NC State
  • Editorialpp 332-333Hubbe, M. A. (2007). "When is a tree not a resource?" BioRes. 2(3), 332-333.AbstractPDF
    Although this journal mainly considers the study of cellulosic materials as sources of structural wood, fibers, chemicals, energy, and products such as paper, it would be short-sighted to view all trees as existing in order to meet such needs. An individual tree may have multiple roles, from a human perspective. The point of this essay is that different groups of trees ought to be managed in one of four ways – as crops, as natural habitat, as an awe-inspiring heritage, as in the case of national parks, and as dear friends in our yards and along our boulevards.
  • Researchpp 334-350Lundquist, K., Parkås, J., Paulsson, M., and Heitner, C. (2007). "Reactions of lignin chromophores of the enal and enone type with sulfite," BioRes. 2(3), 334-350.AbstractPDF
    In NaHSO3-solutions of coniferaldehyde and its methyl ether (models for lignin chromophores of the cinnamaldehyde type) a dynamic equilibrium between the aldehydes and their hydrogen sulfite adducts is set up. A comparatively slow addition of hydrogen sulfite to the double bond leading to 1,3-disulfonic acid derivatives occurs; coniferaldehyde reacts slower than its methyl ether. In Na2SO3-solution both aldehydes are rapidly converted to 1,3-disulfonic acid derivatives. The results suggest that in both NaHSO3-solution and Na2SO3-solution the free cinnamaldehydes and sulfite ion are the reactants in the formation of disulfonic acid derivatives. Alkaline treatment of the 1,3-disulfonic acids leads to regeneration of the cinnamaldehydes. On prolonged storage in Na2SO3-solution, the 1,3-disulfonic acid derivative of the methyl ether of coniferaldehyde undergoes reactions leading to colored products and regeneration of the cinnamaldehyde on alkaline treatment fails. A model compound representative of lignin chromophores of enone type (trans-3,3’,4,4’-tetramethoxychalcone) rapidly undergoes addition to the double bond with formation of a sulfonic acid derivative in Na2SO3-solution. Treatment of a second model of enone type, 2,6-dimethoxy-p-quinone, with NaHSO3/Na2SO3-solution results in formation of a sulfonic acid derivative. The reactions of lignin chromophores of the enone and enal types with hydrogen sulfite/sulfite are discussed.
  • Researchpp 351-362Law, K.-N., Wan Daud, W. R., and Ghazali, A. (2007). "Morphological and chemical nature of fiber strands of oil palm empty-fruit-bunch (OPEFB)," BioRes. 2(3), 351-362.AbstractPDF
    In this work we examined the morphological and chemical characteristics of the fibrous strands of oil palm empty-fruit-bunch which were left behind after being stripped of their fruits used for oil production. The empty-fruit-bunches were mechanically loosened to yield the fibrous strands, which can be used in paper and board making. We found that the fibrous strands had unique structure by having several large-diameter, long vessel elements in their core region, surrounded by vascular fibers. They had numerous silica-bodies attached to craters on their surfaces; the craters were perforated at the bottom. Many other minerals were also present in the strands. Our microscopic observations suggested that the silica-bodies are connected to a network of siliceous pathway within the fibrous matrix, and minerals tend to concentrate adjacent to the silica-bodies. Our findings could be useful in identifying suitable techniques for processing the oil palm fiber strands into value-added products.
  • Researchpp 363-370Bălaş, A., and Popa, V. I. (2007). "The influence of natural aromatic compounds on the development of Lycopersicon esculentum plantlets," BioRes. 2(3), 363-370.AbstractPDF
    The influences of flax lignin and phenolic compounds obtained from spruce bark on the development of Lycopersicon esculentum plantlets were evaluated. Depending on the applied treatment and the concentrations used, the natural aromatic compounds had stimulatory effects on the germination capacity and the plantlets height and leaf area. The influence of lignin on Lycopersicon esculentum was lower compared to the phenolic extract.
  • Researchpp 371-388Wang, B., and Sain, M. (2007). "The effect of chemically coated nanofiber reinforcement on biopolymer based nanocomposites," BioRes. 2(3), 371-388.AbstractPDF
    The aim of this work was to explore how various surface treatments would change the dispersion component of surface energy and acid-base character of hemp nanofibers, using inverse gas chromatography (IGC), and to investigate the effect of the incorporation of these modified nanofibers into a biopolymer matrix on the properties of their nano-composites. Bio-nanocomposite materials were prepared from poly (lactic acid) (PLA) and polyhydroxybutyrate (PHB) as the matrix, and the cellulose nanofibers extracted from hemp fiber by chemo-mechanical treatments. Cellulose fibrils have a high density of –OH groups on the surface, which have a tendency to form hydrogen bonds with adjacent fibrils, reducing interaction with the surrounding matrix. It is necessary to reduce the entanglement of the fibrils and improve their dispersion in the matrix by surface modification of fibers without deteriorating their reinforcing capability. The IGC results indicated that styrene maleic anhydride coated and ethylene-acrylic acid coated fibers improved their potential to interact with both acidic and basic resins. From transmission electron microscopy (TEM), it was shown that the nanofibers were partially dispersed in the polymer matrix. The mechanical properties of the nanocomposites were lower than those predicted by theoretical calculations for both nanofiber-reinforced biopolymers.
  • Researchpp 389-398Yao, R., Qi, B., Deng, S., Liu, N., Peng, S., and Cui, Q. (2007). "Use of surfactants in enzymatic hydrolysis of rice straw and lactic acid production from rice straw by simultaneous saccharification and fermentation," BioRes. 2(3), 389-398.AbstractPDF
    Rice straw (RS) is one of the most abundant lignocellulosic waste by-products worldwide and provides an alternative substrate to produce useful chemicals such as bioethanol and lactic acid. However, higher enzyme loadings are needed to obtain a higher product yield, which makes the large-scale utilization economically difficult. The presence of non-ionic surfactants and poly(ethylene glycol) (PEG) during the enzymatic hydrolysis of lignocellulosics has been found to increase the conversion of cellulose into fermentable sugars. We have found that adding 0.2g g-1 substrate of polyoxyethylene(20) sorbitan monooleate (PSM) or high-mass PEG increased the sugar yield by 22% and 12%, respectively, when enzyme loading was at 10FPU g-1 for 24h. PSM behaved better than PEG when different substrate concentrations, temperatures, and enzyme loadings were investigated. PSM provides an opportunity to reduce enzyme dosage while still keeping the same extent of hydrolysis. We also investigated the effect of PSM on the simultaneous saccharification and fermentation of pretreated RS to lactic acid. Results showed that addition of 0.7g L-1 PSM improved the lactic acid production by 24% compared to the reference without PSM addition at 72h.
  • Researchpp 399-407Mocchiutti, P., and Zanuttini, M. A. (2007). "Key considerations in the determination of polyelectrolyte concentration by the colloidal titration method," BioRes. 2(3), 399-407.AbstractPDF
    Medium or high charge density cationic polyelectrolytes are frequently used for water treatment. In the papermaking wet-end they are used as retention agents or as flocculating aids. Negative polyelectrolytes that enter the papermaking system increase the demand for cationic polyelectrolytes. Polyelectrolyte concentration can be determined by the colloidal titration method, using either of two options for detecting the endpoint: i) visual observation or spectrophotometric determination of the colour change of an indicator, or ii) streaming current measurement. This work discusses the best conditions for the application of the titration using spectrophotometric measurement for the end point detection. Poly-diallyldimethylammonium chloride was used as the cationic polyelectrolyte, potassium polyvinyl sulphate as the negative polyelectrolyte, and o-toluidine blue as the positive indicator dye. The polyelectrolyte concentration range, interference from the metal ions affecting the indicator color change, the optimal indicator concentration to avoid precipitation problems, and the effect of adding a surfactant to the indicator solution were also considered. Titration curves were analyzed and optimized. Under these conditions the technique provided results with acceptable precision.
  • Researchpp 408-418Nenkova, S. (2007). "Study of sorption properties of lignin-derivatized fibrous composites for the remediation of oil polluted receiving waters," BioRes. 2(3), 408-418.AbstractPDF
    The sorption properties of lignin-wool composites towards oil pollution at different concentrations of the contamination were studied. The release ability of oil pollutant was studied by a gravimetric method and by determining the chemical oxygen demand of cleaned water. It has been established that technical hydrolysis lignin–wool composites display a low release ability of oil-based pollutants and a slow rate for achieving release equilibrium.
  • Researchpp 419-429Qi, B., and Yao, R. (2007). "L-lactic acid production from Lactobacillus casei by solid state fermentation using rice straw," BioRes. 2(3), 419-429.AbstractPDF
    In order to make full use of rice straw (RS) produced at large quantity in China and to reduce the production cost of L-lactic acid, attempts were made to utilize the hydrolysate of RS as sole carbon source and the lignocellulose as inert support for producing L-lactic acid using solid state fermentation (SSF). The pretreated rice straw was enzymatically hydro- lyzed by cellulase, and the hydrolyzate, containing reducing sugars supplemented with a minimum of (NH4)2SO4, MnSO4, and yeast extract, was used as moistening agent to impregnate 5g of RS, which was used as the inert support for SSF. Maximum L-lactic acid production of 3.467g per 5g of support was obtained at 37 oC, using Lactobacillus casei as inoculum, after 5 days of fermentation with optimized process parameters such as 72% moisture content, 4g per 5g support of reducing sugars, 2.5ml per 5g support of inoculum size, 3g per 5g support of CaCO3, and pH 6.5.
  • Researchpp 430-441Thomas, R., Singh, S. P., and Subrahmanyam, S. V. (2007)."A study on oxygen delignification of Melocanna baccifera (muli bamboo) kraft pulp," BioRes. 2(3), 430-441.AbstractPDF
    The response of kraft pulp of Melocanna baccifera (Muli bamboo) to different conditions of oxygen delignification and subsequent bleaching using CEHH sequence was studied. Oxygen delignification caused the kappa number of the pulp to drop between 40 and 75% over the range of temperature 70-100 °C, oxygen pressure 2-7 bar, alkali charge 2-4%, and reaction time 5-60 min. The oxygen-delignified pulp could be bleached to a brightness level of 86%. The conditions that favored greater kappa reduction also caused a greater reduction in the pulp viscosity, which called for an economic balance between the environmental benefits and the degradation of the pulp. Reaction temperature during oxygen delignification had an effect on the fiber curl and kink, while other variables such as oxygen pressure, alkali dose, and the reaction time had no significant effect on fiber deformation.
  • Researchpp 442-458Vainio, A. K., and Paulapuro, H. (2007). "Interfiber bonding and fiber segment activation in paper," BioRes. 2(3), 442-458.AbstractPDF
    Bonding and activation in paper were studied with the help of laboratory test sheets and common paper strength tests. Different papermaking furnishes and raw material treatments were used to examine the effects they have on bonding and activation. Furthermore, various boundary conditions during drying were included to single out the influence of bonding and activation on paper properties. It was found that bonding is clearly increased by beating of kraft pulp, starch addition, and thermomechanical pulp fines, whereas activation benefited most from beating and addition of reinforcement fibers to mechanical pulp based furnishes. Subjecting test sheets to increasing amounts of drying stress affected activation positively, and bonding negatively. The increase in activation did not seem to be dependent on the beating degree of chemical pulp fibers. Bonding, on the other hand, deteriorated more significantly in sheets made of extensively beaten kraft fibers, i.e. in sheets where the initial bonding potential was higher. Commonly used paper strength measurements provide dependable and accurate tools for assessing the effect of different variables on both bonding and activation. A short literature survey of bonding and activation is also provided.
  • Researchpp 459-471Parasuraman, P., Singh, R., Bolton, T. S., Omori, S., and Francis, R. C. (2007). "Estimation of hardwood lignin concentrations by UV spectroscopy and chlorine demethylation," BioRes. 2(3), 459-471.AbstractPDF
    Major projects are underway in our laboratory focusing on mildly acidic (pH>3) and alkaline (pH<10) pretreatments of hardwood chips prior to incineration for electric power or prior to pulping for paper manufacture. Production of lignocellulosic ethanol from the hemicelluloses in the hydrolyzates will be attempted. It is of great interest to quantify the concentrations of lignin in these hydrolyzates, since lignin fragments are suspected as fermentation inhibitors. UV spectroscopy is normally used to estimate the concentration of aqueous soluble lignin. However, the 203 nm absorbance gave unreliable results for these hydrolyzates, and on some occasions the 278 nm absorbance was unduly influenced by high absorbance in the 260-265 nm range. A credible method that uses chlorination to generate methanol from the methoxyl groups in lignin will be described. Model compound experiments showed that syringyl lignin units, with two methoxyl groups, gave a methanol yield of ~1.0 mmole/ mmole of aromatic rings.
  • Reviewpp 472-499Taherdazeh, M. J., and Karimi, K. (2007). "Acid-based hydrolysis processes for ethanol from lignocellulosic materials: A review," BioRes. 2(3), 472-499.AbstractPDF
    Bioethanol is nowadays one of the main actors in the fuel market. It is currently produced from sugars and starchy materials, but lignocelluloses can be expected to be major feedstocks for ethanol production in the future. Two processes are being developed in parallel for conversion of lignocelluloses to ethanol, “acid-based” and “enzyme-based” processes. The current article is dedicated to review of progress in the “acid-based-hydrolysis” process. This process was used industrially in the 1940s, during wartime, but was not economically competitive afterward. However, intensive research and development on its technology during the last three decades, in addition to the expanding ethanol market, may revive the process in large scale once again. In this paper the ethanol market, the composition of lignocellulosic materials, concentrated- and dilute-acid pretreatment and hydrolysis, plug-flow, percolation, counter-current and shrinking-bed hydrolysis reactors, fermentation of hexoses and pentoses, effects of fermentation inhibitors, downstream processing, wastewater treatment, analytical methods used, and the current commercial status of the acid-based ethanol processes are reviewed.
  • Reviewpp 500533Hubbe, M. A., and Heitmann, J. A. (2007). "Review of factors affecting the release of water from cellulosic fibers during paper manufacture," BioRes. 2(3), 500-533.AbstractPDF
    The ease with which water is released from cellulosic fiber material during the manufacturing of paper can affect both the production rate and the consumption of energy during the manufacturing process. Important theoretical contributions to dewatering phenomena have been based on flow through packed beds of uniformly distributed fibers. Such descriptions are able to explain why resistance to dewatering increases as a function of the hydrodynamic surface area of fibers. More recent studies have demonstrated a critical role of finely divided matter. If the fines are unattached to fibers, then they tend to move freely through the fiber mat and plug channels in the paper web during the dewatering process. Dewatering also is affected by the deformability of cellulosic fibers and by whether the fibers easily slide past each other, thereby forming a dense mat. By emphasizing the role of fine matter, colloidal forces, and conformability of cellulosic materials, one can gain a more realistic understanding of strategies that papermakers use to enhance initial drainage and vacuum-induced dewatering.