as specialty chemicals. (Courtesy Cheng and Gu, as specialty chemicals. (Courtesy Cheng and Gu, structure, and indeed much work has been done to understand the polysaccharide structure-property relationships [1-6]. Structural features of interest include the types of sugar the polysaccharide contains, linkage positions and configurations, presence or absence of charged groups, molecular weight, branching, and substitution pattern (if applicable). Sometimes the polysaccharide in question contains proteins and/or fatty acids, which can modify its properties. In addition, many polysaccharides have secondary or tertiary structures (e.g., helix, intramolecular hydrogen bonding, and interchain association). These can also affect the polysaccharide properties.

In a commercial context, the end use dictates the properties desired. For solution applications, the rheology of the polysaccharide, its ability to retain water, and its gelling tendency are often the most important. For solids applications, the thermal properties (e.g., Tg and Tm), the mechanical properties (e.g., stiffness, tensile, texture, and adhesion), and other features such as water content, crystallinity, and spatial heterogeneity are relevant. Many polysaccharides are used in interfacial applications, in which case the surface-active properties of the polysaccharide are important.

Sometimes a polysaccharide is desirable in some respects but lacking in others for a given application. In this case a producer may consider improving the poly-saccharide. Improvements may entail simple operations such as purification, frac-tionation, blending, or the addition of an inorganic salt or other organic/polymeric additives. Alternatively, chemical modification or biotransformation (both enzymatic and microbial) can be carried out to alter the chemical or the physical structures of the polysaccharide.

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