Cellulose, Starch, and Chitin

You might have used iodine to detect the presence of starch. The iodine molecule (1 and other forms such as 13 and I ) can fit in the helix of amylose. This complex (of iodine and starch) exhibits the characteristic deep purplish blue color. [The website of Dr. S. Immel of Darmstadt Technical University (http //caramel.oc.chemie. tu-darmstadt.de/ lemmi/graphics/polysaccharides.html) gives a variety of pictures of models of cellulose, amylose, and others as well as the interaction between them and water molecules and iodine]. 

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The addition (loading) of nanomaterials to polymers leads to significant changes in their physical, mechanical as well as thermal properties. Due to the hierarchical stmcture and semicrystalline nature of polysaccharides (cellulose, starch, and chitin), nanoparticles can be extracted from these naturally occurring polymers (Dufresne 2010). 

Well established names such as cellulose, starch, inulin, chitin, amylose and amylopectin are retained. Carrageenan and laminaran are now often used rather than the older names ending in -in . 

There are several kinds of natural biodegradable polymers in addition to bacterial PHAs, such as proteins, nucleic acids and polysaccharides. Among them, particulary important polymers such as industrial materials are polysaccharides, such as starch, cellulose, chitin and chitosan. The solid-state structure and properties of starch and amylose [127], cellulose [128] and chitin... 

Monosaccharides are constituents of such widely abundant biomolecules as starch, cellulose, pectin and chitin. They are units of the sugar chains of glycoproteins and other important glycoconjugates in bacteria and in eukaryotic... 

Doner, L. W. (1988). High-performance thin-layer chromatography of starch, cellulose, xylan, and chitin hydrolyzates. Methods Enzymol. 160 176-180. 

Thermodynamic characteristics and physical-chemical properties of natural polymers (cellulose, starch, agar, chitin, pectin and inulin), their water mixtures and some biologically active substances extracted from vegetable substances using carbon dioxide in a supercritical state are reviewed. In addition, several aspects of practical application of thermodynamic characteristics of biologically active substances are demonstrated. 

The interest on natural-based materials for reinforcement of polymer matrices has been increased in recent years. In this section, we focus the attention on the reinforcement effect of cellulose, starch or chitin fillers on the thermal properties of PU-based materials. These nanofillers can be obtained from natural and renewable sources and can be processed in several ways presenting different morphologies, such as nanowhiskers, nanofibers, or nanoparticles. In particular, cellulose can be processed by hydrolysis reaction of different cellulose sources in order to obtain cellulose nanocrystals (CNC) [72]. In Figure 7.3, the CNC structure is shown. The CNC present a diameter of about 19 nm. [72]. 

The most widespread natural polymers are polysaccharides such as cellulose and starch and chitin, but also lignin, proteins and others find several applications. Most polysaccharides are composed of five or six-membered rings, usually with two or three hydrolysis attached, respectively. Chemically, they are hemiacetals with ether linkages joining the monomeric units. Cellulose in particular is enjoying a worldwide consumption volume for paper and cardboard manufacturing comparable to the overall synthetic polymeric materials that is above 205 Mtons [18]. 

Following the method developed by Davis and Flitsch [90] using a mixture of sodium hypochlorite, sodium bromide and 2,2,6,6-tetramethyl-l-piperidine oxoammonium radical, the TEMPO-NaBr-NaClO system was applied to a wealth of products including many polysaccharides. This method was first proposed for water-soluble polysaccharides [3, 5-8], namely starch, inulin, amylodextrin, pullulan, alternan, amylopectin, chitosan, galactomannan, and later extended to water-insoluble products [7-12], such as cellulose, amylose, and chitin. 

The natural polymers in common use are cellulose, lignin, chitin, starch and guar gum. The natural products had complete... 

More complex polysaccharides play important roles in connective tissues and elsewhere. For example, hyaluronic acid is universally present in connective tissues of animals, as well as in their vitreous and synovial fluids. It helps to provide the fluids present in joints with shock-absorbing and lubricating properties. Unlike cellulose, chitin, starch, and glycogen, hyaluronic acid contains two different monomers glucose and N-acetylglucosamine alternate in the structure. Thus, hyaluronic acid is a regular alternating copolymer ABABABA —... 

Many polysaccharides besides starch and cellulose are important components of animal tissues, or play a vital role in biochemical processes. One example is chitin, a celluloselike material that is the structural component of the hard shells of insects and crustaceans. The difference between chitin and cellulose is that instead of being a polymer of glucose, chitin is a polymer of 2-deoxy-2-A-ethanamidoglucose (M-acetyl-jS-D-glucosamine) ... 

Carbohydrates form the major structural components of the cell walls. The most common form is cellulose which makes up over 30 per cent of the dry weight of wood. Other structural forms are hemicellulose (a mixed polymer of hexose and pentose sugars), pectins and chitin. Apart from contributing to the structure, some polymers also act as energy storage materials in living systems. Glycogen and starch form the major carbohydrate stores of animals and plants, respectively. Carbohydrate structure, like that of nucleic acids and proteins, is complex, and various levels of structure can be identified. 

The reaction appears to be well suited for selective conversion of biomass carbohydrates into their corresponding oxidized derivatives. This system serves to oxidize several polymeric carbohydrates including starches and pullulan.445 49 More recent work has described the TEMPO-catalyzed introduction of carboxyl groups in native cellulose and its different morphological forms,45(M52 cellulose derivatives,453 and the surface of cellulose nanocrystals.454 The related biopolymer, chitin, also is oxidized under these conditions.455... 

As I have already indicated, the polymeric carbohydrate materials available from natural sources include gums, starch and dextrins, cellulose, hemicellulose, chitin, and bacterial polysaccharides. 

Lack of the amine group "NH2 makes chitin almost chemically inactive. In addition, the availability of chitin as the second most abundant material after cellulose allows its use as an excipient in processing solid drug dosage forms. This facilitates its use with other common excipients, namely microcrystalline cellulose (MCC), lactose, starch, and calcium hydrogen phosphate. Consequently, this monograph will focus on chitin applications as a solid dosage form excipient. 

Polysaccharides are the most abundant group of biopolymers on earth, since they make up a large proportion of all plant life, and they also form a major part of many marine and bacterial organisms. The two major plant polysaccharides of interest are cellulose and starch, but chitin, which forms the... 

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