Volume 14 Issue 1

The antimicrobial activities and potential mechanisms of natural essential oils (EOs) derived from the leaves of Phyllostachys heterocycla cv. pubescens (bamboo) against a broad range of food-borne pathogens, which included Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and yeast (Saccharomyces cerevisiae), were investigated. The chemical characterization of bamboo leaf essential oils (BLEOs) was determined by gas chromatography-mass spectrometry (GC-MS). Hexadecanoic acid (19.35%) and phytol (10.54%), the antimicrobial ingredients that have been reported in previous studies, were found to be the major components in the BLEOs. According to the antimicrobial tests, Escherichia coli was most sensitive to BLEOs, showing the largest DIZ (12.77 ± 0.25 mm) and the lowest MIC (0.56 mg/mL). In addition, the pathogen growth in the presence of BLEOs at two-times the minimum inhibitory concentration (MIC) revealed that the EOs were bacteriostatic after 12 h to all tested strains. According to the results from the cellular constituents, the fatty acids profiles, and the atomic force microscope (AFM) observations, the membranes of the treated cells were severely damaged. Therefore, it was concluded that the mechanism of action of BLEOs could be described as a disruption to the pathogen’s membrane integrity. The results indicated that the EOs from the leaves of bamboo could be a potential source of antimicrobial agents in the future.

Multilayer panels that have paper cores with hexagonal cells continue to have a limited application in furniture production. In contrast, there are no sandwich honeycomb panels with cores containing rectangular cells employed in this industry. Such cores should distinguish themselves by strong orthotropic advantages, in particular, for designing shelves and partitions of cabinet furniture. Hence, the objective of this study was to determine the effect of core rectangular paper cells on the mechanical properties of three-layer furniture panels. The authors decided to ascertain relative density and elasticity constants of the designed cells. The results of empirical experiments of cell elasticity moduli were compared with the results of the analytical calculations. The impact of sample width on their mechanical properties was determined. It was demonstrated that cores with hexagonal cells in furniture panels could be replaced by cores with rectangular cells.

The morphological and biochemical properties were investigated for 18 types of thermophilic bacteria isolated from a woody-chip pile at a wood processing plant in Northern Russia. Genetic fingerprinting and 16S rRNA identification were used to divide the investigated microorganisms into groups according to their genetic affiliation. It was found that the isolated bacteria belonged to a minimally studied genus of Parageobacillus and exhibited optimum temperature and pH in the ranges of 57 to 60 °С and 7.0 to 8.5, respectively. The amylase activity was determined for all of the 18 isolated strains. Catalytic properties of the bacteria-produced xylanases were evaluated with respect to their activity towards xylan and xylan-containing carbon substrates. Biotechnological potential of the two most promising bacterial strains (Parageobacillus caldoxylosilyticus and Parageobacillus thermoglucosidasius) and their possible use in xylanase production was evaluated. The results showed that bacteria present in the chipped woody waste is an important source of thermoalkalophilic enzymes.

The thermal characteristics and kinetics of teak sawdust (TS), sewage sludge (SS), and their blends were evaluated during combustion by thermogravimetric analysis (TGA). The samples were prepared as pure fuel, TS and SS; blends, where TS was mixed with SS at the ratios of 75:25, 50:50, and 25:75; and as fuels with additives, where the fuels above were mixed with activated carbon (AC), CaO, MgO, and ZnO individually at a proportion of 5 wt%. Some characteristic values of combustion were evaluated, such as Ti, Tb, and Mf, and the combustion behaviors of the fuels were compared. The difference between measurement and weighted calculation of the weight left proportion (∆M), weight loss rate (∆DTG), and activation energy (∆E) were introduced for analysis. Blending with teak sawdust improved the combustion performance of sewage sludge. As the content of the sewage sludge increased, the pre-exponential factor varied from 1.76 x 105 s-1(100T) to 1.01 x 101 s-1(100S), while the global activation energy decreased from 74 kJ/mol (100T) to 38 kJ/mol (100S). Sewage sludge burned more completely when blended with teak sawdust at ratios of greater than 50 wt%. All four additives inhibited the oxidation of the blends around the ignition point.

To expand the applications of low-density wood, solid white poplar (Populus tomentosa) wood with a moisture content of 10.6% was compressed 5 mm radially at 90 °C, 120 °C, 150 °C, 180 °C, and 210 °C, and the density profile characteristics were analyzed. It was found that compressed wood with a non-uniform density profile contributed to the peak density and average density of the compressed layer, where the highest values were 0.87 g/cm3 and 0.72 g/cm3, respectively. The density peak and compressed layer were formed at various distances from the wood surface according to the pressing temperatures tested. It was concluded that the pressing temperature had a great effect on the density profile of the compressed wood and the pressing temperature effectively controlled the shape of the density profile.

The influence of elevated temperatures on mechanical behavior was studied for curaua, hemp, and sisal natural fibers. Tensile tests were performed on fibers heated at 100 °C, 150 °C, and 200 °C for 24 h, and reference samples were maintained without thermal treatment for comparisons. The cross sectional area of the fibers was measured using a scanning electron microscope (SEM), and the image analysis was performed using the open source software Fiji/ImageJ. These data allowed the computation of the tensile stresses and the correlation of the fiber morphology with its macro-mechanical behavior. The thermal degradation behavior of the natural fibers was measured via thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD). The morphological and mechanical characteristics were described and discussed on a microstructural basis. The results showed that the loss of moisture leads to a significant increase in tensile strength before reaching the limits of the degradation range.

Effects of modified insoluble fiber originating from steam-exploded Quercus mongolica were studied relative to growth performance, blood parameters, intestinal morphology, and other intestinal characteristics in poultry broilers. First, the effect of steam-explosion on physicochemical properties of insoluble fiber from Q. mongolica was investigated. Steam-explosion (severity factor Log (Ro) = 3.94) was found to increase the physical properties (water-holding capacity, oil-holding capacity, and swelling capacity) of Q. mongolica chip to different extents. Effects of feeding different concentrations of steam-exploded Q. mongolica on performance characteristics of broilers were investigated. Experimental diets of broilers consisted of a control diet (free of steam-exploded Q. mongolica), and four diets containing 0.5% to 2.0% steam-exploded Q. mongolica (severity factor Log (Ro) = 3.94). A diet containing 1.0% steam-exploded Q. mongolica promoted broiler growth performance (body weight (858.9 g) and improved blood characteristics (130.0 mg/dL), intestinal morphology (V:C ratio 7.50), and organ weights (length of intestine 17.6 cm/100 g body weight).

The basic manufacturing feasibility and load carrying capacity of computer numerical control (CNC) were evaluated for router-cut joints. More precise and complex shaped geometry was cut on a CNC machine so that joint strength increased via providing a better self-locking system. Using the design for manufacture and assembly (DFMA) analysis, the raw material type and joint design were determined as the main drivers that have direct influence on the processing time and yield of the manufacturing process. Moreover, the bending moment capacity of the joints was determined in compression and tension testing and benchmarked those of rectangular mortise and tenon (RM&T) and dowel joints. The results showed that joints constructed of plywood performed better than those of medium-density fiberboard according to DFMA compliance score values. Moreover, the load capacity level of joints constructed of plywood provided stronger joints than MDF. In compression tests, CNC router-cut joints constructed of both plywood and MDF reached equal or higher strength relative to traditional joints. Furthermore, in tension tests, those of strength were lower compared to compression test results. The outcome of this study will contribute to the theoretical and practical knowledge of furniture joinery design.

Currently there are limited markets in Australia for small-diameter native forest logs. This has resulted in much of this resource being underutilized and regarded as sub-optimal in quality and of low value. This is despite the fact that the wood properties are favorable for a wide range of high-value products. Traditional processing approaches either have not been able to accommodate small-diameter logs or the resulting product recovery is too low for profitable production. Alternative processing approaches are necessary to enable the efficient recovery of wood from this resource in a form that is usable for high-value product manufacturing. Processing small-diameter spotted gum (Corymbia citriodora) and white cypress pine (Callitris glaucophylla) logs into rotary veneer using new spindleless veneering technology has been demonstrated to yield more acceptable recoveries compared with more traditional sawing approaches. The veneer processing approach was also found to be less impacted by the diameter than sawing, with more consistent recovery rates across the three small-diameter log groups included in this study. The resulting veneer, especially the spotted gum veneer, had visual qualities and mechanical properties well suited to the manufacturing of veneer-based engineered wood products.

Masterbatch composites made from starch/glycerol mixtures having 50 parts per hundred resin (phr) of three cellulose nanofibrils (CNFs) with different chemical compositions were prepared by pre-gelatinizing starch to create better dispersion of CNFs. The CNF contents were adjusted to 1, 5, 10, and 30 phr by adding ungelatinized starch and glycerol to the obtained masterbatch composite. The composite was then extruded at 150 ºC using a twin-screw extruder. The average diameters of the lignocellulose nanofibrils (LCNF), holocellulose nanofibrils (HCNF), and pure cellulose nanofibrils (PCNF) were 53.1, 24.4, and 22.4 nm, respectively. By increasing the CNF content in all nanocomposites, the tensile strength and elastic modulus were improved, whereas the elongation at break was diminished. Tensile properties were higher in the order of thermoplastic starch (TPS)/HCNF > TPS/PCNF > TPS/LCNF nanocomposites when the same CNF content was used. The addition of LCNF and PCNF also improved the thermal and moisture stability, whereas a negative effect was found in the TPS/HCNF nanocomposite. The effect of the LCNF on the thermal and water stability was greater than that of the HCNF and PCNF composites. The water uptake of the TPS/HCNF nanocomposite was higher than that of the TPS without CNFs.