Research Articles

Heat and enzyme treatments were used to increase the prebiotic oligosaccharides from palm kernel expeller (PKE), and the prebiotic efficacy of three types of PKE-extracts, namely raw PKE-extract (PKERAW), enzyme-treated PKE-extract (PKEENZ), and steam + enzyme-treated PKE-extract (SPKEENZ) was evaluated in vitro using three strains of Lactobacillus (L. brevis I 218, L. salivarius I 24 and L. gallinarum I 16), and in vivo using Sprague-Dawley rats as an animal model. Results of the in vitro study showed that the PKE-extracts were able to support the growth of Lactobacillus sp. strains. However, their growth varied significantly among strains and PKE-extracts (P<0.05), with L. brevis I 218 recording the highest growth compared to the other two strains, and the highest growth in the steam plus enzyme (SPKEENZ) extract. Results of the in vivo study reaffirmed that all the PKE-extracts tested can support growth of beneficial bacteria (Lactobacillus and Bifidobacterium), but only SPKEENZ treatment group had significantly higher Lactobacillus and Bifidobacterium counts and lower population of E. coli compared to the control. It was demonstrated that PKE is a potential source of prebiotic, which may be used to effectively improve host health and wellbeing by modulating the host gut microflora, and by proper pre-treatment, the release of prebiotic oligosaccharides from PKE can be enhanced.

The effects of SuperBatch™ (SB), CompactCooking™ (CC), and Lo-Solids™ (LS) modified cooking processes on pulp properties of Eucalyptus globulus and Eucalyptus nitens were investigated. The syringyl/guayacil (S/G) lignin ratio in the wood of E. globulus was significantly higher (4.7) than that of E. nitens (3.5). From the brown stock pulps, the viscosity, total lignin, carbohydrate composition, acetone extractives, and hexenuronic acids were measured. For the same Kappa number level (17 ± 0.5), pulps from E. globulus needed lower H-factor. They also presented a higher brightness and more cooking rejects, independent of the cooking method. CC presented a slightly higher cooking yield and pulp viscosity compared to the other modified cooking methods. At the same Kappa number level, the pulps of E. nitens presented a greater amount of total lignin, whereas E. globulus presented a higher amount of hexenuronic acid content, independent of the cooking method.

A composting treatment was employed in an effort to improve the processability of rice husks. Changes in the chemical composition, physical structure, and rheological properties of modified rice husks were analyzed. The results indicated that the average diameter of compost-treated samples was significantly higher than that of the untreated samples because they were able to adhere to each other by the bacterial protein. Scanning electron microscopy images showed that the epidermis became rugged and lumpy because the composition of rice husks (cellulose, hemicellulose, lignin, and pectin) was partially decomposed, an effect confirmed by the chemical composition and FTIR analysis. Thermogravimetric analysis showed that the composted samples had better thermal stability than the untreated ones. Stress-strain curves showed that the treated samples displayed a moderately significant change of slope at about 0 to 10% strain, and they had better mechanical properties than untreated samples. Juxtaposing the rheological properties of both untreated and treated samples determined that the latter had higher apparent viscosity as a result of degradation and bacterial protein effects. All results indicated that the composting treatment changed the physical, chemical, and rheological properties of the rice husks, which are beneficial for its utilization and processability.

In this work, kraft pulping was carried out on moso bamboo residues as a pretreatment and its impact on the chemical compositions and the digestibility of the sample was investigated. Meanwhile, steam explosion and sulfuric acid pretreatments were also carried out on the sample to determine their impacts on enzymatic saccharification. Results showed that kraft pulping pretreatment removed a significant amount of lignin from the sample, and its enzymatic saccharification was enhanced. Approximately 95% of the lignin was removed with the optimized kraft pulping pretreatment (26% effective alkali charge, 24% sulfidity, 160 °C, and 70 min cooking time). Consequently, about 79% and 77% yields of glucan and xylan, respectively, were achieved with enzymatic saccharification from the pretreated sample. As a result, 352 g, 128 g, and 88 g sugars were generated from 1000 g of samples pretreated by kraft pulping, steam explosion, and sulfuric acid, respectively. The results suggested that kraft pulping can be a remarkably effective pretreatment applied on mosobamboo residues (i.e., lignin-rich biomass) for sugars released, compared to steam explosion and sulfuric acid pretreatment.

Through alkali treatment, bleaching, and sulfuric acid hydrolysis, cellulose nanocrystals (CNCs) were prepared from kenaf fibers and were used as reinforcement materials in biocomposites based on κ-carrageenan. Biocomposites in the form of films were prepared by solution casting of a mixture of κ-carrageenan, glycerol, and various amounts of CNCs (0 to 8 wt%). Fourier transform infrared spectroscopy (FTIR) revealed that alkali treatment followed by bleaching totally removed lignin and hemicellulose from the kenaf. Morphological analysis of the fibers, cellulose, and κ-carrageenan of biocomposite films were carried out using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The effects of filler content on the mechanical and thermal stability of the k-carrageenan biocomposite films were analyzed through tensile strength measurements and thermogravimetric analysis (TGA). At an optimum CNC content of 4%, the κ-carrageenan biocomposite films showed good dispersion, superior mechanical properties, and improved thermal stability.

The internal friction energy loss of vibration is an important indicator showing the vibrational performance of wood. This paper analyzed vibration signals based on the fast Fourier transform spectrum. The logarithmic average, logarithmic regression slope, and exponential function fitting methods were used to calculate the attenuation coefficient of friction energy of wood vibration in the full time and different time periods. The correlations of δ gained from different methods were compared and analyzed. The results showed that the linear correlations between different methods were significant in the entire period. The values obtained using the logarithmic average and logarithmic regression slope methods were similar. For different time periods, the rate of amplitude decay decreased over time. The values obtained using the logarithmic average method had the smallest fluctuation. In different time periods, the logarithmic average and logarithmic regression slope methods showed a significant linear correlation. However, the exponential function fitting method showed a low correlation with the logarithmic average and logarithmic regression slope methods.

Microwave pretreatment can increase the transverse permeability of wood. The effects of impregnation on microwave-pretreated wood with low-molecular weight phenol formaldehyde resin was investigated. The results showed that the improved transverse permeability of poplar wood that had received microwave pretreatment resulted in a positive influence on the effect of the impregnation. The maximum impregnation weight gain rate was 51.08%, with the average being approximately 40%. The average density of the specimens impregnated for 1.50 h at 0.8 MPa was 584.8 kg•m^-3. During the course of the study, the resin present in the wood became distributed evenly in the vessel elements, wood fiber lumens, and intercellular spaces. Finally, the chromogenic reaction area accounted for 78.11% of the total area in the fluorescent staining diagram of the cross section.

This article investigates the modulus of elasticity of solid and laminated aspen wood of various thicknesses after cyclic loading. A three-point static bending test was carried out to determine the modulus of elasticity. Cyclically loaded samples were compared with samples without cyclic loading. For the laminated wood, the results demonstrated a statistically significant impact of cyclic loading on the elasticity modulus. In contrast, no significant impact of cyclic loading was shown for the solid wood. The impact of the number of cycles was significant for both laminated and solid wood. When this number increased, the elasticity modulus values decreased. Generally, higher elasticity modulus values were confirmed for the laminated wood.

A systematic evaluation tool for natural fibers’ capabilities based on moisture content criterion (MCC) was developed and introduced as a new evaluation method. This MCC evaluation tool is designed to predict the behavior of the available natural fibers regarding distinctive desirable characteristics under the effect of the moisture absorption phenomenon. Here, the capabilities of different natural fiber types commonly used in industry, in addition to date palm fibers, were systematically investigated based on MCC. The results demonstrated that MCC is capable of predicting the relative reduction of fiber performance regarding a particular beneficial property because of the effect of moisture absorption. The strong agreements between the predicted values of MCC and results reported in the literature verify its usefulness as an evaluation tool and demonstrate its added value steps in predicting the relative behavior of fibers with a minimal range of errors compared with experimental measurements. Therefore, MCC is capable of better evaluating natural fibers regarding distinctive criteria in a systematic manner, leading to more realistic decisions about their capabilities and therefore enhancing the selection process for both better sustainable design possibilities and industrial product development.

The processing of Australian plantation-grown Eucalyptus globulus and E. nitens into rotary veneer was shown to produce acceptable recoveries. Three plantation sites for each species were sampled. Silvicultural treatments (thinning and pruning) and growing environments varied between sites. Graded veneer recoveries were dominated by D-grade veneer across all six sites. Variation between the E. nitens sites was evident, with recoveries differing between sites reflecting silvicultural treatments. However, only minimal variation in recovery was shown between the E. globulus sites. The presence of similar levels of defects across all E. globulus sites indicates that the intensive silvicultural management at one site studied was not effective in the production of clear wood, and may possibly have adversely affected grade recovery. Veneer value analysis demonstrated only minimal differences between E. globulus sites. More variation was observed in the E. nitens value analysis; however, intensive silvicultural management implemented did not necessarily result in higher veneer value.