Abstract: Fifteen strains of Bifidobacterium infantis were screened for their promoting effects on the proliferation of human fetal colon epithelial cells (CCD841 CoN) in this study. The biological properties of the selected strains such as morphological characteristics, growth characteristics, environmental tolerance, adhesion properties and safety were evaluated, and the optimal conditions for promoting cell proliferation were also determined. The effect of live and inactivated cell suspensions, culture supernatants, and lysates of each strain on the proliferation activity of CCD841 CoN cells was evaluated by CCK-8 method. The results of principal component analysis (PCA) showed that Bifidobacterium longum K2-21-4 had the best overall cell proliferation-promoting effect. The adhesion rate of K2-21-4 to CCD841 CoN cells was 6.6%, only slightly lower than that of the commercial strain Lactobacillus animalis BB12. However, the tolerance of K2-21-4 to acid and bile salt was poor. K2-21-4 had resistance to aminoglycosides and quinolones but was to a certain extent sensitive to penicillin and macrolide, and highly sensitive to amoxicillin, vancomycin, tetracycline, rifampicin and chloramphenicol. It had no hemolytic activity. The live cell suspension of B. longum K2-21-4 at 107 CFU/mL had the best effect on promoting cell proliferation when co-cultured for 24 h. To sum up, B. longum K2-21-4 can be potentially applied to promote the proliferation of CCD841 CoN cells.

Key words: Bifidobacterium; CCD841 CoN cells; cell proliferation; biological characteristics; baby feces