NC State
  • Researchpp 268-284Patel, H., Gupte, A., and Gupte, S. (2009). "Effect of different culture conditions and inducers on production of laccase by a basidiomycete fungal isolate Pleurotus ostreatus HP-1 under solid state fermentation," BioRes. 4(1), 268-284.AbstractPDF
    The production of laccase by an indigenous strain of Pleurotus ostreatus HP-1 was studied on solid state fermentation. Culture parameters such as type and concentration of substrate, inoculum size, moisture content, pH, surfactant presence, temperature, and nitrogen source were optimized by conventional “one factor at a time” methodology. A maximum laccase yield of 3952 U g-1 of dry substrate optimized was obtained with wheat straw as substrate with five agar plugs as the inoculum, 60% moisture content, pH 5.0, surfactant concentration 0.015 gl-1, and nitrogen source (combination of L-asparagine and NH4NO3 at 10 mM concentration each) at incubation temperature 28oC. Enhancement in laccase activity was achieved with the use of various aromatic inducers and copper sulphate. Highest laccase activity of 14189 U g-1 of dry substrate was achieved using 0.28 mM copper sulphate under optimized conditions. Thus, the indigenous isolate seems to be a potential producer of laccase using SSF and can be exploited for further biotechnological applications. The process also promises economic utilization and value addition of agro-residues.
  • Researchpp 285-291Valchev, I., Nenkova, S., Tsekova, P., and Lasheva, V. (2009). "Use of enzymes in hydrolysis of maize stalks," BioRes. 4(1), 285-291.AbstractPDF
    Lignocellulosic biomass is the most abundant organic raw material in the world. Cellulose and hemicellulose from plants and other biomass can be hydrolyzed to produce sugars. Native lignocellulosic biomass provides limited accessibility to cellulase enzymes due to structural features. The investigations were carried out with waste lignocellulosic raw material, consisting of maize stalks and cobs. Enzyme hydrolysis was performed after acid hydrolysis with a cellulasic product. It was established that the enzyme stage, as a first treatment phase, was inefficient. It was found that cellulase activity was considerably improved after acid hydrolysis of a crushed mass. A two-stage process with acidic and then enzyme hydrolysis method was most efficient and promising for obtaining sugars for ethanol production.
  • Researchpp 292-308Singha, A. S., and Thakur, V. K. (2009). "Study of mechanical properties of urea-formaldehyde thermosets reinforced by pine needle powder," BioRes. 4(1), 292-308.AbstractPDF
    Lignocellulosic fibers have received much more attention than ever before from the research community all over the world during the past few years because of their enormous advantages. A study on the preparation of new series of polymer composites using Pine Needles as a reinforcing material in Urea - Formaldehyde resin has been made. Mechanical properties of intimately mixed particle reinforced (Pine Needles) composites have been studied. Effects of different loading of reinforcement in terms of weight % on static mechanical properties such as tensile, compressive, flexural and wear properties have also been evaluated. The Urea-Formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. The reinforcing of the resin with Pine Needles was accomplished in particle size of 200 micron by employing optimized resin. The present work reveals that mechanical properties of the Urea- Formaldehyde resin increases to a considerable extent when reinforced with Pine Needle Particles. Thermal (TGA/ DTA/DTG) and morphological studies (SEM) of the resin and polymer composites thus synthesized have also been studied. The results obtained suggest that Pine Needles can be a premium candidate for the reinforcement of high-performance polymer composites.
  • Researchpp 309-320Dehkhoda, A., Brandberg, T., and Taherzadeh, M. J. (2009). "Comparison of vacuum and high pressure evaporated wood hydrolyzate for enthanol production by repeated fed-batch using flocculating Saccharomyces cerevisiae," BioRes. 4(1), 309-320.AbstractPDF
    With the aim of increasing the sugars concentration in dilute-acid lignocellulosic hydrolyzate to more than 100 g/l for industrial applications, the hydrolyzate from spruce was concentrated about threefold by high-pressure or vacuum evaporations. It was then fermented by repeated fed-batch cultivation using flocculating Saccharomyces cerevisiae with no prior detoxification. The sugars and inhibitors concentrations in the hydrolyzates were compared after the evaporations and also fermenta-tion. The evaporations were carried out either under vacuum (VEH) at 0.5 bar and 80°C or with 1.3 bar pressure (HPEH) at 10 7.5 °C, which resulted in 153.3 and 164.6 g/l total sugars, respectively. No sugar decomposition occurred during either of the evaporations, while more than 96% of furfural and to a lesser extent formic and acetic acids disappeared from the hydrolyzates. However, HMF and levulinic acid remained in the hydrolyzates and were concentrated proportionally. The concentrated hydrolyzates were then fermented in a 4 l bioreactor with 12-22 g/l yeast and 0.14-0.22 h-1 initial dilute rates (ID). More than 84% of the fermentable sugars present in the VEH were fermented by fed-batch cultivation using 12 g/l yeast and initial dilution rate (ID) of 0.22 h-1, and resulted in 0.40±0.01 g/g ethanol from the fermentable sugars in one cycle of fermentation. Fermentation of HPEH was as successful as VEH and resulted in more than 86% of the sugar consumption under the corresponding conditions. By lowering the initial dilution rate to 0.14 h-1, more than 97% of the total fermentable sugars were consumed, and ethanol yield was 0.44±0.01 g/g in one cycle of fermentation. The yeast was able to convert or assimilate HMF, levulinic, acetic, and formic acids by 96, 30, 43, and 74%, respectively.
  • Researchpp 321-340Liimatainen, H., Haavisto, S., Haapala, A., and Niinimäki, J. (2009). "Influence of adsorbed and dissolved carboxymethyl cellulose on fibre suspension dispersing, dewaterability, and fines retention," BioRes. 4(1), 321-340.AbstractPDF
    The effect of adsorbed and soluble carboxymethyl cellulose (CMC) on dispersing, dewaterability, and fines retention of pulp fibre suspensions was investigated. CMC was added to a suspension in the presence of electrolytes, causing its adsorption to the fibre surfaces, or to a suspension without electrolytes, so that it stayed in the liquid phase. Both the CMC adsorbed on fibre surfaces and that in the liquid phase were able to disperse the fibre suspension due to the ability of CMC to reduce fibre-to-fibre friction in both phases. Adsorbed CMC promoted the formation of a water-rich microfibrillar gel on the fibre surfaces through the spreading out of microfibrils, leading to a decrease in friction at the fibre-fibre contact points and to the increased dispersion of fibres. CMC in the liquid phase of the suspension was in turn thought to prevent fibre-to-fibre contacts due to the large physical size of the CMC molecules. CMC in both phases had detrimental effects on dewatering of the pulp suspension, but adsorbed CMC caused more plugging of the filter cake, and this was attributed to its ability to disperse fibre fines, in particular. Thus, adsorbed CMC also reduced fines retention considerably more than did CMC in the liquid phase of a suspension.
  • Reviewpp 341-369Gronowska, M., Joshi, S., and MacLean, H. L. (2009). "A review of U.S. and Canadian biomass supply studies," BioRes. 4(1), 341-369.AbstractPDF
    An improved understanding of lignocellulosic biomass availability is needed to support proposed expansion in biofuel production. Fifteen studies that estimate availability of lignocellulosic biomass quantities in in the U.S. and/or Canada are reviewed. Sources of differences in study methods and assumptions and resulting biomass quantities are elucidated. We differentiate between inventory studies, in which quantities of biomass potentially available are estimated without rigorous consideration of the costs of supply, versus economic studies, which take into consideration various opportunity costs and competition. The U.S. economic studies, which included reasonably comprehensive sets of biomass categories, estimate annual biomass availability to range from 6 million to 577 million dry metric tonnes (dry t), depending on offered price, while estimates from inventory studies range from 190 million to 3849 million dry t. The Canadian inventory studies, which included reasonably comprehensive sets of biomass categories, estimate availability to range from 64 million green t to 561 million dry t. The largest biomass categories for the U.S. are energy crops and agricultural residues, while for Canada they are expected to be energy crops and logging residues. The significant differences in study estimates are due in large part to the number of biomass categories included, whether economic considerations are incorporated, assumptions about energy crop yields and land areas, and level of optimism of assumptions of the study.
  • Reviewpp 370-404Esteves, B. M., and Pereira, H. M. (2009). "Wood modification by heat treatment: A review," BioRes. 4(1), 370-404.AbstractPDF
    Wood heat treatment has increased significantly in the last few years and is still growing as an industrial process to improve some wood properties. The first studies on heat treatment investigated mainly equilibrium moisture, dimensional stability, durability and mechanical properties. Mass loss, wettability, wood color, and chemical transformations have been subsequently extensively studied, while recent works focus on quality control, modeling, and study the reasons for the improvements. This review explains the recent interest on the heat treatment of wood and synthesizes the major publications on this subject on wood properties, chemical changes, wood uses, and quality control.
  • Reviewpp 405-451Hubbe, M. A., Chen, H., and Heitmann, J. A. (2009). "Permeability reduction phenomena in packed beds, fiber mats, and wet webs of paper exposed to flow of liquids and suspensions: A review," BioRes. 4(1), 405-451.AbstractPDF
    Filter media, including those prepared from cellulosic materials, often suffer from permeability loss during continued use. To help understand such issues, one can take advantage of an extensive body of related research in such fields as industrial filtration, water purification, enhanced oil recovery, chromatography, paper manufacture, and the leaching of pollutants from impoundments. Though the mechanisms that appear to govern permeability-loss phenomena depend a lot on the details of various applications, the published research has revealed a number of common features. In particular, flow through a porous bed or fiber mat can be markedly reduced by deposition of particles or colloidal matter in positions that either block or partially restrict fluid flow. Progress has been achieved in the development of mechanistic models, as well as the use of such models in numerical simulations to explain various experimental findings. Further research of this type needs to be applied to cellulosic materials, which tend to be much more elongated in comparison to the bed materials and suspended matter considered most often by most researchers active in research related to permeability loss.