Lignocellulosic Polymers Research Articles

The preparation of lignocellulosic aerogels from ionic liquid solutions

Nanofibrillar aerogels were prepared from cellulose, spruce wood and from mixtures of cellulose, lignin and xylan. The lignocellulosic polymers were first dissolved in an ionic liquid and coagulated from solution by adding aqueous ethanol. The obtained gel was washed with ethanol and liquid carbon dioxide and finally dried by releasing the carbon dioxide from the porous structure at supercritical temperature to obtain the aerogel. The bulk densities of the biopolymer aerogels ranged from 25 to 114 g/l and the internal surface areas (BET) from 108 to 539 m 2/g depending on the biopolymer mix and on the polymer concentration in the ionic liquid solution. All aerogels were compressible and consisted of nanofibrillar biomaterial network with open-pore structure.

γ-Radiation Induced Changes in the Physical and Chemical Properties of Lignocellulose

gamma-radiation induced effects on the physical and chemical properties of natural lignocellulose (jute) polymer were investigated. Samples were irradiated to required total doses at a particular dose rate. The changes in the parameters such as the tensile strength, elongation at break, and work done at rupture for the lignocellulose samples on irradiation with the gamma-rays from a cobalt-60 source were measured. The mechanical properties were found to have nonlinear relations with the radiation doses. The chemical stability of irradiated fibers was found to degrade progressively with the increase of radiation dose. Additionally, other chemical changes of the samples due to exposure to high-energy radiation were also investigated using fluorescence and infrared spectroscopic analysis. Differential scanning calorimetry and thermogravimetric studies showed a significant reduction in thermal stability. The wide-angle X-ray diffraction study showed that structural changes of cellulose appeared due to the radiation-induced chemical reaction of lignocellulose.

Lignocellulose-degrading enzymes produced by the ascomycete Coniochaeta ligniaria and related species: Application for a lignocellulosic substrate treatment

Lignocellulose-degrading microorganisms are of interest for biomass upgrading. In a previous work, we isolated the ascomycete Coniochaeta ligniaria NRRL 30616 that metabolized phenolics and furans in lignocellulosic acid hydrolysates. This fungal isolate was investigated in the present work for the ability to produce lignocellulose-degrading enzymes during batch cultivation using different substrates as carbon source. This microorganism produced cellulase, xylanase and two lignin peroxidases (manganese peroxidase, MnP and lignin peroxidase, LiP), but laccase activity was not detected. The same enzyme activities were also found in 23 related fungal strains, and C. ligniaria NRRL 30616 showed the highest levels for some of the enzymes. Treatment of pepper plant residues (PPR) with this fungus was monitored during 20 days in solid and semisolid-state cultures. It was found that all enzymes initially detected were produced under these conditions at the early culture stages (5 days) and lignocellulose polymers were consequently degraded. Losses of about 75%, 50% and 40% were obtained for hemicellulose, cellulose and lignin, respectively, in semisolid cultures after 20 days. The lignocellulolytic activity of C. ligniaria detected in this study may be exploited for lignocellulosic biomass treatment.

Comparison of the surface energetics data of eucalypt fibers and some polymers obtained by contact angle and inverse gas chromatography methods

This study compares two approaches to determine the surface energy of solids, and its acid-base components in particular: inverse gas chromatography (IGC) and analysis of contact angle data using the Good-van Oss theory. The comparison is made in the context of wood fibers from Eucalyptus globulus and Eucalyptus regnans pulped by the kraft and neutral sulfite semi-chemical (NSSC) processes, and of selected polymers. Contact angles on wood fibers were measured using the Wilhelmy method and on polymer samples using the sessile drop technique. For the dispersive component of the surface energy, the level of agreement between the two approaches was reasonable, using alkanes for the IGC measurements and diiodomethane for the Wilhelmy and sessile drop techniques. However, agreement was poor for the acid and base characteristics when monopolar probes were used for IGC and water, formamide, and diiodomethane for contact angle measurements. The Good-van Oss approach suggested that all fibers and polymers are monopolarly basic, whereas IGC measurements suggested that they are bipolar. When new values were used for the acid and base components of the surface energy of the liquid probes based on the values for water proposed by Della Volpe and Siboni, all samples still appeared strongly basic. This is inconsistent with the chemical nature of the lignocellulosic fibers. Thus, the Good-van Oss approach provides a poor indication of acid-base properties of the surfaces of solids in suggesting that lignocellulosic fibers and polymers are strongly basic. The above issues as well as potential problems in measuring the surface energy of lignocellulosic fibers using the three-liquid procedure and the Good-van Oss approach are discussed.

Free and bound fatty acid oxidation products in archaeological ceramic vessels

While oxidation products of unsaturated fatty acids, for example dicarboxylic acids (hereafter diacids), must form during the use of unglazed ceramic vessels for the processing of animal and plant products, such components have never been observed during studies of absorbed lipids. Their absence from the extractable lipid fraction is presumed to be the result of their loss from potsherds through groundwater leaching. Lipid oxidation products including short-chain dicarboxylic acids, ω-hydroxy acids and longer-chain hydroxy and dihydroxy acids have now been observed as components probably covalently bound into solvent insoluble residues of potsherds recovered from waterlogged deposits. These components were only revealed following alkaline treatment of the insoluble residues. A similar mixture of diacids was observed in high abundance in the free lipid fraction of vessels recovered from an exceptionally arid deposit where groundwater leaching would never have occurred. These results confirm the formation of oxidation and probable polymerization products of unsaturated fatty acids during vessel use and burial.

Pyrolysis/gas chromatography/mass spectrometry of lignocellulose

The use of pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) to determine the molecular composition of lignocellulose is reviewed and the technique illustrated with applications on some novel systems. Constituents and structural arrangement of lignocellulosic polymers in plant cell wall are briefly described. The basic principles of pyrolysis and the main advantages and disadvantages of PY/GC/MS are discussed. PY/GC/MS analyses of (a) paper industry effluents, (b) agricultural by-products subjected to biological processes of delignification and (c) recycled paper are presented as examples of the amount of information that PY/GC/MS can provide on lignin classification and monitoring of delignification treatments as well as on the fingerprinting of lignocellulosic materials. The ion trap detector mass spectra of 56 pyrolysis products of lignocellulose, including compounds of phenolic, furanic and pyranic nature, are shown.

The finishing of zebu bulls on steam-hydrolysed sugar cane bagasse with different supplements

The fibrous residue remaining after juice extraction from the sugar cane stalk is commonly referred to as bagasse. It consists mainly of the ligno-cellulosic polymer matrix and small amounts of ash and water soluble solids which are mostly sucrose. In sugar industry mills, most of the bagasse is used as fuel, and although figures vary within each factory, energy efficient units can have 2 tonnes of surplus bagasse (dry basis) per 100 tonnes of fresh cane processed (Rolz et al). The bagasse can be supplemented with urea and legume protein in cattle diets. Research in Mauritius (Wong et al. 1974) showed that high pressure steam treatment (200°C) for 2-5 minutes raised rumen “in situ” digestibility from 30 to 60%. Subsequent work (Naidoo et al.1977) emphasised the critical role of supplements providing bypass nutrients (protein and glucose precursors) , in addition to urea-N and minerals for rumen microbes. In Colombia this technology is now being applied commercially for cattle fattening, using the foliage from the legume tree, Gliricidia sepium as the main source of bypass protein.

Biological pretreatment of coffee pulp

The presence of several antiphysiological factors limit the use of coffee pulp in monogastric and ruminant feeding. Among these the characteristics of its lignocellulosic fraction is important. Twenty-six white rot fungi were grown under solid substrate conditions, using previously ensiled and pressed coffee pulp without adding additional sources of nitrogen; the objective was to quantify the changes of the lignocellulosic polymer matrix and the enzymatic digestibilities. All grew and wholly covered the surface of the substrate. Six of the fungi produced fruiting bodies, which were easy to see since basidiomycetes produce large fuiting bodies. The weight loss interval ranged between 6·7 and 28·0% dry matter before fructification and from 17·0 to 48·7% after fructification. Trametes versicolor was a very fast grower and showed the highest rates of holocellulose and lignin degradation. Hemicellulose was selectively preferred over cellulose by most fungi and at least two degraded more than 80% of the original hemicellulose. Six white rots produced a solid residue with less lignin content than the one found in the original substrate. Two of them, Sporotrichum pulverulentum and Stropharia rugosoannulata, also increased the water-soluble solids and produced a solid residue with the same enzymatic digestibility as the one found for the original coffee pulp.

Differential scanning calorimetric studies of the reaction between lignocellulosic materials and hydrogen peroxide using model compounds

Reaction of hydrogen peroxide with twenty lignocellulosic polymers and model compounds was studied by differential scanning calorimetry at 6722 kPa (975 psi) in nitrogen and oxygen atmospheres. Two exotherms were identified. Exotherm A peaked between 109 and 186°C in N 2 and O 2 with the heat of reaction Δ H a ranging from 738 to 2638 cal g −1. Exotherm B peaked between 180 and 254° C in either atmosphere with Δ H b = 109–346 cal g −1 in N 2 and with Δ H b= 1356–4325 cal g −1 in O 2. With one exception, exotherm B appeared in N 2 only in the case of the materials which possessed acetal or hemiacetal linkages. It was concluded that exotherm A resulted from decomposition of H 2O 2 under formation of O 2 and oxidation of organic compounds, while exotherm B resulted from oxidation of hydroxyl groups by O 2. A mechanism was proposed for the formation of O 2, which involved hydrolysis of acetal or hemiacetal linkages to aldehydes or ketones, formation of α-hydroxyperoxides by addition of H 2O 2, oxidation of a-hydroxyperoxides by hydroxyl radicals, decomposition of the resulting free radicals under formation of superoxyl radicals and oxidation of superoxyl radicals either by hydrogen peroxide or by hydroxyl radicals to oxygen.

Lignocellulose polymer composites as γ-dosimeter in the kilorad range

The induced changes in the electrical resistance by γ-irradiation was measured for some cellulose-polymer composites. Increasing the percentage of the polymer in the composite samples results in an increase of the activation energy. When the polymer is replaced by another, the activation energy changes accordingly. The addition of glass to the composite gives rise to lower activation energy. Still further decrease is achieved if glass is replaced by cupric oxide. The results obtained show that the resistance was changed to a lower value by γ-irradiation. This may allow such composites be used as γ-dosimeters in the kilorad range.