Volume 7 Issue 2

Demand for hardwood from plantation-grown stands for pulp and bio-energy in the southern US is more than 90 million tons per year and is increasing. In the specific case of bio-energy and pulp, demand for biomass from eucalypts could approach 20 million tons/year by the year 2022. Fast growing species and hybrids of Eucalyptus are being evaluated to partially fill this demand gap. Though widely grown in a number of countries for pulp as well as for bio-energy, eucalypts in the southern US have not been extensively researched. Initial growth rates of 18 to 36 green tons/ha/year on rotation lengths of 6 to 8 years are possible. Current estimated costs for energy production from eucalypts in the Southern US are estimated at $3.10 to $3.49 per MBtu, where landowner required return rates on reforestation capital invested range from 6 to 14 percent. Eucalypts as a bio-energy feedstock can be competitive with coal in cost per BTU in the southern US.

Graft copolymerization of Grewia optiva fiber with acrylic acid (AAc) was carried out by using a Ce(IV) redox initiator under two different conditions, i.e. in air and under the influence of microwave radiation. Different reaction conditions affecting grafting percentage (Pg) for both methods were optimized and compared. Optimized reaction parameters for maximum Pg (7.86%) for graft copolymerization of AAc onto Grewia optiva fiber in air were 90 min reaction time, a temperature of 45° C, 1.82X10-2 mol/L CAN, 2.88X10-1 mol/L nitric acid, and 3.50X10-1 mol/L AAc. However, the maximum Pg (5.56%) for graft copolymerization in the case of MWR were 15 min reaction time, 110 W power, 2.73X10-2 mol/L CAN, 2.88X10-1 mol/L nitric acid, and 2.91X10-1 mol/L AAc. Both raw and graft copolymerized fibers were subjected to the evaluation of some of their properties such as swelling, moisture absorbance, and chemical resistance behavior. The AAc-graft copolymerized Grewia optiva showed 19.23% more swelling when compared with that of raw fiber. Further morphological and structural changes, thermal stability, and the crystallanity of raw, Grewia optiva-g-poly(AAc) in air, and Grewia optiva-g-poly(AAC) under MWR fibers were also studied by SEM, FTIR, TGA, and XRD techniques.

In this work, a gene (lacP83) encoding a Pleurotus ostreatus laccase isoenzyme expressed in submerged fermentation conditions is described. A 2,887 bp sequence was obtained from a genomic library of P. ostreatus by using a PCR inverse strategy. The coding sequence, 1,527 bp long, showed 17 exons and encoded a protein of 509 amino acids, with a putative signal peptide and conserved copper binding domains. The promoter region of the lacP83 gene (466 bp upstream of ATG) contains putative binding transcription factors such as MRE, XRE, a defense response element, and a stress response element. The protein and gene sequences of lacP83 showed, respectively, 90 to 96% and 78 to 92% of similarity to laccases of Pleurotus previously reported. However, it showed differences in its apparent molecular weight and promoter sequence.

The aim of this work is to open up the structure of wood while retaining a large amount of hemicelluloses, in particular (galacto)glucomannans. The effects of pre-treatments on wood meal from spruce (Picea abies) with a reducing agent (NaBH4) combined with steam explosion at very mild conditions were investigated. The effects of steam explosion at 160 °C were studied for various residence times (5 to 35 min) on both water-impregnated wood meal and samples pre-treated with NaBH4. The findings showed that pre-treatment with sodium borohydride stabilized the reducing end-groups of glucomannans and that the treatment was effective both during mild steam explosion, for both long and short residence times, as well as during subsequent treatment in alkali. Extraction experiments at different pH and temperatures showed that the main part of the hemicelluloses still remained in the wood residue after treatment. The molecular weight distributions of the extracted material from the liquors indicated that there were broad molecular distributions and that the molecular weight averages were between 3 and 6 kDa.

The effects of a double polyelectrolyte adsorption of poly(allylamine hydrochloride) (PAH) and xylan (Xyl) on a recycled unbleached softwood kraft pulp were studied. The kinetics of PAH adsorption on this pulp was analyzed by building adsorption isotherms and by estimating the surface nitrogen adsorbed through the X-ray photoelectron spectroscopy (XPS) technique. It was found that at pH 7.5, 0.01N NaCl, and short adsorption time, PAH is mainly adsorbed on the fiber surface. Adsorption isotherms of xylan on untreated and on previously PAH-treated pulps at different ionic strengths were built, and the effects of the amount of PAH on xylan adsorption were considered. It was found that when ionic strength was lower than 0.01N NaCl, a PAH pretreatment was necessary to achieve high levels of xylan adsorption at room temperature and short adsorption times. Nevertheless, when ionic strength was 0.1N NaCl, 0.3% xylan on pulp could be directly adsorbed on untreated pulp. Finally, it is shown that the dual-polyelectrolyte adsorption on this pulp is a feasible technique for improving paper tensile strength.

A layer-by-layer (LbL) self-assembly technique using polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) was employed to build up polyelectrolyte multi-layers on pretreated thermomechanical pulp fibres. These pretreated fibres previously had been oxidized by means of a 4-acetamido TEMPO-mediated process in order to create carboxylic functions. These allow the subsequent formation of amide bonds between PAH and fibres. X-ray photo-electronic spectroscopy (XPS) analyses confirmed the formation of amide bonds between the carboxylic function on the fibres and the primary amine function of the PAH. Besides, the surface charge intensity of the coated fibres was determined by measuring the zeta potential after each treatment step.

Ailanthus altissima (Miller) Swingle is a tree used in Chinese traditional medicine as a bitter aromatic drug and in the treatment of colds and gastric diseases. Previous phytochemical studies have demonstrated the presence of quassinoids in the plant, as well as indole alkaloids. The purpose of this work was to determine the phenolic, flavonoid, and total alkaloid contents of the ethanolic, methanolic, acetone, and hydroalcoholic crude extracts of A. altissima and then try to correlate them with antioxidant activity of corresponding extracts. Moreover, the phenolic compounds present in the extracts were analyzed by RP-HPLC. Extracts from leaves have greater phenolic content than the other parts of this tree. Concerning the extraction process, it is possible to conclude that the mixture of water and ethanol is the best solvent to extract substances with antioxidant activity. Analysis by RP-HPLC showed that ferulic acid was the most dominant hydroxycinnamic acid, with an occurrence percentage of 25.59%. These results presented a positive linear correlation between antioxidant activity index and total phenolic content of all the extracts.

A three-factor, three-level Box-Behnken Design (BBD) was used with enzyme dosage (0.05-0.15‰ o.d. fiber), enzymatic contact time (20-40 min), and pulp consistency (3-7%, o.d.) as independent variables to understand and optimize the enzymatic pretreatment conditions of mixed office waste (MOW) for maximum improvement of its drainability. All the independent variables considered were found to have significant influence on the drainability of the pulp. The enzyme dosage had a predominate effect, the pulp consistency took second place, and the contact time seemed to have low priority. A quadratic polynomial model had high Adj-R2 value and low p value for predicting the decrement of beating degree of the pulp. Applying desirability function method, the optimal pretreatment conditions were found to be an enzyme dosage of 0.11‰ o.d., enzymatic contact time of 31.0 min, and pulp consistency of 4.50% o.d. The optimal pretreatment resulted in a maximum decrement of 10 units of beating degree, a decrease by 20% when compared with the control sample. The observed and predicted values of beating degrees were in close agreement. Results of fiber morphology analysis and physical property tests showed that the optimal pretreatment partially recovered the fiber flexibility and retained the strength properties of the handsheet even under the lower beating degree. Isothermal (Thermogravimetric Analyzer) TGA experiments of the fibers confirmed that the enzymatic pretreatment decreased the fiber hornification.

Sorption of metal ions from aqueous solutions to birch wood and spruce heartwood and sapwood has been studied. Functional groups in wood were determined by acid-base titrations. The sorption of metal ions to wood of the different tree species was investigated by a column chromatographic technique. The mechanism of sorption is mainly ion exchange by complexation of metal ions to the functional groups, e.g. carboxyl groups and phenolic hydroxyl groups, in the wood phase. By combination of the sorption experiments with four different metal ion mixtures, the following affinity order was established for spruce sapwood particles: Fe3+>>Pb2+>>Cu2+>>Fe2+>Cd2+>Zn2+>Ni2+>Mn2+≥Ca2+≥Sr2+≥ Ba2+>>Mg2+>>K+>Na+≈Li+. For all three types of stemwood studied, the affinity orders were almost the same. The ion exchange properties of wood were comparable to those of a weakly acid cation exchanger. The affinity order obtained for the synthetic resin was quite similar to the order given above for wood. The metal sorption properties of wood materials imply that they could be a potential material for removal of metal ions from aqueous solutions.

Nanocomposites were prepared using two bioresources, viz., cellulose nanofibers (CNFs) extracted from bamboo paper-pulp waste as the reinforcing phase and natural rubber (NR) as the matrix phase. CNFs with diameters up to 50 nm were isolated from bamboo pulp waste, and nanocomposites with 5 and 10% CNFs were obtained via two-roll mill mixing of solid natural rubber with a master batch containing 20 wt% CNFs. The NR phase was cross-linked using sulphur vulcanization. The morphology studies showed that the dispersion of CNF in NR matrix was not optimal, and some aggregates were visible on the fracture surface. The tensile strength and modulus at 50% elongation increased for the nanocomposites with the addition of CNFs, accompanied by a moderate decrease in elongation at break. The storage modulus of the natural rubber significantly increased above its glass-rubber transition temperature upon nanofiber addition. The addition of CNFs also had a synergistic impact on the thermal stability of natural rubber. The susceptibility to organic solvents decreased significantly for the nanocomposites compared to crosslinked NR, which indicated restriction of polymer chain mobility in the vicinity of the nanosized CNFs in the NR matrix.