Properties of dextrans isolated from whole cultures at various stages of incubation

1. 1. The decrease in viscosity which dextran from Leuc. mesenteroides NRRL B-512 exhibits when left in the culture fluid after synthesis is complete was shown to result from partial degradation to smaller macromolecular size. 2. 2. Other dextrans representing a diversity of structures from three species were shown to remain unchanged in cultures as long as 49 days. 3. 3. Length of incubation appeared not to influence the presence in cultures of two strains studied of polysaccharide products separable from the dextran component on the basis of solubility. 4. 4. Leuc. dextranicum NRRL B-1146 produces a dextran closely comparable in structure to that from the B-512 strain, but which is not degraded in the culture fluid. The only polysaccharide produced by this strain is dextran; in contrast to the B-512 strain, it produces no 50–65% ethanol-insolubles. 5. 5. Dextrans isolated prior to and at the time of complete fermentation showed differences so small as to be of questionable structural significance.