## 3 Results and Discussion
### Antimicrobial Activity of the CFS  
The efficacy of the CFSs produced by the selected strains as a potential protective culture against various species of pathogenic and spoilage micro-organisms is shown in Figure 1 and with more detail in Table S4. In the case of the pathogenic target strains, the resulting inhibition halo for the CFS of the strain _P. acidilactici_ CNTA 1059 against _L. monocytogenes_ was 24.53 \(\pm\) 0.21 mm, indicating robust antimicrobial activity. This observation aligns with the results obtained by [PERSON] et al. [9] for their strain IDE0550 against three different _L. monocytogenes_ strains. Similarly, the CFS of the selected strain _L. plantarum_ CNTA 600 exhibited a strong antimicrobial effect against _L. monocytogenes_ (15.27 \(\pm\) 0.47 mm), consistent with the findings of [PERSON] et al. [53]. A medium antimicrobial activity against _B. cereus_ (13.36 \(\pm\) 0.67 mm) was observed, corroborating similar previous results by [PERSON] and [PERSON] [54]. _L. brevis_ CNTA 1374 CFS showed no antimicrobial activity against any of the pathogenic strains. This contradicted the findings of [PERSON] et al. [55], who reported the antimicrobial activity of the _L. brevis_ KU15153 strain against food pathogens, including _L. monocytogenes_, _S. aureus_, _Salmonella_ Typhimurium, and _E. coli_. Such discrepancies may be highlighting the variability in antimicrobial activity among different strains of the same species. Finally, the antimicrobial activity of CFS _B. subtilis_ CNTA 517 was strong against _L. monocytogenes_ (28.98 \(\pm\) 0.07 mm) and against _S. aureus_ (19.36 \(\pm\) 0.07 mm). Different authors have reported the strong antimicrobial activity of purified bacterios produced by _B. subtilis_ against these two pathogenic micro-organisms. [PERSON] et al. [56] documented the antimicrobial activity of subtilis13-4, while [PERSON] et al. [57] described that of peptide-Ba49. However, the reported activity of these peptides was lower than the antimicrobial activity of _B. subtilis_ CNTA 517 described in this paper. Figure 1: Depiction of the inhibition zone achieved by each selected culture-free supernatant: \(<\)9.2 mm (white), 9.2 mm \(\leq\) inhibition zone \(<\) 15.0 mm (green), 15.0 mm \(\leq\) inhibition zone \(<\) 25.0 mm (red), and \(\geq\)25.0 mm (blue). Tested bacterial species: K.m. = _Kluyveromyces marraimus_ CNTA.1649, P.f. = _Pseudomonas fluorescens_ CNTA 571, L.p. = _Lentilalactobacillus parabuchneri_ DSMZ 5987, R.m. = _Rothia mucliaginous_ DSMZ 18184, P.a. = _Pseudomonas aeruginosa_ CECT 110T, L.m. = _Listeria monocytogenes_ CECT 7467, B.c.193 = _Bacillus cereus_ CECT 193, B.c.503 = _Bacillus cereus_ CNTA 503, S.T. = _Salmonella_ Typhimurium CECT 443, S.a. = _Staphylococcus aureus_ CECT 976, and E.c. = _Escherichia coli_ DSMZ 19206. A dendrogram showing the taxonomic hierarchical relationship between the different tested  
strains is also shown. 1 = _Lactiplantihacillus plantarum_, 2 = _Lactiplantihacillus pentosus_, 3 = _Pediococcus acidilactici_, 4 = _Lacticaseibacillus paracasi_, 5 = _Lacticaseibacillus rhamnosus_, 6 = _Lacticaseibacillus casei_, 7 = _Lacticaseibacillus maninditivorans_, 8 = _Limosilatechobacillus fermentu_, 9 = _Limosilatechobacillus rewteri_, 10 = _Levilactobacillus brevis_, 11 = _Lacobacillus delbrueckii_, 12 = _Lactobacillus jolonsoni_, 13 = _Leuconostoc mesenteroides_, 14 = _Leuconostoc citreum_, 15 = _Leuconostoc pseudomenteroides_, 16 = _Latilactobacillus curvatus_, 17 = _Weissella confusa_, 18 = _Companilatechobacillus alimentarius_, 19 = _Liquorilactobacillus nageli_, 20 = _Ligilactobacillus salivarius_, 21 = _Oenococcus oeni_, 22 = _Enterococcus ununditi_, 23 = _Bacillus subtilis subtilis_. Selected cultures: a = _Lactiplantihacillus plantarum_ CNTA 600, b = _Pediococcus acidilactici_ CNTA 1059, c = _Levilactobacillus brevis_ CNTA 1374, and d = _Bacillus subtilis_ CNTA 517. The strain _L. monocytogenes_ CECT 7467 was selected as the pathogenic indicator microorganism to be used in the next assays for the CFSs of _P. acidilactici_ CNTA 1059, _L.