Synergistic antibacterial effects of low-intensity ultrasound and peptide LCMHC against Staphylococcus aureus.

The increasing demand for ready-to-eat fresh foods requires the use of non-thermal sterilization, hence, the application of antimicrobial peptides (AMPs) combined with ultrasound could serve as a novel food preservation method to prevent foodborne diseases. In this study, in silico tools were used to predict and screen potential AMPs from the antimicrobial amino acid sequence of myosin heavy chain of Larimichthys crocea. A novel AMP, designated as LCMHC, had strong antibacterial activity against Staphylococcus aureus when combined with low-intensity ultrasound treatment. The minimal inhibitory concentration (MIC) of LCMHC was 125 μg/mL when used alone but 31.25 μg/mL when combined with 0.3 W/cm2 ultrasound treatment. Structural analysis using circular dichroism (CD) revealed that peptide LCMHC has α-helical structure, which had slightly untwisting effect with increasing ultrasonic intensity. Transmission electron microscopy and permeability analysis of bacteria cell membrane showed that low-intensity ultrasound combined with peptide LCMHC could greatly improve the cell membrane permeability of S. aureus. Moreover, low intensity-ultrasound could assist the entry of more peptide LCMHC into bacterial cells to bind DNA. The findings here provide new insight into the potential application of peptide LCMHC combined with low-intensity ultrasound in the food industry.