Volume 12 Issue 4

A mild and successive method was proposed and evaluated for fractionating lignin samples from Eucalyptus globulus. The extraction efficiency and structural features of the extracted lignin samples were comprehensively investigated by a yields analysis, 1H-nuclear magnetic resonance (NMR), 13C-NMR, and two-dimensional heteronuclear single quantum coherence (2D-HSQC) NMR. The catalyzed ethanol systems consisting of ethanol, 4-methyl-2-pentanone, dimethyl sulfoxide (DMSO), formic acid, and distilled water were effective for extracting lignin from Eucalyptus globulus, and the yield of lignin was 75.2% when the extraction process was held at 145 °C for 180 min. Compared with that of the milled wood lignin (MWL), the NMR spectra of the extracted lignin fractions supported the destruction of β-O-4 units for the disappearance of Hα signals. Moreover, the striking characteristics of the extracted lignin were the destruction of ether bonds of S3,5 and the condensation of syringyl (S) and guaiacyl (G) units. In short, lignin fractions with relatively complete structures were effectively extracted with the catalyzed ethanol systems.

The preparation of bleached pulp from Eucalyptus globulus pulp was evaluated after utilizing chlorine dioxide (ClO2) with or without microwave irradiation. The three ClO2-bleaching processes examined were water-bath heating; microwave heating; and microwave pretreatment combined with water-bath heating. These processes were applied to eucalypt pulps that were oxygen-delignified. The effects of the treatments on the levels of lipophilic extractives and properties of the resulting pulps were compared with one another. The microwave-induced treatment had a remarkable effect, leading to an increase in pulp brightness and a decrease in lipophilic extractives when compared with the control (i.e., A). The sample under the condition of microwave pretreatment combined with water-bath heating achieved a higher brightness and reduced lipophilic extractives, which were increased by 45.8% and reduced by 37.4%, respectively. This study demonstrated an effective microwave-pretreated method in ClO2 bleaching process, which provides a promising route for alleviating pitch deposition problems occurring during pulp manufacture.

Carnauba wax is a natural material with high hydrophobicity. In this study, molten carnauba wax was stably self-emulsified in ethanol without using additional emulsifiers. Hydrophobic titanium dioxide (TiO2) nanoparticles were dispersed into carnauba wax-ethanol emulsion to form a composite coating on filter paper. The results showed that immersion in the composite coating that contained wax and hydrophobic TiO2 conveyed to filter paper good hydrophobicity (water contact angle over 140°) and stability against acid or alkali solution. The scanning electron microscopy (SEM) images indicated the presence of micro bead/flake structures on the surface of filter paper. These obtained filter papers could effectively expel water from a water/diesel mixture. The water content in the water/diesel mixture decreased from 10% to 0.01% through the separation from the filter paper.

Mechanical characteristics were evaluated of wood-bamboo-based particleboard having the proportions of 100% wood and 0% bamboo, 75% wood and 25% bamboo, and 50% wood and 50% bamboo. This particleboard used Eucalyptus urophylla × grandis wood, Dendrocalamus asper bamboo, and castor oil-based polyurethane resin. Through destructive testing, the values of perpendicular tensile, static bending, modulus of elasticity, and screw pullout strength in the top and face surfaces were analyzed. For 0%, 25%, and 50% bamboo the values were 1.68 MPa, 1.37 MPa, and 1.4 MPa, respectively, for perpendicular tensile; 15.2 MPa, 17.6 MPa, and 18.5 MPa, respectively, for static bending; 2466 MPa, 2694 MPa, and 2922 MPa, respectively, for modulus of elasticity; 1256 MPa, 1922 MPa, and 1362 MPa, respectively, for screw pullout strength in top; and 1392 MPa, 1342 MPa, and 1414 MPa, respectively, for screw pullout strength in face. These results were superior to those presented by ABNT NBR 14810 (2013) and ANSI 208.1 (1999). After performing a Tukey test at 5%, the values for each treatment did not show a significant difference among them.

Corn stalk enzymatically hydrolyzed lignin (EHL) was used to modify bisphenol A-type epoxy resin. The curing reaction processes of the epoxy resin/polyamine blends and the lignin/epoxy resin/polyamine blends were studied via isothermal differential scanning calorimetry (DSC), and the effect of enzymatically hydrolyzed lignin on the curing reaction of epoxy resin was also analyzed. The results showed that the curing kinetics for two blends were not in full compliance with the autocatalytic curing kinetic model, especially the lignin/epoxy resin/polyamine blends. The apparent activation energy of the epoxy resin/polyamine blends increased with the increased presence of the lignin. The presence of enzymatically hydrolyzed lignin was beneficial to the curing process of epoxy resin/polyamine blends at high temperatures. The addition of the lignin increased the final curing reaction conversion rate, improved the glass transition temperature (Tg) and increased the bending strength for the epoxy resin/polyamine blends. However, the impact strength decreased in this process.

The synthesis of bio-based chemicals, such as 5-hydroxymethylfurfural (HMF) and its derivatives, from cellulosic biomass resources has been attempted for years. However, the harsh reaction condition, toxicity of the catalysts applied, and low efficiency of the conversion process have deterred its industrial implementation. Herein, the authors investigated the degradation and conversion of cellulose into HMF in a concentrated zinc chloride solution. The effects of reaction conditions and co-catalysts on the conversion were evaluated. A 69.5% HMF yield from cellulose was obtained in the condition of 1 h and 150 °C using 0.2 mol·L-1 of HCl without co-catalyst during the conversion. Moreover, the ZnCl2 aqueous solution displayed good reusability. Finally, a simplified kinetic model of the conversion of cellulose to HMF in a concentrated zinc chloride solution was developed, and the reaction kinetics were investigated.

The effect of fiber orientation was studied relative to the static and dynamic properties of sisal/polyester composites. Different composites were developed using the compression moulding technique with the aid of a specially designed mould. Composite laminates were formulated by stacking a number of fiber lamina with different orientations such as 90º/0º /90º, 0º /90º /0º, 90º /0º /0º /90º, 0º /45º /0º, 0º /90º /45º /45º /90º /0º, and 0º /45º /90º /90º /45º /0º. In general, the performance of static and dynamic characteristics was found to be significantly influenced by the effect of interlaminar fiber orientation. Experimental results exhibited a higher flexural strength of 68 MPa and an impact strength of 320 J/m in the case of 0º /90º /45º /45º /90º /0º oriented composites. Dynamic characteristics such as natural frequency and damping were found to be higher in the case of 0º /45º /0º and 0º /90º /0º, respectively. Morphological analysis was performed for understanding the interlaminar orientation and failure mechanisms between the fiber and the matrix.

The performance of cellulase in the enzymatic saccharification of lignocellulose depends on the characteristics of lignocellulosic biomass feedstocks and the pretreatment method used. Efficient hydrolysis of specifically pretreated lignocellulose necessitates the knowledge of the characteristics of the optimal commercial cellulases. In this study, commercial cellulase preparations (Accellerase™ 1000, Accellerase® 1500, and Spezyme® CP from DuPont and Cellic® CTec2 from Novozymes) were evaluated for their hydrolysis efficiency of hydrothermally pretreated empty fruit bunches (EFBs). The highest glucose yields of 91.3% and 84.7% were achieved for 30 FPU of Cellic® CTec2/g glucan with and without Cellic® HTec2, respectively. Of the four cellulases tested, Cellic® CTec2, which showed the highest cellobiohydrolase, xylanase, and β-glucosidase activities, showed the highest glucose yield in the enzymatic hydrolysis of hydrothermally pretreated EFBs. The results of this study are valuable for those who plan to enzymatically hydrolyze hydrothermally pretreated EFBs.

Current methods of reducing giant Moso bamboo (Phyllostachys pubescens Mazel) to elements for composite manufacture are often inefficient and waste valuable biomass. This study employed geometric modelling to analyze and optimize the recovery of strands for oriented strand board manufacture. Three geometric models for calculating the numbers of strands, their widths, and their distribution based on culm diameter, wall thickness, target strand thickness, and flitch size were developed to determine an optimum slicing configuration. Real strands were produced by a disk flaker at the model strand thickness of 0.65 mm. Optimum configuration for the maximum number of usable strands per culm was from splitting culms into quarters, tight stacking, and radial slicing through the culm wall, which produced 37% more ‘usable’ strands 10 mm to 30 mm in width, fewer fines, and fewer excessively wide strands. Proportions of real strands fell into three size classes: < 10 mm, 10 mm to 30 mm, and > 30 mm, and closely matched modelled predictions. A slightly bimodal strand width frequency distribution observed from stranding full rounds was reflected in the distribution of the model strands calculated from slicing a full round into 0.65 mm increments.

High-productivity lactic acid bacteria (LAB) strains were screened and their capability to ferment lignocellulose-derived sugars into lactic acid were evaluated. Fifteen LAB strains were successfully isolated from cow dung, haystack, and sheep manure, respectively. Four relatively good strains were selected based on Gram stain, colony morphology, and catalase activity tests. The four strains and commercial inoculants (Lactobacillus pentosus and Enterococcus faecalis) were used to ferment cellobiose/ glucose/xylose to produce high-purity L-lactic acid. One of the strains (N4) presented the highest production of L-lactic acid after fermentation for 12 h and showed a L-lactic acid production of 15.1 g/L, 18.5 g/L, and 2.8 g/L and a productivity of 1.01 g∙L−1∙h−1, 3.68 g∙L−1∙h−1, and 0.47 g∙L−1∙h−1 by metabolizing cellobiose, glucose, and xylose, respectively. Through a phylogenetic tree analysis, strain N4 was identified as Enterococcus faecium and named Enterococcus faecium N4. Enterococcus faecium N4 has a great potential to ferment lignocellulose-derived sugars into L-lactic acid.