Volume 7 Issue 1

The tensile strength and bending strength of natural coir fiber are lower than many other natural fibers. Therefore, coir fiber is unsuitable for many fiber reinforcement applications. This study exploits the better shock resistance and toughness of coir fiber, which suggest that coir fiber can be used as a type of replacement material in plywood. Fast-growing poplar was chosen as the surface material, and coir fiber was selected as the core layer material for their buffering ability and toughness, and fiberglass fabrics were added in the core layer as strengthening components. The optimization of this plywood structure was carried out with an orthogonal experiment and the intuitive analysis method. The mechanical performance of some samples even exceeded that of natural wood. Through analysis of test results and scanning electron microscope (SEM) observations, the buffering and toughening mechanisms of the coir fiber mats were revealed. This new material can be used to replace wood in plywood and in the transportation industry as a packaging material and as platform floors for freight vehicles.

Formosan subterranean termites (Coptotermes formosanus Shiraki) and other wood-feeding insects have the ability to digest cellulose and structurally modify or degrade lignin. We examined the physical and chemical changes to lignocellulosic components of Chinese red pine (Pinus massoniana) after passing through the termite (C. formosanus) digestive system. The purpose of this research was to evaluate biochemical digestive processes in the C. formosanus gut as potential models for biofuels processing. Results suggest that demethylation, demethoxylation, and propyl side-chain modification are responsible for higher lignin removal and cellulose crystallinity reduction after structural alteration. SEM images also further indicated that unlike the fungus- growing termites Odontotermes formosanus, the lower termites C. formosanus disrupted the lignocellulose structure, and thus resulted in an increase of surface area to cellulase. Comparative enzymatic hydrolysis tests between raw wood and C. formosanus faeces revealed an enhanced level of enzymatic digestibility in digested material. Based on the results, C. formosanus can efficiently modify lignin at ambient temperatures and pressures in contrast to current methods used in biofuels production.

Fifty-three algal cultures were isolated from freshwater lakes in Hainan, China. Four microalgal isolates were selected because they could be successfully cultivated at high density and demostrated a strong fluorescence after being stained with nile red. These cultures were identified as strains of Chlorella sp. C11, Chlamydomonas reinhardtii C22, Monoraphidium dybowskii C29, and Chlorella sp. HK12 through microscopic and 18S rDNA analysis. Under similar conditions, the lipid productivity of Chlorella sp. C11, Chla. reinhardtii C22, M. dybowskii C29 , and Chlorella sp. HK12 were 1.88, 2.79, 2.00, and 3.25 g L-1, respectively. Chla. reinhardtii C22 yielded a higher lipid content (51%), with a lower biomass concentration (5.47 g dwt L-1). Chlorella sp. HK12 reached a growth rate of 0.88 day-1 at OD540nm and yielded a biomass concentration of 7.56 g dwt L-1, with a high lipid content of 43%. Gas chromatography/ mass spectrometry analysis indicated that lipid fraction mainly comprises hydrocarbons including palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acids. Our results suggest that Chlorella sp. HK12 is a promising species for biodiesel production, because of its high lipid productivity and a relatively high content of oleic acid.

The decay resistance of oil-heat treated aspen wood (Populus tremula l.) against white rot fungi (Coriolus versicolor) and brown rot fungi (Coniophora puteana) was investigated. Three different temperature stages and two time levels for oil heat treatment for the selection of optimum conditions were determined. Linseed oil as a heating medium was used. The mass loss of treated samples that were exposed to both fungi was significantly lower than that of the control samples. Results also showed improvement in dimensional stability after oil heat treatment. Decay resistance and dimensional stability of aspen wood were increased significantly with temperature increasing, but time seemed to have no effect on those properties. Oil heat treatment is a suitable method to improve decay resistance of aspen wood as it reduced the mass loss by 71% and 77% against Coriolus versicolor and Coniophora puteana compared with control samples, respectively. On the other hand, oil heat treatment improved the dimensional stability by about 20.5%.

Stenotrophomonas maltophilia AAP56, laccase-producing bacteria, growing under different conditions, exhibit laccase activity that is highly affected by some environmental factors. Response surface methodology (RSM) was applied for the determination of laccase factor dependence using two substrates: ABTS (2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) and DMP (2,6 Dimethoxy-phenol). RSM was carried out with a 24 factorial design using four variables, namely, dye (0 to 0.1 mg mL-1), Cu in Med (0 to 400 µM), shaking (0 to 150 rpm), and CuSO4 in assay (0 to 0.2 mM). Significant correlation between the effects of these variables on R1 (ABTS oxidase activity) and R2 (DMP oxidase activity) responses was detected. Astonishing results showed differences between these two activities with respect to copper activity dependence. Anoxic conditions exhibited a significant ability to induce the enzyme. This bacterial laccase activity (produced under optimal conditions according to RSM) was used to decolorize an azoic dye, Reactive Black 5 (RB5). It was efficient only in the presence of a redox mediator to degrade RB5 after 20 min of incubation time.

The biochemical properties of a purified enzyme of a new alkalophillic endo-1,4-beta-xylanase gene, KRICT PX2 (GU967374), which was isolated from Paenibacillus sp. HPL-002 (KCTC11410BP) and expressed in E. coli, were investigated. The specific activity of the purified xylanase was 51.26 μmol/min/mg proteins. The Km and Vmax values of the protein for birch wood xylan were also verified to have 0.061 μM and 55.3 μmol/min/mg proteins, respectively. The optimum pH and temperature for the activity of the enzyme were pH 8~9 and 50oC, respectively, and, the activity was stably maintained at 40oC. Most metallic salts, ethylenediamine tetra-acetic acid, 2-mercaptoethanol, phenylmethane-sulphonyl fluoride, and furfural, have no impact on the enzyme’s activity at 1 mM. The simulated 3-D structure of this xylanase is similar to Xyn10B from Paenibacillus barcinonensis. Further research on the degradation of different-origin xylans and enzyme production will be necessary for practical applications.

The biochemical properties of a purified enzyme of a new alkalophillic endo-1,4-beta-xylanase gene, KRICT PX2 (GU967374), which was isolated from Paenibacillus sp. HPL-002 (KCTC11410BP) and expressed in E. coli, were investigated. The specific activity of the purified xylanase was 51.26 μmol/min/mg proteins. The Km and Vmax values of the protein for birch wood xylan were also verified to have 0.061 μM and 55.3 μmol/min/mg proteins, respectively. The optimum pH and temperature for the activity of the enzyme were pH 8~9 and 50oC, respectively, and, the activity was stably maintained at 40oC. Most metallic salts, ethylenediamine tetra-acetic acid, 2-mercaptoethanol, phenylmethane-sulphonyl fluoride, and furfural, have no impact on the enzyme’s activity at 1 mM. The simulated 3-D structure of this xylanase is similar to Xyn10B from Paenibacillus barcinonensis. Further research on the degradation of different-origin xylans and enzyme production will be necessary for practical applications.

Alkaline oxidation (AlkOx) is an effective fractionation technique for lignocellulosic raw materials. The efficiency of the AlkOx treatment can further be enhanced by using a catalyst (CatOx). Both CatOx and AlkOx provide a fiber fraction containing readily hydrolysable carbohydrates that can be utilized in biotechnical processes and a liquid fraction containing solubilized lignin and reaction products from various biomass components. The effects of different fractionation conditions on yields and chemical composition of solubilized and insoluble fractions were investigated. Two temperatures and two reaction times were studied with and without a catalyst. The composition and content of carbohydrates in the fiber and liquid fractions were examined. The generation of aliphatic carboxylic acids as oxidation products was also investigated. The catalytically assisted oxidation was more efficient than the alkaline counterpart in dissolution of wood components under a four-hour treatment period resulting in higher dissolution of hemicelluloses. A longer reaction time of 20 hours leveled out the differences between the oxidation processes. Comparison of different bases showed that similar solubilisation of dry matter was obtained with NaOH, KOH, and Na2CO3. Oxidation in Na2CO3 caused higher dissolution of glucomannan and greater acid production. The dissolution of hemicellulose and lignin, and their oxidation to acids was most efficient in the first 4 hours of oxidation.

Nitrogen fixation of wheat straw ammonium sulfite pulping spent liquor and the chelating property of nitrogen-fixed ammonium lignosulfonate were studied. Results showed that free ammonium nitrogen in spent liquor could be fixed by formaldehyde. When the amount of formaldehyde was 10% based on the dry weight of lignosulfonate, 30% of inorganic nitrogen was converted into organic nitrogen, of which 87.4% was ammonium lignosulfonate and 12.6% was urotropine. The proper chelating condition of nitrogen-fixed ammonium lignosulfonate was as follows: pH:3, hydrogen peroxide:10%, FeSO4: 40.9%, and 50 oC for 30 min. Under this reaction condition, the chelating ratio of Fe2+ was measured as 15.1%. Chelation did not result in Fe(OH)3 precipitation under alkaline conditions. Effects of H2O2 dosage on the structure of ammonium lignosulfonate were also studied. The content of carboxyl, phenolic hydroxyl, and conjugated carbonyl groups in lignosulfonate that could be chelated with metal ions increased after ammonium lignosulfonate was oxidized. Average molecular weight and distribution were also determined with GPC. Results showed that the proportion of higher molecular weight components increased after oxidation of ammonium lignosulfonate, indicating that oxidative degradation and condensation reaction proceeded during oxidative treatment and condensation was the main reaction. The increase of molecular weight could improve the chelating ability of ammonium lignosulfonate.

The purpose of this study is to develop a low-formaldehyde-emitting resin system for medium density fibreboards (MDF). A combination of polyamines with phenolic resins seems to be suitable for this purpose. To produce panels with such a resin system, polyethylenimine, and a phenolic resin were separately applied on fibres and subsequently made into boards in a thermal pressing process. It was demonstrated that thickness swelling and the mechanical properties of the boards produced with the new adhesive system were comparable to those conventionally manufactured with urea-formaldehyde resins. Even with adhesive contents of just 2 to 3%, the panels attained satisfactory internal bond strength. MDF panels with a total adhesive content of between 1.25 and 5% were produced from a mixture of polyethylenimine and phenolic resins (resol type) at different ratios. All boards were tested for physical (thickness swelling and water absorption) and mechanical properties (internal bond, modulus of elasticity, flexural strength). It was demonstrated that thickness swelling and the mechanical properties of the boards produced can be improved by a combination of polyethylenimine and phenolic resin.