Changes In Cellulose Crystallinity Research Articles

Chemical changes of polysaccharides in heat-treated European beech wood

This work deals with the influence of different heat treatment temperatures (140, 150, 160, 170, 180, 190, 200, and 210 °C) on changes in sapwood and red heartwood of European beech (Fagus sylvatica L.). According to the results of wet chemistry methods, HPLC (high-performance liquid chromatography), FTIR (Fourier transform infrared spectroscopy), SEC (size exclusion chromatography), the wood constituents in sapwood and red heartwood behaved similarly to heat treatment, but the individual proportions were different. The loss of hemicelluloses and the increase in extractives with increasing temperature were more pronounced in sapwood. The amount of cellulose in sapwood and red heartwood showed similar behaviour with increasing temperature. Thermal treatment causes changes in cellulose crystallinity, and the formation of aromatic structures, mainly in beech sapwood. However, the increase in the lignin content of red heartwood was significantly lower than that of sapwood due to its auto condensation, and formation of pseudo-lignin. Among the carbohydrates, the most significant changes were observed in xylose content, which was almost twice as high in red heartwood as in sapwood. Other carbohydrates (glucose, mannose, galactose, and arabinose) reached similar values in sapwood and red heartwood.

Depolymerization of Cellulose Components from Oil Palm Empty Fruit Bunches in Bleaching and Delignification Process

Oil palm empty fruit bunches (OPEFB) are oil palm industry waste which is indeed abundant. OPEFB waste has been explorated to make fiber, cellulose, and its derivatives. In the process of extracting cellulose, there is depolymerization of several components, both hemicellulose, lignin, color, and structural elements. The combination of bleaching under acidic conditions and alkaline delignification gave different changes, one of which depends on the type of bleacher, concentration, reaction time, and the number of stages carried out. This study aimed to examine the effect of NaClO2 concentration and bleaching time on the physical and chemical characteristics that indicate the depolymerization process of OPEFB fiber. Depolymerization can be indicated by changes in the cellulose color, the content of cellulose, and the changes in cellulose crystallinity. The change of cellulose mass was affected by the bleacher concentration and the bleaching time. High concentrations of bleacher will reduce the cellulose mass significantly. Similarly, the depolymerization of the chromophore elements in OPEFB fiber will show a change in color from brown to gray-white with different brightness intensities. The XRD test indicated that there was a correlation between low crystallinity with the use of high bleacher concentrations.

Discriminating the viscoelastic properties of cellulose textile fibers for recycling

The viscoelastic properties of cellulose fibers play an important role in chemical recycling of textiles. Here we discriminated the intrinsic viscosity of cotton roll towels and bed linens using near-infrared imaging spectroscopy and supervised pattern recognition. The classification results showed training and test set accuracies of 84–97% and indicated that the relevant spectral features were related to water, cellulose, and cellulose crystallinity. We hypothesized that the decreasing intrinsic viscosity of cotton was associated with changes in cellulose crystallinity and water adsorption, which was supported by additional X-ray and sorption measurements. These results are important as they indicate the potential to non-invasively estimate the degree of polymerization and the suitability of different cotton materials for chemical recycling. We propose that changes in the degree of polymerization and cellulose crystallinity could be used as an indicator of the chemical quality of cellulose fibers, which would have wider impacts for textile recycling.

High-value compounds obtained from grape canes (Vitis vinifera L.) by steam pressure alkali extraction

The main by-product generated by the wine industry is the grape canes derived from the pruning process. The aim of the current work was the valorisation of this highly polyphenolic lignocellulosic material, by alkali extraction methodology avoiding alcoholic solvents use.In lignocellulosic by-products valorisation, it is important to take into account the variability of the raw material. In the case of vine pruning this may be due to the different varieties used, the geographical area, the climate, or the processing. It is, however, important to develop a global strategy for valorisation, from a biorefinery and circular economy point of view. In this work, the grape canes were characterised, before and after the extraction process, by Fourier transform infrared spectroscopy – attenuated total reflectance (FTIR-ATR) spectroscopy. Changes in cellulose crystallinity, hemicellulose content and structural conformation of proteins, due to the alkali thermal extraction process were identified and evaluated. For the first time, a steam pressure alkali extraction method was used on this material. The products were characterised by FTIR-ATR and Matrix Assisted Laser Desorption Ionisation-Time of Flight (MALDI-TOF) mass spectrometry. The presence of high-value compounds such as stilbene oligomers and condensed tannins was demonstrated in the extracts. The work shows the viability of the steam pressure alkali extraction, a simple and environmentally friendly method, for grape cane valorisation.

Study on Bamboo Longitudinal Flattening Technology.

In this paper, we introduced a bamboo longitudinal flattening technology and analyzed the effects of the softening–flattening process on the physical and mechanical properties of moso bamboo. This is a newer bamboo processing technology that can enhance the utilization and reduce pollution compared with traditional bamboo-based products. Results showed that the parenchyma cells distorted and compacted due to the flattening process. The hemicellulose and cellulose content decreased, while the content of lignin presented an increasing tendency. As expected, the dimensional stability of moso bamboo enhanced due to the decrement of hemicellulose. The softening–flattening process positively contributed to the micro-mechanical properties of treated bamboo specimens. For example, the hardness and modulus of elasticity of the untreated bamboo sample increased from 0.58 and 15.7 GPa to 0.8 and 17.5 GPa, respectively. In addition, the changes in cellulose crystallinity and mechanical properties were also investigated in this paper. The cellulose crystallinity increased from 37.5% to 43.2%, significantly. However, the modulus of rupture of the flattened bamboo board decreased from 9000 to 7500 MPa due to the grooves made by the flattening roller. The MOE of flattening bamboo board showed the same decreasing tendency.

Cellulose Structural Changes during Mild Torrefaction of Eucalyptus Wood.

The changes in the cellulose structure of eight Eucalyptus species (E. botryoides, E. globulus, E. grandis, E. maculata, E. propinqua, E. rudis, E. saligna and E. viminalis) in a mild torrefaction (from 160 °C to 230 °C, 3 h) were studied in situ and after cellulose isolation from the wood by solid-state carbon nuclear magnetic resonance (13C NMR), wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR) and by analytic pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS). Changes in molecular weight were assessed by viscosimetry. A small decrease in cellulose crystallinity (ca. 2%–3%) was attributed to its amorphization on crystallite surfaces as a result of acid hydrolysis and free radical reactions resulting in the homolytic splitting of glycosidic bonds. The degree of the cellulose polymerization (DPv) decreased more than twice during the heat treatment of wood. It has been proposed that changes in the supramolecular structure of cellulose and in molecular weight during a heat treatment can be affected by the amount of lignin present in the wood. The limitations of FTIR and Py-GC/MS techniques to distinguish the minor changes in cellulose crystallinity were discussed.

Chemical changes within solids during liquid hot water pretreatment of wood

The chemical properties of willow were studied following liquid hot water pretreatment. Three different temperatures of liquid hot water pretreatment were used (160, 180, and 200 °C) for periods of 30, 60, 120, and 240 min. The contents of extractives, lignin, holocellulose, glucose, and xylose was determined. Compared with the original sample, the results indicated that lignin and extractives content increased after pretreatment. Further, the content of xylose decreased significantly with increasing pretreatment time for all three temperatures. The highest glucose content was obtained under the conditions of 180 °C for 240 min. In addition, a significant correlation was found between the content of xylose in the solid fraction and the severity factor of treatment. To determine the changes in cellulose crystallinity, the total crystallinity index (TCI) and the lateral order index (LOI) were calculated from the Fourier-transform infrared spectroscopy spectra of cellulose. An increase in both of these structural characteristics was observed at all experimental temperatures.

Wettability, surface free energy and cellulose crystallinity for pine wood (Pinus sp.) modified with chili pepper extracts as natural preservatives

Fresh chili peppers (Malagueta, Red Savina and Bhut Jolokia) were used as natural finishing agents for Pinus sp. (Pinus). The solvent extraction of dried peppers produced a viscous liquid primarily containing capsicin, a pungent, lipophilic compound, and known as oleoresin capsicum (OC). Changes in surface wettability were monitored by the sessile-drop technique for samples treated with OC. The contact angles for untreated and treated Pinus provided the values of surface energy, with its polar and dispersive components, and polarity ratios. When treated with OC extracted from more pungent peppers, such as Bhut Jolokia, Pinus showed higher contact angles in non-polar probe liquids and higher polarity. The protective efficacy of OC was investigated against two wood-decay fungi, Paecilomyces variotii (soft-rot fungus) and Pycnoporus sanguineus (white-rot fungus). The treated samples, when submitted to fungal decay, exhibited reduced percentage of mass loss, which indicated that OC can afford surface protection under the conditions studied here. Changes in cellulose crystallinity were observed owing to distinct contributions from amorphous and crystalline zones of Pinus after fungal decay.

Influence of hot water extraction on cell wall and OSB strand mechanics

The exposure of wood to elevated temperatures during hot water extraction (HWE) has been shown to significantly influence a variety of physical and chemical properties of the wood. Aspen (Populus tremuloides) and hemlock (Tsuga canadensis) strands underwent HWE at 160 °C for four different periods of time. The weight loss (WL) associated with the processes ranged from 2.9 to 17.3% for the aspen, and from 2.9 to 12.8% for the hemlock. The higher WL associated with the hardwood was attributed to higher hemicellulose content in the hardwood than in the softwood as well as differences in chemical composition. Substantial increases in cell wall hardness (up to 34%) and modulus of elasticity (MOE) (up to 28%) were obtained at the intermediate extraction conditions. Extended exposure conditions resulted in decreases. The axial MOE of strands showed significant differences only in aspen. These changes are hypothesized to be related, in part, to changes in cellulose crystallinity.

Monitoring the Crystalline Structure of Sugar Cane Bagasse in Aqueous Ionic Liquids

The use of aqueous ionic liquids as a pretreatment for enhancing enzymatic saccharification of lignocellulosic biomass is well-known, with a focus on lignin and hemicellulose removal. However, in-depth knowledge of changes in cellulose crystallinity during the pretreatment is limited. To this effect, detailed Fourier transform infrared (FT-IR) spectroscopy, cross-polarized magic angle spinning 13C nuclear magnetic resonance (CP/MAS 13C NMR), and X-ray diffraction (XRD) studies on sugar cane bagasse that has been pretreated with aqueous ionic liquids is presented. Secondary derivatives of FT-IR spectra and Gauss deconvolution of XRD patterns were applied to give a detailed understanding of the crystalline changes in sugar cane bagasse cellulose upon pretreatment. The results showed that aqueous ionic liquid pretreatment destroys the semicrystalline region of sugar cane bagasse cellulose, thus disordering the orientation of the cellulose crystallites.

The Advantages of Soaking with Aqueous Ammonia Pre-treatment Process of Oil Palm Empty Fruit Bunches

Oil palm empty fruit bunches (OPEFB) as one of lignocellulosic biomass, consists of three main components: cellulose, lignin, and hemicelluloses. Cellulose may occur in a crystalline form in addition to amorphous form. Cellulose and hemicelluloses can be converted into fermentable sugar, i.e. glucose and xylose, by chemical or enzymatic hydrolysis. These sugar usually used as a feedstock of bio ethanol production. Lignin and high-crystallinity of cellulose are inhibits the performance of enzymatic hydrolysis process. Therefore pretreatment is necessary to remove lignin, decrease the crystallinity and improve the yield of enzymatic hydrolysis. One of the developed pre-treatment processes is soaking with aqueous ammonia solution or called by SAA process. In this study, the advantage of SAA pre-treatment process was investigated using ammonium solution prior to the enzymatic hydrolysis. The pre-treatments were carried out in various ammonium concentrations (5%, 7.5%, and 10%) at mild conditions (25 o C and 1 atm) for 24 hrs, and with or without a following additional diluted-acid pre-treatment (92 – 98 o C and 1 atm for 1 hour). The pre-treated materials were then enzymatic hydrolyzed by cellulose and β-glycosidase for 96 hrs and anaerobic digested by inoculums microbial. The changes in cellulose crystallinity were analyzed by FTIR Spectroscopy. The OPEFB pre-treated by 10% ammonium solution without a following dilute-acid pre-treatment shows low crystallinity with a crystallinity index (CI) of 0.80 compared to that of the untreated material (2.11). The method could increase the yield of hydrolyzed glucose to 79% compared with that of untreated material (13 g/g glucan added). The results also show increasing the methane production from 0.18 Nm 3 /g volatile solid to 0.35 Nm 3 /g volatile solid via anaerobic digestion.

Enhanced Bioethanol Production from Industrial Xylose Residue Using Efficient Delignification

Xylose residue (XR), the abundant industrial residue from commercial xylose production, was delignified using alkali as a substrate for ethanol production via simultaneous saccharification and fermentation (SSF). It was found that pretreatment with 1.5% (w/v) NaOH at 140 °C for 1.5 h was optimal for delignification efficiency (72.2%) and low cellulose loss (7.1%). The physical changes in samples after alkaline pretreatment were characterized for crystallinity and imaged using scanning electron microscopy (SEM), which demonstrated that the surface of samples became coarser with lignin removal. There were rather significant changes in cellulose crystallinity. The widespread accessibility of cellulose in XR favored enzymatic hydrolysis and achieved considerable bioconversion (98.8% with 15 PFU/g substrate). The maximum for ethanol concentration using SSF bioconversion reached 16.3 g/L, which was about four times more than that of the untreated sample. XR treated using the processes of alkaline pretreatment and SSF was an excellent substrate for bioconversion.

Changes in the cellulose crystallinity of moso bamboo cell walls during the growth process by X-ray diffraction techniques

We investigated the changes in cellulose crystallinity in the cell walls of moso bamboo (Phyllostachys pubescens Mazel) during the growth process. Changes in crystallinity in bamboo cell walls were traced along the longitudinal and radial directions using flat-sawn specimens obtained from each internode using X-ray diffraction measurements. Cellulose crystallinity in cell walls in the same culm was higher around the base of the bamboo culms in less than 10 days after the emergence of bamboo shoots, while the upper internodes remained lower in crystallinity. Thereafter, crystallinity in the upper internodes of bamboo culms became higher. This suggests that cellulose crystallinity within bamboo cell walls has gradually increased from the base to the top with the elongation of the internode during the growth process of bamboo shoots. In addition, cellulose crystallinity in cell walls increased particularly in the outer part of the bamboo culms in all internodes. Moreover, increases of crystallinity occurred after elongation growth of internodes. It is considered that increases in crystallinity in the outer portion of each internode are one of the countermeasures of bamboo culms against increased bending moment due to the elongation growth.

The Preparation of Soluble Cellouronic Acid Sodium Salt by 4-Acetamide-TEMPO Mediated Oxidation of Ultrasound-Pretreated Parenchyma Cellulose from Bagasse Pith

Abstract The parenchyma cellulose isolated from bagasse pith was used as an alternative resource for preparation of water-soluble cellouronic acid sodium salt (CAS). The influence of ultrasound treatment on the cellulose was investigated for obtaining CAS by regioselective oxidization using 4-acetamide-TEMPO and NaClO with NaClO2 as a primary oxidant in an aqueous buffer at pH 6.0. The yield, carboxylate content and polymerization degree (DP) of CAS were measured as a function of ultrasonic power, agitating time and cellulose consistency by an orthogonal test. The ultrasound-treated conditions were further improved by discussion of ultrasonic power, the most important factor influencing the yield and DP. An optimized CAS yield of 72.9% with DP value (DPv) of 212 was found when the ultrasonic strength is 550 W, agitating time is 3 h and cellulose consistency is 2.0%. The oxidation reactivity of cellulose was improved by ultrasonic irradiation, whereas no significant changes in crystallinity of cellulose were measured after ultrasonic treatment. Moreover, the ultrasound treatment has a greater effect on yielding CAS from parenchyma cellulose than from bagasse fibrous' one. The CAS was further characterized by Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM).

Cellulose amorphization by swelling in ionic liquid/water mixtures: a combined macroscopic and second-harmonic microscopy study.

Amorphization of cellulose by swelling in ionic liquid (IL)/water mixtures at room temperature is a suitable alternative to the dissolution-precipitation pretreatment known to facilitate enzymatic digestion. When soaking microcrystalline cellulose in the IL 1-ethyl-3-methylimidazolium acetate containing 20 wt % water, the crystallinity of the cellulose sample is strongly reduced. As less than 4 % of the cellulose dissolves in this mixture, this swelling method makes a precipitation step and subsequent energy-intensive IL purification redundant. Second-harmonic generation (SHG) microscopy is used as a structure-sensitive technique for in situ monitoring of the changes in cellulose crystallinity. Combined optical and SHG observations confirm that in the pure IL complete dissolution takes place, while swelling without dissolution in the optimal IL/water mixture yields a solid cellulose with a significantly reduced crystallinity in a single step.

A Comparison of Low Temperature Alkali and High Temperature Acid Pretreatments for Improving Saccharification of Spent Mushroom Substrate

Low temperature alkali (LTA) pretreatment and high temperature acid (HTA) pretreatment methods were applied to spent mushroom substrate (SMS) for providing comparative performance data on the enhancement of enzymatic saccharification and the change of composition and structure. LTA pretreatment contributed to higher lignin removal (67.6%) and enzymatic digestibility (85.6%) during enzymatic hydrolysis, while HTA pretreatment resulted in higher hemicellulose reduction (85.3%) but lower enzymatic digestibility (43.5%). The physical structure was destroyed at certain degree and changes in cellulose crystallinity occurred after both LTA and HTA pretreatments. Besides, the effect of lignin reduction in alkali pretreatment on glucose yield was studied. These results indicated that LTA pretreatment had the potential to be developed into a cost effective process for producing bioproducts from lignocellulosic materials.

Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin

Cholinium amino acids ionic liquids ([Ch][AA] ILs), a novel type of bio-ILs that can easily be prepared from renewable biomaterials, were investigated for pretreatment of rice straw by selective extraction of lignin from this abundant lignocellulosic biomass material. Of the eight ILs examined, most were demonstrated to be excellent pretreatment solvents. Upon pretreatment using these ILs, the initial saccharification rates of rice straw residues were substantially improved as well as the extent to which polysaccharides could be digested (>90% for cellulose and >60% for xylan). Enzymatic hydrolysis of pretreated rice straw by Trichoderma reesei cellulase/xylanase furnished glucose and xylose with the yields in excess of 80% and 30%, respectively. Detailed spectroscopic characterization showed that the enhancement of polysaccharides degestibility derived mainly from delignification rather than changes in cellulose crystallinity. The yields of fermentable reducing sugars were significantly improved after individual optimization of pretreatment temperature and duration. With [Ch][Lys] as the solvent, the sugar yields of 84.0% for glucose and 42.1% for xylose were achieved after pretreatment at 90°C for 5 h. The IL [Ch][Lys] showed excellent reusability across five successive batches in pretreatment of rice straw. These bio-ILs performed as well as or better than previously investigated non-renewable ILs, and thus present a new and environmentally friendly way to pretreat lignocellulose for production of fermentable sugars and total utilization of the biomass.

Analysis of crystallinity changes in cellulose II polymers using carbohydrate-binding modules

Carbohydrate-binding modules (CBMs) are a set of tools that can be used as molecular probes for studying plant cell walls and cellulose-based substrates. CBMs from enzymes of bacterial and fungal origin present a range of recognition capabilities for crystalline and amorphous cellulose. Here cellulose-directed CBMs have been used to visualize and quantify crystallinity changes in cellulose II-based polymers following NaOH treatment. Cellulose II polymers used were in the form of lyocell fibers, which are derived from eucalyptus wood pulp. The supramolecular structure, morphology, and existence of ‘skin-core’ model in the fiber were examined using CBM-labeling techniques. Changes in cellulose crystallinity showed maxima at 3.33moldm−3 NaOH (under treatment conditions of 49Nm−1 at 25°C) and 4.48moldm−3 NaOH (under treatment conditions of 147Nm−1 at 40°C); CBM methods were also suitable for quantifying changes within amorphous regions. Quantification of crystallinity changes using CBM labeling techniques was achieved in combination with image analysis, which was shown to reflect the same crystallinity changes as measured using ATR-FTIR methods. It was demonstrated that CBM-labeling techniques were able to validate the proposed ‘skin-core’ model of lyocell fibers, comprising a semi-permeable fiber skin and a porous core.

The effects of thermal modification on crystalline structure of cellulose in soft and hardwood

In this study the crystallinity and estimations of relative triclinic ( I α ) and monoclinic ( I β ) structure content of cellulose isolated from heated spruce ( Picea orientalis) and beech ( Fagus orientalis) wood samples were determined by using Fourier Transform Infrared (FT-IR) spectrometry. Heat treatment was applied on the test samples in an oven at three different temperatures (150, 180 and 200 °C) and two different durations (6 and 10 h) under atmospheric pressure. It was determined that crystallinity of cellulose in wood samples increased with thermal modification. The results indicate that the changes in crystallinity of cellulose in wood samples related to not only temperature but also time during thermal modification. I α / I β ratio of cellulose in spruce and beech wood samples changed with thermal modification, but it was established that monoclinic structure was dominant in cellulose crystalline structure. It was designated that the crystalline structure of cellulose in spruce wood samples affected from thermal modification more than in beech wood samples.

Ion-exchange behavior of carboxylate groups in fibrous cellulose oxidized by the TEMPO-mediated system

When native cellulose is treated by catalytic oxidation with 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)/NaBr/NaClO under aqueous conditions, significant amounts of carboxylate and aldehyde groups can be introduced on surfaces of cellulose I crystallites and into disordered regions without any changes in crystallinity of cellulose I or in the original fibrous morphology. In this study, behavior of ion exchange of carboxylate groups in the TEMPO-oxidized fibrous cellulose prepared from cotton linters was compared with that of fibrous carboxymethyl cellulose (F-CMC) with almost the same carboxylate content as that of the TEMPO-oxidized cellulose. These fibrous celluloses were soaked in various metal salt solutions, and metal ion contents in the celluloses were determined by X-ray fluorescence analysis after washing with water and drying of the celluloses. In all metal salts examined in the ion-exchange experiments, the TEMPO-oxidized cellulose had metal ion contents higher than those of F-CMC. Especially, lead, calcium and silver ions were greatly introduced into the TEMPO-oxidized cellulose with the metal ion/carboxylate molar ratio of about 1:1. The adsorption selectivity of metal ions on the TEMPO-oxidized cellulose was also studied using aqueous solutions containing multiple metal salts for soaking, and the following selectivity order was obtained: Pb 2+>La 3+>Al 3+>Cu 2+>Ba 2+>Ni 2+>Co 2+>Cd 2+, Sr 2+, Mn 2+, Ca 2+>Mg 2+ Moreover, swelling ability of the TEMPO-oxidized celluloses having various metal carboxylate groups in water and wet tensile strength of handsheets prepared thereof were studied in terms of kinds of metal ion introduced. Degree of dissociation of the metal carboxylate groups in these celluloses is likely to affect the results of the above characteristics of the TEMPO-oxidized celluloses.