Polysaccharides, cellulosics

Plant stmctural material is the polysaccharide cellulose, which is a linear P (1 — 4) linked polymer. Some stmctural polysaccharides iacorporate nitrogen iato thek molecular stmcture an example is chitin, the material which comprises the hard exoskeletons of kisects and cmstaceans. Chitki is a cellulose derivative whereki the OH at C-2 is replaced by an acetylated amino group (—NHCOCH ). Microbial polysaccharides, of which the capsular or extracellular (exopolysaccharides) are probably the most important class, show more diversity both ki monomer units and the nature of thek linkages. 

The structural polysaccharides have properties that are dramatically different from those of the storage polysaccharides, even though the compositions of these two classes are similar. The structural polysaccharide cellulose is the most... 

Methylcellulose and carboxymethylcellulose are forms of the familiar polysaccharide cellulose that have been treated to make them more soluble in water. Cellulose is a long chain made of the sugar glucose. The long chains mix with water to create a thick syrup or gel. 

Plant cell walls provide the obvious functions of stmctural support and integrity and can vary tremendously in size, shape, composition and stmcture depending on cell type, age and function within the plant body. Despite this diversity, plant cell walls are composed of only three major classes of polysaccharides cellulose, hemicellulose and pectins. Pectins, or polyuronides, are imbedded throughout the cell wall matrix and are particularly abundant in the middle lamella region. Pectins generally account for 10-30% of the cell wall dry weight and... 

Polysaccharides Cellulose-Based Fluid Loss Additives... 

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... 

The FP cellulose per unit (ml) volume and enzyme yield per unit (g) cellulose or substrate obtained on wheat straw, wood, and CTMP in SSF were higher than those obtained in LSF on wheat straw and wood (Tables I, II, and III). And wheat straw proved to be a better substrate than wood for cellulose production in SSF. This could be attributed to the polysaccharides (cellulose and hemicelluloses) of wheat straw being more readily available for the organism s growth and cellulose synthesis than those of wood. The hemicelluloses and cellulose were presumably not as available in wood, because of its high lignin content and high cellulose crystallinity, as in wheat straw. 

Pleurotus sajor-caju utilizes polysaccharides (cellulose and hemicelluloses) from various agricultural residues to produce mushrooms for human consumption throughout the world (5). It is also known to degrade lignin (6,7). 

Fillers are relatively inert materials that usually add bulk but when well chosen, they can enhance physical and chemical properties. Many natural and synthetic materials are used as fillers today. These include polysaccharides (cellulosics), lignin, carbon-based materials, glass, and other inorganic materials. 

Plants and animals synthesize a number of polymers (e.g., polysaccharides, proteins, nucleic acids) by reactions that almost always require a catalyst. The catalysts present in living systems are usually proteins and are called enzymes. Reactions catalyzed by enzymes are called enzymatic reactions, polymerizations catalyzed by enzymes are enzymatic polymerizations. Humans benefit from naturally occurring polymers in many ways. Our plant and animal foodstuffs consist of these polymers as well as nonpolymeric materials (e.g., sugar, vitamins, minerals). We use the polysaccharide cellulose (wood) to build homes and other structures and to produce paper. 

The important difference between a and 3 glycosidic bonds can be seen in the digestibility of the major plant polysaccharides cellulose and starch. 

Figure 2. The structure of the polysaccharides cellulose, amylose, starch and dextran.

The monosaccharide D-( + )-glucose, an aldohexose, is formed by plants in photosynthesis and is converted to the polysaccharides cellulose and starch. Simple saccharides are called sugars. Polysaccharides are hydrolyzable to monosaccharides e.g., a mol of trisaccharide gives 3 mol of monosaccharides. 

Problem 22.36 Cellobiose, isolated from the polysaccharide cellulose, has the same chemistry as maltose except that it is hydrolyzed by emulsin. Give the structure of this disaccharide. ... 

Maltose is hydrolyzed by the enzyme maltase (specific for a-glycosidic linkage) to two units of glucose, but for the hydrolysis of cellobiose the enzyme emulsin (specific for (3-glycosidic linkage) is necessary. While maltose is the building block of the polysaccharide starch, cellobiose is the building block of another polysaccharide, cellulose. 

Considering the close resemblance in general structure and food-reserve function of these polysaccharides, a certain similarity in properties might be expected, and this similarity will be discussed in later Sections. Also, the parent polysaccharides cellulose, mannan, and esparto xylan are all intrinsically water-insoluble the progressive introduction of the monosaccharide and disaccharide stubs, if... 

Cotton, by contrast, is made of the polysaccharide cellulose, which has many water-attracting polar hydroxyl groups. Cotton, therefore, will soak up water much more readily than will silk. 

The fibrous tissue in the cell walls of plants contains the polysaccharide cellulose, which consists of long chains of glucose units, each of which is connected by a /3-glucoside link to the C4 hydroxyl of another glucose as in the... 

It is well known that polysaccharide cellulose is - in general - a very important and fascinating biopolymer and an almost inexhaustible and sustainable polymeric raw material. The trend towards renewable resources and the tailoring of innovative products for science, medicine, and technology has led to a global renaissance of interdisciplinary cellulose research and the use of this abundant organic polymer over the last decade [1]. 

As the most important skeletal component in plants and also a substance produced by certain bacteria, polysaccharide cellulose is an almost inexhaustible polymeric raw material with a fascinating structure and interesting properties. The fusion of both carbohydrate and polymer chemistry in a macromolecule biosynthetically composed of repeating glucose units generates surprising specificity and impressively diverse supramolecular/morpho-logical structures, reactivities, and functions. 

The cell wall surrounding a plant cell is made up of the polysaccharide cellulose. In woody plants, the phenolic polymer called lignin gives the cell wall additional strength and rigidity. 

The polysaccharides cellulose and hemicellulose are two major components of lignocellulosic biomass and form an abundant, non-edible and renewable source of carbohydrates. Other sources include starch, chitin, inulin and smaller... 

Figure 9.25 Chemical structure of the polysaccharide cellulose, composed of long linear chains of glucose units connected as l -fi-glycoside linkages.

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