A combined metabolomic and phylogenetic study reveals putatively prebiotic effects of high molecular weight arabino-oligosaccharides when assessed by in vitro fermentation in bacterial communities derived from humans
Sulek, Karolina1; Vigsnæs, Louise Kristine1; Schmidt, Line Rieck1; Holck, Jesper6; Frandsen, Henrik Lauritz1; Smedsgaard, Jørn1; Skov, Thomas Hjort1; Meyer, Anne S.3; Licht, Tine Rask7
1 National Food Institute, Technical University of Denmark2 Division of Food Microbiology, National Food Institute, Technical University of Denmark3 Department of Chemical and Biochemical Engineering, Technical University of Denmark4 Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark5 Division of Food Chemistry, National Food Institute, Technical University of Denmark6 Department of Chemistry, Technical University of Denmark7 Copenhagen Center for Health Technology, Center, Technical University of Denmark
Prebiotic oligosaccharides are defined by their selective stimulation of growth and/or activity of bacteria in the digestive system in ways claimed to be beneficial for health. However, apart from the short chain fatty acids, little is known about bacterial metabolites created by fermentation of prebiotics, and the significance of the size of the oligosaccharides remains largely unstudied. By in vitro fermentations in human fecal microbial communities (derived from six different individuals), we studied the effects of high-mass (HA, >1 kDa), low-mass (LA, <1 kDa) and mixed (BA) sugar beet arabino-oligosaccharides (AOS) as carbohydrate sources. Fructo-oligosaccharides (FOS) were included as reference. The changes in bacterial communities and the metabolites produced in response to incubation with the different carbohydrates were analyzed by quantitative PCR (qPCR) and Liquid Chromatography–Mass Spectrometry (LC–MS), respectively. All tested carbohydrate sources resulted in a significant increase of Bifidobacterium spp. between 1.79 fold (HA) and 1.64 fold (FOS) in the microbial populations after fermentation, and LC–MS analysis suggested that the bifidobacteria contributed to decomposition of the arabino-oligosaccharide structures, most pronounced in the HA fraction, resulting in release of the essential amino acid phenylalanine. Abundance of Lactobacillus spp. correlated with the presence of a compound, most likely a flavonoid, indicating that lactobacilli contribute to release of such health-promoting substances from plant structures. Additionally, the combination of qPCR and LC–MS revealed a number of other putative interactions between intestinal microbes and the oligosaccharides, which contributes to the understanding of the mechanisms behind prebiotic impact on human health.