Polysaccharide utilization

To illustrate some characteristrics of polysaccharide utilization systems of Bacteroides species, we will compare the systems involved in utilization of a host-produced mucopolysaccharide (chondroitin sulfate), a plant galactomannan (guar gum) and polygalactaronic acid. Bacteroides thetaiotaomicron... 

Although most seeds contain starch as the principal food reserve, many contain other polysaccharides and some have industrial utility. The first seed gums used commercially were quince, psyUium, flax, and locust bean gum. However, only locust bean gum is stiU used, particularly in food appHcations quince and psyllium gums are only used in specialized appHcations. 

Hemicellulose [9034-32-6] is the least utilized component of the biomass triad comprising cellulose (qv), lignin (qv), and hemiceUulose. The term was origiaated by Schulze (1) and is used here to distinguish the nonceUulosic polysaccharides of plant cell walls from those that are not part of the wall stmcture. Confusion arises because other hemicellulose definitions based on solvent extraction are often used in the Hterature (2—4). The term polyose is used in Europe to describe these nonceUulosic polysaccharides from wood, whereas hemicellulose is used to describe the alkaline extracts from commercial pulps (4). The quantity of hemicellulose in different sources varies considerably as shown in Table 1. 

The separation of the polysaccharide components utilizes their different solubUities, polar groups, extents of branching, molecular weights, and molecular flexibUities and may be accompUshed batchwise or with easUy automated column techniques such as column or high performance Uquid chromatography. These procedures have been summarized in several reviews (3,141—143). 

Xanthan gum [11138-66-2] is an anionic heteropolysaccharide produced by several species of bacteria in the genus Aanthomonas A. campestris NRRL B-1459 produces the biopolymer with the most desirable physical properties and is used for commercial production of xanthan gum (see Gums). This strain was identified in the 1950s as part of a program to develop microbial polysaccharides derived from fermentations utilizing com sugar (333,334). The primary... 

Dextran gels have been utilized since the late 1950s (1) for the separation of biopolymers. First attempts on Sephadex (2-5) and Sephadex/Sepharose (6-8) systems are documented for hydrolyzed and native starch glucans. Up until now, particularly for the preparative and semipreparative separation of polysaccharides, a range of efficient and mechanically stable Sephacryl gels (9-14) have been developped. 

Mourier s report was quickly followed by successful enantiomeric resolutions on stationary phases bearing other types of chiral selectors, including native and deriva-tized cyclodextrins and derivatized polysaccharides. Many chiral compounds of pharmaceutical interest have now been resolved by packed column SFC, including antimalarials, (3-blockers, and antivirals. A summary is provided in Table 12-2. Most of the applications have utilized modified CO, as the eluent. 

The reported effect of konjac GaM on the glass transition of high-sugar/polysaccharide mixtures [242] can be utilized in sugar, hard-boiled and frozen confectionery products and might replace gelatin, which is refused by some consumers due to diet and health problems. 

Due to the lack of a commercial supply, as well as their usually low molecular weight and poor solubility, xylans have found little industrial utility and interest in their modification has been rather low in comparison to commercially available polysaccharides such as cellulose or starch. With the aim of improving the functional properties of xylans and/or imparting new functionalities to them, various chemical modifications have been investigated during the past decade. Most of them were presented in recent reviews [3,399]. 

Besides water, the diet must provide metabolic fuels (mainly carbohydrates and lipids), protein (for growth and turnover of tissue proteins), fiber (for roughage), minerals (elements with specific metabolic functions), and vitamins and essential fatty acids (organic compounds needed in small amounts for essential metabolic and physiologic functions). The polysaccharides, tri-acylglycerols, and proteins that make up the bulk of the diet must be hydrolyzed to their constituent monosaccharides, fatty acids, and amino acids, respectively, before absorption and utilization. Minerals and vitamins must be released from the complex matrix of food before they can be absorbed and utifized. 

The relaxation data for the anomeric protons of the polysaccharides (see Table II) lack utility, inasmuch as the / ,(ns) values are identical within experimental error. Obviously, the distribution of correlation times associated with backbone and side-chain motions, complex patterns of intramolecular interaction, and significant cross-relaxation and cross-correlation effects dramatically lessen the diagnostic potential of these relaxation rates. 

Rice bran hemicelluloses reduce thymus atrophy in rats (Takenaka, 1992). Hikino et al. (1988) isolated and purified four glycan fractions from rice bran hemicelluloses and named them as Oryzabrans A, B, C, and D. All these glycans were shown to improve the peripheral utilization of insulin, resulting in significant hypoglycemic activity (Hikino et al., 1988 Hikino and Hayashi, 1989). Several investigations into rice bran polysaccharides and hemicelluloses (Masayoshi et al., 1987) have indicated a strong improvement in the immune... 

Dextran is the first microbial polysaccharide produced and utilized on an industrial scale. The potential importance of dextran as a structually (and property) controlled feedstock is clearly seen in light of the recent emphasis of molecular biologists and molecular engineers in the generation of microbes for feedstock production. Dextran is employed as pharmaceuticals (additives and coatings of medications), within cosmetics, as food extenders, as water-loss inhibitors in oilwell drilling muds and as the basis for a number of synthetic resins. 

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