D- -Glucopyranosyl units

Maltose and cellobiose (Section 25 14) are examples of disaccharides denved from D glucopyranosyl units... 

Fig. 2. A simplified schematic representation of glucomaiman, where Glc is the D-glucopyranosyl unit Man is the D-maimopyranosyl unit Gal is the...

Welan is produced by 2is Pilcaligenes species (ATCC-31555) by aerobic fermentation, and marketed under the trade name BIOZAN (Merck and Co., Inc.) early reports also referred to it as S-130 (229). The polymer is stmcturaUy similar to geUan, sharing the same backbone sequence. It has an additional side group of an a-L-rhamnopyranosyl or an a-L-maimopyranosyl (Man ) unit linked (1— 3) to a P-D-glucopyranosyl unit in the backbone of the polymer ... 

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The stmcture of amylose has been estabUshed by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed stmcture (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

Xanthan. Xanthan, known commercially as xanthan gum [11138-66-2], has a main chain of (1 — 4)-linked P-D-glucopyranosyl units therefore, the chemical stmeture of the main chain is identical to the stmeture of cellulose [9004-34-6]. However, in xanthan, every other P-D-glucopyranosyl unit in the main chain is substituted on 0-3 with a trisaccharide unit. The trisaccharide side chain consists of (reading from the terminal, nonreducing end in towards the main chain) a -D-mannopyranosyl unit linked (1 — 4) to a P-D-glucopyranosyluronic acid unit linked (1 — 2) to a... 

These products are characterized in terms of moles of substitution (MS) rather than DS. MS is used because the reaction of an ethylene oxide or propylene oxide molecule with ceUulose leads to the formation of a new hydroxyl group with which another alkylene oxide molecule can react to form an oligomeric side chain. Therefore, theoreticaUy, there is no limit to the moles of substituent that can be added to each D-glucopyranosyl unit. MS denotes the average number of moles of alkylene oxide that has reacted per D-glucopyranosyl unit. Because starch is usuaUy derivatized to a considerably lesser degree than is ceUulose, formation of substituent poly(alkylene oxide) chains does not usuaUy occur when starch is hydroxyalkylated and DS = MS. 

Non-mutant normal) reserve and transitory starch granules are composed primarily of amylose and amylopectin. Amy lose is essentially a linear polymer consisting of (1—4)-linked a-D-glucopyranosyl units. Amylopectin is a branched polymer of a-D-glucop-yranosyl units primarily linked by (1—>4) bonds with branches resulting from (1—6) linkages. Properties of these two major starch components are summarized in Table 3.1. 

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