Research Articles

With the use of Paulownia wood as a substrate and a vacuum impregnation method, CaCO₃/wood composites were prepared. The XRD results showed that a variety of types of calcium carbonates coexisted in the composite and the elevated temperature was favorable for the aragonite type. The SEM results showed the modified wood retained the original wood structure and that CaCO₃ was uniformly distributed in the wood cell cavity and clung to the wood cells. The mechanical testing results showed that the mechanical properties of all the composites were obviously improved; the maximum value of strength of compression (SC) and modulus of elasticity (MOE) of the CaCO₃/wood composites were 32.23 MPa and 0.92 GPa, respectively, values 44.2% and 53.3% higher than those of the original wood. The maximum value of proportional limit (PL) of the composites was 29.4 MPa (38.5% increase from original wood). A cone calorimeter was used to investigate the flame retardation properties of CaCO₃ on the composites. The value of the heat release rate and total heat release of composites were lower than those of the original wood; the CaCO₃ wood composites showed good flame retarding effects.

The objective of this study was to investigate the impact performance of bamboo oriented strand board under different impact energy. Bamboo oriented strand board with two types of strand orientation distribution, both with mainly parallel aligned strand orientation (LVSL) and three-layer assembly with orthogonally oriented strands (BOSB), were prepared. The impact properties of the boards, both untreated and treated with submersion, were investigated at seven energy levels. Additionally, the damage morphology was characterized using an X-ray computed tomography (CT) scanner. The results indicated that BOSB provided a larger maximum load carrying capacity, and represented superior impact properties compared to LVSL. The shapes of force/energy–time history of BOSB and LVSL were different from projectile energy levels, and they were related to the specimen destruction forms via CT scanning. Moreover, CT scanning revealed that LVSL and BOSB exhibited similar damage behaviors, which mainly included delamination and fibers breakage. The dent depth of BOSB on the impact site was less than LVSL’s for touch types, and there was more internal fracture inside the layers of LVSL at relatively higher energy levels of 300 J and 450 J. Furthermore, BOSB still exhibited better impact performance than LVSL under the condition of submersion.

Approximately 18 million tons of soybean straw are produced annually in China, with its disposal becoming an increasingly serious problem. Moreover, the Chinese government has banned the open burning of agricultural straw for environmental reasons. One potential solution is to use soybean straw for lactic acid (LA) production, avoiding open burning and waste. In this study, a Ca-alginate-immobilized Lactobacillus casei strain was used to produce LA from soybean straw enzymatic hydrolysate. Optimized conditions for the production of LA were initially established, consisting of Ca-alginate beads made from 2.5% sodium alginate with a diameter of 2 mm and a fermentation process using a 10% inoculum at 30 °C for 30 h. Lactic acid productivity was increased with only a slight decrease in overall yield by raising the initial sugar concentration from 8 g L-1 to 35 g L-1. Finally, immobilized cells could be reused at least 10 times without a noticeable performance decrease. These results indicated that production of LA from soybean straw enzymatic hydrolysate is a sustainable and feasible method to utilize these resources.

Biorefinery lignin was carbonized under a carbon dioxide atmosphere at various temperatures viz., 500 °C, 600 °C, 700 °C, and 800 °C, separately. The results indicated that with increasing temperature, the mass yield decreased from 49.2% to 39.8%. Carbonization at a high temperature resulted in an increment of carbon (C) content and decreased both the hydrogen (H) and oxygen (O) contents. With the increase of carbonization severity, the ratios of O/C and H/C decreased mainly due to the demethanation, dehydration, and decarboxylation reactions. The carbonization resulted in the transformation of aromatic rings as well as the rearrangement of the aromatic polymers, and the enhancement of the thermal stability of the charcoal formed.

Cellulosic paper is widely used in various applications, such as for decoration and in cold-rolled stainless steel. The thermal stabilities of cellulosic fibers were investigated with a thermogravimetric analyzer. Additionally, the impact of mechanical refining on the heat resistance of cellulosic paper was evaluated by testing the tensile strength and brightness of the samples derived from pulp with various beating degrees. The morphology of the paper was characterized with scanning electron microscopy and the monose content of the pulp samples was determined with high performance liquid chromatography. The results showed that the different pulps had different thermal stabilities. Because of pulp refining, the heat tolerance was enhanced in terms of the strength and optical properties. Compared with the original papers, the tensile strength and brightness of the 40°SR papers on average increased by 217% and 114%, respectively, all evaluated after heating at 240 °C. Therefore, the heat tolerance of cellulosic paper can be tuned with pulp refining.

Virgibacillus pantothenticus, Bacillus cereus, and B. subtilis were screened from an activated sludge that had become acclimated to white water in the laboratory. The effects of the pH on the ability of biological treatment to reduce the biological oxygen demand of white water was studied for three dominant bacteria. The pH ranged from 4 to 8, and the optimum treatment efficiencies for white water treatments with the single dominant bacterium V. pantothenticus, B. cereus, and B. subtilis occurred at pH values of 5, 6, and 6, respectively. The results also indicated that the best treatment effect was achieved at a hydraulic retention time of 14 h. When each dominate species was tested under their optimum pH value and hydraulic retention time, the chemical oxygen demand removal rate was 67.7%, 77%, and 75.4%; the electrical conductivity decreased by 0.18 mS/cm, 0.93 mS/cm, and 0.51 mS/cm; and the cationic demand decreased by 69.7%, 70.0%, and 70.9% for V. pantothenticus, B. cereus, and B. subtilis, respectively. These results are helpful for promoting the practical application of dominant bacteria in white water treatment.

Quercus species represent 18% of the total forest area in Romania, of which 2% refers to common oak and 10.5% refers to sessile oak. These species are of special importance for Romanian silviculture due to their value in multiple industrial uses. The finest and most efficient use of valuable timber is wood veneer. This paper presents a comparative analysis of the efficiency in veneer cutting for two Quercus species, common oak and sessile oak, originating from the Snagov area in Romania. The statistical parameters of veneer efficiency were estimated with high accuracy by using the least squares method with a 95% normal confidence interval based on the Anderson-Darling test and the correlation coefficient. The analysis of inferential statistics used the estimation of the 87th percentile, determining the cumulative density functions for the species under study. More defects were found in common oak logs than in sessile oak logs, which produced more veneer sheets. The veneer efficiency for sessile oak logs was superior to that of common oak logs. These findings might have practical applications in industrial conditions when screening for the best log species with high efficiency in veneer cutting.

To investigate the potential of Hibiscus sabdariffa var. altissima (Thai kenaf) biomass as a feedstock for bioethanol production, Thai kenaf bark and core were pretreated at a moderate temperature with different phosphoric acid (H3PO4) concentrations. It was revealed that there was a higher glucan content in the Thai kenaf bark (57.97% ± 0.36%) compared with that in the core (43.10% ± 0.15%). The H3PO4 pretreatment resulted in a reduction in the lignin content and total removal of hemicellulose. This exposed the cellulose to attack by cellulase enzymes and resulted in an increased enzymatic digestibility. A high glucose concentration (GC; 7.02 g/L) and hydrolysis efficiency (HE; 95.79%) were achieved with 75% H3PO4 for the bark after 72 h of enzymatic hydrolysis. However, these values were not that different from those of the 70% H3PO4-pretreated bark (6.89 g/L and 95.43%, respectively). Nevertheless, the Thai kenaf core pretreated with 75% H3PO4 recorded a higher GC (6.30 g/L) and HE (91.67%) after 72 h of enzymatic hydrolysis. The scanning electron microscopy and X-ray diffraction analyses revealed the destruction of the surface structure and an increase in the porosity and crystallinity index of the Thai kenaf biomass, which corresponded to an increased enzymatic digestibility.

As an efficient fungus in secreting cellulase, Trichoderma orientalis EU7-22 has an important value in the degradation of biomass. Compared with other filamentous fungi, it has an important, unique nature, and it deserves intensive study. Therefore, the function of positive transcriptional regulator ACE3 was investigated for cellulase and hemicellulase production in the strain. As the ace3 knockout strain, the Δace3 mutant was constructed by homologous recombination, so that the enzyme activities (FPA, CMC, CBH, BG, XYN) and the extracellular protein concentration in the mutant strain decreased to 17.8%, 8.3%, 0.14%, 1.8%, 6.8%, and 19.2% of the parent strain, respectively. The transcription level of cellulase and hemicellulase genes also decreased significantly. The result of SDS-PAGE demonstrated that the Δace3 mutant only clearly showed a protein band, which was characterized by protein profiling with LC-MS/MS and identified as the GH10 family of xylanases. It was proposed that ACE3 is a main up-regulation transcriptional factor of T. orientalis EU7-22 and expected to be applicable to further genetic modification.

Kraft lignin was plasticized with ε-caprolactone via twin-screw extrusion at 150 °C, and its glass transition temperature was decreased from 155 to 96 °C. The lignin or plasticized lignin (p-lignin)/polycaprolactone (PCL) composites with and without lignocellulose nanofibril (LCNF) or polymeric methylene diphenyl diisocyanate (pMDI) were prepared, and their properties were compared. The p-lignin was better dispersed in the PCL than neat lignin, and the p-lignin/PCL composites exhibited a homogenous fractured surface despite the addition of LCNF. An increase in the lignin or p-lignin content decreased the tensile strength and elastic moduli but increased the melt flow index (MFI). With the addition of pMDI and LCNF, the tensile properties and MFI improved and declined, respectively. The strength improvement by pMDI and LCNF was better in the p-lignin/PCL composite than in the lignin/PCL composite.