Isolation and characterization of quinoa antimicrobial peptides and its effect on the microbial diversity of fresh apple juice.

This study developed antimicrobial peptides (AMPs) from quinoa with high antibacterial activity and stability by mixed-bacteria fermentation. Furthermore, among 9 peptide fractions purified by membrane separation and chromatography, F1 could effectively inhibit the growth and propagation of bacterial microorganisms in apple juice. Subsequently, F1 identified LC-MS/MS as 95 peptides, molecular weights 494.25 Da to 1253.55 Da, notably, AGAAPE peptide (556.25 Da), negatively charged (-1), highly hydrophobic (50 %), with significant inhibitory effects on both Escherichia coli and Staphylococcus aureus (MIC 5 mg/mL). The antimicrobial mechanism of AGAAPE was determined to damage membrane through hydrogen-bond and hydrophobic interactions, resulting in leakage of intramembrane substances and inhibition of intracellular ATPase activity. Moreover, AGAAPE was pH resistant (pH 4-12), thermally stable (121 °C, 30 min), resistant to salt ion interference (Na, Ca), and protease hydrolysis resistant (neutral protease, pepsin, trypsin). Overall, identifying AMPs from quinoa provides a promising new approach for fresh juice preservation.