Our study aim is to investigate the role of Intestinimonas, Nε-fructosyllysine (FL)-degrading bacterium, in infants and adults. We used lysine and subsequently FL in anaerobic serial dilutions of stools of infants and adults to enrich lysine and FL-degrading species. The fecal microbiota of adults were able to ferment lysine and FL to butyrate. Different groups of Intestinimonas spp. were detected from all lysine enrichments whereas the FL enrichments consisted of broader taxonomic groups with a reduced abundance of Intestinimonas-related species. Remarkably, the capability to degrade FL was only observed in formula-fed but not in breast-fed infants, which may relate to high contents of FL in formulas after thermal treatment. This possibility was supported by analyzing metagenomic datasets of 3-month and 4-month infants. Our data indicate the key role of Intestinimonas-like bacteria in FL degradation in formula-fed infants and adults as a profound example of adaptation of intestinal bacteria to dietary components. Peer reviewed