Polysaccharides microbial exocellular

Microbial, Exocellular Polysaccharides Containing Acidic Sugar Residues... 

Hot water-extractable C accounts for 1-5% of soil organic C (Leinweber et al. 1995 Sparling et al. 1998 Chan and Heenan 1999) and about 50% of this is thought to be present as carbohydrate (Haynes 2005). Because it is usually extracted from air-dried soils much of the pool originates from desiccated microbial cells but it also includes exocellular polysaccharides, root exudates, lysates and humic material (Redl et al. 1990 Leinweber et al. 1995 Sparling et al. 1998). Both hot water extractable C (Sparling et al. 1998 Chan and Heenan 1999) and hot water-extractable carbohydrate (Ball et al. 1996 Haynes and Beare 1997 Debrosz et al. 2002) have been used as indices of soil quality. 

Xanthan is the extracellular (exocellular) polysaccharide produced by Xanthomonas campestris. As with other microbial polysaccharides, the characteristics (polymer structure, molecular weight, solution properties) of xanthan preparations are constant and reproducible when a particular strain of the organism is grown under specified conditions, as is done commercially. The characteristics vary, however, with variations in the strain of the organism, the sources of nitrogen and carbon, degree of medium oxygenation, temperature, pH, and concentrations of various mineral elements. 

Sandford, P. A. (1979). Exocellular microbial polysaccharides. Adv. Carbohydr. Chem. Biochem. 36 265-313. 

Sandford, P. A., "Exocellular microbial polysaccharides". In Advances in Carbohydrate Chemistry and Biochemistry, Vol. Tipson, R. S. and Horton, D., Eds., Academic... 

Sandford P.A. "Exocellular, Microbial Polysaccharides" Adv. Carb. Chem. Biochem., 1979, 36, 297. 

At present, the discovery of new polysaccharides relies on screening of the extracellular polysaccharides produced by microorganisms. Fungi and yeasts are also potential sources of new polysaccharides. The production of microbial polysaccharide has the advantages of controlled cost, abundant supply and ease of modification of the chemical structure. These new polysaccharides with new properties may generate new market opportunities. Microbial polysaccharides can be classified as extracellular structural or intercellular storage forms. Extracellular polysaccharide can be either exocellular capsules of the cell wall or loose slime components that accumulate outside the cell wall and then diffuse into the medium. 

Singh RP, Shukla MK, Mishra A, Kumari P, Reddy CRK, Jha B (2011) Isolation and characterization of exopolysaccharides from seaweed associated bacteria Bacillus licheniformis. Carbohydr Polym 84 1019-1026 Stanford PA (1979) Exocellular, microbial polysaccharides. In Tipson RS, Horton D (eds) Advances in carbohydrate chemistry and biochemistry, vol 36. Academic, London/New York, pp 266-303 Stingele F, Neeser JR, Mollet B (1996) Identification and characterization ofthe eps (exopolysaccharide) gene cluster from Streptococcus thermophilus Sfi6. JBacteriol 178 1680-1690... 

The partially-purified extract oxidised a range of phenolic substrates, and also contained proteinases and amino acid decarboxylases. Preincubation of a toluene-treated soil enzyme preparation for 12h at 37°C did not affect diphenol oxidase activities, ie. the oxidases appeared to be resistant to attack by the coextracted soil proteinases. Addition of hyaluronidase before preincubation also was without effect. Preincubation with the microbial proteinase, Pronase for I8h at 37°C decreased diphenol oxidase activities by 307o, and by 100% when both Pronase and hyaluronidase were added. The results suggested that the polysaccharides associated with the extracted soil oxidases protected the enzymes from proteolysis and may play a role in stabilizing exocellular enzymes in soils. 

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