Volume 14 Issue 1

Parallel strand bamboo (PSB) is a high-strength bamboo composite that has been used in construction in recent years. Crack growth is a major concern in the design of PSB components for building structures. This study investigated the mode II fracture properties of PSB composite under in-plane shear action, starting from the end notched flexure (ENF) test as the prototype of specimens. The compliance based beam method (CBBM) was used to analyze the crack propagation process. The results showed that crack propagation of mode II fracture of PSB was self-similar cracking with cracks parallel to the strand. The fracture process contained two stages: the development of the Fracture Process Zone (FPZ) and the crack propagation stage. The critical energy release rate GIIc was a constant independent of the initial crack length, with a mean value of 2.61 N/mm; the mean value of fracture toughness KIIc was 4436 kN·m-3/2, which is greater than those of commonly used timber products. The R-curve showed a gradual increase before crack extension due to the development of the FPZ but became approximately horizontal during crack propagation.

Fungicides can have a good result against phytopathogens, but alternatives, such as a biological control agents, have also been found to be effective and ecofriendly. In this experiment, Alternaria solani was isolated from rotten tomato fruit. The culture filtrates of Trichoderma harzianum gradually inhibited the radial growth of A. solani at higher concentrations, but growth was not completely inhibited until a high filtrate percentage of 75% was reached (75% by volume). The microscopic study revealed that the T. harzianum culture filtrate and its spores changed the size, number, and shape of the A. solani conidiospores. A. solani produced both cellulolytic and pectinolytic enzymes in vitro. The activity of these enzymes decreased with an increase in the T. harzianum filtrate percentage and chemical fungicide concentration. A. solani failed to produce hydrolytic enzymes, particularly pectinase, at high concentrations of fungicide (100 ppm and 150 ppm). When T. harzianum was used as a biocontrol agent, the detected hydrolytic enzyme activities increased compared with the other treatments.

Three experimental groups were designed to study the effects of different exogenous nutrients on a composting process and the degradation extents of cellulose, hemicellulose, and lignin. Hickory shell was the main raw material, and spent mushroom substrate and composted chicken manure were used as exogenous nutrients. The C/N ratios of these groups were adjusted to 34 by using soybean meal. The study results showed that the duration of high-temperature stage of composting was shortened and the maturity of composting products was improved by adding exogenous nutrients. The seed germination index with spent mushroom substrate and composted chicken manure were 112% and 101%. The addition of exogenous nutrients reduced the composting weight loss and increase the degradation extents of cellulose (≥64.6%), hemicellulose (≥82.4%), and lignin (≥64.3%). In particular, the degradation of compost products with composted chicken manure was higher than that of the composting products with the spent mushroom substrate. In the hickory shell composting system, bacteria played a dominant role in the initial and thermophilic phase, and the lignin degradation is related to the quantity of fungi and actinomycetes in composting process.

The use of wood-base panels in humid environments, in general, presents low durability due to contact with water. In order to increase durability and reduce the attack of fungi, studies had been developed using resin with zinc oxide (ZnO) nanoparticles. This work aimed to produce medium density fiberboard with urea-formaldehyde resin and melamine-formaldehyde adding 0.5% and 1.0% of ZnO nanoparticles for the physical properties evaluation. All treatments were classified as medium density according to ABNT NBR 15.316-2 (2015) with values ranging between 550 and 800 kg*m-³. No differences were found between the two commercial adhesives used. The addition of 1.0% of nanoparticles resulted in lower density panels, higher moisture contents, and, after immersion in water for 24 hours, higher values of swelling in thickness. These results are explained by the lower compaction of the boards due to rapid cure of the adhesive using higher percentages of ZnO nanoparticles. The best treatment of the panels was with melamine-formaldehyde resin and 0.5% of nanoparticles.

Cellulolytic enzymes from fungi are complex compound enzyme structures that generally include three kinds of hydrolytic enzymes, which are called endo-β-1,4-glucanases, exo-β-1,4-glucanases, and β-1,4-glucosidases (β-glucosidases). The fungus Mucor ardhlaengiktus isolated from field rice straw produced a β-glucosidase (MaBgl). Maximal MaBgl production occurred when M. ardhlaengiktus was incubated for 6 days in fermentation liquor at 30 °C and an initial pH of 6. Purified MaBgl was obtained from M. ardhlaengiktus fermentation broth by ammonium sulfate fractional precipitation and DEAE-Sepharose FF ion exchange chromatography. The molecular weight of MaBgl as determined by SDS-PAGE electrophoresis was approximately 72 kDa. The kinetic parameters, Michaelis constant (Km) and maximum velocity (Vmax), of MaBgl were 78.2 μmol/L and 28.5 μmol/(L·min), respectively. Assays of MaBgl produced by M. ardhlaengiktus RSC1 under different conditions were investigated by the 3,5-dinitrosalicylic acid (DNS) assay for glucose. The pH and temperature optima for catalytic activity of MaBgl were pH 4.8 and 50 °C, respectively. MaBgl exhibited good thermal stability in the range of 20 to 30 °C, but the thermal stability of MaBgl decreased rapidly over 60 °C. MaBgl had better pH stability between pH 4.6 and 5.0, and the stability of MaBgl decreased when the pH value was lower or higher than this range.

Miscanthus (Geodae-Uksae in Korean, GU) is a promising source of biomass for biosugar production due to its superior mass yield and minimal need for nitrogen fertilizer and herbicides. In this study, the biomass productivity, chemical composition, and physical properties of Miscanthus were investigated for two harvest dates. The total biomass of early harvest GU (EH-GU; 20.1 t DM/ha) was greater than that of the delayed-harvest GU (DH-GU; 18.0 t DM/ha). There was no noticeable difference in the carbohydrate content between the EH-GU and DH-GU, while the lignin content remarkable decreased after pretreatment. The enzymatic conversion rates of GU to biosugar increased after pretreatment, to approximately 86 to 90%. After enzymatic hydrolysis, 381 g and 147 g of glucose and xylose were produced, respectively. Consequently, 528 g of biosugar was obtained from 1 kg of EH-GU. Determining the optimal harvest date of Miscanthus has enabled a more efficient enzymatic hydrolysis and higher biosugar yields.

The effect of metal ions and surfactants on the enzymatic hydrolysis of pretreated wheat straw lignocellulose was investigated. Scanning electron microscopy, infrared spectrum analysis, dynamic light scattering, and fluorescence spectra analysis were used to characterize the influence of Fe3+/ polyoxyethylene (20) sorbitan monooleate (Tween 80). The interaction between Fe3+/Tween 80 and enzyme was further investigated by enzyme kinetics and enzyme activity measurements. The best synergistic effect was obtained when the ratio of Fe3+ and Tween 80 was 0.06. The scanning electron microscopy images showed that the Fe3+/Tween 80 combination was associated with high porosity substrates. The infrared spectrum analysis indicated that the components of the substrates depended on additive types. The highest relative enzymatic activity increase rate was obtained with added Fe3+/ Tween 80. The Vmax and Km values of the group with added Fe3+/Tween 80 were much higher than that of the group without additives. With the addition of Fe3+/ Tween 80, the intensity of the fluorescence emission peak decreased and the peak shifted towards a longer wavelength.

Wood flour (WF) of poplar, acid hydrolysis residue (AHR) of corn cob from xylose production, and cellulose fibers (CF) from bleached eucalyptus pulp were compared as functional fillers of lignocellulosic-plastic composites (LPC) in terms of tensile strength and thermal stability. WF showed a negative effect on tensile strength of LPC. AHR-filled LPC at 10% of filling level exhibited an improvement by 8.9%, whereas higher filling level led to a decrease of tensile strength due to poor interfacial compatibility, as revealed by SEM analysis. Remarkably, tensile strength achieved a maximum of 25.8 MPa for CF-filled LPC at 2.5% of filling level, which was an approximately 76.7% improvement compared to the control. Dependence of LPC thermal stability on chemical compositions of fillers was revealed. WF-filled LPC showed a lower onset decomposition temperature compared to the control due to the presence of xylan, while thermal stability of AHR-filled LPC was enhanced due to the presence of cross-linked phenolic polymer lignin.

The exploitation of agroindustrial lignocellulose, such as oil palm trunk bagasse (OPTB), as a raw material in the production of succinic acid (SA) may serve as an effective strategy to propel the bio-based industry. This study aimed to optimise the recovery of fermentable sugar, i.e., glucose, from enzymatic hydrolysis of the dilute acid pretreated OPTB (DA-OPTB). The dilute acid pretreatment used in this study was able to remove 59.5% of hemicellulose and 13.3% of lignin. Response surface methodology (RSM) based on central composite design (CCD) was then applied to investigate four independent variables – enzyme loading (10 to 50 U/g), agitation speed (50 to 250 rpm), reaction time (0 to 96 h), and surfactant concentration (0.025 to 0.125%, v/v). The experimental glucose concentration of 21.7 g/L was in good agreement with the RSM-predicted value of 20.5 g/L. Among the parameters investigated, supplementation of a surfactant during enzymatic hydrolysis was significant in influencing glucose recovery, while the extent of the agitation speed was the least influential. The maximum recovered glucose was estimated at 217 g per kg of raw OPTB, with 7.3 g/L of SA attainable from the fermented DA-OPTB hydrolysate using Actinobacillus succinogenes 130Z. The results demonstrated that OPTB can be practically utilised in the economical production of high value-added SA.

An investigation was conducted of the modification of bamboo fibers (BF) by nano-hydroxyapatite (N-HA) and its impact on the mechanical and thermal properties of BF/PLA composites. The functional groups, and crystallinity of the N-HA modified BF were investigated with Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), respectively. The effects of different N-HA contents on the properties of the BF/PLA composites were evaluated using mechanical testing (bending, tensile, and impact properties), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the most suitable N-HA content was 7.5 wt.%. Treating BF with an optimum concentration of N-HA decreased the polarity of the bamboo fiber, while maintaining the crystal structure of the cellulose. Compared with the control group, the mechanical properties and the crystallinity of the modified BF/PLA composites were improved, and the flexural, tensile, and impact strengths increased by 10.2%, 11.6%, and 28.1%, respectively. The thermogravimetric analysis results indicated modified BF/PLA composites has higher thermal stability.