant desorption occurred only when LS colloids dissociated in the multilayers. LS colloids were harder to dissociate in the multilayers than in the solutions because of electrostatic attraction between LS and PDAC.

Bagasse from early species of Saccharum officinerum-Co 89003 has 71.36% useful, long, and thick-walled fibers with good slenderness ratio, but the rigidity coefficient is less than that of Eucalyptus tereticornis and Leucaena leucocephala. The kink index and kink per mm length are lower in bagasse fiber than E. terticornis, which gives rise to fewer weak points in the fiber. Low alcohol–benzene soluble substances in bagasse induce less pitch problems and favor more homogeneity in the paper. Lignin content in bagasse is comparable to Eucalyptus globulus and Leucaena leucocephala, but α-cellulose, and pentosans are slightly lower. A higher proportion of carbon content compared to hydrogen and oxygen increases the energy value of bagasse. It produces 42.2% pulp yield of kappa number 28.2 at optimum cooking conditions, such as active alkali 12% (as Na2O), temperature 150oC, and time (at temperature) 60 min. An addition of 0.1% anthraquinone at the optimum condition improves pulp yield by 2.6% and mitigates kappa number by 3.9 units.

Wheat straw was used to produce medium-density fiberboard (MDF). The chemical and physical characteristics of fractionated size-reduced wheat straw were investigated. The pH, pH-buffering capacity, ash, and silicon content increased as wheat straw particle size decreased. Ash of the finest straw, <0.2 mm, had high ash (15%) and silicon (18%) contents. The outer and inner parts of size-reduced straw were analyzed using scanning electron microscopy (SEM). The SEM micrographs revealed a complex ultrastructure containing a notable portion of thin-walled cells approximately 1 µm thick. Pressurized defibration of size-reduced wheat straw produced lignocellulosic fibers nearly 1.0 mm long combined with approximately 24% of small particles and dust. The high water uptake of straw-based MDF was significantly reduced using melamine-modified urea-formaldehyde (UF) resin and removing wheat straw particles and dust by screening. UF resin was added at levels of 12.5%, 13.1%, and 14%. In terms of water resistance, 12-mm-thick straw MDF displayed thickness swelling below 10%, acceptable according to the EN 622-5 MDF standards. It was concluded that manufacturing wheat straw MDF entails straw size reduction (hammer-milling), removing small particles and dust, and adding melamine-modified UF resin to attain necessary MDF quality standards.