Functional Properties of Lactic Acid Bacteria Postbiotics Isolated from Tarhana Samples

This study aimed to characterize postbiotics derived from lactic acid bacteria (LAB) isolated from tarhana, a traditional fermented Turkish soup consumed after cooking. LAB isolates from tarhana were used to prepare postbiotics through two methods: In the first of these, cell-free supernatants (CFS) were obtained by centrifugation method. In the second method, due to the fact that tarhana is consumed by cooking, heat-killed (HK) cell fragments of LAB isolates were obtained. The antimicrobial activity of the postbiotics against Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium was evaluated by well diffusion. A total of 150 postbiotic samples were obtained from 75 LAB isolates, with 41 inhibiting S. aureus and 18 inhibiting L. monocytogenes growth. The antimicrobial activity diminished after pH neutralization, indicating acidic compounds as the active agents. Ten postbiotic samples with the highest antimicrobial activity were selected and were identified as Pediococcus pentosaceus via 16S rRNA sequencing. DPPH Radical scavenging activity ranged from 8 and 75 µg/ml. Cytotoxicity assays showed that 24-h treatment of HT-29 cells with 20 mg/ml of P1-CFS, P2-CFS, P1-HK, and P2-HK reduced cell viability by 66%, 78%, 75%, and 72%, respectively, with IC₅₀ values ranging from 8.52 to 9.20 mg/ml. HPLC and FT-IR analyses reveled no significant differences in activity or structure between the CFS and HK forms of postbiotics (p > 0.05). In conclusion, postbiotics from tarhana demonstrated significant potential for a broad range of applications in the food and health industries, offering advantages over probiotics.