Fermentation of Glucose, Lactose, Galactose, Mannitol, and Xylose by Bifidobacteria

Abstract

For 6 strains of Bifidobacterium bifidum, (Lacto-bacillus bifidus), fermentation balances of glucose, lactose, galactose, mannitol and xylose were determined. Products formed were acetate, L(+)-lactate, ethyl alcohol and formate L(+)-Lactate dehydrogenase of all strains studied has an absolute requirement for fructose-1,6-diphosphate. The phosphoroclastic enzyme could not be demonstrated in cell-free extracts. Cell suspensions fermented pyruvate to equimolar amounts of acetate and formate. Alcohol dehydrogenase was shown in cell-free extracts. Possible explanations were suggested for the differences in fermentation balances found for different strains and Ca sources. By enzyme determinations, it was shown that bifidobacteria convert mannitol to fructose-6-phosphate by an inducible polyol dehydrogenase and fructokinase. For 1 strain of B. bifidum, molar growth yields of glucose, lactose, galactose and mannitol were determined. The mean value of Y (ATP), calculated from molar growth yields and fermentation balances, was 11.3.