Venema K.
Beneficial Microbes® Consultancy, Wageningen, the Netherlands

Over the past two decades it has become clear that the gut microbiota is heavily involved in health and disease, not only for the gut itself, but also for the rest of the body. Correlations have been found between the presence/absence of certain bugs and many diseases and disorders. One of the major activities of the gut microbiota is the fermentation of carbohydrates. In breast-fed infants these are the human milk-oligosaccharides (HMO). Oligosaccharide amount and composition vary between women and over the course of lactation and vary from 5-15 g/L human breast milk. Breast-feeding is considered the ‘golden standard’ for infants, and hence infant-formula rpoducing companies are trying to mimic the composition of HMO with prebiotics. Prebiotics are defined as non-digestible carbohydrates that specifically stimulate one or a few members of the gut microbiota, leading to improved health for the host.

We have developed tools making use of 13C-labeled substrates to trace fermentation of these by the gut microbiota. These were used in a validated, dynamic, computer-controlled in vitro model of the large intestine, nick-named TIM-2, inoculated with microbiotas originating from babies, adults or elderly. This presentation will discuss use of the 13C-labeled HMO 6’-sialyl lactose (6’-SL) by these microbiotas, in comparison to the commercial prebiotics galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS). Due to the 13C label, metabolites that were produced from the substrates by the three different microbiotas could be analyzed by gas-chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR).

Clear differences were observed between the microbiotas. For instance, in the elderly microbiota label was incorporated in the amino acid alanine. Also label incorporation in ethanol was observed. Breakdown of 6’-SL could be traced using NMR, and was shown to be different between the three microbiotas. Also label incorporation in microbial biomass and gene-expression were analyzed, using stable-isotope-probing and a customized gene-microarray, respectively. This indicated that bifidobacterial species were important in fermentation of all three substrates that were compared. The data obtained gives a nice indication about similarities and difference in metabolism of HMOs by the different microbiotas.

Significance and impact of the results, as well as limitations will be discussed. E.g. development of novel prebiotics that mimic even better the metabolism of HMO could be tested using the current set-up. If time allows results of experiments performed with Lacto-N-neotetraose (LNnT) and mixtures of other HMO will be shown as well. The latter experiments are based on differences in secretor stage of lactating women.

Keywords: Human milk oligosaccharides, Probiotics

Venema K. (2016). Fermentation of 13C-labeled 6´- sialyl lactose by microbiotas originating from babies, adults and elderly – tracing the label. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 78.). IPC2016

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