Volume 9 Issue 3

Medium components for β-glucosidase (BGL) production in Schizophyllum commune KUC9397 were optimized using a central composite design and response surface methodology. 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 BGL production was obtained with 2.96% cellulose, 2.30% soy peptone, and 0.11% thiamine HCl. BGL production in the optimized medium was increased 7.2-fold compared to production in an unoptimized medium. Crude enzyme preparation from S. commune KUC9397 was used to saccharify pretreated lignocellulosic biomass. The crude enzyme preparations showed statistically equal saccharification rates as Cellobiase, a commercial BGL. This finding indicates that crude enzymes produced by S. commune KUC9397 have good potential for application in cellulosic biomass conversion systems in place of Cellobiase.

A porous lignin-containing hydrogel was developed for dye removal via graft copolymerization of acetic acid lignin (AAL) and acrylamide (AAm), in the presence of ethyleneglycol dimethacrylate (EGDMA) as a crosslinker and H2O2 as an initiator. AAL was characterized by FT-IR and TGA. After being washed to remove impurities, the hydrogel was characterized by FT-IR, TGA, SEM, and swelling ratio. FT-IR spectra suggested that AAL was present in the hydrogel. The TGA curves revealed that the introduction of AAL had no significant impact on the thermal stability of PAAm. SEM images showed that the honeycomb-like structure of the hydrogel was improved with increasing AAL content. The swelling ratio data showed that the hydrogel with a high AAL/AAm ratio was sensitive to pH. Furthermore, increased lignin content of the hydrogel favors the dye adsorption.

Ball-milled rice straw was dissolved in a lithium chloride/dimethyl sulfoxide (LiCl/DMSO) solvent system, regenerated, and subjected to enzymatic hydrolysis to obtain regenerated cellulolytic enzyme lignin (RCEL). The structure of the isolated lignin was characterized by elemental analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR). Alkaline nitrobenzene oxidation (NBO) was conducted to analyze the structural characteristics of the in-situ lignin. The results showed that the rice straw RCEL was composed of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) phenylpropane units, with relatively high amounts of H units. The yield of RCEL is about 5% units higher than that of cellulolytic enzyme straw lignin (CEL) on the basis of total lignin in the original rice straw. When compared to the CEL obtained by the traditional method, there were no observed differences versus RCEL in terms of the elemental compositions, NBO product yields, and S/G ratio. The weight-average molecular weight of RCEL was 6835, which was lower than that of CEL, indicating that some rice straw lignin linkages were cleaved during LiCl/DMSO dissolution.

Dynamic mechanical analysis (DMA) is a powerful analytical technique to study wood structure and properties. In order to draw firm conclusions from results obtained by DMA, strain rate of tests conducted by DMA should be within the linear viscoelastic region (LVR) of the tested material. In this study, the LVR limit of sugar maple (Acer saccharum Marsh.) wood specimens was determined in the three directions under a range of temperature and relative humidity (RH) conditions. The results demonstrated that wood had very different LVR limits in the different directions. The longitudinal direction had much lower LVR limits than the radial and tangential directions. While LVR limits were not strongly affected by changes in temperature and RH in the longitudinal direction, they proved very sensitive to these factors in the tangential direction. The results of this study showed the importance of determining LVR limits before running any test by DMA.

There are health and safety risks involved in the production and storage of forest biomass. Fungi that are formed in the stored piles of wood chips pose a high potential risk for human health. Three experimental piles, containing wood chips from three species of trees, were created. They included European beech (Fagus sylvatica), common aspen (Populus tremula), and European spruce (Picea abies). The piles created were in the shape of a pyramid with the base measuring 4 m x 4 m. In each pyramid, 3 points of measurements were established at 0.5 m, 1.0 m, and 1.5 m above the ground. Temperature, relative moisture, and the number of microscopic fungi colonies were monitored at each point of measurement in the period between 13th December 2011 and 6th June 2012. The highest relative moisture content was recorded in the pile with the European spruce. The aim of the experiment was to identify the genus and species of fungi that are formed in the chip piles during long-term storage and which pose a potential risk for human health. In total, 5 species and 8 genera of fungi were identified in the collected samples, whereby there was significant growth only during the first 4 to 6 months of storage.

A fluorinated poly-acrylate emulsion with various fluorine contents was prepared by a seeded semi-continuous emulsion polymerization method and applied to filter paper for oil-water separation applications. The effects of surface wetting behavior on the oil-water separation efficiency of the prepared filter paper were studied. The results show that the prepared highly hydrophobic and superoleophilic filter paper presented 94.45 wt% water separation efficiency and strong mechanical strength. In addition, the oil-water separation stability and durability of the filter paper were also tested and shown to be suitable for use in real oil-water separation applications. These properties indicate that the filter paper has great potential applications in the oil-water separation industry.

The effect of time-dependent moisture absorption on the surface roughness in natural fiber/polypropylene composites after a hot-press molding was studied. The results showed that the moisture absorption in both bagasse and oil palm natural fiber composites correlated closely with time-dependent surface roughness in the composites. The surface roughness in all natural fiber composites increased with an increase of moisture absorption up to 50 d. The fibers absorbed moisture and swelled due to hydroxyl groups of celluloses in the natural fibers, which caused an increase in surface roughness. Time-dependent tests found that the surface roughness in long fiber composites was larger than that in short fiber composites due to inhomogeneous dispersion of long fibers in the vicinity of the surface of composites. The increase in surface roughness of oil palm composites was 55% that of the bagasse composites due to the lower temperature of thermal decomposition in oil palm fibers than in bagasse fibers. Thermal decomposition decreased the number of hydroxyl groups in fibers during heating and resulted in a decrease in moisture absorption in the palm fibers. Furthermore, the effect of the carbodiimide treatment on bagasse fibers was confirmed to reduce moisture absorption for both the fibers and the composites.

The in situ Fourier transform infrared (FTIR) spectroscopy technique was used as an online method for fundamental mechanistic studies of the pyrolysis of a lignin monomeric model compound. The formation of important reaction intermediates was revealed. Three major decomposition routes were shown: P1, dehydration at approximately 270 °C; P2.1, demethylation at approximately 350 °C; and P2.2, H-abstraction at approximately 430 °C. A free reaction of the pyrolysis of the lignin model compound was suggested based on the results. The comparative results showed that the methyl group was the initiator of many secondary reactions.

Columbian coffee trees are subject to frequent replacement plantings due to disease and local climate changes, which makes them an ideal source of wood fibers for wood plastic composites (WPC). Composites of polypropylene (PP) consisting of 25% and 40% by weight of coffee wood flour (CF) and 0% or 5% by weight of maleated PP (MAPP) were produced by twin screw compounding and injection molding. Composites containing MAPP had significantly improved tensile and flexural properties compared to neat PP or composites without MAPP. Excellent mechanical properties were obtained with CF relative to conventional wood fillers. Izod impact resistances of CF composites were significantly lower than neat PP although WPC containing MAPP were superior to WPC without MAPP. Bio-based fiber composites made by mixing CF in equal portions with other fiber sources were evaluated to determine the compatibility of using CF with other sources of filler materials. Soaking of tensile bars of the various CF blends in distilled water for 35 days may alter their mechanical properties and result in weight gain. Differential scanning calorimetry and thermogravimetric analysis were conducted on the neat PP and bio-composites to evaluate their thermal properties as they relate to potential degradation during conventional thermoplastic resin processing.

The goal of this study was to develop and test an appropriate method for the evaluation of surface quality and to identify and quantify the quality of a surface modified by 3D molding. New software was developed to evaluate the surface quality based on the identification of macroscopic defects such as cracks within a scanned area. The influence of specific factors that affect the development of cracks during the uneven pressing process was assessed. Based on the measured and evaluated results, a process combination of factors was designed which yielded an embossed surface that was formed with the lowest proportion of cracks and with sufficient shape stability. In this work, 432 groups of test pieces were monitored, with each piece exposed to different combination of factors. Based on the measured and evaluated results, we found a combination that provided the lowest crack ratio. This innovative method will contribute to the knowledge of embossed surface quality and to the improvement of the uneven pressing process for wood surfaces.