Antimicrobial activity, environmental sensitivity, mechanism of action, and food application of αs165-181 peptide

alpha s165-181 is a peptide derived from alpha s(2)-casein of ovine milk. Herein, we report the antimicrobial activity and mechanism, and food application of the peptide. alpha s165-181 showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Bacillus cereus, and Salmonella enterica serovar Enteritidis in a dose-dependent manner. The minimum inhibitory concentration of the peptide was 3.9 mg/ml for E. coli and 7.8 mg/ml for the other bacteria. The peptide did not show antimicrobial activity against Lactobacillus plantarum up to 3.9 mg/ml concentration. The minimum bactericidal concentration of alpha s165-181 peptide was 7.8 mg/ml for E. coli, S. aureus, L. monocytogenes, and B. cereus. The peptide was sensitive to monovalent and divalent cations, pH, and high temperatures. Transmission electron microscopy, cytoplasmic 13-galactosidase leakage, and DNA electrophoresis analyses showed that alpha s165-181 peptide affects bacteria by damaging cell membrane and binding to the genomic DNA. When alpha s165-181 peptide was applied to minced beef or UHT cream, the antimicrobial activity (7.8 mg/g) was almost the same as or even better than nisin (0.5 mg/g). This study helps understand the antimicrobial mode of action of alpha s165-181 peptide and develop strategies for application in food products.