| Lactic acid bacteria have many probiotic functions,such as improving immunity,regulating intestinal flora and promoting nutrient absorption.They have been widely used in various foods and drugs.The most ideal probiotics are from the human body itself.In this study,colostrum and infant meconium of Yugu,Dongxiang and Baoan healthy volunteers living in Gansu were collected as an important screening Bank of probiotics.Through the analysis of microbial diversity,it can be seen that there are a large number of Lactobacillus in breast milk;Further,the collected fresh breast milk and infant meconium were isolated and screened by microbial pure culture technology and identified by 16 S r DNA sequence analysis,and the potential probiotic characteristics of the screened probiotics were studied.It is expected to provide strain resources for the development of fermented milk food and the research of infant simulated breast milk supplement,and provide a healthier guarantee for infants who cannot realize breast feeding.The main results are as follows:(1)At the level of phyla,a total of 28 phyla were identified in the breast milk samples,and the dominant phyla with a richness greater than 5% were Proteobacteria,Firmicuters and Bacteroidetes.A total of 296 genera were identified at the genus level,and the genera with a richness greater than 1% were as follows: Aeromonas,Acinetobacter,Staphylococcus,Bacillus,Lactobacillus,Enterobacter,Stenotrophomonas and others.Based on the analysis of ɑ diversity and β diversity of microbial communities in breast milk samples of Baoan,Dongxiang and Yugur ethnic groups,there were some differences in microbial diversity among the three ethnic groups,but the differences were not significant.(2)The results of agar culture,microscopic observation and molecular biology identification of test samples: 228 strains were screened out from 20 breast milk and 20 infant meconium samples,including 45 strains of Staphylococcus,64 strains of Bacillus,48 strains of Lactobacillus,2 strains of Bifidobacterium,4 strains of Lactococcus,4 strains of Streptococcus,22 strains of Enterococcus,25 strains of Enterobacter and 5 strains of Klebsiella,1 strain of Acinetobacter,5 trains of Aeromonas and 3 strains of Aeromonas.According to the growth of the strains as the selection standard,20 representative strains of lactic acid bacteria probiotics were finally selected and re screened through acid resistance,bile salt resistance and human gastrointestinal fluid resistance.Finally,7 probiotics were obtained: DM9-7 Lactobacillus plantarum,YF9-4 Lactobacillus rhamnosus,DM6-2Lactobacillus delbrueckii subsp,DM-10 fermented lactobacillus,BM7-6 Bifidobacterium,DM7-6 fermented Lactobacillus and YM7-6 Bifidobacterium were used for follow-up test.(3)The biochemical test,in vitro safety test,bacteriostatic test and drug sensitivity test were carried out for 7 strains of probiotics.The results showed that the 7 probiotics from breast milk infants could be used to aescin,fibrin ertan,maltose,mannitol,salicin,sucrose,inulin and lactose,but could not be used to 1% equine sodium urate.No hemolysis and harmful metabolites were found in the safety tests.In addition,these 7 probiotics had different degree of antibacterial effect on Escherichia coli,Staphylococcus aureus,Salmonella and Enterobacter sakazakii,and had different degree of sensitivity to 10 antibiotics.(4)The hydrophobicity and self-coagulability of the surface properties of 7 probiotic strains were measured,as well as the scavenging ability of supernatant and suspension of the strains to superoxide anion,DPPH and hydroxyl radical and the total reducing ability were measured.The results showed that the seven strains had certain hydrophobicity and self coagulability,but their hydrophobicity and self coagulability were different,and the fermentation supernatant and bacterial suspension of the seven strains had varying degrees of antioxidant activity on free radical scavenging ability,indicating that the seven probiotics had potential probiotic characteristics. |
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