Volume 6 Issue 4

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.

In this study, glyoxalated alkaline lignins with a non-volatile and non-toxic aldehyde, which can be obtained from several natural resources, namely glyoxal, were prepared and characterized for its use in wood adhesives. The preparation method consisted of the reaction of lignin with glyoxal under an alkaline medium. The influence of reaction conditions such as the molar ratio of sodium hydroxide-to-lignin and reaction time were studied relative to the properties of the prepared adducts. The analytical techniques used were FTIR and 1H-NMR spectroscopies, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Results from both the FTIR and 1H-NMR spectroscopies showed that the amount of introduced aliphatic hydroxyl groups onto the lignin molecule increased with increasing reaction time and reached a maximum value at 10 h, and after they began to decrease. The molecular weights remained unchanged until 10 h of reaction time, and then started to increase, possibly due to the repolymerization reactions. DSC analysis showed that the glass transition temperature (Tg) decreased with the introduction of glyoxal onto the lignin molecule due to the increase in free volume of the lignin molecules. TGA analysis showed that the thermal stability of glyoxalated lignin is not influenced and remained suitable for wood adhesives. Compared to the original lignin, the improved lignin is reactive and a suitable raw material for adhesive formulation.

Oil palm ash (OPA), a bio-agricultural waste from oil palm mills, was subjected to high-energy ball milling for 30 h and was converted into a nano-structured material. The nano-structured OPA was characterized for its particle size and crystallinity index by using Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) analysis. The crystallite size obtained from TEM and XRD was found to be 50 nm and 54.32 nm respectively, and the crystallinity index of OPA was 66.54%. The shape and texture of raw and nano-structured OPA were studied using scanning electron microscopy. The raw OPA had an irregular shape with spongy and porous structure, while the nano-structured powder had a mostly irregular and crushed shape. The elemental studies of OPA used Energy Dispersive X-ray (EDX) analysis, XRD, and Fourier Transform Infrared Spectroscopy (FT-IR). The elemental compositions found in OPA were silica, potassium oxide, calcium oxide, magnesium oxide, aluminium oxide, and iron oxide.

Non-isothermal crystallization of neat high density polyethylene (HDPE), wood flour (WF)/HDPE composite (WPC), virgin Kevlar fiber (KF) reinforced WPC (KFWPC), and grafted Kevlar fiber (GKF) reinforced WPC (GKFWPC) was investigated by means of differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Several theoretical models were applied to describe the process of non-isothermal crystallization. The results showed that the Avrami analysis modified by Jeziorny and a method developed by Mo and coworkers successfully described the non-isothermal crystallization behavior of HDPE and composites. The Ozawa analysis, however, failed to provide an adequate description of non-isothermal crystallization. The values of crystallization peak temperature (Tp), half-time of crystallization (t1/2), and kinetic parameters KJ and F(T) showed that the crystallizability followed the order: FKWPC > GKFWPC > HDPE > WPC. The effective activation energy for non-isothermal crystallization of HDPE and composites based on both Kissinger and Friedmen methods was evaluated. WAXD indicated that the crystalline thickness perpendicular to the reflection plane (Lhkl) increased with the addition of KF. The results demonstrated that KF and GKF can act as nucleating agents and increase the crystallization rate of HDPE. Compared with GKF, KF is a more effective nucleating agent for HDPE, and wood flour cannot act as a nucleating agent for HDPE. PDF

Lignin recovered from the near-neutral hemicellulose extraction process was investigated as a precursor suitable for production of carbon fiber. Crude lignin was precipitated from the wood extract by adding sulfuric acid to lower the pH value to 1.0. The crude lignin extract was then upgraded by using hydrolysis to cleave lignin-carbohydrate bonds and to remove carbohydrates that contaminate the lignin. The precipitated solids were separated by filtration, washed with water, and then dried. Lignin recovered using the hydrolysis method was found to be high in carbon, high in total lignin, low in inorganic contamination, and low in insoluble material, but high in volatile material. The recovered lignin could be thermally spun into lignin fibers, but the spun fibers proved to be brittle, which was thought to be due to its low-molecular mass and the glassy nature of lignin. Micrographs obtained using scanning electron microscopy (SEM) illustrated imperfections on the surface and in the interior microstructure of the carbon fiber when compared to micrographs taken of commercial carbon fiber manufactured using PAN and pitch. These imperfections were thought to be related to the high volatile material content in the samples and the slow rate of heating during the carbonization process. Baker (2011) suggests that increasing the rate of heating during carbonization can reduce the degree of brittleness and improve mechanical properties.

This study was performed to determine the effects of thermal aging on the film hardness of some wood varnishes. For this purpose, Scots pine (Pinus sylvestris L.), Eastern beech (Fagus orientalis L.), and oak (Quercus petraea L.) samples coated with synthetic (alkyd), two-part polyurethane (urethane-alkyd), and waterborne (self cross-linked polyurethane) varnishes were evaluated at a moisture content of 8% and 12%. Afterwards, thermal aging processes were performed for periods of 25, 50, 75, and 100 days at 25 ºC, 50 ºC, 75 ºC, and 100 ºC. Hardness changes in the varnish films were measured in accordance with ISO 1522-2006. According to the test results, the samples prepared with polyurethane varnishes at 8% moisture content give the best results.