Solution-Based Deconstruction of (Ligno)-Cellulose (original) (raw)

2013

https://doi.org/10.34663/9783945561195-14

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Abstract

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AI

The chapter addresses the challenges of cellulose hydrolysis, emphasizing the importance of understanding cellulose's supramolecular structure. It outlines how cellulose, although recalcitrant in its solid-state, can be effectively deconstructed in solution, thus becoming more reactive. The discussion includes the distinct properties of cellulose, its structural characteristics, and the influences of its composition on the hydrolysis process.

Peer-Reviewed Review Article Cellulose as a Nanostructured Polymer: A Short Review

Bioresources

Cellulose has a complex, multi-level supermolecular architecture. This natural polymer is built from superfine fibrils having diameters in the nano scale, and each such nanofibril contains ordered nanocrystallites and low-ordered nano-domains. In this review, the nano-structure of cellulose and its influence on various properties of the polymer is discussed. In particular, the ability of nano-scale crystallites to undergo lateral co-crystallization and aggregation, as well as to undergo phase transformation through dissolution, alkalization, and chemical modifica-tion of cellulose has been the subject of investigation. The recent investigations pave the way for development of highly reactive cellulosic materials. Methods for preparation nanofibrillated cellulose and free nano-particles are described. Some application areas of the nanostruc-tured and nano-cellulose are discussed.

An Update on Overview of Cellulose, Its Structure and Applications

Cellulose (C 6 H 10 O 5) n is one of the most ubiquitous organic polymers on the planet. It is a significant structural component of the primary cell wall of green plants, various forms of algae and oomycetes. It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1 → 4) linked d-glucose units. There are various extraction procedures for cellulose developed by using different processes like oxidation, etherification and esterification which convert the prepared celluloses in to cellulose derivatives. Since it is a non-toxic, biodegradable polymer with high tensile and compressive strength, it has widespread use in various fields such as nanotechnology, pharmaceutical industry, food industry, cosmetics, textile and paper industry, drug-delivery systems in treating cancer and other diseases. Micro-crystalline cellulose in particular is among the most frequently used cellulose derivatives in the food, cosmetics, pharma industry, etc. and is an important excipient due to its binding and tableting properties, characterized by its plasticity and cohesiveness when wet. Bacterial cellulose's high dispensability, tasteless and odourless nature provides it with lot of industrial applications. Currently, about half of the waste produced in India contains about 50% cellulose which can be used productively. This chapter deals with the chemistry of cellulose, its extraction and its properties which help various industries to make the most of it.

Chemistry of Cellulose

2020

Among the natural organic polymers, cellulose is the most abundant member, which exists as cell wall components of a main plant. It carries immense importance because it is a biodegradable organic resource which is renewable. Due to these, studies on cellulose have been on for over 20 decades, but there is still need for further research to fully elucidate its chemical synthesis, biosynthesis, regiospecific substitution reactions, crystal structure, interrelationships between the structure and function of its derivatives, etc. Specifically, synthesis of cellulose is highly important, but also a severely difficult problem to solve. Enzymatic synthesis of cellulose with the help of cellulase came as a welcome development, however the approach seems not to meet the modern molecular design of function-specific cellulose derivatives. This is because it does not support regiospecific introduction of functional groups into the hydroxyl group of interest in the repeating cellulose pyranose units. The available functional cellulose derivatives include cellulose esters and liquid crystalline ethers, ethers with chiral recognition features, sulfated anticoagulant cellulose, antitumor branched cellulose, etc. [1]. Despite all these, certain areas still remain unclear, such as structure-property relationship, the most actively functional derivatives with respect to the substituted positions (2, 3-or 6-). For molecular design of advanced cellulose based materials, it is pertinent to use an approach which gives room for preparation of cellulose derivatives such that functional groups can be easily incorporated into either of the 2,3,6-hydroxyl groups of the repeating cellulose pyranose units. Cellulose occupies a large percentage (35-50%) of lignocellulosic materials and it has been identified as a potential renewable source of bio-based chemicals and biofuels. Several important industrial fuels and chemicals, such as ketones, carboxylic acids, hydrocarbons, and ethanol can be obtained from the hydrolysis of cellulose followed by fermentation of saccharides [2, 3]. It has been noted however that production of chemical from cellulose is sometimes not cost effective compared to those obtained from petrochemicals and they are sometimes even more expensive than those obtained from other renewable sources, such as starch. This is as a result of the relatively

Conformation effects in the hydrolysis of cellulose

1978

It is proposed that the different conformations of the glycosidic linkages, which are indicated by the Raman spectra of the various polymorphic forms of cellulose, result in differences in their degree of sussceptibility to hydrolysis in acid or enzyme media. The basis for interpretation of structural data on cellulose has been reexamined and the view that anhydrocellobiose is the basic repeat unit, rather than anhydroglucose, has been developed. Crystallographic studies of cellobiose and B-methyl cellobioside suggest that both right and left handed departures from twofold helix conformations can be more stable than structures possessing a twofold screw axis of symmetry. Raman spectral studies further indicate that the glycosidic linkage conformation in B-methylcellobioside is representative of the form dominant in cellulose I, while that in cellobiose is representative of cellulose II. The conformation of the anhydrocellobiose unit represented by B-methylcellobioside and, in particular, participation of the primary hydroxyl group in a bifurcated intramolecular hydrogen bond, provide a basis for explaining the high resistance of native crystalline celluloses to hydrolytic agents. This paper has been submitted for publication in Advances in Chemistry.

Conformational Effects in the Hydrolysis of Cellulose

Advances in chemistry series, 1979

It is proposed that the different conformations of the glycosidic linkages, which are indicated by the Raman spectra of the various polymorphic forms of cellulose, result in differences in their degree of sussceptibility to hydrolysis in acid or enzyme media. The basis for interpretation of structural data on cellulose has been reexamined and the view that anhydrocellobiose is the basic repeat unit, rather than anhydroglucose, has been developed. Crystallographic studies of cellobiose and B-methyl cellobioside suggest that both right and left handed departures from twofold helix conformations can be more stable than structures possessing a twofold screw axis of symmetry. Raman spectral studies further indicate that the glycosidic linkage conformation in B-methylcellobioside is representative of the form dominant in cellulose I, while that in cellobiose is representative of cellulose II. The conformation of the anhydrocellobiose unit represented by B-methylcellobioside and, in particular, participation of the primary hydroxyl group in a bifurcated intramolecular hydrogen bond, provide a basis for explaining the high resistance of native crystalline celluloses to hydrolytic agents. This paper has been submitted for publication in Advances in Chemistry.

Dilute acid depolymerization of cellulose in aqueous phase: Experimental evidence of the significant presence of soluble oligomeric intermediates

The Canadian Journal of Chemical Engineering, 1986

The objective of this investigation is to show that rapid hydrolysis can be achieved by passage of aqueous cellulosic suspensions (2-10% solids) through capillaries followed by sudden decompression and post-treatment under dilutes acid conditions. Through detailed experimentation within the 200-240°C temperature range and at low sulfuric acid concentrations (0.2-I .O% w/w) it was found that liquefaction of the cellulose proceeds via extensive formation of soluble oligomeric intermediates. A simple kinetic model has been developed to explain the liquefaction-saccharification patterns of the cellulose. The sequence considered is: Cellulose-+ Oligo-derivatives + Glucose + Decomposition products Quantitative values of the rate constants have been determined and a discussion on the selectivity of the overall reaction sequence is presented. L'objectif de ce travail est de montrer que I'hydrolyse de la cellulose peut 6tre effectude par passage rapide de suspensions aqueuses (ayant 2 a 10% de solides) travers de capillaires suivi d'une dtcompression soudaine et post-traitement en prtsence d'acides diluts. Dans la plage de temp6ratures comprise entre 200 et 240°C et B des concentrations d'acide sulfurique de 0.2 a I .O% (base pondtrale) nous avons trouvt que la liqutfaction de la cellulose procbde par voie de formation d'oligombres solubles. Un simple modtle cinttique dtveloppi? afin d'expliquer les profils de liqutfaction-saccharification de la cellulose. La stquence rtactionnelle considtde peut Stre repdsentke par: Cellulose + Oligo-dtrivts + Glucose + Produits de dkcomposition Des valeurs quantitatives des constantes cinttiques ont 6t6 dttermintes. Une discussion sur la stlectivitt de la &action d'hydrolyse est prtsentte.

Controlled Depolymerisation of Cellulose to a Given Degree of Polymerisation

Cellulose Chemistry and Technology, 2016

The degree of polymerization of cellulose is very relevant for physical and chemical properties of highly engineered biomaterials. The ability to control the level of depolymerisation to a final specific value opens new opportunities to design cellulose-based nanostructured materials. In this paper, the controlled hydrolysis of cellulose in 0-96% ethanol environment and with nine chosen acids (pKa -10-4.7) was studied in order to tailor the pretreatment of dissolving and kraft pulps for various applications. The acid hydrolysis of cellulose in aqueous environment decreased the viscosityaveraged degree of polymerisation (DPν) and relative cellulose content. However, the addition of small amounts of ethanol preserved the cellulose content nearly at the original level, while decreasing the DPν. Furthermore, when the ethanol concentration increased, the DPν decreased manifoldly. The treatment with strong mineral acids in ethanol environment decreased the DPν by 75-80%, regardless of the...

The relevance of structural features of cellulose and its interactions to dissolution, regeneration, gelation and plasticization phenomena

Physical chemistry chemical physics : PCCP, 2017

Cellulose is the most abundant polymer and a very important renewable resource. Since cellulose cannot be shaped by melting, a major route for its use for novel materials, new chemical compounds and renewable energy must go via the solution state. Investigations during several decades have led to the identification of several solvents of notably different character. The mechanisms of dissolution in terms of intermolecular interactions have been discussed from early work but, even on fundamental aspects, conflicting and opposite views appear. In view of this, strategies for developing new solvent systems for various applications have remained obscure. There is for example a strong need for using forest products for higher value materials and for environmental and cost reasons to use water-based solvents. Several new water-based solvents have been developed recently but there is no consensus regarding the underlying mechanisms. Here we wish to address the most important mechanisms des...

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Changes of supramolecular cellulose structure

Abstract A newly identified cellulase with a high polysaccharide degrading potential and a processive mode of action, has been evaluated on cellulose fibers. Cellulase Cel9B from Paenibacillus barcinonensis is a modular endoglucanase with the domain structure GH9-CBM3c-Fn3-CBM3b, consisting of a family nine catalytic module GH9, an auxiliary module CBM3c, a fibronectin-like module Fn3, and a functional cellulose binding module CBM3b. The whole cellulase Cel9B (E1) and two truncated forms of the enzyme that consist of the catalytic module linked to the auxiliary module, GH9-CBM3c (E2), and of the cellulose binding module of the enzyme, CBM3b (CBD), were applied to softwood dissolving pulp. The changes in the supramolecular structure and morphology of the fibres after the enzymatic treatment were evaluated by viscosimetry, X-ray diffraction (XRD), thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy (SEM). XRD studies provided the crystallite size, interplanar distances and crystallinity index of the samples before and after the enzymatic treatment. The treatment with cellulases E1 and E2 decreased the degree of polymerization and increased the crystallinity index of the pulp. Both E1 and E2 had a pronounced capacity for removing fuzz and improved the smoothness and surface appearance of the fibers, as shown by SEM. On the other hand, CBD proved to be less effective under the tested conditions. Moreover, the solubility of dissolving pulp in alkaline solutions has been evaluated as an indirect measure of cellulose accessibility. A notable enhancement in alkaline solubility of the samples treated with the cellulases was observed.

Tailoring the Degree of Polymerization of Low Molecular Weight Cellulose

2011

The degradation of cellulose to lmw samples with DP w varying from 15 to 130 is investigated. Cellulose samples prepared from the hydrolysis of regenerated cellulose fibers in dilute HCl possess DP w ¼ 50. Applying homogenous degradation of microcrystalline cellulose in H 3 PO 4 at RT for 3 weeks, samples with DP w ¼ 35 and a PDI of 1.58 are obtained. Decreasing the hydrolysis temperature to 8 8C results in lmw cellulose with DP w > 70. Fractionation in DMA/LiCl provides samples with DP w ¼ 12 to 130, together with a narrow molecular weight distribution. Detailed structural analysis by 2D NMR spectroscopy reveals that the prepared lmw celluloses are suitable as mimics for cellulose.

Cellulose as a nanostructured polymer: A short review

Bioresources

Cellulose has a complex, multi-level supermolecular architecture. This natural polymer is built from superfine fibrils having diameters in the nano scale, and each such nanofibril contains ordered nanocrystallites and low-ordered nano-domains. In this review, the nano-structure of cellulose and its influence on various properties of the polymer is discussed. In particular, the ability of nano-scale crystallites to undergo lateral co-crystallization and aggregation, as well as to undergo phase transformation through dissolution, alkalization, and chemical modifica-tion of cellulose has been the subject of investigation. The recent investigations pave the way for development of highly reactive cellulosic materials. Methods for preparation nanofibrillated cellulose and free nano-particles are described. Some application areas of the nanostruc-tured and nano-cellulose are discussed.

Review Analyzing cellulose degree of polymerization and its relevancy to cellulosic ethanol

Biofuels Bioproducts Biorefining , 2011

The degree of polymerization (DP) of cellulose in cellulosic biomass and how it changes during enzymatic and chemical transformations has remained a fundamental property of interest to numerous researchers. Currently, with increased interest in cellulosic biofuels, more attention is being focused on determining changes in cellulose DP before and during pre-treatment, as well as the effect of DP on enzymatic deconstruction of cellulose to glucose. Different sources of celluloses from woody and non-woody biomass have been isolated and the DP has been frequently examined as a key parameter contributing to efficient biomass deconstruction. The isolation and derivatization/dissolution of cellulose are crucial steps in determining cellulose DP. This review summarizes approaches to measuring DP developed over the past six decades and highlights opportunities for further mprovements.

The relationship between intramolecular hydrogen bonds and certain physical properties of regioselectively substituted cellulose derivatives

Journal of Polymer Science Part B: Polymer Physics, 1997

This article tries to provide some direct evidence about the relationship between the intramolecular hydrogen bonds in cellulose and their corresponding effect on physical properties. The formation of intramolecular hydrogen bonds has been proved to contribute directly to certain physical properties of cellulose, such as its solubility in solvents having different polarities, the relative reactivities of the hydroxyls in a repeating unit and its crystallinity, using a 6-O-methylcellulose (6MC) film that was known 1 to have intramolecular hydrogen bonds. The excellent solubility of 6MC when compared with other cellulose derivatives indicated a lack of interchain hydrogen bonds. A comparison of the relative reactivities between the C-2 and C-3 position hydroxyls in 6MC also indicates that intramolecular hydrogen bonds once formed in 6MC films are possibly maintained even after dissolution in solvents. In addition, the poor crystallinity exhibited by 6MC supports the idea that crystallization in cellulosics may be dependent more upon preferencial interchain hydrogen bonding at the C-6 position hydroxyls than upon a uniform structure such as that found in 6MC, where every structural unit is completely and regioselectively substituted, distinguishing it from other synthetic polymers such as polyolefins and polyesters. ᭧ 1997

High yield production of microcrystalline cellulose by a thermo-mechano-solvolytic treatment

The Canadian Journal of Chemical Engineering, 1990

By thermally treating a commercial cellulose in ethylene glycol, celluloses of controlled low degree of polymerization, DP,. = lo00 to 70, can be derived. Two general behaviors are observed in the range studied. At first, the depolymerization reaction is predominant down to a DP equal to 130. Beyond this level. the depolymerization process leads to extensive solubilization of the cellulose. The treated celluloses have been analyzed by X-ray diffraction, FTIR, TGA, elemental analysis and enzymatic hydrolysis. No chemical change of the cellulose could explain the two different behaviors. A physical modification in the form of depolymerization and destructuration is suspected.

Glucose, not cellobiose, is the repeating unit of cellulose and why that is important

Cellulose, 2017

and Molecular Biology, the repeating unit of cellulose is often said to be cellobiose instead of glucose. This review covers arguments regarding the repeating unit in cellulose molecules and crystals based on biosynthesis, shape, crystallographic symmetry, and linkage position. It is concluded that there is no good reason to disagree with the official nomenclature. Statements that cellobiose is the repeating unit add confusion and limit thinking on the range of possible shapes of cellulose. Other frequent flaws in drawings with cellobiose as the repeating unit include incorporation of O-1 as the linkage oxygen atom instead of O-4 (the O-1 hydroxyl is the leaving group in glycoside synthesis). Also, n often erroneously represents the number of cellobiose units when n should denote the degree of polymerization i.e., the number of glucose residues in the polysaccharide.