Isolation of exopolysaccharide from lactic acid bacteriaand determination of their biological activities

In this thesis study, exopolysaccharide extraction was performed from lactic acid bacteria isolated from colostrum. Exopolysaccharides have many effects such as improving the immune system, lowering cholesterol, antiulcer and antitumor. Lactic acid production, hemolytic activity, pH, bile salt and acid resistance, identification by classical and molecular methods, autoaggregation, coaggregation, biofilm formation abilities, antibiotic susceptibility and antimicrobial activity of the isolated lactic acid bacteria were determined. The isolated exopolysaccharides were lyophilized and their cytotoxic effects were investigated using the MTT method and apoptotic effects were investigated using the Annexin V-PI method on the HepG-2 cell line. Intracellular and extracellular cytokine levels were also determined on a flow cytometer. According to the molecular identification results, all strains were determined to be L. rhamnosus. IC50 values were found between 3.02 and 6.5 mg/mL. According to flow cytometry results, it was found that lyophilized EPS samples caused early apoptosis. According to the cytokine results, it was determined that there was a decrease in TNF-α, IL-1β and IL-6 cytokines in the cells treated with lyophilized EPS sample compared to the control, and an increase in the IL-10 cytokine. Exopolysaccharides isolated from lactobacilli have important potential in terms of both immunity and cytotoxic activity.