Volume 15 Issue 4

Xylose derived from lignocellulose can be utilized to produce ethanol and other high-value chemicals, such as xylitol. The xylitol production through fermentation of lignocellulosic hydrolysate by microorganisms offers advantages of high product yield, high selectivity, and efficacy in mild conditions. In this study, non-detoxified hemicellulose hydrolysate from napiergrass was used for xylitol production by a recombinant flocculating strain of Saccharomyces cerevisiae. An optimization study was conducted with the strain at 35 °C. A promising xylitol yield of 0.96 g/g xylose with no addition of glucose required during the fermentation process, which suggests an extensive potential improvement for the economics of lignocellulosic xylitol production.

The friction welding method has been an effective criterion in determining the mechanical performance of wood joints in wood industry applications compared to traditional methods. Although it is used in structural applications, joints from linear vibration are quite sensitive to water. In this study, the water resistance of the heat-treated woods, iroko (Chlorophora excelsa), ash (Fraxinus excelsior L.), tulip wood (Liriodendron tulipifera) and ayous (Triplochiton scleroxylon), were investigated by friction linear welding. The weld line density profiles were examined. The resistance of heat-treated welded wood joints to water remarkably decreased compared to the control sample, depending on water immersion time. The highest shear strength loss was found in tulip wood (60% to 65%) and the lowest shear strength loss was found in ash wood (3%) for the heat-treated group and in Iroko wood (17%) for the control. The heat-treated samples increased in density with welding but had a slightly lower density than the control group. According to the TGA results, it was found that the thermal degradation of untreated welded woods was lower than that of heat-treated welded woods. This difference could be due to the chemical constituents of hardwood and tropical wood. X-ray computed tomography (CT-scanning) is feasible and usable for welding line density change.

Poplar (Populus) wood was subjected in this work to thermo-hydro-mechanical treatment. The influence of the treatment parameters on the physical and mechanical properties were investigated. The wood samples were densified under three compression ratios (0%, 30%, and 50%), and thermally treated at three temperatures (180 °C, 200 °C, and 220 °C), at three thermal treatment durations (3 h, 4 h, and 5 h). The density, modulus of elasticity, modulus of rupture, radial hardness, and thickness swelling were measured. The results showed that the densities of the samples increased by 36.6% to 49.7%. As the compression rate increased, the temperature, duration, modulus of elasticity, modulus of rupture, and hardness increased. However, the dimensions of the densified samples were less stable. Compared to the densified samples, the maximum thickness swelling could be reduced by 74% (from 29.7% to 7.8%) when subjected to a thermal treatment at 220 °C for 3 h.

This paper presents a time-efficient approach to the drill wear classification problem that achieves a similar accuracy rate compared to more complex and time-consuming solutions. A total of three classes representing drill state are recognized: red for poor state, yellow for elements requiring additional evaluation, and green for good state. Images of holes drilled in melamine faced chipboard were used as input data, focusing on evaluating differences in image color values to determine the overall drill state. It is especially important that there are as few mistakes as possible between the red and green class, as these generate the highest loss for the manufacturer. In green samples presented in gray-scale, most pixels were either black (representing the hole) or white (representing the chipboard), with very few values in between. The current method was based on the assumption that the number of pixels with intermediate values, instead of extreme ones, would be significantly higher for the red class. The presented initial approach was easy to implement, generated results quickly, and achieved a similar accuracy compared to more complex solutions based on convolutional neural networks.

Lignin biomass is an important renewable woody material that can be converted into high value-added products through physical and chemical reactions, such as paper strength additives. In this study, a cationic methacryloyloxyethyl trimethylammonium chloride monomer (DMC) and anionic acrylic monomer (AA) were grafted onto softwood kraft lignin through free radical polymerization to prepare an amphoteric lignin copolymer. Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), elemental analysis, and charge density analysis methods confirmed that the anionic and cationic monomers were successfully grafted onto the lignin. The grafting ratios of AA and DMC monomer in the lignin-DMC-AA copolymer were 62.4% and 51.3%, respectively. The application of lignin-DMC-AA copolymer as a paper additive for enhancing the physical properties of paper sheets was studied in the papermaking industry. The results indicated that the copolymer had a maximum increase in physical strength at around 2 wt% lignin-DMC-AA. The amount absorbed on the fibers was 18.5 mg/g, and the retention of the lignin-DMC-AA copolymer was over 90%.

Samples from the two most common pines grown in Portugal (Pinus pinaster Ait) and Spain (Pinus radiata, D. Don) were heat-treated in industrial facilities in accordance with ThermoWood ® class D. For both species, the variation in surface properties, of untreated and heat-treated wood after artificial weathering from 75 to 750 h, is presented. The analysis included the determination of color, roughness, gloss, and wettability before exposure and after each artificial weathering period. Untreated woods became darker faster, while in heat-treated woods, lightness remained approximately constant until 750 h of artificial weathering. Both untreated and heat-treated wood became more reddish in the beginning of the weathering process, turning greener for longer exposure times. Untreated woods became yellower in the beginning, turning into blueish tones later. Heat-treated wood turned slightly yellower until 750 h of weathering. Gloss decreased for untreated wood with no significant changes in heat-treated wood. Despite the changes, the gloss of both untreated and heat-treated wood converged to similar values. Roughness increased for both untreated and heat-treated woods. Artificial weathering increased the wettability of heat-treated wood.

Different concentrations of ethanolic extracts of thyme (Zataria multiflora) and rosemary (Rosmarinus officinalis) were evaluated to determine their antimicrobial activity using the agar-well diffusion method. The values of inhibition zone diameter (IZD) for Candida albicans fungus and Staphylococcus aureus Gram-positive bacteria were determined. The bioactivities of two various extracts were studied, and the chemical composition of the extracts were identified using gas chromatography-mass spectrometry (GC-MS) technique. The results of the test showed that at concentrations of 10% and 40% thyme extract, the values of IZD were 12.5 mm and 23.3 mm, respectively, against the growth of S. aureus, which were higher than C. albicans (7.0 mm and 22.5 mm, respectively). The rosemary extract at concentrations of 20% and 60% showed lower antibacterial activity against S. aureus (4.7 mm and 8.7 mm IZD, respectively) and lower antifungal activity against C. albicans (12.2 mm and 1.7 mm IZD, respectively). At a concentration of 40% thyme extract, the highest antibacterial (23.3 mm IZD) and antifungal (22.5 mm IZD) activities were observed. The GC/MS analysis showed that carvacrol (52.3%), linalool L (16%), and thymol (9.6%) were the main components of thyme extract, while in the rosemary extract β-amyrone (18.0%), verbenone (8.0%), and 1,8-cineole (7.26%) were the major constituents.

Because some of the critical events during the removal of water before the dryer section on a paper machine happen very rapidly within enclosed spaces – such as wet-press nips – there have been persistent challenges in understanding the governing mechanisms. In principle, a fuller understanding of the controlling mechanisms, based on evidence, should permit progress in achieving both higher rates of production of paper and more reliable control of paper attributes. In addition, energy can be saved, reducing environmental impacts. The goal of this article is to review published work dealing both with the concepts involved in water removal and evidence upon which existing and new theories can be based. The scope of this review includes all of the papermaking unit operations between the jet coming from the headbox and the final wet-press nip of an industrial-scale paper machine. Published findings support a hypothesis that dewatering rates can be decreased by densification of surface layers, plugging of drainage channels by fines, sealing effects, flocculation, and rewetting. Ways to overcome such effects are also reviewed.

Biomass waste has become a new source for producing graphene due to its carbon-rich structure and renewable nature. In this paper, the research on the conversion of bio-based graphene from different biomass wastes is summarised and discussed. This paper reviews the methods for converting biomass to bio-based graphene. There are two approaches for thermal degradation of biomass: thermal exfoliation and carbon growth. The purpose of the thermal treatment is to increase the carbon content by removing volatile matter from the biomass polymer chain. Pre-treatments that help to break down the complex structure of the biomass are discussed; pre-treatments also remove impurities from the said biomass. Lastly, the characteristics of bio-based graphene produced from different biomass and thermal treatments are summarised.

The biodegradability of polymers depends on several factors. However, the most critical aspects are the accessibility of the structure for moisture and enzyme diffusion and the capacity of the microbes in the environment to assimilate the final monomers. The accessibility of the polymer structure to enzymes and water depends primarily on crystallinity, hydrophobicity, and the steric effects of the side groups in the polymer backbone. In general, biologically synthesized polymers are readily biodegradable in natural environments but synthetic polymers are either less biodegradable or degrade very slowly. However, such generalizations should be avoided. To understand the compatibility of biomaterials and the environment, both the disintegration step of the biodegradation process and the assimilation and mineralization of these fragments by microorganisms must be investigated. Mineralization occurs when the oligomers and monomers assimilated within the cells are converted to CO2 and H2O (aerobic), and CO2, CH4, and H2O (anaerobic). Although the disintegration of the polymeric structure limits the biodegradation rate and is most easily detected, the final pieces may accumulate in the environment if they are not fully mineralized. Such accumulation could contribute to an issue with microplastics that may be much more difficult to address than the removal of macroscopic, large polymer-based debris.