Microbiological and Functional Assessment of Lactobacillus casei: Probiotic, Antimicrobial, and Antioxidant Properties

Probiotics are beneficial microorganisms that promote health when consumed in adequate amounts. This research explores the probiotic characteristics of Lactobacillus casei, emphasizing its antimicrobial and antioxidant activities. The bacterial strain was obtained from cultured dairy sources and identified using 16S rDNA sequencing. To assess its potential for its ability to survive in the gastrointestinal tract, the strain was subjected to tolerance assays for acidic pH, bile salts, and sodium chloride (NaCl), demonstrating a high capacity to withstand these harsh conditions. The anti microbial activity of L. casei was analyzed utilizing the well-diffusion assay, revealing significant inhibitory effects against a range of foodborne pathogens. The strain effectively suppressed the growth of Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Candida albicans, indicating its potential as a natural antimicrobial agent. Additionally, an antibiotic susceptibility test was performed, showing that L. casei exhibited resistance to ceftriaxone, gentamicin, and cefotaxime, while remaining susceptible to commonly used antibiotics such as erythromycin, ofloxacin, and ampicillin. This selective antibiotic sensitivity profile supports its safety as a probiotic candidate. Furthermore, the antioxidant potential of L. casei was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The cell-free supernatant of L. casei exhibited a strong dose-dependent antioxidant effect, with an IC50 value of 15.62 mg/ml. This highlights its potential as a natural source of antioxidants, which may contribute to oxidative stress reduction in various applications. Overall, these findings reinforce the suitability of L. casei as a promising probiotic strain with notable antimicrobial and antioxidant properties. Its potential applications extend to functional foods and pharmaceutical formulations, where it may enhance gut health, inhibit pathogenic microorganisms, and provide natural antioxidant benefits.