Isolation, identification, and synergistic mechanism of a novel antimicrobial peptide and phenolic compound from fermented walnut meal and their application in Rosa roxbughii Tratt spoilage fungus

[Display omitted] •FGGDSTHP, ALGGGY, YVVPW, and PLLRW were identified.•The synergistic MIC was 1.0 mg/mL of YVVPW and 0.27 mg/mL of SA.•Hydrogen bonds in YVVPW + SA were related to Tyr and Val residue.•π-π stacking was correlated with the five-membered ring of Trp residue. This study aimed to identify an antimicrobial peptide and phenolic compound combination derived from fermented walnut meal against Penicillium. victoriae, a fungus responsible for Rosa. roxbughii Tratt spoilage, and ultimately investigate their synergistic mechanism. YVVPW and salicylic acid (SA) had the highest antifungal activity among identified 4 antimicrobial peptides, including FGGDSTHP, ALGGGY, YVVPW, and PLLRW, and 15 phenolic compounds, respectively. Molecular docking verified that YVVPW bound to regulatory subunit via hydrogen-bond, hydrophobic, and π-π conjugate interactions. YVVPW and SA exhibited synergistic effects with average minimal inhibitory concentration decreasing by 85.44 ± 8.04%. Fluorescence spectroscopy demonstrated quenching of intrinsic Trp and Tyr fluorescence by interaction. FTIR and molecular docking results revealed formation of 3 hydrogen bonds via OH, CO, NH, and CH bonds in YVVPW + SA, with π-π stacking occurring between the benzene ring and five-membered ring. These reinforce potential application of this combination as an effective fungistatic combination in fruit preservation.