Identification and characterization of a new antifungal peptide in fermented milk product containing bioprotective Lactobacillus cultures.

FEMS Yeast Res. 2018 Dec 1;18(8). doi: 10.1093/femsyr/foy094. McNair LKF1, Siedler S2, Vinther JMO1, Hansen AM1, Neves AR2, Garrigues C2, Jäger AK1, Franzyk H1, Staerk D1. Author information 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark. 2 Discovery, R&D Microbial Platform, Chr. Hansen A/S, 10-12 Bøge Allé, 2970 Hørsholm, Denmark. Abstract Mold and yeast contamination constitutes a major problem in food commodities, including dairy products, hence new natural preventive measures are in high demand. The aim of the current study is to identify and characterize novel antifungal peptides produced by lactic acid bacteria (LAB) in sour cream. By the use of a newly developed image-based 96-well plate fungal growth inhibition assay targeting Debaryomyces hansenii, combined with a range of analytical tools comprising HPLC-high-resolution mass spectrometry, ultrahigh-performance liquid chromatography-Triple Quadrupole MS and nuclear magnetic resonance spectroscopy, we successfully identified a new antifungal peptide (DMPIQAFLLY; 1211 Da) in sour cream enriched with two bioprotective LAB strains. This peptide represents a fragment of casein, the most abundant protein in milk. Presumably, the proteolytic activity of these bioprotective strains results in the observed 4-fold higher concentration of the peptide during storage. Both bioprotective strains are able to generate this peptide in concentrations up to 0.4 μM, independently of the sour cream starter culture employed. The peptide attenuates the growth rate of D. hansenii at concentrations ≥35 μM, and results in smaller cells and more compact colonies. Hence, the peptide is likely contributing to the overall preserving effect of the investigated bioprotective LAB strains. PMID: 30137293 DOI: 10.1093/femsyr/foy094