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BioResources, Volume 1, Issue 2

November 2006

NOTE: Each current issue of BioResources continues to build as new articles are approved.

ABSTRACTS

Hubbe, M. A. (2006). "From here to sustainability," BioRes. 1(2), 172-173. PDF

Many readers and contributors to BioResources are working to develop sustainable technology. Such research attempts to use products of photosynthesis to meet long-term human needs with a minimum of environmental impact. Archeological and historical studies have concluded that the long-term success or failure of various past civilizations has depended, at least in part, on people's ability to maintain the quality of the resources upon which they depended. Though it is possible for modern societies to learn from such examples, modern societies are interconnected to an unprecedented degree. It is no longer realistic to expect one region to be immune from the effects of environmental mistakes that may happen elsewhere in the world. Research related to renewable, lignocellulosic resources is urgently needed. But in addition to the research, there also needs to be discussion of hard-hitting questions, helping to minimize the chances of technological failure. The next failed civilization may be our own.

Green, C. (2006). "Improved pulp evaluations with restrained drying," BioRes. 1(2), 174-175.

Pulp evaluations traditionally use plate-dried handsheets. The evalu-ation of pulp could be improved significantly by using side-by-side comparison of handsheets that freely shrink when dried, in addition to handsheets dried in the usual way. PDF

Janardhnan, S., and Sain, M. (2006). "Isolation of cellulose microfibrils - An enzymatic approach," BioRes. 1(2), 176-188.

Isolation methods and applications of cellulose microfibrils are expanding rapidly due to environmental benefits and specific strength properties, especially in bio-composite science. In this research, we have success-fully developed and explored a novel bio-pretreatment for wood fibre that can substantially improve the microfibril yield, in comparison to current techniques used to isolate cellulose microfibrils. Microfibrils currently are isolated in the laboratory through a combination of high shear refining and cryocrushing. A high energy requirement of these procedures is hampering momentum in the direction of microfibril isolation on a sufficiently large scale to suit potential applications. Any attempt to loosen up the microfibrils by either complete or partial destruction of the hydrogen bonds before the mechanical process would be a step forward in the quest for economical isolation of cellulose microfibrils. Bleached kraft pulp was treated with OS1, a fungus isolated from Dutch Elm trees infected with Dutch elm disease, under different treatment conditions. The percentage yield of cellulose microfibrils, based on their diameter, showed a significant shift towards a lower diameter range after the high shear refining, compared to the yield of cellulose microfibrils from untreated fibres. The overall yield of cellulose microfibrils from the treated fibres did not show any sizeable decrease. PDF

Wu, B., Zhao, Y., and Gao, P. J. (2006). "A new approach to measurement of saccharifying capacities of crude cellulase," BioRes. 1(2), 189-200

A practical, quantitative approach has been designed, which makes it possible to accurately estimate the saccharifying activities of crude cellulase preparations for insoluble cellulosics. The challenge in activity determination imposed by changes in hydrolysis time and concentration of cellulase and cellulosics on the assay could be overcome by selection of the specific conversion percentage of cellulose as a function of cellulase concentration, that is, the hydrolysis percentage of filter paper by unit cellulase per minute, as the objective function with respect to different concentrations of crude cellulase. A rational and governing equation for crude cellulase assay was derived , and reliable results for quantitatively estimating the saccharifying activities of crude cellulases during the progress of hydrolysis of several cellulosic substrates were obtained. PDF

Papadopoulos, A. N. (2006). "Property comparisons and bonding efficiency of UF and PMDI bonded particleboards as affected by key process variables," BioRes. 1(2), 201-208.

The purpose of this paper was to compare physical properties of conventional particleboard bonded with amounts of UF and PMDI resin and to examine the effect of mat moisture content (MC), wax content and platen temperature on their bonding efficiency, as determined by internal bond strength. It was found that PMDI not only gave superior board properties compared with the UF, but the amount required was reduced considerably as well. The MC of the mat and the platen temperature did not significantly affect the bonding efficiency of PMDI bonded boards, but the bonding efficiency of UF bonded boards. The inclusion of 1% wax significantly affected the bonding efficiency of both resins, however the loss in strength was higher in UF than in PMDI bonded boards. PDF

Dobreva, D., Nenkova, S., and Vasileva, St., "Morphology and mechanical properties of polypropylene-wood flour composites," BioRes. 1(2), 209-219.

The microstructure and mechanical properties of polymer composites based on polypropylene and wood flour modified with monochloroacetic acid were investigated. Scanning electron microscopy and wide-angle X-ray diffraction were used as methods to probe the composite microstructures, while the tensile test was used to measure the physical strength. The wood flour modification was performed at different levels of monochloroacetic acid, ranging from 0.01 to 1 mol, while the modified wood flour was used as filler for polypropylene at 10, 20 and 30 wt.-%. It was found that increasing the monochloroacetic acid fraction influences the microstructure of the composites and leads to more homogeneous products. The introduction of non-modified wood flour decreases the polypropylene crystallization degree, but it improves after introduction of monochloroacetic acid. Physical-mechanical tests showed positive effects on tensile tests and Charpy notched impact strength. The new composites appear to be promising materials for construction purposes. PDF

Abdul Khalil, H. P. S., Siti Alwani, M., and Mohd Omar, A. K. (2006). "Chemical composition, anatomy, lignin distribution, and cell wall structure of Malaysian plant waste fibers," BioRes. 1(2), 220-232.

The chemical composition, anatomical characteristics, lignin distribution, and cell wall structure of oil palm frond (OPF), coconut (COIR), pine-apple leaf (PALF), and banana stem (BS) fibers were analyzed. The chemical composition of fiber was analyzed according to TAPPI Methods. Light microscopy (LM) and transmission electron microscopy (TEM) were used to observe and determine the cell wall structure and lignin distribution of various agro-waste fibers. The results revealed differences in anatomical characteristics, lignin distributions, and cell wall structure of the different types of fibers investigated. Nevertheless, transmission electron microscopy (TEM) micrographs have confirmed that the well wall structure, in each case, could be described in terms of a classical cell wall structure, consisting of primary (P) and secondary (S 1 , S 2 , and S 3 ) layers. PDF

Gruver, T. M., and Brown, N. R. (2006). "Penetration and performance of isocyanate wood binders on selected wood speciels," BioRes. 1(2), 233-247.

The penetration and performance of polymeric diphenylmethane diisocyanate (pMDI) wood binder was investigated according to three factors: substrate species (aspen, yellow-poplar, or southern yellow pine); anatomical bonding plane (radial or tangential); and moisture content (0%, 5%, or 12%). Compression shear block tests and fluorescence microscopy were used to examine bond performance and resin penetration. Statistically, each of the aforementioned factors impacted results. As moisture content increased, observed bond strengths and wood failure increased. Bond formation did not occur when the substrates were equilibrated to 0% moisture content, except for the radial bonding surfaces of pine, which did adhere. At 5 and 12% moisture contents, tangential bonding surfaces out-performed radial bonding surfaces. In terms of resin penetration, moisture content was clearly the most important variable. Little penetration was observed at 0% moisture content, while extensive resin penetration was observed at elevated moisture contents. Pine was the only wood species to exhibit resin flow through radial cells, possibly explaining the enhanced resin penetration depths observed in pine samples. PDF

Liang, L., Mao, Z., Li, Y., Wan, C., Wang, T., Zhang, L., and Zang, L. (2006). "Liquefaction of crop residues for polyol production," BioRes. 1(2), 248-256.

The liquefaction of crop residues in the presence of ethylene glycol, ethylene carbonate, or polyethylene glycol using sulfuric acid as a catalyst was studied. For all experiments, the liquefaction was conducted at 160 ° C and atmospheric pressure. The mass ratio of feedstock to liquefaction solvents used in all the experiments was 30:100. The results show that the acid catalyzed liquefaction process fit a pseudo-first-order kinetics model. Liquefaction yields of 80, 74, and 60% were obtained in 60 minutes of reaction when corn stover was liquefied with ethylene glycol, a mixture of polyethylene glycol and glycerol (9:1, w/w), and ethylene carbonate, respectively. When ethylene carbonate was used as solvent, the liquefaction yields of rice straw and wheat straw were 67% and 73%, respectively, which is lower than that of corn stover (80%). When a mixture of ethylene carbonate and ethylene glycol (8:2, w/w) was used as solvent, the liquefaction yields for corn stover, rice straw and wheat straw were 78, 68, and 70%, respectively. PDF

Huang, C. B., Jeng, R., Sain, M., Saville, B. A., and Hubbes, M. (2006). "Production, characterization, and mechanical properties of starch modified by Ophiostoma spp.," BioRes. 1 (2), 257-269.

Microbial modification of starch with Ophiostoma spp . was investigated, with the purpose of developing a novel packaging material for the food or pharmaceutical industries. Various starch sources, such as tapioca, potato, corn, rice and amylopectin were tested as raw materials. The initial screening demonstrated that tapioca and potato starch had better performance for biopolymer production. The yield was about 85%. Preliminary characterization of the modified biopolymer was also conducted. Following microbial conversion, the percentage of molecules with at least a Mw of 10M Daltons increased from 25% to 89% after 3 days, confirming that the modification increased the weight of the starch polymer. Fourier Transform Infrared (FT-IR) revealed changes in the chemical structure of the starch after the modification. Both pure starches and the modified biopolymers were cast into films and tested for mechanical properties. The tensile tests showed that after treatment with the fungus, the peak stress and modulus of the films increased about 10 and 40 times, respectively. Also, the water barrier property was improved. Therefore, microbial modification positively impacted proper-ties relevant to the proposed application s . Although the role of the fungus in the modification and the function-property relationship of the biopolymer are not yet completely clear, the results of this study show promise for development of a novel biopolymer that competes with existing packaging materials. PDF

Hoenich, N. (2006). "Cellulose for medical applications: Past, present, and future," BioRes. 1 (2), 270-280.

Films and tubes manufactured from cellulose have historically been used in the treatment of renal failure, but their use for this purpose has declined in recent years in favour of films manufactured from synthetic material blends. As the clinical application of cellulose for dialysis declines, new applications for its use are emerging, of which the most promising appears to be the use of microbial cellulose synthesized by Acetobacter xylinum as a novel wound healing system and as a scaffold for tissue regeneration. PDF

Hubbe, M. A. (2006). "Bonding between cellulosic fibers in the absence and presence of dry-strength agents - A review," BioRes. 1(2), 281-318.

Various hydrophilic polyelectrolytes, including cationic starch products, are used by papermakers to promote inter-fiber bonding and increase paper's dry-strength. Thus, papermakers can meet customer require-ments with a lower net cost of materials, more recycled fibers, or higher mineral content. In the absence of polymeric additives, key mechanisms governing bond development between cellulosic fibers include capillary action, three-dimensional mixing of macromolecules on facing surfaces, conformability of the materials, and hydrogen bonding. Dry-strength additives need to adsorb efficiently onto fibers, have a hydrophilic character, and have a sufficiently high molecular mass. Though it is possible to achieve significant strength gains by optimal usage of individual polyelectrolytes, greater strength gains can be achieved by sequential addition of oppositely charged polyelectrolytes. Superior strength can be achieved by in-situ formation of polyelectrolyte com-plexes, followed by deposition of those complexes onto fiber surfaces. Polyampholytes also hold promise as efficient dry-strength additives. Opportunities for further increases in performance of dry-strength agents may involve fiber surface modification, self-assembled layers, and optimization of the dry film characteristics of dry-strength polymers or systems of polymers. PDF