Heteropolysaccharides

Heteropolysaccharides Based on u-D-Linked Mannan Main-chains 

In addition to chitin, a polysaccharide-containing cell-wall extract, termed trichophytin, was obtained by Bloch and coworkers from dermatophytes. As part of an immunological study. Bishop, Blank, Perry, and others have conducted investigations on the structural units contained in the constituent polysaccharides. 

Hydrolysis Products from Methylated Calactomannans I from Trichophyton species  

Methylated fragment Trichophyton granulosum Trichophyton interdigitale Microsporum quinckeanum Trichophyton rubrum Trichophyton schonleini 

The capsular polysaccharide of the pathogenic yeast Cryptococcus neoformans (Torula histolytica) is serologically active, and there is evidence that it is responsible for the antigenic reaction in man. The capsule is generally quite thick, and can be larger in diameter than the cell body. Three polysaccharide types, namely. A, B, and C, have been differentiated on the basis of precipitin, agglutination, and quellung reactions.  

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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... 

Peptidoplycans (14,16) are the primary component of bacterial cell walls. They consist of a heteropolysaccharide called murein cross-linked with short peptide chains. 

Pectin is a collective name for heteropolysaccharides, which consist essentially of polygalacturon acid. Pectin is soluble in water only after a partial neutralization with alkali or ammonium hydroxide [18]. 

Alginates are unusual in that although they are heteropolysaccharides they are synthesised as homopolymers in the cell. Final epimerisadon from mannuronic add to glucuronic add then occurs extracellularly. 

Polysaccharides composed of only one kind of monosaccharide are described as homopolysaccharides (homoglycans). Similarly, if two or more different kinds of monomeric unit are present, the class name heteropolysaccharide (heteroglycan) may be used. (See 2-Carb-39.)... 

The first heteropolysaccharide for which a cyclic structure has been proposed is the enterobacterial common antigen (ECA), which was shown by f.a.b.-m.s. to be a mixture of three cyclic components containing 4, 5, and 6 repeats, respectively, of a previously characterized trisaccharide (31) in which the GlcNAc residues were known to be partially acetylated at 0-6. 

Pectins are heteropolysaccharides with axial-axial a(1, 4)-D galactopyranosyluronic acid units condensed in the Ci conformation and interrupted by a-(1,2)-L rhamnopyranosyl residues. The structure is based on blocks of galacturonan partly esterified (the smooth zones) and blocks of highly ramified rhamnogalacturonan regions (hairy zones). The exact structure depends on the sources but also on the methods used to isolate the pectins [1,5]. Few data are given in Table 1. 

Pectin as one of the major plant cell wall constituents has received much attention both from a scientific and a technological point of view. Although pectin has been known to be a very complex heteropolysaccharide for quite some time, most progress on the elucidation of its structure has been attained in the last decade as a result of refinement and development of new more powerful techniques like HPAEC, HPGPC, NMR and the application of purified enzymes able to degrade specific parts of the complex molecule. 

R. M. Hodge. Particle transport fluids thickened with acetylate free xanthan heteropolysaccharide biopolymer plus guar gum. Patent US 5591699,1997. 

Gellan gum is a linear, anionic heteropolysaccharide produced by a microorganism. Most applications of gellan gum are based on its outstanding gel-forming ability in the presence of certain cations at low polymer concentrations. Gellan gum can form gels with various physical... 

The bulk of the heteropolysaccharides in the green coffee bean are formed from mannan, galactan, and araban.95 96 Three fractions can be... 

Monosaccharides, present only in trace amounts in green coffee, increase to 2.6% in roasted coffee due in part to the production of galactose, mannose,103 arabinose, and ribose,104 as the heteropolysaccharides are broken down. 

This substance often constitutes the terminal unit in heteropolysaccharide chains, and contributes greatly to the surface charge of the membrane. 

During start-up, the microbial population distribution in the biofilm varies with time. Initial colonization of the particle may be by one or more species that alter the surface favorably for colonization by other species. For instance, in the operation of a butyrate-degrading fluidized bed bioreactor, methanogens attached to the sand particles early in the start-up process and produced a primary matrix of heteropolysaccharides that allowed attachment of other bacterial species (Sreekrishnan et al., 1991 Zellner et al., 1991 Yongming et al., 1993). This is contrary to findings in an acetate-propionate-butyrate degrading reactor, in which facultative anaerobes were found to be the initial colonizers (Lauwers et al., 1990). 

Pectin and pectic acid, which are the natural substrates of pectic enzymes, are branched heteropolysaccharides in which the backbone contains L-rhamnose residues and a-D-(l — 4)-linked residues of D-galactopyranosiduronic acid. The neutral sugars D-galactose and L-arabinose, and sometimes D-xylose and L-fucose, form the side... 

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