Volume 14 Issue 2

Endopolygalacturonases characterized until now have either low working temperatures, working pH in acidic range, high Michaelis–Menten constant (Km), or a high production cost. These characteristics are a hurdle in the industrial applications of these endopolygalacturonases. The purpose of this work was to characterize a novel endopolygalacturonase produced by Bacillus licheniformis IEB-8. Phylogenetic analysis of Bacillus licheniformis IEB-8 showed that the isolate was unique. Citrus peels were used as the only nutrient source for the growth of Bacillus licheniformis IEB-8, allowing a cheap production of endopolygalacturonase. All the synthetic carbon sources showed a negative impact on the production of endopolygalacturonase, while ammonium sulfate enhanced its production. Among different metal ions, Zn+2 showed a negative effect while Mg+2 and Ca+2 did not have any significant effect on the endopolygalacturonase activity. A Lineweaver-Burk plot was prepared for the characterization of the kinetic parameters including Km and Vmax, which were 0.45 mg/mL and 285.7 µM/min, respectively. A comprehensive comparison of the endopolygalacturonase from this study with the available literature indicated that it is better than the reported and commercially available endopolygalacturonases in having the optimum working temperature of 55 °C, a low Km of 0.57 mg/mL, and pH of 7 to 8, which indicated its novelty.

The feedstock type and pyrolytic temperature used in producing biochar influence the characteristics of the obtained product and affect the adsorption behavior of naphthalene. In this study, different biochars were pyrolyzed from wheat straw, soybean straw, and corn straw at four temperatures (400 °C to 700 °C). Analyses of the elemental composition, pH, ash content, and specific surface area, scanning electron microscopy, and Fourier transform infrared spectroscopy were performed. The adsorption variations of the naphthalene for the different biochars were evaluated. The results showed that as the pyrolytic temperature increased, the carbon content, ash content, and pH of the biochars increased, the hydrophilicity, aromaticity, and polarity decreased, and the naphthalene adsorption was enhanced. The pseudo-second-order model fit the naphthalene adsorption kinetics better. Both the Langmuir and Freundlich isotherm models confirmed that naphthalene adsorption by all of the produced biochars were effective. Under moderate pyrolytic temperatures, the soybean straw-derived biochar showed a greater naphthalene adsorption capacity and faster adsorption rate than the wheat straw- and corn straw-derived biochars. This study provides a theoretical basis for selecting crop residues and optimizing the pyrolytic temperature with a high efficiency of naphthalene removal from water.

The morphology, physical, and mechanical properties were investigated for single-layer particleboard made with various proportional contents of wood and rape stalk particles glued with urea-formaldehyde resin. Fine crushed rape stalk particles were used for the experimental particleboards. The weight ratios of rape-to-wood particles were 0:100, 10:90, 30:70, 50:50, and 70:30. Mixed beech and spruce wood particles with percentages of 30% for beech wood and 70% for spruce wood were considered for the configuration. Urea-formaldehyde resin with a solid content of 66 ± 1% was added to the single-mat configuration at a level of 12%, based on the weight of the particles. Physical (density, water absorption, and thickness swelling) and mechanical (modulus of elasticity, bending strength, internal bond strength) investigations on the particleboards obtained in the laboratory conditions were conducted. The results were compared to the requirements of the EN 312 (2004) standard. In addition, morphological observation at macro- and micro-scale and vertical density profile analysis was conducted on particleboards in order to characterize the interaction between wood-rape particles and resin. Variations of the structure and density were observed relative to thickness, providing information concerning to the internal bond performance of the panels.

The availability of traditional wood species used for musical instrument manufacturing has decreased in recent years. To overcome this problem, there is a need for alternative woods with acoustical properties similar to those traditionally used. This study investigated the acoustical properties of neem wood (Azadirachta indica A. Juss.) from trees irrigated with treated wastewater as a substitute for traditional wood and to indicate its suitability for musical instrument manufacturing. The results revealed a strong linear relationship between the dynamic modulus of elasticity (Ed) and shear modulus (G). Moreover, density (ρ) was a good predictor for both Ed and G. The findings showed that this wood has potential use in backs and ribs of stringed musical instruments. Comparison with traditional European wood species used for this purpose showed that this wood can be a successful alternative. Increased demand for water and diminishing availability of water resources have led to the use of treated wastewater in irrigation. Thus, extension of the cultivation of several tree species with close properties to traditional tonewood species under wastewater irrigation can play an important role in the future of the musical instrument industry.

Important physical and mechanical properties were evaluated for Douglas-fir wood produced in a non-native environment. The specimens were obtained from 15 healthy co-dominant trees growing in three different sites located in the Czech Republic; they were studied for density, shrinkage, compression, and bending strength. The average density of the wood was 562.74 ± 62.47 kg·m-3 at 12% MC. The total volumetric shrinkage was in line with the respective literature, whereas the compression strength and modulus of rupture were found to be higher than the native Douglas-fir wood as well as several European softwoods. The properties of the wood produced in the Czech forests indicate the possibility of producing Douglas-fir timber of high quality.

Finger joints enable the full utilization of wood. The finger joint technique is used to eliminate wood defects that would otherwise weaken the wood strength. This research project evaluated how the wood species, adhesive type, and number of teeth affect the elastic stiffness of finger joints. The adhesives used were polyurethane and polyvinyl acetate, and the wood species were beech (Fagus sylvatica L.) and spruce (Picea abies L.). This study also determined the elastic stiffness of finger joints with 2 teeth and 5 teeth. For this purpose, the samples were loaded via a bending moment reaction, with tensile or compression forces in the angular plane. The highest elastic stiffness was obtained from the beech wood samples with 5 teeth bonded with polyvinyl acetate adhesive under tensile stress. Therefore, it was concluded that the elastic stiffness increased when the number of teeth increased. However, further studies on the elastic stiffness of finger joints are necessary in relation to the finger teeth length and surface area of the glue between the finger joint connections.

This research focuses on the statistical evaluation of the feedstock attributes of the biomass supply chain and the estimation of attribute costs as a function of the feedstock variability. Challenges of using cellulosic feedstocks include the variability of feedstock quality (e.g., ash content and moisture content), which impacts the final cost of the manufactured product. Statistical Process Control (SPC), Taguchi Loss Function, and components of variance techniques were illustrated for quantifying cumulative variance in the biomass supply chain. Costs in the presence of cumulative variance were estimated for switchgrass (Panicum virgatum L.) and loblolly pine residues (Pinus taeda L.). Findings of the study indicated that additional costs from ash content variability in switchgrass increased the net cost by $19.15 per dry tonne. Additional costs from densification due to particle size variation increased net cost by $11.59 per dry tonne. Moisture content variation increased costs by $14.86 per dry tonne. This would represent a 50 to 100% increase in costs due to variation based on a $60 to $70 per dry tonne manufactured product cost. This study illustrates that total costs may be considerably underestimated if the influence of variance for key factors in the supply chain and associated costs are not estimated.

The literature lacks comparisons of analytical and numerical calculations that have been verified experimentally for elastic constants of auxetic cells in cores manufactured from wood materials. The aim of this study was to determine the effect of auxetic cell geometry and the type of material used in their manufacture on elastic properties of the honeycomb panel core. This paper describes properties of the materials, from which core cells were modeled and presents mathematical models of cell properties. The method of numerical optimization of cell shape was specified, and the numerical calculations concerning modeled cells are given along with the course and results of experimental tests. Additionally, the results of analytical, numerical, and experimental tests were compared. Cell geometry had a considerable effect on elastic properties of honeycomb panel cores, particularly the angle of the cell wall. Moreover, geometric imperfections had a significant effect on the results of analytical calculations. Based on numerical calculations, satisfactory consistency between these results and experimental tests was obtained.

The aim of the paper is to evaluate the price development of timber assortments in selected countries in Central Europe, to compare the prices and identify the factors influencing the prices, and to quantify the extent of their impact on the prices. A further aim is to predict the price development based on comparing various models for predicting time series of prices. The analyses of the price development was carried out for the assortments of spruce, fir, and beech sawlogs in Slovakia, Czech Republic, and selected Austrian provinces. The analyzed period covered the years from 2001 to 2017 per individual months. Following the selected factors, the study was focused on the timber price development, and subsequently the prediction up to the end of 2019 was calculated. The most significant factor having a negative impact on the price development was the global economic crisis. Following all the prediction methods, the next two years can expect an increase in the prices of sawlogs, except the beech sawlogs in Austria. Analysis of the price developments in the selected countries confirmed that all global factors reflected the price level trends approximately equally in all countries.

Enzymatic treatment of flax is gaining more interest as a promising alternative for dew retting, which is known for its dependence on weather and climate. Therefore, the effect of enzymatic treatments of flax on the effectiveness of fiber separation from each other and chemical fiber composition was investigated in this study. Chemical composition was determined by a gravimetric method, while ease of separation (in the composites society, the process to obtain natural fibers from the plant is usually defined as extraction) was determined based on the amount of long fibers obtained as well as total time needed to release this fiber fraction, providing necessary insights in the extent to which fibers are loosened from the stem. Flax treatment with pectate lyase and polygalacturonase resulted in purified fibers with a cellulose content of 78 and 79% w/w and promising yield values of 24 and 17%, respectively. Besides these pectinases, xylanase activity also showed high potential for enzymatic retting. Hence, pectate lyase, polygalacturonase, and xylanase are promising enzymes to successfully replace the dew retting process.