Abstract
Traditional dairy products play an important role in both local family economies and human nutrition in Algeria. This research focused on isolating lactic acid bacteria (LAB) from traditional Algerian Lben samples prepared from a blended raw milk matrix. Through phenotypic characterisations, morphological evaluations, and physiological and biochemical assessments, an isolate was identified as belonging to the genus Lacticaseibacillus, tentatively identified as a presumptive Lacticaseibacillus sp. The cell-free supernatant (CFS) of this strain was pH-neutralized, membrane-filtered, and tested for its antagonistic effects against three major pathogenic and spoilage microorganisms: Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 6538, and Listeria monocytogenes ATCC 13932, utilising the agar well diffusion method. Under laboratory conditions, the strain demonstrated clear antibacterial activity, with inhibition zone diameters of 18.00 ± 0.58 mm for L. monocytogenes, indicating the highest susceptibility, followed by S. aureus (16.00 ± 0.45 mm), while P. aeruginosa showed the greatest resistance with the smallest inhibition zone of 14.00 ± 0.50 mm. Statistical analysis performed using one-way Analysis of Variance (ANOVA) and Tukey’s HSD post hoc test revealed that the differences in susceptibility among the target pathogens were statistically significant (p < 0.05). Enzymatic and stability characterization indicated that the activity is mediated by a heat- and pH-stable proteinaceous substance. These preliminary findings highlight the potential of this strain, isolated from traditional Algerian dairy products, as a potential candidate bio-preservative agent in the food industry, subject to further molecular confirmation and food matrix validation.