Streptococcus dextran synthesis

The synthesis of exocellular polysaccharides by lactic acid bacteria is a very widespread character. L. mesenteroides and Streptococcus mutans produce glucose homopolymers such as dextran and glucan fructose homopolymers (levans) and heteropolymers are also synthesized. Dextran of L. mesenteroides is the best known, as much for its different structures and its biosynthesis as for its various applications. 

The synthesis of dextran from sucrose by a cell-free bacterial culture filtrate was first reported by Hehre in 1941 [152]. The genera of bacteria that are recognized to produce enzymes capable of synthesizing polysaccharides from sucrose are principally Leuconostoc and Streptococcus. These genera are gram positive, facultatively anaerobic cocci that are very closely related to each other. One notable difference between them is that the L. mesenteroides strains required sucrose in the growth medium to induce the formation of the enzyme(s), whereas the Streptococcus species did not require sucrose in the medium to form the enzymes [153]. 

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