Human Nutrition and Metabolism

The gastrointestinal tracts of breast-fed infants are colonized more easily with bifidobacteria than are those of formula-fed infants. Colonization is thought to reduce infant diarrhea. Amendments to formulas that improve colonization by bifidobacteria are being actively investigated. Colonization studies almost invariably require measurements of the concentration of the bifidobacteria in feces to assess their importance in the colon. We investigated the use of nuclear magnetic resonance (NMR) analysis of products of fermentations of 1and 3-Cglucose to evaluate the importance of bifidobacteria in the colonic ecosystem. Bifidobacteria use a unique pathway of hexose catabolism to produce primarily acetate and lactate. The fermentation yields 3 mol of acetate from 2 mol of glucose. Two of the acetates are formed from C1 and C2 of glucose and the third is formed entirely from C3 of glucose. We first employed high resolution NMR to verify the pathway used by a pure culture of Bifidobacterium bifidum. The major products of fermentation of 1and 3-C-glucose were acetate and lactate. Most of the C from 3-C-glucose was in CH3COOH with equal enrichment in the methyl and carboxyl groups. The Cacetate from 1-C-glucose was almost entirely enriched in the methyl of acetate and no CH3COOH was produced. NMR analysis of glucose fermentation by the colonic flora of a 158-d-old strictly breast-fed infant showed production of CH3COOH from 3-C-glucose. The amount of CH3COOH formed established that the Bifidobacterium pathway was the major pathway used for glucose fermentation by this infant’s colonic microbes. J. Nutr. 128: 91–96, l998.