Lacticaseibacillus paracasei-Derived Antibacterial Peptide NGJ1D and Its Mechanism of Action Against Staphylococcus aureus

Staphylococcus aureus is a common Gram-positive pathogen that causes food poisoning and foodborne illnesses. In this study, a peptide-designated NGJ1D (GAPNDLTARFIAKK) was found among 8 peptides in the fermentation broth of Lacticaseibacillus paracasei. NGJ1D had a minimum inhibitory concentration (MIC) of 62.5 μg/mL against Staphylococcus aureus and could kill the bacteria within 3 h. In a mimicked bacterial cell membrane environment, NGJ1D could change its secondary structure from a random coil to an α-helix to increase its membrane permeability and subsequent interaction with bacteria genomic DNA. Further analysis using SDS–polyacrylamide gel electrophoresis, ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS), and molecular docking revealed that NGJ1D affects the DNA-binding protein HU of S. aureus to interfere with DNA synthesis. These results indicate that novel peptides with antimicrobial potential, such as NGJ1D, could be identified in fermentation broths and can be used for application in food preservation and the prevention and treatment of infections caused by S. aureus.