Isolation and Characterization of Lactic Acid Bacteria from Raw Cow Milk and Evaluation of Their Probiotic Potential

Abstract

<title>Abstract</title> Lactic acid bacteria (LAB) have diverse applications in dairy, food, feed, and health, yet their probiotic potential from cow milk remains under-researched. This study aimed to identify and characterize LAB isolates from raw cow milk and evaluate their probiotic suitability. A total of 23 pure bacterial isolates were obtained from seven milk samples, with nine gram-positive, catalase-negative isolates selected for further analysis. These isolates were citrate-negative, non-motile, and indole-negative, with seven exhibiting homo-fermentative traits, and two (M5 and M9) identified as hetero-fermentative. Physicochemical analysis of milk samples showed notable variation in composition, including protein (2.2–3.2%), lactose (3.3–4.4%), fat (1.6–2.6%), ash (0.4–0.6%), salt (0.4–0.6%), titratable acidity (0.1–0.4%), pH (5.7–6.7%), moisture (83.9–87.5%), density (25.9–27.3), and freezing point (0.4–0.6). Antibacterial tests revealed strong inhibition of <italic>S. aureus</italic> by M1 (11 mm) and <italic>P. aeruginosa</italic> by M6 and M8 (9 mm and 13 mm), while <italic>E. coli</italic> showed complete resistance. Hemolysis tests confirmed LAB isolates as non-pathogenic, with no α- or β-hemolysis observed. Antibiotic susceptibility varied, with M2, M3, M4, and M8 completely resistant, while M1, M5, M6, M7, and M9 showed susceptibility to meropenem, ampicillin, penicillin G, and other antibiotics. Sensory evaluation indicated M1 and M7 had the highest overall acceptability, while M3 and M8 scored lower in color and taste. LAB isolates were tentatively classified under <italic>Lactobacillus, Enterococcus</italic> , and <italic>Leuconostoc</italic> , indicating their probiotic potential and viability as starter cultures in dairy and food industries. Further molecular identification and characterization are needed to determine specific strains and commercial applications.