SAFETY AND FUNCTIONAL CHARACTERIZATION OF LACTIC ACID BACTERIA WITH PROBIOTIC POTENTIAL

Lactic acid bacteria (LAB) are widely investigated as probiotic candidates due to their potential to promote microbial balance, inhibit pathogens, and provide functional benefits in food and health applications. However, probiotic suitability is strain-specific and requires systematic safety and functional characterization. Because safety and probiotic performance may differ among related isolates, strain-level screening remains essential for responsible probiotic research and development programs. This study evaluated the safety profile and selected in vitro probiotic properties of ten LAB strains isolated from sourdoughs from different climatic regions of Paraíba identified as Companilactobacillus paralimentarius (34, 39) Lactiplantibacillus plantarum (47, 53, 79, 80, 113) and Levilactobacillus brevis (83, 84, 121). The strains were evaluated for autoaggregation, cell-surface hydrophobicity, phytase activity, and antagonistic activity against Escherichia coli and Staphylococcus aureus. Safety analyses included hemolytic, gelatinase, DNase, and biogenic-amine production assays. Antibiotic susceptibility was assessed by the disk-diffusion method using ampicillin, chloramphenicol, erythromycin, clindamycin, tetracycline, gentamicin and tobramycin. Inhibition-zone diameters were measured, and susceptibility categories were interpreted according to the study criteria. None of the ten strains exhibited hemolytic, gelatinase, DNase, or biogenic-amine production activity, indicating a satisfactory safety profile for the phenotypic traits evaluated. Antagonistic activity against S. aureus was detected for all strains. Against E. coli, inhibition was observed for strains 34, 47, 53, 79, 80, 83, 84, 113, and 121, whereas strain 39 showed no detectable inhibition. Autoaggregation ranged from 49.23 ± 0.02% in strain 47 to 88.66 ± 0.01% in strain 80. Cell-surface hydrophobicity varied from 7.23 ± 0.02% in strain 84 to 88.86 ± 0.01% in strain 80. Phytase activity ranged from 7.12 ± 0.46 mm in strain 39 to 9.46 ± 0.52 mm in strain 80. The antibiotic susceptibility profile indicated overall susceptibility to the antibiotics evaluated. Strains 84 and 47 showed intermediate susceptibility to ampicillin; strains 39 and 84 showed intermediate susceptibility to tetracycline; and strain 34 was resistant to tetracycline. The remaining isolates were susceptible to all antibiotics evaluated. The evaluated LAB strains showed promising functional properties, including pronounced antagonistic activity against S. aureus, high to moderate autoaggregation capacity, variable cell-surface hydrophobicity, and phytase activity. Combined with their safety-related phenotypic characteristics, these findings support the potential of the evaluated strains for further investigation in biotechnological applications. Overall, the results provide a basis for selecting promising LAB candidates for further characterization and validation in food or health-related systems.

The authors acknowledge the financial support of FAPESQ-PB (Call No. 49/2024), the CNPq Universal Call No. 44/2024 – Emerging Research Groups (Track A), and the INOVCACT project, funded through the MCTI/FINEP/FNDCT/CT-AGRO Public Call – Bioeconomy Production Chains Program – ICT Support (Call No. 01/2022).