In Vitro Screening of Short Synthetic Antimicrobial Peptides Toward Food-Relevant Microorganisms: Antifungal Activity and Molecular Docking Analysis

Food spoilage and foodborne microorganisms remain major challenges for food safety and preservation, stimulating the search for alternative antimicrobial agents compatible with minimally processed and clean-label products. In this study, six short synthetic peptides containing arginine, or both lysine and arginine residues, were evaluated as potential antimicrobial agents against Staphylococcus aureus, Salmonella enterica, and Candida albicans. Minimum inhibitory concentrations were determined by broth microdilution, and molecular docking was performed against C. albicans lanosterol 14α-demethylase to provide molecular-level insights. None of the peptides inhibited S. enterica within the tested concentration range, indicating limited activity against the Gram-negative bacterium. Peptides 1, 3, 5, and 6 inhibited S. aureus only at relatively high concentrations, with MIC values between 1598.7 and 1782.0 µmol L−1, without confirmed bactericidal activity. In contrast, peptide 4, FEFKFEFKGGGRGDS, was the only sequence active against C. albicans, showing an MIC of 19.93 µmol L−1. However, no minimum inhibitory concentration (MIC) was obtained within the tested concentration range, indicating that the observed antifungal effect should be interpreted as inhibitory rather than confirmed fungicidal activity. Docking analysis was consistent with this experimental trend, as peptide 4 exhibited the most favorable predicted binding energy, −8.4 kcal mol−1, and established predicted contacts with catalytic site of ERG11, including Lys143, Arg381, His468, Arg469, and Cys470. These findings indicate that antimicrobial activity was strongly sequence- and microorganism-dependent. Peptide 4 represents a promising antifungal lead sequence for further optimization and validation in food-relevant systems.