Antibacterial peptides from black soldier fly (Hermetia illucens) larvae: mode of action and characterization.

Antibacterial peptides from black soldier fly larvae extract were prepared using Flash column chromatography. Three out of five fractions (F, F and F) showed antibacterial activity against Listeria monocytogenes DMST 17303 with a minimum inhibitory concentration (MIC) of 1 mM, followed by Salmonella enterica Enteritidis DMST 15679 and Escherichia coli O157:H7 DMST 12743 with a MIC ranging from 4 to 8 mM. Due to the higher yield, F and F were further analyzed on their mode of action against L. monocytogenes DMST 17303. Both fractions, particularly F, exerted antibacterial activity through inducing bacterial cell membrane disintegration and interaction with intracellular compounds including fatty acids, proteins, and nucleic acids. The F did not show significant hemolytic activity up to 4 mM, while F showed lower than 5% hemolysis up to 8 mM. Time-to-kill analysis revealed that F was more effective and exerted a sustainable killing effect after 2 and 4 h, depending on the concentration of 1 and 2×MIC, respectively, while the F at 2×MIC could completely kill the test bacteria within 24 h. Among the identified peptides in the fractions, those with charged, either positively or negatively, and moderate hydrophobicity of ranging 6.68-15.70, namely CGPPRQGPFPR, HLEEELK, LEEAEERAD, TEELEEAKKK, and KGNSELEEAKKK, are potential antimicrobial peptides.