Leuconostoc mesenteroides dextran formation

The number of enzymes responsible for the formation of polysaccharides from sucrose is also restricted. The two best known enzymes that form polysaccharides from sucrose are the dextran, synthesized by the microorganism Leuconostoc mesenteroides (8) and related organisms, and the levan, produced from the same substrate by Acetobacter levanicum (9) and other species. 

Some lactic acid bacteria have the ability to metabolize sucrose to produce polymers known as dextrans (viscous, slimy). While most strains of Oeno-coccus oeni are negative for this attribute (Edwards et al., 1991), some strains of Lactobacillus (Edwards et al., 1993) and Leuconostoc mesenteroides (Garvie, 1984) are positive. The outlined method originates from Pilone and Kunkee (1972). To test for dextran formation, touch a sterile inoculating needle straight down into an isolated colony and move the needle straight back up. A positive reaction is one where threads or strands are drawn up on the needle. 

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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