Purification and structural characterization of APTs, a novel antifungal peptide produced by Lactobacillus paracasei ALAC-4, and its inhibitory effect on Candida albicans

Abstract

Fungal contamination poses significant food safety risks. Lactobacillus paracasei ALAC-4, originally isolated from traditional fermented foods in Inner Mongolia, exhibits antifungal properties. Here, we isolated and purified the active fraction from ALAC-4 to derive the antifungal peptide, demonstrating its antifungal efficacy against Candida albicans. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed severe deformation of C. albicans cell surfaces upon exposure to the antifungal peptide, resulting in membrane rupture and pore formation. Simultaneously, a decrease in Zeta potential and K+ ion leakage occurred on the C. albicans cell surface. Treatment with antifungal peptides reduced the hydrophobicity of the cell surface, indicating decreased adsorption rates of C. albicans cells. Additionally, LC-MS/MS analysis identified the antifungal peptide APTs with a molecular mass of 423.18 Da and an amino acid sequence of S-G-G-G-F, representing a novel and previously unreported antifungal peptide. Circular dichroism analysis indicated that the secondary structure of APTs primarily comprised α-helices. This study underscores the potential of APTs as a natural biopreservative for food preservation.