# Antibacterial Effects of Synthetic Plantaricins Against Staphylococcus aureus

## TL;DR

This study shows that synthetic plantaricins can kill Staphylococcus aureus, a harmful bacteria, and could be used as natural antimicrobial agents.

## Contribution

The study introduces synthetic plantaricin combinations and evaluates their antibacterial mechanisms and stability against S. aureus.

## Key findings

- Synthetic plantaricin combinations showed minimal inhibitory concentrations between 1.4 and 1.8 μg/mL against S. aureus.
- Raman spectra and electron microscopy confirmed cell lysis caused by the synthetic plantaricins.
- Antibacterial activity was stable at temperatures below 40°C and pH 4–7, but decreased in the presence of proteases.

## Abstract

Background/Objectives: Plantaricins without a signal sequence were synthesized based on bacteriocins, plantaricins A, E, F, J, and K, of Lactiplantibacillus plantarum KM2. The antibacterial activities of four combinations of synthetic plantaricins—spPlnA, E&F, E&J, and J&K—were identified against Staphylococcus aureus ATCC 12692. And in this experiment, we aimed to identify the antimicrobial mechanism of the synthesized plantaricin sample against S. aureus. Methods/Results: The minimal inhibitory concentrations for each combination were 1.4 μg/mL, 1.8 μg/mL, 1.6 μg/mL, and 1.6 μg/mL, respectively. Raman spectra changed after treating S. aureus ATCC 12692 with synthetic plantaricins. Furthermore, transmission electron microscopy results revealed that the four synthetic plantaricin combinations could induce the cell lysis of S. aureus ATCC 12692. Finally, the four synthetic plantaricin combinations maintained their antibacterial effect at temperatures below 40 °C, and at pH levels of pH = (4–7). Except for spPlnJ&K, they are stable against the action of α–amylase and lysozyme. Overall, these results indicate that, excepting spPlnJ&K, the three synthetic plantaricin combinations exhibit similar antibacterial activity. Conclusions: Through this study, we confirmed that synthetic plantaricin exhibited antimicrobial activity against S. aureus, demonstrating its potential as a direct antimicrobial agent. However, since the antimicrobial activity decreased due to protease, it was confirmed that its use is limited in environments where protease is present.