Screening of Antagonistic Lactic Acid Bacteria Isolated from Fermented Goat Milk in Morocco’s Souss-Massa Region

Fermented goat milk from the Souss-Massa region in southern Morocco constitutes a valuable reservoir of beneficial microorganisms, particularly lactic acid bacteria (LAB) known for their antagonistic and antimicrobial properties. This study aimed to isolate, characterize, and evaluate the antagonistic potential of LAB strains against major foodborne pathogens. Thirty traditional fermented goat milk samples were collected from local producers, yielding 720 LAB isolates. These were screened for inhibitory activity against Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus using two complementary techniques: the double-layer agar method and the well diffusion assay. A total of 56 isolates exhibited inhibition on solid media, while 10 strains demonstrated significant activity in liquid media, producing inhibition zones ranging from 13 to 25 mm. Preliminary phenotypic characterization revealed that the isolates were Gram-positive, catalase-negative cocci occurring in pairs or chains. Based on the biochemical profiles obtained using API 20 STREP galleries, the strains were identified as belonging to Enterococcus faecium, E. faecalis, and E. durans. The selected strains also exhibited notable resilience to environmental stresses, including growth in 6.5% NaCl, pH 9.6, incubation at 45 °C, and thermal treatment at 60 °C for 30 minutes. These results highlight the potential of Enterococcus spp. from fermented goat milk as promising candidates for bacteriocin production and biopreservation. Future work, including molecular identification and in vivo validation, will further elucidate their suitability for industrial applications in functional dairy product development and food safety enhancement.