母乳源长双歧杆菌的筛选鉴定及耐氧驯化

目的：从母乳中筛选双歧杆菌,并提高双歧杆菌在有氧条件下的耐受性。方法：采用稀释涂布法结合16S rDNA鉴定法从母乳中筛选出双歧杆菌,并采用逐渐增加氧分压和有氧厌氧交替的方法进行驯化。结果：筛选得一株MEFZ-2201菌株,通过16S rDNA测序比对,其与长双歧杆菌模式菌（NCBI登录号：ON631733.1）的同源性达到了100%,鉴定为长双歧杆菌（Bifidobacterium longum）。将长双歧杆菌MEFZ-2201进行驯化后,其有氧培养最高的活菌数为8.9×10⁹ CFU/mL,比未经驯化的菌株活菌数提高了一个数量级;此外,驯化前后菌株的生理生化及形态特征并未发生变异;在短链脂肪酸的产生量上,驯化后菌株在厌氧条件下产酸量也显著高于驯化前的菌株。结论：驯化后的长双歧杆菌MEFZ-2201在有氧条件下的活菌数明显提高,有望成为潜在的益生菌菌株进一步开发利用。

Screening and identification of Bifidobacterium longum from maternal milk and its domestication of oxygen-domestication

Objective: To screen Bifidobacterium from breast milk and improve its oxygen tolerance under aerobic conditions. Methods: Dilution and spread plate methods were performed to separate and screen Bifidobacterium from breast milk. Their Bifidobacterium identifications were characterized by 16S rDNA sequencing. The oxygen tolerant domestications were conducted through gradual increase of oxygen pressure and alternation of aerobic and anaerobic cultivations. Results: A novel Bifidobacterium strain was isolated from human milk and was identified as Bifidobacterium longum by 16S rDNA sequencing, which was named as MEFZ-2201. The homology between MEFZ-2201 and model strain (accession number in NCBI: ON631733.1) reached 100%. After oxygen tolerant domestication, the highest viable bacteria number of Bifidobacterium longum MEFZ-2201d in aerobic cultivation reached 8.9×10⁹ CFU/mL, which was ten times higher than that of its wild-type strain MEFZ-2201. Whereas, the morphological property and physio-biochemical characteristics of Bifidobacterium longum MEFZ-2201d did not change after oxygen tolerant domestication. The short-chain fatty acid production of domesticated strain Bifidobacterium longum MEFZ-2201d was also significantly higher than that of its wild-type strain even under anaerobic conditions. Conclusion: A novel Bifidobacterium longum strain MEFZ-2201 was isolated from breast milk. The viable bacterium number of its domesticated strain MEFZ-2201d was significantly increased under aerobic conditions, indicating that it would be a potential probiotic strain for further development and utilization.