Research Articles

Glucose and mannose, the major structural units found in softwood hemicelluloses, were used to produce 5-hydroxymethylfurfural (HMF) in the ionic liquid 1-butyl-3-methylimidazolium chloride, in the presence of a commercial zeolite (which acted as an acidic catalyst), and in the presence or absence of co-catalysts. Experiments were performed under diverse operational conditions, and the reaction kinetics were interpreted by a mechanism involving three major reactions (non-productive substrate conversion, HMF generation, and HMF decomposition). Activation energies were determined for the best reaction medium.

A bio-inspired approach to coating polydopamine (PDA) onto bamboo fiber (BF) was developed to enhance the poor interfacial bonding of BF/polybutylene succinate (PBS) biocomposites. The macroscopic features, functional groups, nanoscale topography, and crystallinity of the PDA-coated BF (D-BF) were investigated with digital photography, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD), respectively. The effects of the PDA loading rate on the performance of the D-BF/PBS biocomposites were also evaluated through the mechanical properties tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Treating BF with an optimum concentration of dopamine (DOPA) decreased the polarity of the bamboo fiber, while maintaining the crystal structure of the cellulose. The thermal stability, mechanical properties, and storage modulus of the D-BF/PBS biocomposites were noticeably enhanced because of the good interfacial compatibility. Moreover, the glass transition temperature (Tg) and crystallinity of the biocomposites increased with higher DOPA loading rates. The best properties were observed with a DOPA concentration of 1.0 mg/mL. These findings exhibited the feasibility for the application of PDA in the biomass fiber-reinforced biodegradable polymer composites industry.

The ellipticity of hardwood logs is most often observed and measured from either end of a log. However, due to the nature of hardwood tree growth and bucking practices, the assessment of ellipticity in this manner may not be accurate. Trees grown on hillsides often develop supporting wood that gives the first few feet of the log butt a significant degree of ellipticity, while the rest of the log may be more circular. Good log bucking methods dictate that a log be bucked near a fork or a large knot, creating a higher-valued lower log and a jump cut or a lower-valued upper log. This practice and the additional supporting (buttress) wood below the knot can make the upper end of a log exhibit ellipticity. In this study, 703 hardwood logs from Appalachian forests were scanned using a high-resolution laser scanner, and the ellipticity and the angle of the greater axis was recorded for every foot along each log. Approximately one-third of the logs exhibited moderate to severe eccentricity on the small end. However, most logs (99%) did not exhibit significant ellipticity along the entire length. Furthermore, the mean length of the elliptical zone for all species was 3.3 feet.

Flammability characteristics were determined for oak wood (Quercus robur L.), which was thermally modified at 160, 180, and 210 °C. Subsequently, the thermally modified and unmodified wood was treated with a fire retardant. The effect of the thermal modification (TM) and fire retardant treatment (FRT) on the weight loss (WL), burning rate (BR), maximum burning rate (MBR), and time to reach the maximum burning rate (TRMBR) were evaluated. The FRT had an expected positive effect on all of the flammability characteristics, where the WL, BR, and MBR decreased, and the TRMBR increased. The TM temperature did not have a clear effect. As the TM temperature increased, the WL and BR decreased. The highest differences were found at 160 and 180 °C. As the TM temperature increased for the wood without the FRT, the TRMBR decreased. During the burning of the thermally modified wood with the FRT, the trend was the exact opposite.

The microbiological hydrolysis of lignocellulose waste materials, using enzymatic biopreparations and its anaerobic processing, is a promising strategy for the efficient use of renewable energy sources. This article presents the optimization of microbiological media to improve cellulase production by Trichoderma atroviride G79/11 for further application as a cellulolytic biopreparation. The characterization of T. atroviride phenotypic microarrays was performed using the Biolog® PM plates approach. The optimization investigations were aimed at increasing the efficiency of the cellulolytic enzyme production involved in the solid-state fermentation type medium. This medium was based on dried sugar beet and wheat bran, as well as two liquid media based on mineral and soy flour, cellulose, and lactose (MSCL). The basic components of the MSCL were optimized. The study involved optimization of the content of the carbon and nitrogen source and the detergent additive. In order to increase the cellulase production, proper T. atroviride G79/11 culture conditions were established.

Two poplar lignin-carbohydrate complexes (LCCs), LCC-48 and LCC-72, were isolated at different milling times, 48 h and 72 h, respectively. A new hydrogel carrier was prepared from these LCCs in the presence of polyethylene glycol diglycidyl ether as the crosslinker for cell (human hepatocyte (L-02)) culture. The effects of the structure of LCC on the carrier were investigated. The FT-IR spectra indicate that the two LCC samples were composed of lignin and polysaccharide, and showed a typical LCC structure. The galactose contents of LCC-48 and LCC-72 were 3.02% and 5.67%, respectively. The results of cell culture show that a large number of hepatocytes adhered to the porous carriers. Hepatocytes grown on the LCC carriers outperformed the control group in every observed category, including cell proliferation rate and metabolic activity. These results indicate that poplar LCC might be a great potential precursor of biological carriers for human hepatocytes culture.

Butanol was produced from pretreated deoiled rice bran (DRB) in a batch culture of Clostridium acetobutylicum YM1. The DRB was pretreated by acetyl chloride to produce fermentable sugars prior to butanol fermentation. Pretreatment of DRB using 1% acetyl chloride (AC-DRB) resulted in sufficient fermentable sugars (30.88 g/L), which was comparable to that produced by using 1% sulfuric acid (33.5 g/L). Pretreated AC-DRB contained 18.08 g/L glucose, 9.95 g/L xylose, and 2.86 g/L cellobiose. Detoxification of AC-DRB was performed to remove the fermentation inhibitors, such as furfural, 5-hydroxymethyl furfural (HMF), acetic acid, formic acid, and levulinic acid with the removal efficiencies of 92.98%, 98.82%, 51.53%, 38.72%, and 96.21%, respectively, using charcoal. The detoxification with charcoal was more efficient compared to that with XAD-4 resin. Acetone-butanol-ethanol (ABE) fermentation of detoxified AC-DRB (with 1% AC) by XAD-4 produced 5.64 g/L butanol, while detoxification with charcoal of AC-DRB (with 1% AC) produced 6.48 g/L butanol. In detoxified AC-DRB with charcoal, the maximum butanol and ABE yield of 6.48 g/L and 11.82 g/L, respectively, were achieved. This study is the first reported treatment of biomass using acetyl chloride, which was used as a pretreatment method for successful butanol production.

Xylanase is a key enzyme in the conversion of lignocellulosic biomass into various oligosaccharides and simpler monomeric units through the hydrolysis of hemicellulose. Rice straw is readily available around the world and is a rich source of hemicellulose. Recently, there has been growing interest in the exploitation of rice straw as a low-cost substrate for the production of hemicellulolytic enzyme, i.e., xylanase. This study aimed to optimize the nutritional components (rice straw, magnesium sulphate, and calcium chloride concentrations) and physical parameters (temperature and pH) for xylanase production with a newly isolated Aspergillus oryzae LC1 under submerged fermentation using central composite design based response surface methodology. The optimum media constituents were 1% rice straw (w/v), 1.0 g/L calcium chloride, and 0.3 g/L magnesium sulphate, and the optimum physical parameters were pH 5 and 25 °C. The statistical design showed increased xylanase production with a maximum activity of 935 ± 2.3 IU/mL. The enzyme production was 3.8-fold higher than for the un-optimized Mendel’s Stenberg Basal Salt medium (245 ± 1.9 IU/mL). The enzyme was stable over wide ranges of pH (3 to 10) and temperature (25 to 60 °C). The partially purified xylanase enzyme was used for the enzymatic hydrolysis of different lignocellulosic agro-residues.

Binderless rice straw particleboards were successfully manufactured by hot pressing at low temperatures (110 °C) while under pressure (2.6 MPa) using a three-step process. Two particle sizes were used: 0.25 to 1.00 mm and 0.00 to 0.25 mm. Three pressing times (15 min, 30 min, and 60 min) were studied. Eighteen types of boards were made. The physical and mechanical properties were assessed in accordance with the European Standards for wood-based particleboards, namely density, thickness swelling, water absorption, thermal conductivity, modulus of rupture, modulus of elasticity, internal bonding strength, and reaction to fire. Two panels exceeded the requirements for general uses. The panels had a low thermal conductivity (0.076 W/mK to 0.091 W/mK). The panels were classified in the same class as the fire retardants (class Bd0, according to EN ISO 11925-2:2002).

This paper presents a comprehensive study of wheat straw that was alkali-pretreated with NaOH loadings from 60 to 220 mg NaOH/g dry straw and a 0.5% anthraquinone (AQ) loading at 90 °C for 1, 2, and 3 h. Images of the residual solids were taken with a scanning electron microscope. A full compositional analysis of the raw material and residual solids, yield of compounds dissolved in the black liquor (BL), and molecular weight (Mw) after the different pretreatments were presented to track the dissolution process of lignin and carbohydrates. The ratio of the lignin fraction to carbohydrates dissolved in the BL was used for an analysis of the reaction selectivity. The cellulose retained 90% of the carbohydrates in the pretreated straw, while 75% of the lignin was dissolved in the BL gradually with an intermediate value of Mw. Low-molecular weight lignin (Mw ~ 1800 and degree of polymerization ~ 1.05) was dissolved out with the 60 mg NaOH/g dry straw loading. When the NaOH loading was increased to 220 mg NaOH/g dry straw, the Mw of the lignin was 4300 to 4700.