| Breast milk is not only the best nutrients source for newborn infants,but also rich in microorganisms that promote the establishment of normal intestinal flora and the development of immune system.The study of beneficial microorganisms isolated from human breast milk is of great significance for the development of fermented dairy products and infant foods.In this study,lactic acid bacteria and bifidobacteria were isolated and identified from breast milk samples by microbe pure culture methods and 16S rRNA sequence analysis,and 2 strains of Lactobacillus and Bifidobacterium with potential to be developed as probiotics were obtained.Meanwhile,the strains compound starter strains were applied to goat milk for fermentation characteristics.The main results are as follows:(1)A total of 197 strains were isolated and identified from 40 breast milk samples,belonged to 7 genera.Including 5 lactic acid bacteria genera:Lactobacillus,Bifidobacterium,Streptococcus,Enterococcus,Staphylococcus.We also isolated Propionibacterium and Actinomyces.Among them,8 strains of Bifidobacterium in 3 species,10 strains of Lactobacillus in 4 species and the other 179 strains belonged to other genera.Bifidobacterium and Lactobacillus strains were screened for acid and bile salts resistance in vitro,that obtained strains with good tolerances to gastrointestinal fluid and bile salts,namely Bifidobacterium lactis Probio-M8,Lactobacillus rhamnosus Probio-M9.(2)The physiological,biochemical and probiotic characteristics of two strains were studied,such as hydrophobicity,self-aggregation,antioxidant capacity and antibacterial ability of the supernatant.B.lactis Probio-M8 showed survival rates of 85.38%in gastric juice at pH 2.5 and 97.25%in intestinal juice containing 1.8%bile salts.It had high hydrophobicity,self-aggregation ability of 83.51%at 24 h and good antioxidant capacity.The fermentation solution,cell suspension,and non-cell extract of B.lactis Probio-M8 strain all had the scavenging capacity of DPPH,hydroxyl radicals,superoxide anions and reducing ability.The fermentation supernatant had significant inhibitory effects on Staphylococcus aureus,Escherichia coli and Aggregatibacter actinomycetemcomitans.L.rhamnosus Probio-M9 had survival rates of 83.72%in gastric juice at pH 2.5 and 78.33%in intestinal juice containing 1.8%bile salts.It had mediohydrophobicity,self-aggregation ability of 87.15%at 24 h and good antioxidant capacity.The fermentation supernatant of strains had strong bacteriostatic effect on Streptococcus mutans,Porphyromonas gingmorphum,Fusobacterium nucleatum subsp.polymorphum,A.actinomycetemcomitans,S.aureus,E.coli,Bacillus cereus and Candida albicans.So B.lactis Probio-M8 and L.rhamnosus Probio-M9 were potential probiotics.(3)The above isolated strains were applied to the fermentation of goat milk,that combined with basic starter(including Streptococcus thermophilus and Lactobacillus bulgaricus).It was found that the samples of Probio-M8 group and Probio-M8+Probio-M9 group had fast curd,high viscosity and good water holding capacity.The acidity is mild and moderateat,the end of fermentation is 74°T,and the end of storage is 90-100°T.When stored for 28 d,the viable count of probiotic strains was still higher than 1×108 CFU/mL,and the fermented milk products had a tighter gel state and good stability.After adding probiotic strains for fermentation,the content of nutrient elements in the fermented milk met the product requirements,and the produced organic acids and changes of fatty acids by fermentation endowed the fermented milk with better flavor and taste.(4)In summary,B.lactis Probio-M8 and L.rhamnosus Probio-M9 from human breast milk showed good probiotics potential.Their fermentation characteristics indicated that they could be applied to goat milk fermentation.The results of this study provide valuable strain resources and raw data for functional studies of probiotics in breast milk and the development of new human milk-derived probiotics. |
PDF Full Text Request