Bacteria dextran-synthesizing

Particular difficulties exist, however, in purifying dextrans synthesized by many streptococci, because the bacteria simultaneously elaborate exocellular fructans (levansDextrans and levans synthesized concomitantly by Leuconostoc micro-organisms have been separated by fractionally precipitating the polysaccharides from aqueous ethanol. These separative procedures are, however, only effective when considerable differences in molecular weight exist between the main fractions of the two polysaccharides, and, as a result, they are of limited value in effecting separation of levans from many streptococcal dextrans. Reports that some oral bacteria are able to metabolize levans suggest that... 

Polysaccharides are available from plants (starch, cellulose, alginate), animals (chitin), fungi (pullulan) and bacteria (dextran, emulsan, pectin). For a sununary on industrial polysaccharides see Stivala et al. [4, S]. Proteins are produced by all living species in order to maintain their metabolic functions, but from a materials point of view it is the fibrous proteins from plants (soy), animals (wool, silk) [6] and bacteria (polyglutamic acid) that are exploited. Lignin, a polyphenolic compound, [7] and natural rubber, a polyisoprene, [8] are synthesized by plants. Finally, poly(hydroxyalkanoates) are synthesized naturally exclusively by bacteria [9]. Bacterial polymerase genes have also been successfully transferred to plants [10]. 

Dextran is a naturally occurring polymer that is synthesized in yeasts and bacteria for energy storage. It is mainly a linear polysaccharide consisting of repeating units of... 

Dextrans are polysaccharides composed of linear glucose residues. They are produced from a polysaccharide synthesized by the bacteria Leuconostoc mesenteroides grown on sucrose media. Dextrans... 

Dextran is synthesized from sucrose by certain lactic acid bacteria, the best-known being Leuconostoc mesenteroides and Streptococcus mutans. Dextran is also formed by the probiotic Lactobacillus brevis to create the crystals of tibicos or water kefir-fermented beverage with reported health benefits. 

In this article, the term dextran will be used to describe preparations of D-glucans that contain substantial numbers of (1- 6)-linked a-n-gluco-pyranosyl residues. In order to attain an element of cohesion between its various Sections, the Chapter has been confined to dextrans produced by bacteria growing on a sucrose substrate. The great majority of dextrans fall into this group, although dextrans have been synthesized from other substrates by micro-organisms, and a chemical synthesis of an essentially unbranched dextran has been reported. ... 

Large numbers of bacteria synthesize dextrans exocellularly when grown on sucrose-containing media. These bacteria have been confined... 

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