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Starch, a complex carbohydrate, is a polymer of glucose residues. It occurs in two main forms: amylose, consisting of predominantly linear chains of glucose units linked by α(1-4) glycosidic bonds, and amylopectin, in which the chains are highly branched by the addition of α(1-6) glycosidic bonds. Depending upon the plant species and the site of storage, the proportion between these two components varies. In most plant species, amylose comprises about 20% of the starch and the rest is amylopectin. Although in its native form it has some applications in food and non-food industries, the properties of currently available starches (native starch) do not comply with most industrial standard and enhanced commercial applications. To obtain starches with particular properties such as starches with lower retrogradation and more freeze-thaw stability, starch is often chemically modified. Manipulation of the starch structure with chemical reactions or additives will eventually impart certain properties which are desired for industrial uses. Techniques including cross-linking (to strengthen against shear) or acetylation (to reduce the retrogradation) are the most common starch modifications. The use of chemicals, however, may not only cause concern over health and safety, but there is also a cost involved with the chemical modification. Knocking out/ over expression of genes involved in starch biosynthesis, has resulted to alteration of starch physic-chemical properties. Production of biopolymers consisting of glucose residues linked by α(1-3) and α(1-6) or an alternatives [(α(1-3,6), α(1-4,6)] of these linkages, are among hot topics in polysaccharides research fields.

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