Microbiological and sensory characterization of kefir produced from camel milk and its modulation of the gut microbiota in mice

Background Functional foods that modulate the gut microbiota are of growing interest, and camel milk is an attractive substrate for such products. However, the effect of kefir produced from camel milk on the gut microbiota in vivo remains largely unexplored. Objective To characterize the physicochemical, microbiological and sensory properties of kefir produced from camel milk and to evaluate its effect on the colonic luminal microbiota of healthy mice. Methods Camel milk was fermented with kefir grains (2, 3 and 4% w/v) for 22 h at 25 °C, and pH, titratable acidity and microbial counts were monitored over 14 days of refrigerated storage at 4 °C, with sensory evaluation carried out on day 1. The 3% formulation was administered by oral gavage to C57BL/6 mice for 21 days alongside plain pasteurized camel milk (PC) and an untreated control (NC). The fecal microbiota was assessed by culture-based enumeration, while the colonic luminal contents, the kefir grains and the plain pasteurized camel milk were characterized by 16S rRNA gene sequencing; the fungal community of the kefir grains was additionally profiled by ITS sequencing. Results Fermentation acidified the milk from pH 6.54 to 3.5–3.9, yielding a storage-stable product that maintained lactic acid bacteria, bifidobacteria and yeast counts above 7.0 log₁₀ CFU/mL over 14 days of refrigerated storage; the grains were dominated by Lactobacillus kefiranofaciens and the yeast Kluyveromyces marxianus . Grain concentration had no significant effect on any sensory attribute, and the product scored highest for color and texture. In mice, kefir feeding was associated with the highest fecal lactic acid bacteria counts and the lowest yeast and mold counts among the three groups. In the colonic luminal microbiota, sequenced from three mice per group ( n = 3), alpha diversity did not differ significantly among groups, whereas community composition differed significantly, shifting from a Bacteroidota- toward a Bacillota-dominated profile and enriching the butyrate-associated Lachnospiraceae NK4A136 group; PC was instead associated with higher Akkermansia and Faecalibaculum . Conclusion Kefir produced from camel milk altered the composition of the resident colonic luminal microbiota of healthy mice, shifting it toward a Bacillota-dominated profile and enriching the Lachnospiraceae NK4A136 group.