| Compared to infant formula, consumption of breast milk by infants leads to advantages we cannot explain with current knowledge of food composition and nutrition. Thus, rigorous compositional deconstruction of human milk and functional annotation of the constituent parts will provide a broader understanding of the potential of human nutrition.; The third most concentrated component of human milk, after lactose and fat, is soluble oligosaccharides. These molecules are comprised of glucose, galactose, glucoasmine, fucose, and sialic acid, and are synthesized by the sequential addition of monosaccharides to a lactose backbone. Over 130 individual species have been identified. They are heterogeneous between women, and are not digestible by human digestive enzymes. They are presumed to serve as prebiotics, or indigestible carbohydrates which selectively stimulate the growth of beneficial gut bacteria, yet little data has been generated on the specifics of this activity.; The goal of this investigation was to determine which, if any, of these molecules was fermentable by selected members of the gut microflora. A method was developed to separate oligosaccharides from the fat, protein, and lactose in milk. Subsequently, the oligosaccharides were added to a growth media as the sole source of fermentable carbohydrate.; In an initial experiment, it was determined that Bifidobacterium infantis and Staphylococcus epidermis were able to utilize milk oligosaccharides as an energy source, whereas Lactobacillus gasseri was not. An analysis of the carbohydrates in the spent media by matrix assisted laser desorption ionization-Fourier transform mass spectrometry (MALDI-FTMS), confirmed this observation.; Subsequent fermentation studies were conducted with 5 additional strains of bifidobacteria, B. bifidum, B. adolescentis, B. breve, and two B. longum strains. Of all the strains tested, only B. infantis and B. bifidum were able to significantly degrade the oligosaccharides. Analysis of the carbohydrates in the spent media indicated that both of these strains contained the ability to cleave off terminal sialic acid from the milk oligosaccharides, leaving the free sugar. Analysis of the monosaccharides in the spent media using gas chromatography indicated that B. infantis was able to utilize all of the monosaccharide constituents of milk oligosaccharides, whereas B. bifidum utilized only galactose and glucose. |
