Characterization and anti-tumor activity of exopolysaccharide produced by Lactobacillus kefiri isolated from Chinese kefir grains

The exopolysaccharide (EPS) from Lactobacilli play a vital part in their probiotic action; on the other hand, up to date, there is little data exist about the effect of EPS on cancer. The aim of the current study is the EPS isolation produced by Lactobacillus kefiri MSR101 (MSR101 EPS) and examination of structural characteristics as well as their capability to prevent the colon cancer (HT-29) cells growth. For the first time, the structure of EPS from Lactobacillus kefiri MSR101 is identified, which is heteropolysaccharide with a repeating unit containing glucose and galactose. The FT-IR and NMR analysis of MSR101 EPS indicates the occurrence of carboxyl, hydroxyl groups, respectively. The XRD results indicated that the MSR101 EPS has partial crystalline nature. SEM and AFM micrographs revealed an extremely spongy structure which suggests that the MSR101 EPS has plasticized film features. Furthermore, the in-vitro anticancer activity results suggested that the newly isolated MSR101 EPS (400 µg/ml) had satisfactory anticancer action on HT-29 cancerous cells (44.1%) and up-regulate the expression of Cyto-c, BAX, BAD, caspase3, caspase8, and caspase9. In general, the present results suggested that the exopolysaccharide from Lactobacillus kefiri MSR101 not only used in the functional food product but also considered as a topical medication due to their effectiveness against colon cancer.