Probiotic and Metabolic Characterization of Vaginal Lactobacilli for a Potential Use in Functional Foods

Abstract

The main aim of this work was to verify the metabolic and functional aptitude of 15 vaginal strains belonging to Lactobacillus crispatus, Lactobacillus gasseri, and Limosilactobacillus vaginalis (previously Lactobacillus vaginalis), already characterized for their technological and antimicrobial properties. In order to evaluate the metabolic profile of these vaginal strains, a phenotype microarray analysis was performed on them. Functional parameters such as hydrophobicity, auto-aggregation, deconjugation of bile salts, adhesion to an intestinal cell line (Caco-2), and a simulated digestion process were evaluated for these strains. A good number of these strains showed hydrophobicity values higher than 70%. Regarding the auto-aggregation assay, the most promising strains were L. crispatus BC9 and BC1, L. gasseri BC10 and BC14, and L. vaginalis BC17. Moreover, L. crispatus BC4, BC6, BC7, and BC8 were characterized by strong bile salts hydrolase activity (BHS). In addition, L. crispatus BC8 and L. vaginalis BC17 were characterized by a medium ability to adhere to Caco-2 cells. Data related to digestion process showed a strong ability of vaginal lactobacilli to withstand this stress. In conclusion, the data collected show the metabolic versatility and several exploitable functional properties of the investigated vaginal lactobacilli.

Human Breast Milk: A Source of Potential Probiotic Candidates

“…In this context, the recorded data are useful in order to understand the potential functionality of the different strains. As reported by several authors [ 9 , 17 , 18 ], the hydrophobic nature of the surface of a microorganism could be associated with a better attachment of the strain to host cells and consequently represents an advantage for its permanence in the gastrointestinal tract. Other studies [ 19 , 20 ] have discussed about the hydrophilic behavior of bacteria, that occurs with values similar or less than 40% whereas the hydrophobic nature is highlighted for those bacteria with average of more than 40%.…”

“…The bacterial hydrophobicity, as the ability to adhere to hydrocarbons, was evaluated in agreement with [ 9 , 10 ]. Each fresh strain (grown in 24 h of incubation at 37 °C in MRS broth with 0.05% L-cysteine adopting anaerobic conditions) was harvested in the stationary phase after centrifugation at 6000 rpm for 10 min.…”

“…The capability of breast milk strains to adhere to differentiated Caco-2 intestinal cells was evaluated as described previously [ 9 ]. Briefly, Caco-2 cells were grown on glass coverslip in DMEM supplemented with 10% fetal bovine serum, 1% L-glutamine in 5% CO 2 at 37 °C for 21 days to allow differentiation.…”

“…In order to evaluate the resistance of the breast milk isolates to a simulated passage through the stomach and duodenum, the method proposed by [ 9 , 16 ] with certain modifications was performed. More precisely, a sample containing UHT bovine milk with a microbial inoculum of 8–9 log CFU/mL was prepared.…”

“…The origin of human milk's bacteria is still controversial; both facultative anaerobic and aerobic species have been retrieved by molecular and cultural methods. Several authors [1,5,6] have highlighted up to 700 bacterial species in human breast milk, although for an individual, a smaller range (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) of cultivable species was reported. Streptococcus and Staphylococcus were reported not only as the bacterial genera most frequently isolated by human milk, but also as the most abundant, along with Bifidobacterium and Lactobacillus (and related genera); the latter mainly shape the developing of gut microbiota [3].…”