In vitro fermentability of human milk oligosaccharides by several strains of bifidobacteria

Abstract

This study was conducted to investigate the catabolism and fermentation of human milk oligosaccharides (HMO) by individual strains of bifidobacteria. Oligosaccharides were isolated from a pooled sample of human milk using solid-phase extraction, and then added to a growth medium as the sole source of fermentable carbohydrate. Of five strains of bifidobacteria tested (Bifidobacterium longum biovar infantis, Bifidobacterium bifidum, Bifidobacterium longum biovar longum, Bifidobacterium breve, and Bifidobacterium adolescentis), B. longum bv. infantis grew better, achieving triple the cell density then the other strains. B. bifidum did not reach a high cell density, yet generated free sialic acid, fucose and N-acetylglucosamine in the media, suggesting some capacity for HMO degradation. Thin layer chromatography profiles of spent fermentation broth suggests substantial degradation of oligosaccharides by B. longum bv. infantis, moderate degradation by B. bifidum and little degradation by other strains. While all strains were able to individually ferment two monosaccharide constituents of HMO, glucose and galactose, only B. longum bv. infantis and B. breve were able to ferment glucosamine, fucose and sialic acid. These results suggest that as a potential prebiotic, HMO may selectively promote the growth of certain bifidobacteria strains, and their catabolism may result in free monosaccharides in the colonic lumen.

Isolation of Milk Oligosaccharides using Solid-Phase Extraction

“…While it has long been speculated that HMO are used as energy sources for colonic microbiota, definitive evidence for this activity was only provided recently [17,19,20]. Bovine milk also contains oligosaccharides (BMO), yet they are present in much lower levels than in human milk.…”

Carbohydrate metabolism in Bifidobacteria

“…Another study described the gene operon lnpABCD which encodes lacto-N-biose I/galacto-Nbiose metabolic pathway responsible for the intestinal colonization of bifidobacteria through utilization of lacto-Nbiose I from human milk oligosaccharides or galacto-Nbiose from mucin sugars [86]. B. bifidum, on the other hand, is believed to produce a-fucosidases and a lacto-N-biosidase for extracellular degradation of HMO with the concomitant release of lacto-N-biose, which can then be utilized intracellularly [55,158]. B. longum subsp.…”

“…B. longum subsp. longum and B. breve can utilize free lacto-N-neotetraose, one of the dominant components of HMOs, whereas B. breve also consumes various monomers that become available following extracellular HMO degradation [66,158]. These different HMO utilization abilities seem to indicate niche-specific adaptation and cross-feeding abilities among various bifidobacterial species and strains.…”

Oligosaccharides in Milk: Their Benefits and Future Utilization

“…longum ATCC 15707, B. adolescentis ATCC 15703, B. breve ATCC 27539 or B. bifi dum ATCC 29521 were performed using a medium containing 1% human milk oligosaccharides but no lactose, which was incubated at 37˚C for 350 hr (Ward et al, 2007). This resulted in a cell density of B. longum ssp.…”