Pooled faecal inoculum can predict infant fiber fermentability despite high inter-individual variability of microbiota composition

Infants are known for their high inter-individual variability in gut microbiota composition in the first months of life. This poses difficulties when predicting the fate of non-digestible carbohydrates (NDCs) in the infant gut using in vitro models, since numerous experiments with individual faecal inocula of different infants are required. In this study an in vitro fermentation experiment was performed with galacto-oligosaccharides (GOS) using both individual and pooled faecal inocula of five two-week-old infants. It was shown that pooled faecal inoculum can be used to judge the fermentability of GOS, as a similar trend in total organic acid production and relative increase in Bifidobacterium was observed for the pooled faecal inoculum and four out of five individual faecal inocula. An additional fermentation using pooled faecal inoculum of five other infants of the same age confirmed these findings. Additionally, we provided evidence for both size- and isomer-specific fermentation of GOS by infant microbiota, which reveals the potential for the production of tailored NDC mixtures to meet the needs of specific subgroups of infants. Hence, the use of pooled faecal inocula contributes to increasing our knowledge on structure-specific effects of NDCs in infants efficiently.