In recent years, as consumer demand for natural food preservatives has increased, lactic acid bacteria (LAB) and their secondary metabolites have become a focus of research due to their many health benefits. The term ''postbiotic'' is defined as metabolites released by LAB during growth in food or medium. Postbiotics contain bioactive compounds, such as organic acids, bacteriocins, exopolysaccharides, etc. Escherichia coli and Staphylococcus aureus are responsible for numerous public health concerns. The aim of this study was to determine the antimicrobial activity, pH, and titratable acidity parameters of non-concentrated (1×) and concentrated (10×, 12.5×, 15×) postbiotics obtained from Lactiplantibacillus plantarum ATCC 14917. In vitro antimicrobial analyses revealed that 10×, 12.5×, and 15× concentrated postbiotics displayed inhibition zones diameters ranging from 8.05 to 10.78 mm against E. coli and S. aureus strains. Additionally, the pH values of the 10×, 12.5×, and 15× concentrated postbiotics ranged between 4.44 and 4.97, and their titratable acidity values ranged between 1.42 and 14.35 % g lactic acid. It was found that the postbiotic showed larger inhibition zone against the tested strains in a dose-dependent manner (p<0.05). Furthermore, the results revealed that the increase in the condensation ratio of the postbiotic led to considerable decrease in the pH values and an remarkable increase in the titratable acidity (p<0.05). In conclusion, it has been demonstrated that postbiotics derived from the L. plantarum strain exhibit robust antimicrobial activity against bacteria and have the potential to enhance food safety.