The fermentation of sucrose by Leuconostoc mesenteroides.

The slime forming Leuconostoc mesnreroides is distributed widely in nature and is apparently ubiquitous in sugar factories. Neill, Hehre, Sugg, and Jaffe (1939) found dextran, a fermentation product of L. meenteroides, in all samples of cp sucrose examined. This organism, long a nuisance in the factory, has in recent years attracted wide interest because of the commercial possibilities of the dextran it produces and its possible use in the asay of certain of the B vitamins (Gaines and Stahly, 1943; McCleskey and Barnett, 1949) and amino acids (Dunn et al., 1944, 1947; Bienvenu and McCleskey, 1950). The mechanisms of the dissimilation of sucrose by L. mesenteroides are understood imperfectly. L. mewenteroides forms dextran only from sucrose, or traces from glucose under certain conditions (Tarr and Hibbert, 1931). Mixtures of glucose and fructose or the phosphorylated forms of these sugars do not satisfy the requirements of the organisms for gum production, but both of these hexoses are satisfactory energy sources. It is probable that this organism has little or no ability to hydrolyze sucrose, but utilizes the intact molecule, splitting off fructose as the dextran molecule is built up. A curious feature of the fermentation of sucrose by this organism is that it converts the glucose part of the molecule to the dextran which it cannot utilize apparently, and much of the fructose liberated is converted to the polyhydric alcohol, mannitol, which it can utilize only with great difficulty, if at all, as indicated by the delay of 8 days or more before acid formation occurs. Some strains do not attack mannitol within a 30 day incubation period. The amount of gum produced by L. mesenteroides and L. dextranicum from sucrose varies considerably with different strains, and there is some reason to believe that the nature of the gum varies also (Jeanes, Willam, and Miers, 1948). Attempts are being made in this laboratory to gain a better understanding of the metabolism of the dextran forming organisms by a study of the fermentative changes in sucrose brought about by representatives of each of the four types described by McCleskey, Faville, and Barnett (1947). These colonial varieties, designated as types A, B, D, and F, have been shown to be relatively distinct entities as indicated by serological studies (Leiva-Quiros and McCleskey, 1947) and by nutritional requirements (Bienvenu and McCleskey, 1950; McCleskey and Barnett, 1949).