The lactic acid bacteria, Lactiplantibacillus plantarum KU15149 and Levilactobacillus brevis KU15176 were verified through phenotypic and genotypic analyses. Safety evaluation was conducted using multiple assays, including minimum inhibitory concentration assay for nine antibiotics, hemolytic activity, mucin degradation, gelatin liquefaction, urease activity, indole production, β-glucuronidase activity, bile salt deconjugation, cell cytotoxicity, D-/L-lactic acid production, and biogenic amine formation. Genotypically L. plantarum KU15149 and L. brevis KU15176 lacked all virulence and antibiotic resistance genes investigated. Consistent with these results, phenotypic assays showed that both strains were susceptible according to EFSA cut-off values and tested negative for hemolysis, mucin degradation, gelatin liquefaction, urease activity, indole production, β-glucuronidase activity, and bile salt deconjugation. Furthermore, neither strain showed cytotoxicity toward Caco-2 cells at a multiplicity of infection of 250. Production of D-lactic acid and biogenic amines was negligible in both bacteria. Overall, L. plantarum KU15149 and L. brevis KU15176 demonstrated safety and beneficial characteristics and therefore could serve as probiotic strains.

Abstract
Introduction
Materials and Methods
    Bacterial strains and medium
    Safety and functional characterization of strains
    Antibiotic susceptibility assay
    Detection of antibiotic resistance genes
    Genomic analysis of antibiotic resistance andvirulence genes
    Production of D-/L-lactic acid
    Determination of biogenic amine concentration
    In vitro cytotoxicity assessment using Caco-2 cells
    Statistical analysis
Results and Discussion
    Safety and functional characterization of strains
    Antibiotic susceptibility assay
    Detection of antibiotic resistance genes
    Genomic analysis of antibiotic resistance andvirulence genes
    Production of D-/L-lactic acid
    Determination of biogenic amine concentration
    In vitro cytotoxicity assessment using Caco-2 cells
Conclusion
References

• Min Joo Kang(Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Korea)
• Min-Gyu Lee(Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Korea)
• Huijin Jeong(Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Korea)
• Young-Seo Park(Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Korea) Corresponding author
• Sulhee Lee(Korean Culture Center of Microorganisms, Seoul 03641, Korea)
• Dae-Kyung Kang(Department of Animal Biotechnology, Dankook University, Cheonan 31116, Korea)
• Hyun Dong Paik(Department of Food Science and Biotechnology of Animal Resources, Konkuk University, Seoul 05029, Korea)