Cellulose isolation

Purified, crystalline cellulose isolated from secondary walls appears to contain minor proportions of D-glycosyl residues other than D-glucosyl, in hemicellulosic chains of paracrystalline regions within the microfibril structure.223 These hemicelluloses contain xylose and probably lesser proportions of arabinose, mannose, and fucose. It was conceived... 

Cellulose is one of the most widely distributed natural polymers, since it is one of the principal components of vegetable tissue. It always occurs in nature in the form of fibres varying from the knap-like fibres covering cotton seeds, to the woody substance of trees. The name cellulose is used both for cellulose isolated from the plant, and thus a chemical compound, and for cellulose in situ in the form normally occurring in the plant. In the second case cellulose together with hemicelluloses and lignin form the main constituents of the plant. 

More important, from the practical point of view, was the extensive work of Psenica [8] devoted to the question of nitrating fibres of cellulose isolated from nettle, fibres of little interest for the textile industry. By nitrating nettle cellulose in the same way as cotton, nitrocellulose containing 13.4% of nitrogen was produced, of adequate chemical stability provided the cellulose was well purified before the nitration. 

The fact that glucomannan is obtained from GDP-D-mannose as substrate suggests that the particulate enzyme contains an epimerase which converts GDP-D-mannose to GDP-D-glucose. However, such an epimerase has not been observed. In this connection cellulose isolated from wood contains a considerable amount of D-mannose. 

Cross and Bevan Cellulose- An impure cellulose isolated from the complex it forms with lignin, in materials such as wood straw. The method of isolation is described by Doree (Ref 1) Ott (Ref 2). Cross Bevan cellulose contains both furfural-yielding substances (pentosans), and hexosans of the mannan type. It retains, in the case of coniferous woods, 40-60% of the total furfural-yielding substances in the original wood, and about 55 66% iq the case of hard woods. 

By the treatment of Cross and Bevan cellulose, or cellulose isolated by some other purification procedure, with 17.5% sodium hydroxide under carefully controlled conditions, and then carefully washing, a fibrous product is obtained which is termed a-cellulose. As previously indicated, Cross and Bevan used this procedure for determining the purity of cellulose preparations. This product upon further similar treatments continues to lose weight, indicating the empirical nature of the treatment and terminology. Upon acidif3ring the alkaline filtrate a precipitate is formed. This fraction is known as /3-celIulose. The alkali-soluble extract which remains in solution after acidification of the solution is termed -y-cellulose. Since continued extraction of a-cellulose with caustic causes the formation of increasing amounts of /3-and y-cellulose, the incomplete removal of these fractions in one operation or the conversion of o-cellulose into 0- and -y-cellulose is indicated. In practice... 

Copper and zinc were also bound. The metals were released by hemicellulase and peptidase action. These hemi-cellulose isolates included considerable amounts of digestible protein and consequently do not conform to the concept of fiber as a non-digestible residue. However, close associations of fiber and protein do occur and their implications for fiber behavior must be recognized Mod et al (15) assign a role to fiber bound protein in binding of metals. Thompson and Weber (16) observed that ion exchange properties of dietary fiber depended upon method of preparation. 

Furthermore, Hachiga and Hayashi (11) investigated the degradation of cellulose isolated from different seaweeds by T. viride cellulase... 

The chemical formula of cellulose, isolated from plant cell walls, is determined by Anselme Payen, a French chemist... 

Table 2 Average Degrees of Polymerization for Cellulose Isolated from a Variety of Sourees Cellulose source DP ...

Table 2.3 Characteristics of the cellulose isolated from Dendrocalamus strictus (DCS), Lantana camara (LC), and Parthenium hysterophorus (PH)...

Table 2.6 Reaction parameters for hydroxypropylation of a-cellulose isolated from Dendroca-...

SCHEME 3.2 Reactions showing alkaline pre-treatment process during cellulose isolation... 

There are undoubtedly numerous chemical pre-treatment methods used in the literature for the isolation of cellulose fibers from different lignocellulosic sources. The choice of these chemical treatment methods is influenced by the properties of lignocellulosic materials such as their chemical composition, internal fiber stmc-ture, microfibril structure, microfibril angle, cell dimensions and the defects which are in return influenced by the type and the sources of the lignocellulosic materials (Siqueira et al., 2010). The intended use of the cellulosic fiber product could also have an influence on the choice of chemical treatment method (Dufresne et al., 2008). The schematic diagram showing different pre-treatment methods during cellulose isolation are depicted in (Fig 3.11). 

FIGURE 3.14 The 13C CPMAS spectrum of cellulose isolated from raw (Foston and... 

Similarities have been demonstrated in the ultrastructure of xerogels of cellulose isolated from Japanese pears and of chitin. ... 

Keywords Cellulose, isolation, ncmofiber, ncmocrystal, chcffacterization, ncmocomposite... 

The MALDI-MS procedures described here, which were developed for wood and pulp hemicelluloses, should also be suitable for characterizing hemi-celluloses isolated from annual plant materials and such studies are currently being carried out in our laboratory. 

Figure 1. CP/MAS C-NMR spectra recorded at 7.05 T on cellulose / isolated from different sources and one hr aft pulp. From bottom to top the sources are Valonia, Cladophora, Halocynthia, and cotton linters. The top spectrum is bleached birch krcft pulp that contains hemicelluloses. (Reproduced with permission from reference 16. Copyright 1999).

Table I. Fitting the C4 region of spectra recorded at 7.05 T on cellulose isolated from cotton linters...

Macromolecules of natural cellulose various origins may include 2000 to 30,000 elementary units. During process of cellulose isolation from plant materials and cellulose modification, a partial depotymerization of the macromolecules is observed. 

Pereira ALS, do Nacimento DM, Souza FiUio MM, Morais IPS, Uasconcelos NF, Feitosa JPA, Brigida Al, Rosa MF (2014) Improvement of polyvinyl alcohol properties by adding nanocrystalline cellulose isolated from banana pseudostems. Caibohyd Polym 112 165-172... 

Trache D, Donnot A, Khimeche K, Benelmir R, Brosee N (2014) Physico-chemieal properties and thermal stability of microcrystalline cellulose isolated from Alfa fibres. Carbohyd Polym 104 223-230... 

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