Volume 11 Issue 2

The production of value-added chemicals from the bioconversion of lignocellulose biomass has been considered a promising venture. In this study, microwave, alkali-pretreated empty fruit bunch (EFB) was used as the substrate, utilizing pelletized filamentous Rhizopus oryzae NRRL 395 and cellulolytic enzymes for lactic acid production in a fed-batch simultaneous saccharification and fermentation (SSF) process. Insoluble solids generally do not affect the SSF process until a certain concentration is exceeded. To achieve a high lactic acid concentration in the broth, a high solids loading was required to allow a higher rate of glucose conversion. However, the results revealed a decrease in the final lactic acid yield when running SSF at a massive insoluble solids level. High osmotic pressure in the medium led to poor cellular performance and caused the Rhizopus oryzae pellets to break down, affecting the lactic acid production. To improve the process performance, a fed-batch operation mode was used. The fed-batch operation was shown to facilitate higher lactic acid yield, compared with the SSF batch mode. Enzyme feeding, as well as substrate feeding, was also investigated as a means of enabling a higher dry matter content, with a high glucose conversion in SSF of cellulose-rich EFB.

The dissolution of sugarcane bagasse cellulose (SBC) in zinc chloride solution was studied at elevated temperatures. Based on single factor experiments, the effects of zinc chloride mass fraction, dissolution time, temperature, and bagasse cellulose mass fraction were investigated by an orthogonal experiment, and the optimal dissolution conditions were obtained. The dissolution process of bagasse cellulose was observed under a microscope. Additionally, the original SBC and regenerated SBC were both characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Temperature was found to be the most important factor affecting dissolution time. The best dissolving process took place at 85 °C to dissolve 2% SBC in 85% zinc chloride for 210 min. It was shown that the zinc chloride was a direct solvent for SBC. After regeneration of cellulose in zinc chloride, the crystallinity of cellulose was decreased greatly, from 77% to 54%, its crystalline form was transformed from cellulose I to cellulose II, its thermal decomposition temperature was reduced, its thermal stability was slightly decreased, and its internal structure was disrupted.

The scale-up of a mechanochemical acetylation operation using 100-L ball mills was performed to produce acetylated Japanese cedar (Cryptomeria japonica) wood meal for wood-polypropylene composite (WPC) production. Finely and coarsely acetylated wood meals (AWMs) were successfully produced with approximately 21% and 19% weight percent gains (WPG), respectively, which was close to the theoretical value. The mechanical properties of WPCs showed similar, rather weak strength compared with the AWM-filled WPCs without maleic anhydride-grafted polypropylene (MAPP) as a compatibilizing agent; however, coarse AWM-filled WPCs showed similar or higher mechanical properties than untreated wood meal (UWM)-filled WPCs when MAPP was added. Clear enhancements in the dimensional stability of AWM-filled WPCs were observed, but no significant differences in dimensional stability were observed between WPCs filled with fine and coarse AWMs, even when MAPP was added. Morphological analyses of the fracture surface showed the retention of some wood cell wall structures in coarse AWM, and fine loadings of the thermoplastic into the lumen were clearly observed. These properties were not found on the fracture surface of fine AWM-filled WPCs; therefore, high polymer loadings into the retained wood structure with high interfacial adhesion by MAPP could be suggested for improving the mechanical properties of coarse AWM-filled WPCs.

This research emphasizes the isolation of nanocrystalline cellulose (NCC) from palm tree cellulose (PTC) and α-cellulose (AC), using acidic FeCl3-assisted catalytic pretreatment coupled with ultrasonication. The cavitation effect of ultrasonication affects the microstructure of the fibers, ultimately enhancing the crystallinity index of the prepared nanocrystalline cellulose (NCC) sample. In this research, Fourier transform infrared spectroscopy (FTIR) was used to identify the specific functional groups on both types of NCC sample. X-ray diffraction (XRD) analysis demonstrated that the isolated NCC from PTC and AC showed a higher crystallinity index of 73.51% and 89.03%, with diameters of 20 to 70 nm and 15 to 50 nm, respectively. The change in surface morphological features was observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopic (TEM) analysis. It was observed that PTC-based NCC had higher thermal stability than the starting cellulosic sample, whereas NCC isolated from AC showed an opposite trend of reduced thermal stability relative to the raw sample. The results indicated that catalytic acid hydrolysis with ultrasonication was able to yield up to 80.88% and 81.20% of NCC from PTC and AC, respectively, which is comparatively high enough for economic viability of the process.

This study investigated a new potential hot-pressing method for wood modification, in which densification, drying, and heat-treatment were carried out in sequence. The effects of heat treatment on the chemical components of wood were evaluated. The specimens were treated at different temperatures (180 to 220 °C) for 2 to 5 h. Holocellulose, α-cellulose, and lignin were extracted from the treated and untreated milled wood. The changes in these components were analyzed by thermogravimetry (TG) and Fourier-transform infrared spectroscopy (FTIR). Due to its amorphous structure, most hemicelluloses were degraded when it was exposed to 220 °C for 3 h and to 200 °C for 5 h. Conversely, the lignin contents increased continuously throughout the treatment due to the loss of polysaccharides and the formation of cross-links. Because of the crystallinity, α-cellulose degradation was slight. According to the analysis of functional groups, FTIR showed treated wood was more hydrophobic than the untreated one.

Microcrystalline cellulose (MCC) was successfully prepared from bleached kenaf bast fiber through hydrochloric acid hydrolysis. The influence of hydrolysis time (1 to 3 h) on the MCC physicochemical properties was examined. Scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analysis, Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA) were utilized to characterize the isolated MCC. According to FTIR analysis, the chemical composition of MCC was not changed with the reaction time. The reaction times, however, did affect the thermal stability of MCC. The thermal stability decreased linearly with increasing hydrolysis time. The optimum hydrolysis time was determined based on the morphological, structural, and thermal properties of the kenaf bast MCC.

Extracted wood samples of Fagus orientalis with different solvents were analyzed for their antifungal activity against white-rot fungus (Trametes versicolor) in an agar plate. The most active extract was analyzed for its antioxidant activity by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, and the chemical composition were analyzed using gas chromatography-mass spectrometry. After the solvent removal of extractives, especially using chloroform (Chl) and Chl-water mixture, losses in the resistance of beech wood had occurred. However, Chl extract was found to be the most active antifungal agent, and the weight loss (30.38%) of specimens after 14 weeks of incubation was higher than that of other extracted specimens. At the concentration of 0.016 mg/mL, the highest activity observed was by Chl extract (89.45%), which was lower than the value of vitamin C (96.63%) at the same concentration. The lowest weight loss values obtained from the decay test were 0.35% and 0.64% for ethanol and ethanol-water extracted beech wood samples, respectively. The highest weight loss values were 30.38% and 23.98% for Chl and Chl-water extracted samples, respectively.

Construction of modern timber bridges has greatly increased during the last 20 years in Sweden. Wood as a construction material has several advantageous properties, e.g., it is renewable, sustainable, and aesthetically pleasing, but it is also susceptible to deterioration. To protect wood from deterioration and ensure the service life, the wood is either treated or somehow covered. This work evaluates a technology to monitor the moisture content in wood constructions. Monitoring the moisture content is important both to verify the constructive protection and for finding areas with elevated levels of moisture which might lead to a microbiological attack of the wood. In this work, a timber bridge was studied. The structure was equipped with six wireless sensors that measured the moisture content of the wood and the relative humidity every hour. Data for 744 days of the bridge are presented in this paper. Results show that the technology used to monitor the bridge generally works; however, there were issues due to communication problems and malfunction of sensors. This technology is promising for monitoring the state of wood constructions, but a more reliable sensor technology is warranted continuous remote monitoring of wood bridges over long periods of time.

Composite production of polypropylene polymers was considered in this work as the matrix, filled with the fiber of wheat straw and paper mill sludge; different ratios were evaluated relative to their potential as reinforcement materials. Maleic anhydride polypropylene (MAAP) was used at 3% by weight. The bending modulus of elasticity of the composites significantly increased with both types of filler. The highest bending modulus of the composites was found with 40% of paper mill sludge. Using 40% wheat straw fiber decreased bending strength, but the addition of paper mill sludge increased bending strength. The highest bending strength of the composites related to polypropylene/10% of wheat straw fiber and 30% of paper mill sludge. In terms of impact strength, the use of paper mill sludge had a higher impact on strength than wheat straw fiber composites. The inclusion of MAPP improved the mechanical properties of all composites. Scanning electron micrographs showed that the composite paper mill sludge improved the adhesion and dispersion of the filler (paper mill sludge/fiber paper instead of wheat) in the matrix.

Bio-chars were produced by co-pyrolysis of lignin with high-density polyethylene at 350 °C, 450 °C, and 550 °C. X-ray diffraction (XRD), Raman spectroscopy, automated surface area and pore size analysis, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR) spectroscopy were performed on bio-char to reveal the effect of temperature on its physical structure and chemical properties. All of the bio-chars demonstrated a highly disordered, turbostratic structure and exhibited a wide pore distribution. Dramatic losses of carbonyl, hydroxyl, and C-H groups indicated the development of condensed aromatic structure in the bio-chars. Specifically, biochar produced at 450 °C showed the highest degree of aromaticity, which is the relative content of aromatic structure with small fused rings and free radical concentration. This structure has more potential application in composite production and as solid fuel for its combustion or gasification. Moreover, biochar produced at 550 °C had the greatest porosity development, favoring its use as a precursor for activated carbon production.