Alginate oligosaccharides (AOS) are non-digestible carbohydrates from brown kelp. As such, they are dietary fibers and may have prebiotic potential. Therefore, we investigated the capacity of gut bacteria to utilize AOS with single-strain cultures and as a complex bacterial community. Bifidobacterium adolescentis, Lacticaseibacillus casei and Lacticaseibacillus paracasei showed weak growth (relative to unsupplemented medium; p < 0.05) in the presence of AOS and alginate, while strong growth (p < 0.01) was observed for Bacteroides ovatus when grown with alginate as carbohydrate source. Enterococcus faecium and Enterococcus hirae were for the first time reported to be able to grow on AOS. Further, AOS as substrate was investigated in a complex bacterial community with colonic fermentations in an in vitro gut model. The in vitro gut model indicated that AOS increased short-chain fatty acid (SCFA) levels in donors with a low endogenous SCFA production, but not to the same level as inulin. Bacteroides was found to dominate the bacteria community after in vitro gut simulation with alginate as substrate. Further, stimulation of Bacteroides was observed with AOS in the gut model for two out of three donors with the third donor being more resistant to change. Our results allowed the identification of AOS utilizers among common gut species. The results also demonstrated the capacity of AOS to elevate SCFA levels and positively modulate the gut microbiota during in vitro simulated colon fermentations, although some subjects appear to be resilient to perturbation via substrate changes.

Background/Objectives: After birth, mothers provide the best nutrition for the healthy growth and development of their infants and the developing gut microbiota through breastfeeding. When breastfeeding is not or insufficiently available, infant formula is the only safe alternative. The production of infant formula includes heat-processing, which may induce protein glycation. Protein glycation has been shown to reduce protein digestion and absorption. The reduction in protein digestion and absorption because of protein glycation has been speculated to also impact gut comfort parameters as well as overnight sleep. Methods: As this could be partially due to the effect on the bacteria that reside in the infant’s gastrointestinal tract, we investigated whether protein glycation in infant formula impacts the composition and activity of infant gut microbiota by performing an in vitro study using the CoMiniGut colon model and fecal inocula obtained from a healthy six-month-old term infant. Incubations were performed for 24 h using a predigested infant formula-supplemented medium with varying levels of glycation (6.5–44.5%). Results: Our data indicate that high protein glycation increases microbial diversity and the relative abundance of Clostridium neonatale from 6.4% of the inoculum to around 25.5% of 20.8% glycation. Interestingly, propionate levels were inversely correlated with protein glycation levels after 24 h of incubation, with the 44.5% blocked lysine sample giving rise to 60% lower propionate levels as compared to the 6.4% sample. Higher propionate levels have been linked with longer uninterrupted sleep overnight, which could be indicative of the underlying mechanism of reduced crying/fussy time during nights for infants fed with a formula containing lower amounts of glycated protein.