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L. kefiri DH5 exerts anti-obesity effects by direct reduction of cholesterol in the lumen and upregulation of PPAR-α gene in adipose tissues.

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Kefir is a unique fermented dairy product produced by a mixture of lactic acid bacteria, acetic acid bacteria, and yeast. Here, we compared the antimicrobial spectra of four types of kefirs (A, L, M, and S) fermented for 24, 36, 48, or 72 h against eight food-borne pathogens. Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, and Cronobacter sakazakii were used as test strains, and antibacterial activity was investigated by the spot on lawn method. The spectra, potencies, and onsets of activity varied according to the type of kefir and the fermentation time. The broadest and strongest antimicrobial spectrum was obtained after at least 36-48 h of fermentation for all kefirs, although the traditional fermentation method of kefir is for 18-24 h at 25°C. For kefir A, B. cereus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited, while B. cereus, S. aureus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited to different extents by kefirs L, M, and S. Remarkably, S. aureus, S. Enteritidis, and C. sakazakii were only inhibited by kefirs L, M, and S, and L. monocytogenes by kefir M after fermentation for specific times, suggesting that the antimicrobial activity is attributable not only to a low pH but also to antimicrobial substances secreted during the fermentation.

Kefir is a natural complex fermented milk product containing more than 50 species of probiotic bacteria and yeast, and has been demonstrated to have multiple properties conferring health benefits, including antiobesity, anti-hepatic steatosis, antioxidative, antiallergenic, antitumor, anti-inflammatory, cholesterol-lowering, constipation-alleviating, and antimicrobial properties. To better understand the underlying mechanisms of these benefits, we here review research on the effect of kefir (and kefir microorganisms) consumption to modulate the host gut microbiota. Owing to its excellent gastrointestinal resistance and colonization ability and wide ranges of microbial interaction, kefir has shown significant and wide-spectrum modulatory effects on the host gut microbiota. In particular, as a bacteria- and yeast-containing food, kefir can modulate both the gut microbiota and mycobiota. Since the association of this modulation with health benefit has only been addressed in a small number of recent studies thus far, further studies are needed to determine the precise mechanisms of the beneficial effects of kefir in relation to the modulation of the gut microbiota and mycobiota. Gaining this insight will surely help to take full advantage of this unique probiotic food.

Background: Streptococcus mutans and Streptococcus sobrinus are major causative bacterial pathogens of dental caries.Objective: We investigated the applicability of three Lactobacillus strains (L. kefiranofaciens DD2, DD5, and DD6) isolated from kefir and three commercial Lactobacillus strains (L. plantarum ATCC 10,012, L. johnsonii JCM 1022, and L. rhamnosus ATCC 7469) as potential oral probiotics with respect to their survivability in an experimental oral environment, antimicrobial activity, and anti-biofilm formation activity against S. mutans and S. sobrinus.Results: Strains DD2, ATCC 10012, ATCC 7469, and JCM 1022 had the best oral survivability, including aerotolerance and enzymatic resistance, and inhibited the growth and biofilm formation of S. mutans and S. sobrinus. In particular, DD2 suppressed all three classes of biofilm formation-associated genes: those associated with carbohydrate metabolism and those encoding regulatory biofilm and adhesion proteins.Conclusions: These results indicate that the novel kefir isolate L. kefiranofaciens DD2 effectively and directly inhibits S. mutans and S. sobrinus.

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