Research Articles

Properties of composite boards from oil palm frond agricultural waste were researched. Phenol and urea formaldehyde resins were used as the binders. The oil palm fronds were obtained from 20 year-old trees in an oil palm plantation in Kota Belud, Sabah. The fronds were segregated into three groups of matured, intermediate, and young oil palm fronds and further subdivided into bottom, middle, and top sections. The leaflets and the epidermis were removed from the fronds before they were sliced longitudinally into thin layers. The layers were then compressed into uniform thickness of 2 to 3 mm. The layers were air-dried and later mixed with resins using 12 to 15% of phenol and urea formaldehyde and recompressed with other layers, forming composite boards. The composite boards samples were then tested for their physical and mechanical properties. Testing was conducted in accordance with the International Organization for Standardization (ISO) standard. The results for physical and mechanical properties showed that the oil palm composite boards were better than composite boards from oil palm trunks and slightly worse than the rubberwood. Statistical analysis indicated significant differences between composite boards made from each group and section, but no differences were observed in the type of resin used. The composite boards from oil palm fronds agricultural residues has the potential to be used as an alternative to wood to overcome the shortage in materials in the wood industry.

Funalia trogii and Trametes versicolor were grown on agro byproduct wheat bran moistened with various natural moistening agents, and their effects on laccase production under solid substrate condition were investigated. Laccase was the main enzyme detected under this condition. High levels of laccase activity were obtained with solid substrate cultures moistened with olive oil mill wastewater (OOMW) or alcohol factory wastewater (vinasse). Among the cultures without inducer, T. versicolor culture was detected as a more effective laccase producer than F. trogii culture. Copper and xylidine were used as laccase inducers, and copper induced laccase production more than xylidine. The maximum laccase activity was detected as 14.18 U/mL with F. trogii grown on wheat bran moistened with 5 mM CuSO4.5H2O added 25% vinasse. Azo dye decolorization activity of the supernatants from solid substrate cultures was also tested. While the use of 0.063 U/mL F. trogii laccase in reaction solution gave 66% decolorization in a minute, it was 14% for T. versicolor. This method can be a possible alternative for valorization of lignocellulosic materials and industrial wastewaters during solid substrate fermentation and for obtaining enzyme source with very high decolorization activity.

Xylo-oligosaccharides were obtained from Miscanthus x giganteus. The process was designed as a biorefinery scheme, which seeks the separation of the three main components: cellulose, hemicelluloses, and lignin. To extract the hemicelluloses, particularly xylans, in an efficient way, Miscanthus was subjected to autohydrolysis. The system was evaluated for the effects of temperature (160 to 200oC) and reaction time (15 to 60 min) on various parameters, reflecting the changes undergone during the process. The results showed that autohydrolysis is a suitable method for obtaining high yields of xylo-oligosaccharides, reaching values close to 65% of the dissolved xylans (based on the initial amount of potential xylose). Analysis of the process by using the severity factor (RO) allowed for the identification of a set of time-temperature values for which the fractionation was optimal.

and 3-methacryloxy-propyltrimethoxysilane (MPS) for the lack of compatibility with UF resin adhesive. The modified NCC was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), and wetting property. and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standards GB/T 17657-1999 and GB/T 9846-2004. The results of XRD, TG, and wetting property from NCC modified by APTES showed more significant improvements than that from NCC modified by MPS. The HCHO emission of UF resin adhesive with 1.5% NCC modified by APTESdecreasedby 53.2% and bonding strength increased by 23.6%, while the results from the NCC modified by MPS were 21.3% and 7.0%, respectively.

The main objective of this study was to explore the suitability of Vitis vinifera as a raw material and alkaline lignin as a natural binder for fiberboard manufacturing. In the first step, Vitis vinifera was steam- exploded through a thermo-mechanical vapor process in a batch reactor, and the obtained pulp was dried, ground, and pressed to produce the boards. The effects of pretreatment factors and pressing conditions on the chemical composition of the fibers and the physico-mechanical properties of binderless fiberboards were evaluated, and the conditions that optimize these properties were found. A response surface method based on a central composite design and multiple-response optimization was used. The variables studied and their respective variation ranges were: pretreatment temperature (Tr: 190-210ºC), pretreatment time (tr: 5-10 min), pressing temperature (Tp: 190-210ºC), pressing pressure (Pp: 8-16MPa), and pressing time (tp: 3-7min). The results of the optimization step show that binderless fiberboards have good water resistance and weaker mechanical properties. In the second step, fiberboards based on alkaline lignin and Vitis vinifera pulp produced at the optimal conditions determined for binderless fiberboards were prepared and their physico-mechanical properties were tested. Our results show that the addition of about 15% alkaline lignin leads to the production of fiberboards that fully meet the requirements of the relevant standard specifications.

An indigenous locally isolated white rot fungal strain Phanerochaete chrysosporium IBL-03was investigated for the hyper-production of ligninolytic enzymes from different agro-industrial wastes including wheat straw, rice straw, banana stalks, corncobs, corn stover, and sugarcane bagasse as substrate material in still culture fermentation technique. Screening experiments were performed at 30oC from 1 to 10 days and maximum enzyme activities were recorded after the 5th day of incubation on banana stalk. P. chrysosporium IBL-03 produced highestactivities of lignin peroxidase (LiP) and manganese peroxidase (MnP) but no laccase activity was detected in any fermented culture media. Production of ligninolytic enzymes was substantially enhanced through the optimization process. When banana stalk at 66.6 % moisture level and pH 4.5 was inoculated with 5mL spore suspension of P. chrysosporium IBL-03 at 35oC in the presence of molasses (1%) as carbon source, ammonium sulfate (0.2%) as nitrogen supplement, (1%) Tween-80 (0.3 mL) as surfactant and mediators (MnSO4 and veratryl alcohol) enhanced the LiP and MnP production up to 1040 and 965 (U/mL), respectively.

This study demonstrated the use of a pressurized mechanical refining system for the continuous steam explosion pretreatment of wheat straw. Wheat straw was first impregnated with either dilute acid (0.5% sulfuric acid) or water and then steam exploded in an Andritz pressurized refiner. The effect of a range of pretreatment conditions, including refining retention time and steam pressure/temperature on the resulting substrate composition and hydrolysability as well as overall sugars yield was investigated. For autohydrolysis, the optimum conditions, 198 oC/6 min gave an enzymatic hydrolysis yield of 93.3% and an overall glucose yield of 85.8%, while 198 oC/4 min gave an enzymatic hydrolysis yield of 88.7% and overall glucose yield of 88.4%. Longer retention time increased the enzymatic hydrolysability but reduced the overall glucose yield owing to the degradation reaction during pretreatment. For acid pretreatment, the most favourable condition for enzymatic hydrolysis and overall glucose yield coincided at 178 oC /6 min.

Fiber dimensions, chemical composition, and soda and soda-AQ pulping of tobacco stalks were examined to assess if they were suitable for pulp and paper production. The results showed that the morphological characteristics of tobacco stalks were similar to those of nonwoods and hardwoods. The average values of length, diameter, and cell wall thickness of tobacco stalks fibers were determined as 1.23 mm, 24.31 μm, and 8.93 μm, respectively. The holocellulose and alpha-cellulose in tobacco stalks were lower than those of hardwoods and common nonwoods. In addition, lignin content of tobacco stalks was lower than that of hardwood. The holocelluloses, alpha-cellulose, lignin, and ash contents of tobacco stalks were examined to be 67.79, 39.20, 18.90, and 6.86 wt%, respectively. The optimum cooking conditions for a bleachable pulp of tobacco stalks were found to be as follows: active alkali 25%, temperature 165°C, cooking time 180 min, and 0.2% anthraquinone. Addition of anthraquinone resulted in lower screening rejects and lower kappa number, higher screen yield, and higher brightness. The bleaching of tobacco stalk pulp did not respond very well. The brightness of pulp made by tobacco stalks reached about 73.06% on DED and 78.2% on DEDD bleaching sequences.

Several representative ionic liquids (ILs) were synthesized, and [Emim]OAc was chosen as environment-friendly solvent for enzymatic in situ saccharification in view of its biocompatibility with both natural and microcrystalline cellulose, as well as its enzymatic activity. With the microwave pretreatment of natural and microcrystalline cellulose, directly enhancing the in situ enzymatic saccharification, the rate was compared versus an untreated control by the detection of dinitrosalicylic acid (DNS). It is suggested that the molecular structure of cellulose in the process of pretreatment was changed, e.g. intramolecular hydrogen bonds were broken (detected by FT-IR), and the crystallinity (monitored by SEM and XRD) changed significantly from a crystalline to an amorphous pattern. These changes of cellulose led to an increase of reducing sugar conversion during cellulose enzymatic hydrolysis.

A study was conducted to purify and characterize a novel protease produced from Aspergillus niger using different lignocellulosic agro-based by-products including corncobs, wheat bran, and rice bran as substrates under SSF. Maximum protease activity was recorded on wheat bran fermented culture media after the 3rd day of incubation. The optimal conditions found for protease production using wheat bran were cultivation period (3 days), substrate concentration (10 g), pH (7), incubation temperature (45oC), inoculum size (4 mL), and 3% surfactant Tween-80 (2 mL). A purification fold of 2.41 with 29 U/mg specific activity and 70.73 % recovery was achieved after purification. Purified protease from A. niger had a molecular weight of 47 kDa on SDS-PAGE. The enzyme activity profile showed that purified protease was optimally active at pH 7 and 45oC as optimum values. A. niger protease was reasonably stable in the pH range 5-8 and 35-60oC for up to 1 h incubation. Protease was activated by various metal ions/inhibitors tested, Mn2+, Cd2+, Mg2+, Cu2+, PMSF, Pepstatin and Iodoacetic acid at 1 mM, proving the enzyme as metalloprotease, whereas an inhibitory effect was shown by certain agents including EDTA and SDS. The purified protease was compatible with five local detergents with up to 25 days of shelf life at room temperature. The maximum production of protease in the presence of a cheaper substrate at low concentration and its potential as a detergent additive for improved washing makes the strain and its enzymes potentially useful for industrial purposes, especially for the detergent and laundry industry.