Volume 7 Issue 3

With the extensive industrial applications of laccase in mind, this study was performed to investigate the decolorization applicability of sol-gel matrix-immobilized laccase. Indigenous G. leucidum laccase (592±6 U/mL) was purified 6.5-fold with a specific activity of 875 U/mg. The purified laccase had a molecular weight of 66 kDa, as evidenced by a single band on SDS-PAGE. Active laccase fractions were immobilized by entrapping in Sol-Gel matrix of trimethoxysilane (TMOS) and propyltetramethoxysilane (PTMS). A maximum of 90.7% immobilization efficiency was achieved with a purified fraction containing 2 mg/mL laccase. An activity profile revealed that immobilized laccase retained 78 to 80% of its original activity at a pH of 4 and a temperature of 80 °C, compared to free laccase. The tolerance capacity of laccase against inactivating agents (cystein, EDTA, and Ag+) was also enhanced by up to 80% by sol-gel immobilization. To explore the decolorization applicability, the immobilized laccase was tested against four different textile industry effluents. After the stipulated reaction time (24 h), varying decolorization percentages of wastewater effluents (with a maximum of 97.3% decolorization) were achieved.

In response to increasing awareness of the environment and energy, the fields of application for new types of plant fiber functional materials are expanding. In this study, different weight proportions of coir fiber were added to wood particle debris to produce hybrid boards. The two forms of coir fiber used were random distribution and non-woven needle mat. A mixed orthogonal experiment was designed to use the weight mixing ratio of wood debris and coir, the density of the hybrid boards, and the mixing form of the raw material as the experimental factors. The mechanical and sound absorption performances were evaluated. The experimental results provided evidence that the addition of the coir fibers enhanced the mechanical performance and sound absorption performance of the hybrid boards. The non-woven needle mat form in particular was effective at evenly distributing the fibers. The optimal plan for this kind of hybrid composite was obtained through experimental analysis. The excellent sound absorption performance and sufficient strength of the hybrid boards made them suitable for use on inner walls as sound-absorbing material or on interior trim parts in automotive applications. The research results demonstrated the advantages of using coir fiber and wood debris resources.

Defatted soy-based flour (DSF) modified with a combination of acid, salt, dicyandiamide, and alkali for preparing soy-based bio-adhesives (SBA) was investigated in this study. The resulting modified products from different reaction stages were characterized by FTIR, XPS, and TG. The results from FTIR and XPS indicated that the hydrolysis of the amide link and decarboxylation had occurred after the reaction by acid and salt; these reactions resulted in an increase of active groups, such as primary amine, carboxyl, and hydroxyl groups. The active groups were further increased by treatment with dicyandiamide and alkali. Curing the SBA resulted in the condensation and cross-linkage between active functional groups. Moreover, TG analysis proved that the active functional groups were increased during the modification process of the DSF, which was consistent with the results presented in FTIR and XPS. Finally, SBA was applied to plywood made from four wood species (basswood, Pinus massoniana, Triplochiton scleroxylon, and poplar) to test its water resistance performance. The average bonding strength between wood species was close to 0.91 MPa, which demonstrated that the SBA can be regarded as an alternative to petro-based adhesives.

Alkaline Peroxide Mechanical Pulp (APMP) of triploid of Populus tomentosa was modified by laccase and a Laccase-Mediator-System (LMS). The influence of the following main variables on the pulp physical properties were studied: enzyme dosage, reaction time, treatment temperature, and pH. Under the optimum conditions of laccase treatment – pH 5, temperature 50°C, pulp consistency 4%, and a reaction time of 60 min – the optimum charge of laccase was 2u/g. It was also found that the tensile strength and tear indices of the pulps treated with laccase increased significantly. The two-stage method of enzyme-mild acidic hydrolysis was adopted to isolate lignin from the APMP pulps both before and after enzymatic treatments. The functional groups in all lignin samples were qualitatively and quantitatively analyzed with 31P-NMR spectra. The molecular weight distributions of all the lignin samples were obtained through Gel Permeation Chromatography (GPC) after the lignin samples were benzoylated.

Growing attention has been paid to the innovation of ecological products, prompted by rising environmental concerns. As a natural polymer, thermoplastic sago starch has been regarded as an alternative material to petroleum-based plastic owing to its availability, cost, and biodegradability. In order to produce thermoplastic starch materials with enhanced structural and functional stability during use, kenaf fibers were incorporated as the reinforcing filler. In this work, thermoplastic sago starch (TPSS)/kenaf core fiber (KF) biocomposites were prepared at different fiber loadings (0 to 35 wt.%), and the effects of fiber loading were analyzed by mechanical tests, TGA, FTIR, SEM, and water absorption behavior. The tensile analysis showed a linear increase in strength and modulus upon increasing fiber content until it reached an optimum at 30 wt.% fiber loading. The thermal stability of biocomposites was improved slightly by the incorporation of kenaf fibers into TPSS matrices. FTIR results indicated a change in the functional group of the biocomposites. Moreover, the interfacial adhesion properties of biocomposites were evident from morphological studies of tensile fracture surfaces. It is interesting to note that water absorbed by the biocomposites was reduced by the addition of fiber, and it seems that the hydrophilic character was decreased especially for the glycerol-plasticized sample. The results obtained clearly illustrate the potential use of these fiber and biopolymers to establish their suitability as alternative biocomposite materials.

Waste newspaper fiber (WNF) was separated and deinked for use as an absorbent for removal of Malachite Green (MG) from aqueous solutions. The chemical composition of the deinked waste newspaper fiber (DWNF) was analyzed, and its morphology was observed by Scanning Electron Microscopy (SEM). A batch adsorption study was conducted under various adsorbent dosage, solution pH, and contact time. Kinetics and isotherms models were fitted; the thermodynamic parameters were also calculated. The results indicated that the main component in DWNF is cellulose. The SEM photographs showed that the surface became smoother and cleaner after deinking treatment. The equilibrium adsorption capacity was reached within 60 min, and the maximum adsorption capacity was around 27 mg/g. Alkaline pH (around 8) favored the adsorption process. The adsorption of MG was a spontaneous and exothermic process. It was found that the pseudo-second order kinetic equation and Langmuir adsorption isotherm model described the data of dye adsorption onto DWNF very well. The results show that DWNF is an effective absorbent for dye wastewater treatment.

Calcium hydroxide filler dispersions, of various particle sizes, were prepared by mixing sodium hydroxide with calcium chloride, in various concentrations, at room temperature. The resulting filler dispersions were added, in various amounts, to the banana stem mechanical pulp, which was then converted to handsheets. Increasing the filler loading increased the tensile index but reduced the tear index and water absorption of the handsheets. The SEM micrographs of the handsheets surfaces and the tensile fractured surfaces of the handsheets tensile test specimens showed that increasing the filler loading resulted in the formation of more and bigger filler aggregates in the spaces between the fibre. The filler particle size did not have any significant effect on the handsheets properties.

Laminated veneer lumbers (LVLs) were manufactured from half-round sliced I-214 hybrid poplar clone veneers with MUF adhesives using press pressures ranging from 2.5 to 15 kg cm-2. The results showed that the press pressures affected the glue line thickness (GLT) and the physical and mechanical properties of the LVLs. Higher specific gravity (SG) and mechanical properties, but lower GLT were developed as a result of using higher press pressures. The optimum press pressure was found to be 10 kg cm-2 in relation to GLT, SG, and mechanical properties. Significant linear correlations were found between GLT and mechanical properties. GLT can be used to determine the quality of wood bonding and may become a valuable tool for this purpose. Reliable data on the optimum GLT and press pressures can be used to design safe wood bonding applications in all aspects of wood based composites, as well as wood constructions when appropriate techniques are adopted to measure the GLT.

Bark and the tops of E. globulus trees were considered for kraft pulping under industrial conditions. Pulping experiments included wood, bark, tops, and composite samples. Top wood had an average chemical composition most similar to that of wood but with somewhat lower cellulose content (52.8% vs. 56.9%) and higher lignin content (18.8% vs. 17.8%). There was also a small difference between tops and wood for non-polar extractives, which were higher for tops (2.0% vs. 1.4%). Bark had a less favorable chemical composition with more extractives, especially polar extractives (5.3% vs. 1.6%) and 1% NaOH solubility (19.9% vs. 12.2%), pentosans (23.7% vs. 21.3%), and ash (2.9% vs. 1.0%), although the fiber length was higher (1.12 mm vs. 0.98 mm). The kraft pulps obtained using bark showed significantly lower yield, delignification degree, and strength properties but had a quicker response to refining. The incorporation of tops and bark in the wood pulping in levels below or similar to a corresponding whole-stem, however, had a limited effect on pulp yield, kappa number, refining, and pulp strength properties. These additional raw-materials, which were estimated to be 26% of the commercial stem wood (14% bark and 12% tops), may therefore be considered in enlarging the eucalypt fiber feedstock in kraft pulping.

A multiple linear regression analysis was carried out to predict the length of pellets under compression in the die based on moisture, temperature, pressure, hold time, and their interaction terms. Excellent correlations were obtained in the dependency of the considered parameters on length of compressed material inside the die. Springback characteristics based on axial changes after the compaction process were analyzed. The expansion for hardwood pellets (16.28%) was found to be lowest at particle size 0.150 to 0.300 mm with 8% moisture (w.b), 60 °C, 139.3 MPa pressure, and a hold time of 15S. The expansion for softwood pellets (20.56%) was lowest with particle size 0.300 to 0.425 mm, at 8% moisture (w.b), 70 °C, 159.2 MPa, and a hold time of 30S.