Starch polysaccharides, structure

Commercial applications for polysaccharides include their use as food additives, medicines and industrial products. Although plant polysaccharides (such as starch, agar and alginate) have been exploited commercially for many years, microbial exopolysaccharides have only become widely used over the past few decades. The diversity of polysaccharide structure is far greater in micro-organisms compared to plants and around 20 microbial polysaccharides with market potential have been described. However, microorganisms are still considered to be a rich and as yet underexploited source of exopolysaccharides. 

Green coffee beans, as expected, contain storage polysaccharides such as starch, and structural support compounds such as cellulose and lignin. Mono- and di-saccharides are represented, as well as the related compounds quinic acid and myo inositol. 

Gidley, M. (1985). Quantification of the structural features of starch polysaccharides by NMR spectroscopy. Carbohydrate Research, 139, 85-93. 

Since these early studies, the reversion of carbohydrates has proved to be of considerable importance in the hydrolysis of starch,1 in the elucidation of polysaccharide structure, 4r and in the synthesis of oligo-... 

Polysaccharides and generally carbohydrates represent the main carbon sink in the plant cell. Polysaccharides commonly serve nutritional (e.g., starch) and structural (e.g., cellulose) functions in plants. Some polysaccharides are cytotoxic against certain types of cancer, such as mouse skin cancer, or tumor lines in vitro (e.g., mouse Sarcoma-180). However, most polysaccharides exert their action through stimulation of the immune system (cancer immunotherapy). Plants containing polysaccharides with anticancer properties include the following ... 

By using mutants of maize and other species, progress has been made in understanding the pathways and enzymes involved in starch biosynthesis and the fine structure of starch polysaccharides. However, starch biosynthesis (Chapter 4) and granule formation are still not completely understood. Thus, integration of the information on polysaccharide biosynthesis (Section 3.6) with that on mutant effects (Section 3.7), is necessary to fully understand polysaccharide biosynthesis and to delineate the limits of this knowledge. 

Enzymes are used in the determination of polysaccharide structures. Because enzymes have specificity, i.e. they produce specific products of low molecular weight and can cleave specific kinds of bonds they can be used to determine the fine structure of starch. A first premise, however, is that the action patterns and specificity must need to be thoroughly investigated and elucidated before reliable information can be obtained about the structure of the polysaccharide or oligosaccharide being studied. 

This chapter focuses on some aspects of phase transition behavior and other material properties of starch, particularly as they pertain to the structural order and interactions of the starch polysaccharides with water, lipids and other solutes. Understanding the thermally induced structural transitions of starch is helpful in controlling its physical properties and processing behaviors (e.g. plasticization, viscosity), as well as in designing products with improved properties (e.g. texture, stability). 

Nieuwenhuizen, M.S., Kieboom, A.P.G., and van Bekkum, H., Preparation of calcium complexation properties of a series of oxidized polysaccharides structural and conformational effects, Starch/Starke, 37, 192-200, 1985. 

Structural features of starch polysaccharides have been quantified from characteristic signals in high-temperature H and 13C spectra.241 The H-l resonances of (1 — 4)- and (1 —> 6)-linked glucose units occur at 5.4 and 5.0ppm respectively. Integration of these signals gave the ratio of a(l —> 4) to a(l —> 6)... 

Biocatalysis is a key route to both natural and non-natural polysaccharide structures. Research in this area is particularly rich and generally involves at least one of the following three synthetic approaches 1) isolated enzyme, 2) whole-cell, and 3) some combination of chemical and enzymatic catalysts (i.e. chemoenzymatic methods) (87-90). Two elegant examples that used cell-fi-ee enzymatic catalysts were described by Makino and Kobayashi (25) and van der Vlist and Loos (27). Indeed, for many years, Kobayashi has pioneered the use of glycosidic hydrolases as catalysts for polymerizations to prepare polysaccharides (88,91). In their paper, Makino and Kobayashi (25) made new monomers and synthesized unnatural hybrid polysaccharides with regio- and stereochemical-control. Van der Vlist and Loos (27) made use of tandem reactions catalyzed by two different enzymes in order to prepare branched amylose. One enzyme catalyzed the synthesis of linear structures (amylose) where the second enzyme introduced branches. In this way, artificial starch can be prepared with controlled quantities of branched regions. 

Structural Polysaccharides Structural (fibrous) components are found in cell walls of plants and are represented by the linear p (1—4)-linked homopolysaccharides (a) cellulose, (b) chitin, (c) xylan, (d) mannan (10.20). Of these, cellulose is by far the most universally abundant and the most important. Starch (10.20e) derivatives are important in food technology (Chapter 12.4). 

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