Carbohydrate polymers Cellulose

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

The popular polyethylene glycol (PEG) treatment forms hydrogen bonds mainly with the carbohydrate polymers. In archaeological wood (10), the carbohydrate polymers, cellulose and hemicellulose, may no longer be pres-... 

Polysaccharide synthesis is under enzymatic control, but does not occur from a template as in protein synthesis. For this reason, each molecule of a particular polysaccharide will have its own unique molecular weight. The molecular weight of a carbohydrate polymer is usually expressed as an average. Starch or cellulose chains, for example, may vary by several hundred thousand in their molecular weights between individual molecules. For an excellent review of carbohydrate chemistry, see Binkley (1988). 

Several anionic carbohydrate polymers (e.g., carboxymethyl cellulose, xanthomonas campestris polysaccharide, cellulose sulfate ester, etc.) do not adsorb from fresh water solutions, but their adsorption in saline solutions plays an... 

In the present work, we extend the method to compensate for the hydrogen bonds present in carbohydrates. The hydroxylated character of carbohydrate polymers influences between-chain interactions through networks of hydrogen bonds that occur during crystallization. Frequently, several possible attractive interactions exist that lead to different packing arrangements, and several allomorphic crystalline forms have been observed for polysaccharides such as cellulose, chitin, mannan and amylose. The situation is even more complex when water or other guest molecules are present in the crystalline domains. Another complication is that polysaccharide polymorphism includes different helix shapes as well. 

BakeUte Polymer produced by the condensation of phenol and formaldehyde, cellulose Naturally occurring carbohydrate polymer, elastomer Rubber. 

Carbohydrates are the most abundant biomolecules on Earth. Each year, photosynthesis converts more than 100 billion metric tons of C02 and H20 into cellulose and other plant products. Certain carbohydrates (sugar and starch) are a dietary staple in most parts of the world, and the oxidation of carbohydrates is the central energy-yielding pathway in most nonphotosynthetic cells. Insoluble carbohydrate polymers serve as structural and protective elements in the cell walls of bacteria and plants and in the connective tissues of animals. Other carbohydrate polymers lubricate skeletal joints and participate in recognition and adhesion between cells. More complex carbohydrate polymers covalently... 

Fig. 2a. Examples of carbohydrate polymers with interunit and branch position differences (a) cellulose (b) flaxseed gum ...

One of the important fields where carbohydrate polymer/inorganic hybrids may be successfully applied is bioactive materials, e.g., artificial bones expedient for surgery to accelerate the recovery of living bones. There has been increasing interest in hydroxyapatite (HAp) deposition onto the matrix surface of cellulose or related polysaccharide. HAp is a form of calcium phosphate, a main constituent of the inorganic phase of human bone. This kind of study is also a step on the way to exploitation of new biomimetic mineralization methods. 

Kennedy, J. F., Melo, E. H. M., Crescenzi, V., Dentini, M., and Matricardi, P. (1992). A rapid quantitative determination of pectin and carboxymethyl cellulose in solution using poly(hexamethylenebiguanidinium) chloride. Carbohydr. Polym. 17 199-203. 

Shomer, I., Frenkel, H., and Polinger, C. (1991). The existence of a diffuse electric double layer at cellulose fibril surfaces and its role in the swelling mechanism of parenchyma plant cell walls. Carbohydr. Polym. 16 199-210. 

CARBOHYDRATES ARE IMPORTANT, naturally occurring organic compounds. They include simple sugars, or monosaccharides, such as glucose and fructose, and polysaccharides, such as starch and cellulose, which are more complex compounds composed of a number of sugar units. Carbohydrates are one of the initial products of photosynthesis. As such, they serve as the molecules that store the sun s energy for later use in metabolism. In addition, carbohydrate polymers are structural materials used by plants and animals. Even our genetic material, DNA, contains carbohydrate units as part of its polymeric backbone. 

Lignocellulose denotes the mixture of the carbohydrate biopolymers cellulose and hemicellulose with the aromatic polymer lignin that is found in plants. Wooden raw materials consist mainly of cellulose (30-50 wt%), hemicellulose (10-40 wt%), and lignin (15-30 wt%). As the structure of cellulose (C6 carbohydrates) and hemicellulose (C5 carbohydrates) is quite similar, they will be discussed together in Section 2.2.2.1.1, followed by lignin, which has a very different composition (Section 2.2.2.1.2). 

Carbohydrate polymers are available in large quantities from both plant and animal sources. These include cellulose and hemicellulose from woody plants,... 

The trick, of course, is to find a chemical compound that can be reacted readily with the carbohydrate polymer to give the desired reactive moities along the backbone of the carbohydrate polymer. Here, the adhesives chemist will have to borrow from and extend the work that has been and is now being done on the formation of modified starches 62), cellulosics (48-51,63,64), and textiles. Professor Narayan of Purdue University illustrates the potential adhesive applications of grafted cellulosic polymers in Chapter 24. 

Polymeric carbohydrates of an undetermined degree of polymerization have also been used to modify synthetic adhesive resins. In particular, cellulosic papermill sludges have been used to modify PF and UF resins (127). A carbohydrate polymer was reported to be an excellent extender and modifier for polyvinyl alcohol adhesives (128). 

Its origin, development, morphology, chemistry, purification, and utilization have been discussed by many authors [2-12]. The chemistry, structure, and reaction characteristics of cellulose, the carbohydrate polymer that forms the fiber, are thoroughly treated in a number of excellent works [8,9,12-19]. This book is intended to provide an overview of the current state of knowledge of the cotton fiber. Much of the information reported here is taken from the references cited at the end of the book, which should be consulted for a more in-depth treatment. 

Arvanitoyannis, I., and Biliaderis, C.G. (1999). Physical properties of polyol-plasticized edible blends made of methyl cellulose and soluble starch. Carbohydrate Polymers. 38(1), 47-58. 

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