Polysaccharide microbial

The chemistry and biochemistry of the linkage units between teichoic acid and peptidoglycan in bacterial cell walls have been reviewed. Changes in the cell walls of mutants of Bacillus subtilis induced by temperature have been reflected in the production of different proportions of teichoic acid to peptidoglycan.  

Evidence has been presented to show that at least three lipid intermediates participate in the synthesis of the three glycerol phosphate residues which represent the linkage unit between the teichoic acids and peptidoglycan of Staphylococcus aureus H and a Micrococcus species. The structures of the 

Xanthan gum includes D-glucosyl, D-mannosyl, and D-glucuronyl acid residues together with 0-acetyl and pyruvyl residues [4]. The content of pyruvic acid varies substantially based on the species, which in turn leads to varying viscosities of xanthan solutions. Xanthan is considered to assume rigid double-strand helical conformation in its native form [85], with side chains positioned parallel to the helix axis and stabilizing the structure [24]. In solutions, the helical structure turns into flexible coils [85]. 

xanthan enjoys worldwide approval and has become one of the most widely investigated polysaccharides [24]. Xanthan gum enjoys wide application in industrial fields, including food, oil recovery, cosmetics and pharmaceuticals [4]. Its utilization for food uses has been approved by the US Food and Drug Administration (FDA) in 1969 [24]. It is utilized as stabilizer in emulsions and suspensions [4] like toothpaste and ointments, sustained release agent [86,87] and compression enhancer [1]. 

Mixture of xanthan with a galactomannan from Gleditsia sinensis Lam, at different ratios, was investigated as sustained release materials. The synergistic interactions between xanthan and galactomannan were found to effectively retard drug diffusion [86]. 

In another study, carboxymethyl xanthan was converted into Ca-carboxymethyl xanthan matrix by using CaCl solution and the swelling, erosion and drug release behavior of the matrix was investigated. The amotmt of Ca + ion was found to alter the viscosity of gel layer formed arotmd the matrices and affect the swelling and erosion of the matrix, resulting in different drug release profiles. The release data conformed to the Korsmeyer-Peppas model [87]. 

Farooq et al. [1] compared the compressibility of xanthan gum with other polysaccharides, such as sodium alginate, CMC, HPMC, starch and gum acacia, and reported that xanthan gum exhibited the lowest compressibility. 

The cell walls of B. subtilis were able to synthesize teichuronic acid when grown under growth-limiting conditions of phosphate at a low dilution rate, whereas teichoic acid was synthesized at a high dilution rate. The purified teichuronic 

Johnsen, C. Endersen, A. Grov, and P. Oeding, Acta Pathol. Microbiol. Scand. (B), 1975, 

Evidence has been presented to show that peptidoglycan can act as a donor of glycerol and phosphate residues in the synthesis of teichoic and lipoteichoic acids. Thus, a particulate fraction from Streptococcus sanguis catalysed the synthesis of polymers containing glycerol 3-phosphate units from peptidoglycan. 

The antigenic properties of lipoteichoic acids have been reviewed.  

A review has appeared outlining the origin of the glycerol phosphate residues that occur in the linkage between ribitol teichoic acid and peptidoglycan in cell walls. The relations between the synthesis of cell-wall and membrane teichoic acids, and, possibly, between the synthesis of phospholipids and teichoic acids were also discussed. The chemistry and biochemistry of lipoteichoic acids have been reviewed.  

The ribitol teichoic acid from the cell walls of Staphylococcus aureus in solution binds Mg + ions univalently to phosphate groups and to a counter-ion, in contrast to the cell wall where Mg + ions form bridges across phosphate groups of adjacent chains of teichoic acid. Differences in the affinities between cell walls with or without alanyl ester residues were much greater at low concentrations than they were at high concentrations of Mg + ions. Thus, at very low concentrations of Mg + ions, effective binding to the cell wall is significantly improved 

The cell wall of Sporolactobacillus inulinus contains a peptidoglycan of the diaminopimelic acid type and a teichoic acid of the ribitol type containing D-galactose and o-glucose, but no alanine. Based on the cell-wall composition, the phylogenic position of Sporolactobacillus is considered to lie between the ordinary Lactobacilli and the Bacillaceae. 

The location of the D-glucosylated teichoic acid in whole cells and isolated cell walls of S./aecalish-SiS been investigated by electron microscopy after staining. The presence of teichoic acid in certain regions of the cell wall could be demonstrated by binding concanavalin A, but not in regions that were densely stained. 

HCl [134b,c]. The 7-form is converted into the a-form by treatment with a saturated aqueous solution of lithium thiocyanate [134c]. These transformations appear to be irreversible. P- and 7-Chitin occur where the properties of the polysaccharide require flexibility and toughness [134d]. 

The major component of all known bacterial cell walls is a polysaccharide composed of A -acetyl-2-amino-2-deoxy-D-glucopyranose units linked P-1 4 

The peptidoglycan (murein plus polypeptide) is the component of the bacterial cell wall that is responsible for the shape and rigidity of bacterial cells. It is also the site of attack by the enzyme lysozyme that is involved in the lysis of bacterial cells [145]. There is a possible relationship between the chain length of the murein and the shape of the bacterial cell. This is suggested by observations of the cell wall and the shape of Arthrobacter crystallopoietes. This particular bacterium undergoes a reversible coccus-rod transformation that is dependent on the conditions of growth. The murein obtained from the spherical (coccus) form had an av- 

Besides the murein sacculus, many bacteria also produce other polysaccharides that surround and are exterior to the murein cell wall. These polysaccharides serve various purposes in protecting the cell from lysis, virus infection, and changes in the environment including pH, temperature, and concentrations of oxygen. These materials are compact and can be microscopically observed surrounding the cell. They are called capsules. Other bacteria produce more diffuse polysaccharides that also are extracellular but are not so intimately associated with the cell. These less-defined polysaccharides are often called slimes. The dextrans make up such materials. 

In the nineteenth century, there were reports of a mysterious thickening and sometimes gelling of cane and beet sugar solutions. Pasteur [148] reported in 1861, that these viscous fermentations of sucrose resulted from microbial action. Sucrose solutions were observed to be converted into viscous solutions, gels, and/or flocculent precipitates [149]. The material that produced such changes in the sucrose solutions was isolated and found to be a polysaccharide that was called dextran [150]. Van Tieghem isolated and named the bacterium that produced the polysaccharide, Leuconostoc mesenteroides [151]. 

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Dextran. This polysaccharide is produced from sucrose by certain species of l euconostoc (70). Dextran [9004-54-0] was the first commercial microbial polysaccharide. It was used as a blood plasma extender in the U.S. Army during the late 1940s and early 1950s. This program was discontinued in 1955. 

For some appUcations, microbial polysaccharides have supplemented or replaced those derived from plants or algae in other instances, microbial polysaccharides have been developed for specific appUcations that cannot be met by other polysaccharides. Further information is available (5—24). 

Another microbial polysaccharide-based emulsifier is Hposan, produced by the yeast Candida lipolytica when grown on hydrocarbons (223). Liposan is apparentiy induced by certain water-immiscible hydrocarbons. It is composed of approximately 83% polysaccharide and 17% protein (224). The polysaccharide portion consists of D-glucose, D-galactose, 2-amino-2-deoxy-D-galactose, and D-galacturonic acid. The presence of fatty acyl groups has not been demonstrated the protein portion may confer some hydrophobic properties on the complex. 

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... 

P. A. Sandford and A. Laskin, eds., Txtracellular Microbial Polysaccharides, American Chemical Society, Washington, D.C., 1977. 

M. E. BusheU, ed.. Progress in Industrial Microbiology, Vol. 18, Microbial Polysaccharides, Elsevier, Amsterdam, the Netherlands, 1983. 

Polarimetric determination of the sucrose concentration of a solution is vaUd when sucrose is the only optically active constituent of the sample. In practice, sugar solutions are almost never pure, but contain other optically active substances, most notably the products of sucrose inversion, fmctose and glucose, and sometimes also the microbial polysaccharide dextran, which is dextrorotatory. Corrections can be made for the presence of impurities, such as invert, moisture, and ash. The advantage of polarization is that it is rapid, easy, and very reproducible, having a precision of 0.001°. 

Biopolymers are the naturally occurring macromolecular materials that are the components of all living systems. There are three principal categories of biopolymers, each of which is the topic of a separate article in the Eniyclopedia proteins (qv) nucleic acids (qv) and polysaccharides (see Carbohydrates Microbial polysaccharides). Biopolymers are formed through condensation of monomeric units ie, the corresponding monomers are amino acids (qv), nucleotides, and monosaccharides, for proteins, nucleic acids, and polysaccharides, respectively. The term biopolymers is also used to describe synthetic polymers prepared from the same or similar monomer units as are the natural molecules. 

Plant stmctural material is the polysaccharide cellulose, which is a linear P (1 — 4) linked polymer. Some stmctural polysaccharides iacorporate nitrogen iato thek molecular stmcture an example is chitin, the material which comprises the hard exoskeletons of kisects and cmstaceans. Chitki is a cellulose derivative whereki the OH at C-2 is replaced by an acetylated amino group (—NHCOCH ). Microbial polysaccharides, of which the capsular or extracellular (exopolysaccharides) are probably the most important class, show more diversity both ki monomer units and the nature of thek linkages. 

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