In vitro antimicrobial activity of the novel antimicrobial peptide mytimacin-4 and its influence on the microbial community and quality of pork during refrigerated storage

The excessive use of antibiotics and chemical preservatives has led to the emergence of resistant bacterial strains, which has had an adverse impact on food safety. The utilization of antimicrobial peptides (AMPs) in food preservation has garnered attention due to their ability to maintain the quality of food while reducing the likelihood of bacteria developing resistance. Mytimacin-4, an antimicrobial peptide rich in cysteine and positively charged, has been identified in Mytilus galloprovincialis and has been reported to possess antibacterial activity. However, the specific effect of mytimacin-4 on bacteria is still not well understood. Hence, this study aimed to prepare mytimacin-4 using a Pichia pastoris expression system and to investigate its antibacterial properties and mechanism. Our findings indicate that mytimacin-4 exhibits rapid and sustained bactericidal effects against bacteria and no cytotoxicity or hemolytic activity. Additionally, microscopy techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence microscopy have demonstrated that mytimacin-4 disrupts the integrity of bacterial membranes, damages intracellular structures, and binds to bacterial DNA. Furthermore, mytimacin-4 had a great antimicrobial effect against the dominant bacteria of pork, improving the abundance and variety of bacterial flora during refrigeration and controlling the rise in pH, total volatile basic nitrogen (TVBN), and thiobarbituric acid reactive substances (TBARS) in pork, preserving the freshness of pork during storage at 4 °C. Moreover, mytimacin-4 demonstrated significant antibacterial effects against three types of bacteria in a pork spoilage model. Overall, mytimacin-4 holds great potential as a food preservative for storage purposes.