Changes In Cellulose Structure Research Articles

Liquefaction pathway of corn stalk cellulose in the presence of polyhydric alcohols under acid catalysis

In this paper, the experiment of cellulose from corn stalk using 1, 2-propylene glycol (PG) and diethylene glycol (DEG) liquefaction catalyzed by phosphoric acid at atmosphere pressure was carried out. The effect of reaction time on the structural changes of cellulose in the liquefaction process of polyhydric alcohols was investigated, aiming at understanding the mechanism of cellulose liquefaction reaction under the action of acid catalyzed polyhydric alcohols. It was found that the liquefaction yield increased first and then decreased with the extension of reaction time, and reached the highest at 150 min (99.34 %). In the phase of increasing liquefaction yield, cellulose was degraded and translated into glucose, which was then converted into plenty of glycosides with PG/DEG. These glycosides were further converted into low molecular weight (LMW) substances such as hydrocarbons, acids, alcohols, esters, ketones, and ethers. At this time, the biofuel contained 70 %–85 % compounds with carbon number less than 25 and 5 %–10 % compounds with carbon number more than 25. As the prolongation of reaction time (after 150 min), quantities of unstable free radicals formed by cellulose degradation could combine with each other or with hydrogen atoms provided by PG/DEG to produce relatively stable macromolecular substances. That is, the polydispersity (Mw/Mn, abbreviated Ð = 1.28) of the generated biofuel at this stage no longer decreased. However, liquefaction residue produced at 240 min had changed essentially, which was completely different from the liquefaction residue produced in the early stage of liquefaction. In conclusion, this paper revealed the partial reaction process of cellulose by studying the structural changes in the liquefaction process of polyhydric alcohols, which laid a theoretical foundation for exploring the liquefaction mechanism of cellulose.

Ionic Liquids as Potential Cleaning and Restoration Agents for Cellulosic Artefacts

This study explores the efficacy of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-hexyl-3-methylimidazolium chloride as cleaning agents for aged cellulosic artifacts. A 10% v/v acetone solution of these ionic liquids (ILs) effectively removes the brownish-yellow color of aged paper in a 10 min immersion treatment. Colorimetric analysis shows a remarkable increase in lightness (L*) by up to 40% and a decrease in red/brownish tones (b*) after IL treatment. The cleaning process also deacidifies the paper, shifting the pH to neutral-slightly basic levels and enhancing its long-term stability. Optimal pH outcomes are achieved, with ionic liquid consumption values of 0.4–0.6 g/g of paper. The FTIR analysis revealed structural changes in cellulose induced by the washing step, which is mainly due to the reorganization effect imparted by the ionic liquids. Furthermore, ILs mobilized degraded compounds and acidic species, aiding in their extraction during the restoration process. Mechanical testing indicated an enhancement in the overall tensile strength and strain at break values for IL-treated papers by up to 33%. This study demonstrates the multiple benefits of alkylimidazolium ionic liquids for preserving and restoring cultural heritage artifacts made of cellulosic materials.

Cellulose Iβ behaviors in non-solvent liquid media: Molecular dynamic simulations

The structural changes of cellulose in non-solvent liquid media can provide insights into the high-value utilization of cellulose. This study includes molecular dynamics simulations of 36-chain cellulose Iβ microfibril model (Iβ-MF) behavior in 16 non-solvent liquids with different polarities at room temperature using two carbohydrate force fields (CHARMM36, GLYCAM06). Iβ-MF in CHARMM36 retains more than 70% of the tg conformation in 16 liquids, and the retention of the tg conformation increased with decreasing liquid polarity. Liquid polarity can affect the hydroxymethyl conformation of cellulose, which is only an appearance, and the real driving force behind is the electrostatic interaction between liquid molecules and cellulose. Furthermore, changing the 1,4 electrostatic scaling factor of GLYCAM06 can effectively affect the structural convergence of Iβ-MF. The Iβ-MF forms an alternating layer structure in the gg/gt conformation in a medium to high polarity non-solvent liquid, while the model undergoes untwisting. Model untwisting is inextricably linked to the degree of alternate layer structure formation. This paper provides a theoretical basis for the molecular study of nanocellulose structures from an energy-structure-property perspective.

Deconstruction of pineapple peel cellulose based on Fe2+ assisted cold plasma pretreatment for cellulose nanofibrils preparation

An effective method based on Fe2+ assisted cold plasma (CP) to pretreat pineapple peel cellulose for the preparation of cellulose nanofibrils (CNF) was proposed in this study. The mechanism underlying Fe2+ assisted CP pretreatment based on the structural changes of cellulose was investigated. Results showed that the cellulose preabsorbed Fe2+, followed by 60 min of CP treatment, and then was nanofibrillated into CNF via ultrasonication. Fe2+ assisted CP treatment exhibited strong capacity to significantly decrease the degree of polymerization of cellulose and to enhance electrostatic repulsion of fibrils. Furthermore, the roughness and breakage were observed on the surface of pretreated cellulose. The content of inter-molecular hydrogen bonds and average crystallite size (Dhkl) also decreased significantly. The current results provided useful fundamental insights into Fe2+ assisted CP and cellulose interaction, which should be beneficial to developing new pretreatment methods for disintegrating cellulose into CNF.

Conversion of Carbohydrates in Lignocellulosic Biomass after Chemical Pretreatment

The aim of the study was to determine the quantitative and qualitative changes taking place in biomass components actively participating in methane fermentation, i.e., in carbohydrates, as a result of chemical pretreatment. Analyses were conducted on agricultural waste (corn stover, also called corn straw, and corncobs) as materials most commonly used in methane fermentation, as well as poplar wood, a material relatively rarely used in biogas production. Pretreatment with the aim of increasing efficiency of methane fermentation was carried out with the use of acid and alkaline solutions of different concentrations. The effect of pretreatment on carbohydrates was analyzed based on the quantitative and qualitative changes in this component. Due to the structural heterogeneity of carbohydrates, their varied reactivity and fermentability were determined in terms of holocellulose, cellulose, and pentosans. The chemical structure of cellulose was also analyzed. It is shown in this study that chemical pretreatment causes transformations of carbohydrate components, which differ quantitatively and qualitatively in the compared raw materials. It was found that the alkaline treatment caused smaller changes in the percentage shares of the carbohydrate biomass components as compared to the acid treatment. Moreover, it was observed that the compared materials differ in terms of quantitative changes in their chemical composition depending on the composition of the raw material prior to pretreatment. In the case of corn waste subjected to the action of 1 and 3% NaOH, the share of pentosans in the biomass increased. It was established that this is a change with a positive effect on fermentation efficiency. The action of acids and alkalis on the biomass led to similar structural changes in cellulose, which are adverse for the fermentation process.

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.

Investigation into the reaction mechanism underlying the atmospheric low-temperature plasma-induced oxidation of cellulose

Atmospheric low-temperature plasma has been widely applied in surface modification of lignocellulose for manufacturing lightweight, strong composites. This study is aimed at elaborating the structural changes of cellulose after plasma treatment and further understanding the mechanism underlying plasma-induced oxidation of cellulose. Experiments suggested that atmospheric low-temperature plasma exhibits strong capacity to cleave covalent bonds, leading to oxidation and degradation of cellulose. Theoretical analysis revealed that cleavage of C4O covalent bond is the first-step reaction during plasma-induced oxidation due to its low bond dissociation energy (229.2 kJ mol−1). Subsequent pyranose ring-breaking reaction dominates dynamically and thermodynamically. Obtained outcomes are vital for fundamentally understanding the plasma-lignocellulose interaction. On that basis, plasma treatment for activation and oxidation of lignocellulose can be optimized and designed for improved efficiency. Wettability of lignocellulose can be thus improved in a short time, providing an opportunity to manufacture lignocellulose-based composites with enhanced efficiency and mechanical properties in future.

Surface morphology and cellulose structure of Napier grass pretreated with the ionic liquid 1-ethyl-3-methylimidazolium acetate combined with either water or dimethyl sulfoxide as a co-solvent under microwave irradiation

The combination of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate with either water or dimethyl sulfoxide (DMSO) as a co-solvent was applied for the pretreatment of Napier grass under microwave irradiation at 150 °C for 1 h in order to enhance the subsequent cellulase enzymatic hydrolysis of the cellulose to sugars via increased enzyme accessibility. The influence of the IL/water and IL/DMSO (at different IL/DMSO (v/v) ratios) pretreatment on the structural changes of the Napier grass was examined using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyses. The transformation of cellulose I in the IL/DMSO pretreated Napier grass was clearly observed. The results indicated that cellulose structural changes occurred and a higher yield of fermentable sugars was obtained from the subsequent enzymatic hydrolysis for the pretreated Napier grass samples with a high crystallinity index.

The effects of transition metal sulfates on cellulose crystallinity during accelerated ageing of silver fir wood

During the hydrolytic degradation of cellulose caused by acidic transition metal sulphates, new low molecular products such as monosaccharides and their degradation products are usually formed which can increase the cellulose sensitivity to oxidation. This work was aimed at elucidation of the chemical and structural changes of cellulose in silver fir (Abies alba Mill.) wood treated with iron, copper and zinc salts to achieve a detailed understanding of cellulose deterioration during accelerated ageing. Cellulose samples were isolated from the wood by the Kurschner-Hoffer method and the Seifert method. Changes in cellulose structure were evaluated by wide-angle X-ray scattering (WAXS) measurements, Fourier transform infrared spectroscopy (FTIR), and high performance liquid chromatography. The presence of metal cations (Cu2+, Zn2+, Fe3+) caused a significant loss in the content of cellulose for treated and aged wood samples. Wet-thermal accelerated ageing led to a decrease (~ 20%) in the content of monosaccharides. The Seifert cellulose samples had a higher crystallinity than the Kurschner-Hoffer samples. A strong correlation was found between crystallinity indices obtained from the FTIR and WAXS measurements. Two cluster groups of cellulose samples, segregated from each other, were identified within each cellulose type in a multivariate cellulose trait analysis.

Real-time adsorption and action of expansin on cellulose

BackgroundBiological pretreatment is an environmentally safe method for disrupting recalcitrant structures of lignocellulose and thereby improving their hydrolysis efficiency. Expansin and expansin-like proteins act synergistically with cellulases during hydrolysis. A systematic analysis of the adsorption behavior and mechanism of action of expansin family proteins can provide a basis for the development of highly efficient pretreatment methods for cellulosic substrates using expansins.ResultsAdsorption of Bacillus subtilis expansin (BsEXLX1) onto cellulose film under different conditions was monitored in real time using a quartz crystal microbalance with dissipation. A model was established to describe the adsorption of BsEXLX1 onto the film. High temperatures increased the initial adsorption rate while reducing the maximum amount of BsEXLX1 adsorbed onto the cellulose. Non-ionic surfactants (polyethylene glycol 4000 and Tween 80) at low concentrations enhanced BsEXLX1 adsorption; whereas, high concentrations had the opposite effect. However, sodium dodecyl sulfate inhibited adsorption at both low and high concentrations. We also investigated the structural changes of cellulose upon BsEXLX1 adsorption and found that BsEXLX1 adsorption decreased the crystallinity index, disrupted hydrogen bonding, and increased the surface area of cellulose, indicating greater accessibility of the substrate to the protein.ConclusionsThese results increase our understanding of the interaction between expansin and cellulose, and provide evidence for expansin treatment as a promising strategy to enhance enzymatic hydrolysis of lignocellulose.

Cellulose structural change in various biomass species pretreated by ionic liquid at different biomass loadings

High biomass loading is a key technique to reduce the pretreatment cost of lignocellulosic biomass. In this work, various biomass species such as bagasse, erianthus, cedar, and eucalyptus were pretreated using an ionic liquid, 1-ethyl-3-methylimidazolium acetate, at different biomass loadings, particularly focusing on a high loading region. Cellulose structural changes in pretreated biomass were investigated via X-ray scattering and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structural behaviors roughly fell into two categories, corresponding to either grassy (bagasse and erianthus) or woody (cedar and hardwood) biomass. The grassy biomass gradually transformed from cellulose-I to cellulose-II in a monotonic manner against the biomass loading. In contrast, the transformation in the woody biomass occurred abruptly as solids was decreased within the high loadings range (50 wt% to 33 wt%). Below 33 wt%, a reformation of cellulose-I from cellulose-II proceeded readily. In terms of cellulose crystallinity, erianthus as well as bagasse showed a minimum value at 25 wt% loading, whereas the crystallinity for the woody biomass did not possess such a clear minimum. Acid hydrolysis of these pretreated biomass was also conducted and the relationship between the reactivity and the cellulose structural changes was discussed.

Calorimetry, chemical composition and in vitro digestibility of sugarcane treated with calcium hydroxide

Sugarcane is a source of roughage in animal feeding. It presents high production per unit of cultivated area, relatively easy cultivation and low cost of production per hectare, and better quality and a high dry matter (DM) yield in periods when forage is scarce. This study aimed to evaluate the effect of increasing levels of calcium hydroxide (Ca(OH)2) in sugarcane forage on chemical composition, in vitro digestibility values of DM, neutral detergent fibre (NDF) and acid detergent fibre (ADF), and kinetics of thermal decomposition processes of weight loss and heat flow. Sugarcane was collected close to the ground and 50-kg heaps of the fresh material were formed and mixed with four doses of Ca(OH)2 (0, 8, 16 and 24 g kg–1 sugarcane). Concentrations of NDF and ADF decreased linearly with increasing amount of Ca(OH)2, whereas concentration of hemicellulose increased linearly. In vitro digestibilities of DM, NDF and ADF were enhanced in a quadratic manner with increasing amounts of Ca(OH)2. The release of heat, measured by ΔH, increased linearly with increased Ca(OH)2 levels, likely due to enhanced digestibility of the fibre components. Weight loss decreased linearly between 272.2°C and 397.7°C with increased amounts of Ca(OH)2 added to sugarcane, likely due to changes in cellulose structure, which became denser and thermodynamically more stable than native cellulose following the alkaline treatment. Calcium hydroxide changed chemical composition and digestibility of the fibrous fraction of sugarcane, resulting in better nutritional value. The greatest release of heat and highest in vitro digestibility of fibre were observed when adding 15.2 g Ca(OH)2 kg–1 sugarcane; therefore, this dose is recommended to enhance the nutritive value of sugarcane as ruminant feed.

IR SPECTRA AND HEATS OF HYDRATION OF THE OZONATED PULP

Reduce the consumption of chlorine dioxide in the bleaching of pulp is one of the main problems of technology of production of bleached pulp at Russian enterprises. We have developed a modified method of bleaching of sulphate hardwood pulp with a degree of ozonization. The new in work is the identification of the mechanism of ozonation on the structure of cellulose at different stages of the pulp bleaching. To assess structural changes of cellulose in the process of bleaching was used technique for IR spectroscopy. To characterize the hydrophilic properties of the cellulose used a calorimetric method and the method equilibrium sorption.Shown an advantage of using both chlorine dioxide and ozone in the bleaching of sulphate hardwood pulp. The obtained results of physical and chemical research associated with physico-mechanical properties of bleached and unbleached cellulose at different stages of bleaching. Shows the effect of ozonation on the mechanism of interaction of cellulose with bleaching agents. Effective delignification in the joint use of ozone and chlorine dioxide, can reduce the cost of bleaching chemicals. The brightness level corresponds to the world standards. and the content of organochlorine compounds (AOH) decreased by 30%. Reduce the consumption of chlorine dioxide helps to reduce contamination of waste water, reducing the content of organochlorine compounds (AOH).

Conversion of mixtures of dairy manure and soybean curd residue by black soldier fly larvae (Hermetia illucens L.)

The increasing numbers of dairy farms cause massive manure production and its improper disposal poses threats to the environment. Larvae of the black soldier fly (BSF) have the potential to convert this animal manure into valuable biomass; however, the high fiber content of dairy manure (DM) makes conversion difficult. Therefore, the goal of this investigation was to evaluate the impact of co-digestion of DM with another ecologically problematic waste source: soybean curd residue (SCR). The waste sources were fed to BSF larvae using different mixing ratios. DM and SCR mixed in a ratio of 2:3 was found to result in the best outcome measures: development time (21 days), survival rate (98.4%), waste mass reduction (75.4% wet and 56.6% dry waste mass), bioconversion (11.6% on wet and 14.6% dry mass base), feed conversion ratio (6.4 wet and 4.0 dry), nutrient utilization (nitrogen, 62.1%; phosphorus, 52.9%; carbon, 66.4%), and fiber content reduction (cellulose, 64.9%; hemicellulose, 63.7%; lignin, 36.9%). Analysis of the structural changes of cellulose, hemicellulose, and lignin by scanning electron microscopy let us assume that black soldier fly larval activity did leads to structural modifications of the fibers. We assume that those alterations of surface and texture are in favour of associated bacteria and thus contribute to waste reduction and larval growth. Our results show that co-conversion of DM with soybean residues by Hermetia illucens could play a vital role in DM management.

Influence of torrefaction on the characteristics and pyrolysis behavior of cellulose

The influence of torrefaction on cellulose structural characteristics and the resulting pyrolysis behavior was investigated in this study. Torrefaction reduced O/C ratio in cellulose and increased its high heating value. The crystallinity of cellulose increased slightly first and then decreased sharply with the increase of torrefaction temperature, which could be ascribed to competitive degradation between crystalline region and amorphous region, as indicated by 13C CP/MAS NMR analysis. Besides, the cleavage of β-1,4-glycosidic bond and the dehydration of hydroxyl were the major reactions occurring in torrefaction. Avrami-Erofeev model was found to be the most suitable kinetic reaction model for explaining the thermogravimetric weight loss during the pyrolysis of the raw and torrefied cellulose. A distributed activation energy model based on Avrami-Erofeev model was subsequently used to reveal the pyrolytic kinetics. It was found that the changes in cellulose structure influenced the kinetic parameters greatly. Torrefaction also changed pyrolytic product distribution. The yields of furfural, alicyclic ketones and anhydrosugars increased while that of 5-hydroxymethyl-furfural decreased as torrefaction temperature increased.

Preventive Measurement and Online Insulation Evaluation of Power Transformer

Cellulose based non conducting materials and mineral oils have widely been used in liquid filled transformers. Environmental and fire-safety concerns have accelerated the use of Natural Esters (NE) as a sustainable alternative to mineral oil. To ensure a safe and long-term operation of the vegetable oil filled transformers, it is need to clarify the knowledge gaps with respect to the ageing of vegetable oil impregnated cellulose and insulation diagnostic methods. The condition monitoring of mineral oil filled transformers has been well characterised, due to the numerous laboratory and field studies conducted during the past several decades. The application of these available condition monitoring techniques for NE filled transformers is yet to be validated as the use of NE for power transformers is in the tested stage. In this paper the performance of NE as insulation in transformers by evaluating the ageing of NE impregnated cellulose pressboard is presented. For this purpose, an accelerated ageing experiment has been carried out in sealed tubes at 120 ⁰C. The ageing of oil impregnated pressboard has been characterised by decrease in the degree of polymerisation (DP) of pressboard, and the formation of both 2-furfuraldehyde and dissolved carbon dioxide (CO2) in the oil. The structural changes of cellulose have been supported by fuzzy logic algorithm. Moreover, the results have been compared with cellulose insulation samples aged under similar conditions in conventional mineral oil.

The First Space-Related Study of a Kombucha Multimicrobial Cellulose-Forming Community: Preparatory Laboratory Experiments.

Biofilm-forming microbial communities are known as the most robust assemblages that can survive in harsh environments. Biofilm-associated microorganisms display greatly increased resistance to physical and chemical adverse conditions, and they are expected to be the first form of life on Earth or anywhere else. Biological molecules synthesized by biofilm -protected microbiomes may serve as markers of the nucleoprotein life. We offer a new experimental model, a kombucha multimicrobial culture (KMC), to assess a structural integrity of a widespread microbial polymer - cellulose - as a biosignature of bacteria-producers for the multipurpose international project "BIOlogical and Mars Experiment (BIOMEX)", which aims to study the vitality of pro- and eukaryotic organisms and the stability of organic biomolecules in contact with minerals to analyze the detectability of life markers in the context of a planetary background. In this study, we aimed to substantiate the detectability of mineralized cellulose with spectroscopy and to study the KMC macrocolony phenotype stability under adverse conditions (UV, excess of inorganics etc.). Cellulose matrix of the KMC macrocolony has been mineralized in the mineral-water interface under assistance of KMC-members. Effect of bioleached ions on the cellulose matrix has been visible, and the FT-IR spectrum proved changes in cellulose structure. However, the specific cellulose band vibration, confirming the presence of β(1,4)-linkages between monomers, has not been quenched by secondary minerals formed on the surface of pellicle. The cellulose-based KMC macrocolony phenotype was in a dependence on extracellular matrix components (ionome, viriome, extracellular membrane vesicles), which provided its integrity and rigidness in a certain extent under impact of stressful factors.

Understanding the ageing aspects of natural ester based insulation liquid in power transformer

Cellulose based insulation materials and mineral oils have widely been used in liquid filled transformers. Environmental and fire-safety concerns have accelerated the use of Natural Esters (NE) as a sustainable alternative to mineral oil. There is a rapid growth of their application for distribution level transformers. To ensure a safe and long-term operation of the vegetable oil filled transformers, it is necessary to clarify the knowledge gaps with respect to the ageing of vegetable oil impregnated cellulose and insulation diagnostic methods. The condition monitoring of mineral oil filled transformers has been well characterised, due to the numerous laboratory and field studies conducted during the past several decades. The application of these available condition monitoring techniques for NE filled transformers is yet to be validated as the use of NE for power transformers is in the evaluation stage. In this paper the performance of NE as insulation in transformers by evaluating the ageing of NE impregnated cellulose pressboard is presented. For this purpose, an accelerated ageing experiment has been carried out in sealed tubes at 120 °C. The ageing of oil impregnated pressboard has been characterised by decrease in the degree of polymerisation (DP) of pressboard, and the formation of both 2-furfuraldehyde and dissolved carbon dioxide (CO2) in the oil. The structural changes of cellulose have been supported by Fourier Transform Infrared (FTIR) spectra. Moreover, the results have been compared with cellulose insulation samples aged under similar conditions in conventional mineral oil. Acidity value, dissipation factor and viscosity measurements have been used to compare the stability of NE in a transformer operating environment to mineral oil.

Quantitative (13)C MultiCP solid-state NMR as a tool for evaluation of cellulose crystallinity index measured directly inside sugarcane biomass.

BackgroundThe crystallinity index (CI) is often associated with changes in cellulose structure after biological and physicochemical pretreatments. While some results obtained with lignocellulosic biomass demonstrate a progressive increase in the CI as a function of pretreatments, it is also shown that the CI can significantly vary depending on the choice of the measurement method. Besides, the influence of the CI on the recalcitrance of biomass has been controversial for a long time, but the most recent results tend to point out that the efficiency of pretreatments in reducing the recalcitrance is not clearly correlated with the decrease of the CI. Much of this controversy is somewhat associated with the inability to distinguish between the CI of the cellulose inside the biomass and the CI of the full biomass, which contains other amorphous components such as lignin and hemicellulose.ResultsCross polarization by multiple contact periods (Multi-CP) method was used to obtain quantitative 13C solid-state nuclear magnetic resonance (ssNMR) spectra of sugarcane bagasse biomass submitted to two-step pretreatments and/or enzymatic hydrolysis. By comparing the dipolar filtered Multi-CP 13C NMR spectra of untreated bagasse samples with those of samples submitted to acid pretreatment, we show that a 1% H2SO4-assisted pretreatment was very effective in removing practically all the hemicellulose signals. This led us to propose a spectral editing procedure based on the subtraction of MultiCP spectra of acid-treated biomass from that of the extracted lignin, to obtain a virtually pure cellulose spectrum. Based on this idea, we were able to evaluate the CI of the native cellulose inside the sugarcane bagasse biomass.ConclusionsThe results show the validity of the proposed method as a tool for evaluating the variations in the CI of the cellulose inside biomasses of similar kinds. Despite a clear increase in the CI of biomass as measured by X-ray diffraction, no significant variations were observed in the CI of the cellulose inside the biomass after a particular 1% H2SO4/0.25–4% NaOH chemical-assisted pretreatments. The CI of cellulose inside the biomass solid fraction that remained after the enzymatic hydrolysis was also evaluated. The results show a slight increase in crystallinity.

Effects of Delignification on Crystalline Cellulose in Lignocellulose Biomass Characterized by Vibrational Sum Frequency Generation Spectroscopy and X-ray Diffraction

Delignification, a common practice in the pulping industry, has been proposed and explored as a means to selectively remove lignin from lignocellulosic biomass and, thus, increase enzyme accessibility for cellulose hydrolysis. However, without knowing structural changes of cellulose in biomass, it is difficult to fully understand the effects of the delignification process on cellulose hydrolysis. In this study, the amount and aggregation of crystalline cellulose in hardwood biomass delignified using oxygen and sodium chlorite as reactive agents were examined with vibrational sum frequency generation (SFG) spectroscopy and X-ray diffraction (XRD). The results indicated that the amount of crystalline cellulose and the XRD crystallite size increased with both oxygen and chlorite delignification processes. In addition, the “α-cellulose equivalent” fraction estimated by SFG spectroscopy increased greater than glucan amount with the delignification process. Changes in crystal size might be due to the aggregation of cellulose crystals, along with the increase in crystalline cellulose amount.