# Characterization and Selection of _Lactobacillus_ Strains with Potential Robotic Applications
## 3 Results and Discussion
### Antimicrobial Activity of Lactobacillus Strains  
Antimicrobial activity is an important criterion for the selection of probioticic strains as natural antagonists of pathogenic and spoilage microorganisms. To assess whether the inhibitory activity was due to lactic acid production or cell-bound components, each strain was pretreated and tested in the form of _Lactobacillus_ culture (LC), cell biomass (CB), cell-free supernatant (CFS) and neutralized cell-free supernatant to pH = 7.0 (NCFS). As seen from the results illustrated in Figure 5, the four _Lactobacillus_ strains inhibited the growth of Gram-positive and Gram-negative bacteria (at varying degrees) but did not exhibit antifungal activity against the tested yeasts _C. albicans_ NBIMCC 74, _S. cerevisiae_ ATCC 9763 and _P. membranaefaciens_, and fungi _A. niger_ ATCC 1015, _A. ochtracus, P. chrysogenum, F. moniliforme_ ATCC 38932 and _F. oxysporum_ (data not presented). In addition, _L. casei_ ATCC 393 showed the lowest antimicrobial potential in comparison to the other three _Lactobacillus_ strains. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Strain**} & \multirow{2}{*}{
\begin{tabular}{c} **Bile Salts** \\ **Concentration** \\ \end{tabular} } & \multicolumn{3}{c}{**Survival Rate, \%**} \\ \cline{3-5}  & & **4 h** & **8 h** & **24 h** \\ \hline \multirow{3}{*}{_L. casei_ ATCC 393} & 1\% & 82.50 \(\pm\) 0.02 \({}^{\text{AA}}\) & 60.00 \(\pm\) 0.02 \({}^{\text{AB}}\) & 36.72 \(\pm\) 0.06 \({}^{\text{AC}}\) \\  & 0.75\% & 87.50 \(\pm\) 0.01 \({}^{\text{BA}}\) & 61.67 \(\pm\) 0.02 \({}^{\text{BB}}\) & 38.98 \(\pm\) 0.04 \({}^{\text{DC}}\) \\  & 0.5\% & 90.00 \(\pm\) 0.02 \({}^{\text{CA}}\) & 65.00 \(\pm\) 0.04 \({}^{\text{CB}}\) & 41.81 \(\pm\) 0.06 \({}^{\text{CC}}\) \\  & 0.25\% & 92.50 \(\pm\) 0.03 \({}^{\text{AA}}\) & 68.83 \(\pm\) 0.02 \({}^{\text{AB}}\) & 50.85 \(\pm\) 0.08 \({}^{\text{AC}}\) \\  & 1\% & 75.61 \(\pm\) 0.08 \({}^{\text{AA}}\) & 50.63 \(\pm\) 0.08 \({}^{\text{AB}}\) & 42.79 \(\pm\) 0.08 \({}^{\text{AC}}\) \\ _L. casei_ RC-1 & 0.75\% & 78.05 \(\pm\) 0.06 \({}^{\text{BA}}\) & 54.43 \(\pm\) 0.08 \({}^{\text{BB}}\) & 43.26 \(\pm\) 0.12 \({}^{\text{BC}}\) \\  & 0.5\% & 80.49 \(\pm\) 0.04 \({}^{\text{CA}}\) & 59.49 \(\pm\) 0.06 \({}^{\text{GB}}\) & 45.12 \(\pm\) 0.09 \({}^{\text{CC}}\) \\  & 0.25\% & 92.68 \(\pm\) 0.02 \({}^{\text{AA}}\) & 68.35 \(\pm\) 0.03 \({}^{\text{AB}}\) & 50.70 \(\pm\) 0.03 \({}^{\text{AC}}\) \\  & 1\% & 61.19 \(\pm\) 0.01 \({}^{\text{AA}}\) & 40.24 \(\pm\) 0.04 \({}^{\text{AB}}\) & 38.54 \(\pm\) 0.08 \({}^{\text{AC}}\) \\ _L. acidophilus_ RC-2 & 0.75\% & 65.67 \(\pm\) 0.01 \({}^{\text{BA}}\) & 53.25 \(\pm\) 0.09 \({}^{\text{BB}}\) & 48.78 \(\pm\) 0.04 \({}^{\text{DC}}\) \\  & 0.5\% & 68.66 \(\pm\) 0.03 \({}^{\text{CA}}\) & 58.58 \(\pm\) 0.06 \({}^{\text{GB}}\) & 52.68 \(\pm\) 0.10 \({}^{\text{CC}}\) \\  & 0.25\% & 80.60 \(\pm\) 0.09 \({}^{\text{AA}}\) & 76.92 \(\pm\) 0.19 \({}^{\text{AB}}\) & 68.78 \(\pm\) 0.04 \({}^{\text{AC}}\) \\  & 1\% & 61.76 \(\pm\) 0.01 \({}^{\text{AA}}\) & 43.89 \(\pm\) 0.10 \({}^{\text{AB}}\) & 42.86 \(\pm\) 0.06 \({}^{\text{AC}}\) \\ _L. rhamnus_ RC-10 & 0.75\% & 63.24 \(\pm\) 0.08 \({}^{\text{BA}}\) & 48.89 \(\pm\) 0.11 \({}^{\text{BB}}\) & 47.62 \(\pm\) 0.05 \({}^{\text{BC}}\) \\  & 0.5\% & 69.12 \(\pm\) 0.03 \({}^{\text{CA}}\) & 55.56 \(\pm\) 0.12 \({}^{\text{GB}}\) & 50.00 \(\pm\) 0.12 \({}^{\text{CC}}\) \\  & 0.25\% & 73.53 \(\pm\) 0.14 \({}^{\text{AA}}\) & 62.78 \(\pm\) 0.11 \({}^{\text{AB}}\) & 60.95 \(\pm\) 0.10 \({}^{\text{CC}}\) \\ \hline \end{tabular} Values are expressed as means \(\pm\) SD. Letters a–d indicate significant differences (\(p<0.05\)) within a sample exposed to different conditions, while letters A–C denote significant differences (\(p<0.05\)) between the cultivation hours, \(n=3\).  
\end{table}