Volume 10 Issue 4

Trichoderma species are widely used for the commercial production of cellulolytic enzymes. In the present investigation, medium components were optimized using a central composite design and response surface methodology to produce endoglucanase (EG) from Trichoderma harzianum KUC1716. From the various medium components tested, cellulose, soy peptone, and thiamine HCl were selected as the optimal carbon, nitrogen, and vitamin sources, respectively. The highest EG (1.97 U/mL) production was obtained with 1.85% cellulose, 0.48% soy peptone, and 0.10% thiamine HCl. EG production in the optimized medium was 2.6 fold higher than in the unoptimized medium. In addition, the crude enzyme preparation from T. harzianum KUC1716 supplemented with β-glucosidase from Schizophyllum commune KUC9397 was used to hydrolyze various types of lignocellulosic materials and showed significant saccharification yields on all lignocellulosic materials, surpassing that of a commercial enzyme cocktail. It was verified that the crude enzyme preparation derived from T. harzianum KUC1716 could replace the commercial enzymes. This highlights the potential of the crude enzymes for use in biomass conversion systems.

Liquefied wood-based precursors and carbon fibers were prepared by various chemical curing processes to investigate the effects of curing time and temperature on the thermostability and tensile strength of carbon fibers. The primary fibers can be converted into high-performance precursors by directly heating at a targeted curing temperature. With the temperature and duration increasing, the number of methylene bonds in the precursors increased, resulting in the enhancement of cross-linkages among molecular chains and the improvement of the thermostability of the precursors. Carbon fibers prepared from the precursors (95 °C and curing time 3 h) exhibited the minimum value in the average interlayer spacing (d002); however, they displayed the highest tensile strength, at almost 800 MPa, which can be classified as fibers of general grade.

The process of cooking with solid alkali is a novel and efficient technology. In the present work, milled wood lignin (MWL) and water-soluble milled wood lignin (WMWL) were used as the raw materials to research their properties when cooking with MgO and active oxygen. Before and after cooking, the lignin content of the samples was estimated using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), heteronuclear single-quantum coherence-nuclear magnetic resonance (HSQC-NMR), and gel permeation chromatography (GPC). The results showed that the properties of the MWL and WMWL were different. The G unit and A′structure in WMWL were more easily degraded than that in the MWL, where the G unit could be oxidized into a novel G′ unit. The D structure in the MWL with a weak signal could be thoroughly degraded, and the P structure was only present in WMWL and could be generated during the cooking process.

In this study, a numerical model of the tangential tensioning stress distribution of a circular saw blade tensioned by multi-spot pressure was established using theoretical analysis, and the tangential tensioning stress distribution of the circular saw blade calculated by the model was shown to be true and reliable. The effect of yield strength of the circular saw blade on the distribution of tangential tensioning stress was studied using the numerical model. The research achievements showed that a circular saw blade made with high-strength or ultra-high-strength steel yielded a better tensioning effect during the multi-spot pressure tensioning process, which could promote the application of a circular saw blade made by high-strength or ultra-high-strength steel.

Biorefining is a potential pathway to cover the shortage of fuels, power, and chemicals from lignocellulosic biomass in the future. However, pretreatment of the biomass is recognized as a technological bottleneck for the cost-effective development of biorefineries, especially for the production of bio-fuels and chemicals. Active oxygen pretreatment is both an eco-friendly and efficient pretreatment process. To elucidate the effect of different chemicals on corn stalk and its hemicellulosic structure, five pretreatment processes were formed with MgO, H2O2, and O2. Additionally, the MgO was also replaced by NaOH and Mg(HO)2. Results show that MgO, which can be completely replaced by Mg(OH)2, is an alkali source and a protective agent in preventing raw material from carbonizing and cellulose from degrading during pretreatment. High pressure oxygen is the main chemical for depolymerizing corn stalk. The removal degrees of lignin and hemicelluloses in the pretreatment processes with oxygen were 81.1 to 87.7% and 73.3 to 83.0%, respectively. Without oxygen, much lower removal degree were achieved (19.3 to 49.0% and 55.5 to 67.6%, respectively). Corn stalk hemicelluloses were composed of (1→4)-β-D-xylopyranose substituted with α-L-arabinofuranosyl residues and 4-O-methyl-α-D-glucuronic acid units. The molecular weight of hemicelluloses decreased from 22,000 g/mol to the range 3100 to 6400 g/mol.

The aim of this study was to assess wood quality using diagnostic keys related to the main traits of trunk architecture in the most important resource of resonance spruce of the Romanian Carpathians. The material sampled from standing and felled trees yielded 568 individual ring series adding up to over 81,000 growth rings. The resonance xylotype was first recognized in felled trees, already designated for violin manufacture, for which a 6-class quality classification system was proposed. This system was extended to the qualitative classification of the standing trees (diameter at breast height larger than 10 cm). The width and regularity of the growth rings, the width of the sapwood and latewood, and the compression wood ratio are the variables that make recognition of trees containing resonance wood possible. Wood with resonance structural value was detected locally along the tree stem, and the best resonance structural quality was found uniformly distributed from 5 to 9 m above the ground and in the external half of the cross-section. Trees having a proper structure for violin fliches, but not yet with an appropriate size (38 cm underbark diameter), accounted for about 7% of the total tree population.

There is much interest in using less expensive raw materials as precursors for carbon fibre manufacture to increase the utilisation of strong, light-weight composite materials in the transportation sector. One such potential raw material is lignin. Most studies exploring melt spinning of lignin have used lignins from organosolv or hardwood kraft delignification processes. There has been little success reported in utilisation of the more commercially available softwood kraft lignins. In this study, lignins from different softwood kraft cooking processes were investigated with respect to their melt spinning performance and conversion to carbon fibres. The isolated lignins differed mainly in molecular weight, glass transition temperature, and softening temperature. All of the lignins produced from the laboratory cooks could be extruded without any plasticizer addition. However, the lignins contained volatiles that resulted in bubbles being formed along the length of the fibres. After vacuum drying, at elevated temperatures to remove volatiles, only the lignin originating from conventional kraft cooking was able to be melt extruded without plasticiser addition; this lignin had the lowest molecular weight amongst the samples. The stabilisation and carbonisation of these fibres gave carbon fibres with strengths comparable to those produced from lignins of other origins.

Cellulose nanofibril (CNF) aerogels with grafted beta-cyclodextrin (β-CD) were prepared for the adsorption of phenol pollutants from water. Compared with regular wood fibers, CNF aerogel not only can immobilize more β-CDs, but also it provides higher porosity and a larger specific surface area for phenol absorption. The CNF-CD aerogel becomes mechanically robust through chemical crosslinking. It can be easily separated from water after adsorbing phenol pollutants without complicated centrifugation or filtration. A series of studies on phenol adsorption was conducted. The results indicated that the CNF-CD aerogel prepared with a suspension concentration of 3% (w/w) had the highest adsorption capability. In addition, the CNF-CD aerogel showed an excellent reusability. The results indicated that the CNF-CD aerogel is an environmentally friendly and promising adsorbent for removing phenol pollutants from water.

This paper presents a new methodology for detecting the longitudinal location of the hidden hole in a log using impact-echo testing. The hole and the end surface of the log produced two different amplitude peaks in the frequency spectrum after a mechanical tap on the top of the log. The ratio of the two frequencies was used to estimate the longitudinal position of the hole. The major advantage of this method is that it avoids measuring the travel velocity of the stress wave, which is sensitive to many factors and then poses a formidable challenge to the realization of inspection. Experimental studies were carried out using Pine logs with mechanically drilled holes and a Cinnamomum camphora log with natural hole. The results indicated that the estimated positions were in good agreement with the actual position of the hole. The impact-echo testing can be applied to detect the longitudinal position of the internal hole in log.

A combination of steam explosion (SE) and chemical pretreatments, such as acid sulfite (AS), alkali (AL), and alkaline sulfite (ALS), were evaluated using bamboo. Low pressure steam explosion at 1.25 MPa for 4 min was first applied to the bamboo. Then, the pretreated bamboo was delignified using three chemical pretreatments. Enzymatic hydrolysis was also compared among the pretreated bamboo samples. It was found that SE-ALS could be a potential method for bamboo pretreatment, which led to the reduction of lignin from 25.15% to 1.74% at 165 °C for 2 h in 5% (w/v) Na2SO3 and 0.7% (w/v) NaOH; however, little cellulose was solubilized during ALS pretreatment. A maximum glucose yield of 99.35% was achieved during the enzymatic hydrolysis process when combined with the SE-ALS pretreatment. The SE-ALS method resulted in a lower degree of lignin condensation and increased delignification compared to the SE-AS method. In addition, the SE-ALS pretreatment protected carbohydrates from degradation better than the SE-AL methods.