## 3 Results
### Partial Characterization of the Isolated Antibacterial Substance  
The antibacterial substance isolated from strain 124-2 was highly stable in response to heat. The effect of pH on antimicrobial activity showed that the antimicrobial retained 100% of its activity from pH 2 to 6 and decreased at pH 9 (Figure 5A). Based on these values, it can be concluded that the bacteriocin _L. pentosus_ is constant at temperatures between  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Purification Stage** & **Volume** & **Protein** & **Total** & **a Total** & **b Specific** & **c Yield** & **d Purification** \\
**Concentration** & **Concentration** & **Protein** & **Activity** & **Activity** & **(AU/mg)** & **(\%)** & **(fold)** \\ \hline Cell-Free Supernatant (CFS) & 1300 & 51.50 & 66.95 & 1609.91 & 24.05 & 100 & 1 \\ Precipitation Ammonium & 38 & 106.63 & 4.052 & 78.06 & 19.27 & 4.85 & 0.80 \\ Sulfate & 2 & 53.83 & 0.108 & 6.524 & 60.59 & 0.41 & 3.15 \\ \hline \end{tabular}  
* Total activity (AU). Activity level (AU/mL) \(\times\) volume (mL). b Specific activity (AU/mg) represents total activity divided by protein concentration. c Yield (%) represents total activity of purified fraction divided by total activity of crude extract \(\times\) 100. d Purification fold represents specific activity of purified fraction divided by specific activity of crude extract activity (AU/mL) \(\times\) volume (mL).  
\end{table}
Table 2: The antibacterial activity of bacteriocin against _Salmonella_ sp. and _S. aureus_.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & \multicolumn{3}{c}{**Clear Zone (mm)**} \\ \cline{2-4}  & _Salmonella_ sp.** & **S. aureus** \\ \hline Bacterio _L. pentosus_ & 11.79 \(\pm\) 2.51 & 9.96 \(\pm\) 1.31 \\ Antibiotic & 30 & 18 \\ \hline \end{tabular}  
\end{table}
Table 3: Antimicrobial activity of purified bacteriocin.  
25 \({}^{\circ}\)C and 121 \({}^{\circ}\)C, with optimal conditions at temperatures between 25 \({}^{\circ}\)C and 60 \({}^{\circ}\)C. When applying the _L. pentosus_-derived bacteriocin, the recommended temperature for optimal bacteriocin efficacy was below 80 \({}^{\circ}\)C (Figure 5B). A bacteriocin activity test was performed to determine the tolerance of the bacteriocin to salinity. Tests were performed at different concentrations of NaCl: 2%, 4%, and 6%. The results showed that _L. pentosus_ is tolerant to salt conditions (Figure 5C). The activity of the compounds increased after treatment with inhibitors such as SDS, Tween 80, and EDTA (Figure 5D). Relatively small size peptide molecules with uncomplicated structures (no tertiary structure) were expected to be largely unaffected by temperature, pH, metal ions, or various inhibitors.  
Figure 4: SDS-PAGE result of partial and purified bacteriocin. Lanes A and B: partially purified bacteriocin with ammonium sulphate has two protein bands. Lanes C and D: purified bacteriocin with gel filtration chromatography has one protein bands. 1 refers to 26.69 kDa; 2 refers to 17.15 kDa.  
Figure 5: Partial characterization of the isolated antibacterial substance. (**A**) Effect of pH: the stability of the antibacterial substance at various pH values was measured after mixing the antibacterial substance with different pH values (2.0, 4.0, 6.0, and 9.0). (**B**) Effect of temperature: the antibacterial activity substance was heated at 25, 37, 45, 60, and 80 \({}^{\circ}\)C for 30 min, and at 121 \({}^{\circ}\)C for 15 min. (**C**) Antimicrobial activity with different salt concentrations (2%, 4%, 6%). (**D**) Antimicrobial activity with additional surfactant (EDTA, SDS, and Tween 80).