Breast milk is the main source of nutrition for infants; it contains considerable microflora that can be transmitted to the infant endogenously or by breastfeeding, and it plays an important role in the maturation and development of the immune system. In this study, we isolated and identified lactic acid bacteria (LAB) from human colostrum, and screened 2 strains with probiotic potential. The LAB isolated from 40 human colostrum samples belonged to 5 genera: Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus, and Staphylococcus. We also isolated Propionibacterium and Actinomyces. We identified a total of 197 strains of LAB derived from human colostrum based on their morphology and 16S rRNA sequence, among them 8 strains of Bifidobacterium and 10 strains of Lactobacillus, including 3 Bifidobacterium species and 4 Lactobacillus species. The physiological and biochemical characteristics of strains with good probiotic characteristics were evaluated. The tolerances of some of the Bifidobacterium and Lactobacillus strains to gastrointestinal fluid and bile salts were evaluated in vitro, using the probiotic strains Bifidobacterium lactis BB12 and Lactobacillus rhamnosus GG as controls. Among them, B. lactis Probio-M8 and L. rhamnosus Probio-M9 showed survival rates of 97.25 and 78.33% after digestion for 11 h in artificial gastrointestinal juice, and they exhibited growth delays of 0.95 and 1.87 h, respectively, in 0.3% bile salts. These two strains have the potential for application as probiotics and will facilitate functional studies of probiotics in breast milk and the development of human milk-derived probiotics.
Despite recent advances in therapeutic strategies and drug treatments (e.g., statins) for coronary artery disease (CAD), CAD-related mortality and morbidity remain high. Active bidirectional interactions between the gut microbiota and the heart implicate that probiotic application could be a novel therapeutic strategy for CAD.
Interest has been growing in the co-fermentation of starter cultures with probiotic bacteria in milk. However, the representative metabolites and metabolic changes at different key time points during milk fermentation and storage in starter cultures and probiotic bacteria are still unclear. In this study, we used gas chromatography/mass spectrometry-based metabolomics to identify volatile metabolites and discriminate between 6 different time points [fermentation initiation (FI), fermentation curd (FC), fermentation termination (FT), storage 1 d (S1d), storage 7 d (S7d), and storage 14 d (S14d)] during the fermentation and storage of starter cultures and Lactobacillus casei Zhang milk. Of the 52 volatile metabolites identified, 15 contributed to discrimination of the 6 time points. Then, using the profile from the different time points, we analyzed pairwise comparisons (FI vs. FC; FC vs. FT; FT vs. S1d; S1d vs. S7d; S7d vs. S14d); these time-lapse comparisons showed metabolic progressions from one fermentation stage to the next. We found representative and exclusive metabolites at specific fermentation and storage time points. The greatest difference in metabolites occurred between FC and FT, and the metabolic profiles between S7d and S14d were most similar. Interestingly, decanoic acid, octanoic acid, and hexanoic acid reached their highest level at storage 14 d, indicating that the post-fermentation storage of fermented milk with L. casei Zhang may add more probiotic functions. This work provides detailed insight into the time-specific profiles of volatile metabolites and their dynamic changes; these data may be used for understanding and eventually predicting metabolic changes in milk fermentation and storage, where probiotic strains may be used.
There has been a growing interest in cofermentation of starter cultures with probiotics in milk. In this study, we analyzed the effects of adding the single probiotics Lactobacillus casei Zhang (Zhang) or Bifidobacterium animalis ssp. lactis Probio-M8 (M8) or a combination of Zhang and M8 to starter cultures on volatile and nonvolatile metabolomic profiles after 14 d of storage at 4°C and compared using a liquid chromatographytandem mass spectrometry (LC-MS) and GC-MSbased metabolomics approach. Principal component analysis, heatmap plots, and Spearman correlation results showed that Zhang alone had a greater effect on volatile and nonvolatile metabolomic profiles than M8 alone. The combination of Zhang and M8 had additive effects on the production of metabolites. For volatile metabolites, the levels of acetaldehyde, diacetyl, acetoin, and acetic acid were higher for the combination of Zhang and M8 compared with either single probiotic culture. Significantly increased nonvolatile components induced by adding Zhang were identified were enriched in the galactose, amino-and nucleotide sugar, fructose and mannose, purine, phenylalanine metabolism, and arginine biosynthesis pathways. The metabolism and biosynthesis of starch, sucrose, tyrosine, galactose metabolism, and aminoacyl-tRNA biosynthesis were significantly upregulated by adding the combination of Zhang and M8. This work provides a detailed insight into different effects of Zhang and M8 used alone or in combination on the volatile and nonvolatile metabolomic profiles of yogurts.
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