Research Articles

The goal of the present study was to investigate production of cellulase in low cost medium by thermotolerant yeast. After screening, an efficient yeast isolate having capability of C1 (exo-gluconase) and Cx (endo-gluconase) production was isolated and designated as strain R-1. Maximum enzyme production was achieved at 50 °C, pH 5.5 in the medium containing bagasse powder 4% (w/v), and ammonium sulphate 0.1% (w/v) after 72 hours of incubation. The composition containing bagasse powder, 4% (w/v); ammonium sulphate, 0.5 % (w/v); and glucose, 0.5% (w/v) achieved better production after complete medium optimization. The yeast isolate was able to tolerate wide ranges of temperature, pH, and substrate concentration for higher enzyme production. The isolated yeast was able to produce C1 (exo-gluconase) and Cx (endo-gluconase) enzymes in appropriate concentrations on a crude cellulosic substrate. Therefore, yeast may be used to power alcohol production.

The ability of selected plant extracts from wood and foliage to inhibit mold regrowth on fungal colonized wood was evaluated on Douglas-fir sapwood. Most foliage extracts produced some inhibition of Graphium or Trichoderma species, but isolations of other fungi increased following treatment. Five out of eight wood extracts produced 50% reductions in isolations, and those from Alaska cedar, western juniper, and incense cedar produced at least 80% reductions. The results indicate that wood extracts may be useful for reducing the incidence of mold on wood products, but none of the materials evaluated completely inhibited the test fungi. These extracts may provide a useful value-added application for by-products of lumber production from these species.

A glue stick is comprised of solidified adhesive mounted in a lipstick-like push-up tube. Whey is a byproduct of cheese making. Direct disposal of whey can cause environmental pollution. The objective of this study was to use whey protein isolate (WPI) as a natural polymer along with polyvinylpyrrolidone (PVP) to develop safe glue sticks. Pre-dissolved WPI solution, PVP, sucrose, 1,2-propanediol (PG), sodium stearate, defoamer, and preservative were mixed and dissolved in water at 90 °C and then molded in push-up tubes. Chemical composition, functional properties (bonding strength, glue setting time, gel hardness, extension/retraction, and spreading properties), microstructure, and storage stability of the prototypes were evaluated in comparison with a commercial control. Results showed that all WPI/PVP prototypes had desirable bonding strength and exhibited faster setting than PVP prototypes and control. WPI could reduce gel hardness and form less compact and rougher structures than that of PVP, but there was no difference in bonding strength. PVP and sucrose could increase the hygroscopicity of glue sticks, thus increasing storage stability. Finally, the optimized prototype GS3 (major components: WPI 8.0%, PVP 12.0%, 1,2-propanediol 10.0%, sucrose 10.0%, and stearic sodium 7.0%) had a comparable functionality to the commercial control. Results indicated that whey protein could be used as an adhesive polymer for glue stick formulations, which could be used to bond fiber or cellulose derived substrates such as paper.

In the present study, magnesium silicate was produced by using wheat husk ash. Wheat husk was burned at 600 °C to obtain an amorphous ash structure, and the ash was processed with sodium hydroxide solution with heat to extract silica. Sodium silicate solution and magnesium salts were used to synthesize magnesium silicate. The present study investigates effects of the feeding rate on magnesium silicate production (0.6 mL/min, 35 mL/min, 70 mL/min), the type of magnesium salt (MgSO4 • 7H2O or MgCl2 • 6H2O), temperature (25 °C or 50 °C), and the washing agent (water and acetone) on the chemical composition and surface characteristics of magnesium silicate. The results demonstrated that all of the variables affected the surface characteristics of magnesium silicate, such as surface area, particle size, and pore volume. However, it was also observed that the studied parameters did not affect the chemical composition of magnesium silicate. The wheat husk ash-based magnesium silicates obtained in the experimental study had a BET surface area ranging from 79 to 91 m²/g and a particle size varying from 42 to 63 µm.

One-component semi-matte (A) and two-component shiny (B) water-borne varnishes were applied on the surface of the test panels made of Scots pine (Pinus sylvestris L.) and Eastern beech (Fagus orientalis Lipsky) with 8%, 10%, and 12% moisture content in this study. The changes in color caused by the type of wood and moisture content on the water borne varnish layers were then investigated. The change of color in the samples was determined based on the statements in ASTM D 2224. It was determined that variations in the type of wood and moisture content affected water borne varnishes adversely, and the most apparent color change was observed in the Scots pine samples with 12% moisture content when varnish type B was applied.

Pitch deposits originating from alkaline peroxide bleaching of mechanical pulps can seriously decrease the runnability of the paper machine when efforts have been made to increase the reuse of process water. In order to degrade pitch particles present in whitewater, lipase was immobilized on chitosan beads using a binary method. The operational stability of the immobilized lipase and its efficacy for treating whitewater were also preliminary studied. The results showed that the highest activity of immobilized lipase was achieved by using 0.5% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) for activation and 0.0025% glutaraldehyde for cross-linking chitosan. The immobilized lipase also exhibited very good operational stability, and the pitch particles present in whitewater could be reduced by 66.8% after treatment with the immobilized lipase.

A series of glycerol-plasticized starch composites reinforced by rice-husk cellulose nanocrystals was successfully fabricated through the solution casting technique. The rice husks must undergo alkali treatment, bleaching, and sulphuric acid hydrolysis before cellulose nanocrystals can be produced. The cellulose nanocrystal content used as filler was varied from 0 to 10 wt%. The thermal stability of the composite were analysed by thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG). The starch biocomposite films reinforced with rice-husk cellulose nanocrystals showed improved tensile strengths and tensile moduli. Transmission electron microscopy (TEM) was used to determine the diameter and length distribution of the cellulose nanocrystals. Field emission scanning electron microscopy (FESEM) showed that the cellulose nanocrystals (CNCs) were well distributed in the matrix. At the optimum 6% filler loading, the cellulose nanocrystals exhibited a higher reinforcing efficiency in the plasticized starch biocomposites than at any other filler loading.

Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 ºC.

Chitosan (CS)/cellulose (BC) blend films were successfully prepared using ZnCl2·3H2O as a solvent. Homogeneous structures without obvious phase separation between CS and BC for all blend films were observed by scanning electron microscope (SEM) analysis. The tensile strengths of CS/BC blend films decreased with the increase of chitosan content. The results of X-ray diffraction (XRD) analysis indicated that the crystal structures of BC and CS were disrupted during the processes of dissolving and regeneration. Also, the reformation of hydrogen bonds between CS and BC during dissolution and regeneration processes resulted in the shift of diffraction peaks. Fourier transforms infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) analysis results confirmed this observation. Moreover, obvious antimicrobial capability of CS/BC blend films against E. coli has been observed, indicating that antibacterial activity of chitosan has not been significantly inactivated while using ZnCl2·3H2O as a solvent. Therefore, ZnCl2·3H2O can be regarded as a promising solvent to prepare degradable films with antibacterial properties.

Grasses are abundant in many climatic regions of the world and have been regarded as weeds by many. This work investigated the use of Pennisetum purpureum (Napier grass) in the production of bioethanol. Two pretreated grasses were compared as the initial substance in the hydrolysis process followed by bacteria fermentation. For the purpose of breaking down lignin, alkali pretreatment, where grass was soaked in 7% NaOH, was used. For biological pretreatment, grass was incubated for 3 weeks with the white-rot fungus, Phanerochaete chrysosporium. Both types of pretreated materials were subjected to Trichoderma reesei ATCC 26921 enzyme hydrolysis. Glucose content from alkali-pretreated samples was 1.6-fold higher than fungus-pretreated samples. Hydrolysates from the pretreatments were fermented using the ethanol insensitive strain Escherichia coli K011. After 24 hours of fermentation, the ethanol yield from alkali-pretreated material was 1.5 times higher than the biological-pretreated material. It can be concluded that NaOH-pretreated enzyme hydrolysate had a better ethanol yield compared to biological-pretreated enzyme hydrolysate, but biological-pretreated enzyme hydrolysate had better ethanol conversion efficiency, which was 18.5 g/g. These results indicated that wild grass is capable of becoming an important biomass for small local bioethanol production.