Characterization of lactic acid bacteria postbiotics isolated from tarhana samples

Objective: It is aimed to obtain postbiotics from lactic acid bacteria contained in tarhana samples, which is a nutritious and fermented food widely consumed in our country, and to determine the antimicrobial, antioxidant and anti-cancer properties of the postbiotics obtained. Material and Method: LABs were isolated from tarhana samples obtained from Aydın and its surroundings and produced with traditional methods in season, and these LABs were identified at the genus/species level using classical and molecular methods. Postbiotics were obtained by two different methods: obtaining cell-free supernatants from LABs and obtaining dead cells by heat treatment. The antimicrobial properties of the prepared postbiotics were determined by the well diffusion method. The inhibition effect on the pathogens B. cereus CCM 99, L. monocytogenes ATCC 19113, S. aureus ATCC 29213, E. coli ATCC 11229, S. Typhimurium ATCC 14028 was investigated. Characterization analyzes of the samples that stand out with their antimicrobial properties were carried out, and within the scope of the characterization of postbiotics, antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and analyzed by HPLC and FTIR to determine the phenolic composition. The cytotoxic effects of lyophilized postbiotic samples on the HT-29 cancer cell line were determined by the MTT method. Results: Counts were taken from 5 tarhana samples provided and LAB isolation was performed. In the antimicrobial analysis of the postbiotics prepared for the 75 isolates obtained, the S. aureus ATCC 29213 pathogen was evaluated as sensitive against 41 of the postbiotics, and the L. monocytogenes ATCC 19113 pathogen was evaluated as sensitive against 18 of the postbiotics. In the applications made by neutralizing the postbiotics, no inhibition effect was observed and it was determined that the active antimicrobial substance was derived from organic acids and the pH value of the postbiotics varied between 4-5. 10 species that stand out for their antimicrobial properties have been identified as Pediococcus pentosaceus. DPPH radical scavenging activities were found to vary between 8 and 75 µg/ml, and IC50 values were found to be 8.5 to 11.2 mg/ml. No significant difference was observed in terms of activity and structure between the supernatant and heat-treated forms of postbiotics. Conclusion: With this thesis study, the postbiotic potential of tarhana, a fermented food with a rich nutritional composition, was revealed. Since there is no loss of viability problem compared to probiotics, it is predicted that it has the potential to find more application areas in the field of food and health by improving storage conditions, ease of storage and transportation, product distribution to underdeveloped regions and future studies. Keywords: Tarhana, Lactic acid bacteria, Probiotic, Postbiotic, Anticancer, Antimicrobial, Antioxidant