Antimicrobial peptides or "host defense peptides" have the potential to protect the body against some harmful microorganisms including pathogenic bacteria. Researchers have been recently interested in focusing on the activity of antimicrobial peptides released from food sources. The physiological effects of the ingested peptides in vivo rely on their bioavailability (the degree to which the peptides are extracted from food proteins and absorbed in the body). In this regard, physiochemical characteristics of peptides such as molecular size, solubility and lipophilicity are the determining factors in the ability of peptides to exert an effect.
Antimicrobial peptides are found most abundantly in milk. They are present in the protein constituents such as caseins and lactoferrin. Marine protein sources such as tuna and oyster are also believed to contain antimicrobial peptides. In vitro study has shown that cysteine-containing peptides from oyster muscles can offer antimicrobial benefits due to their ability to inhibit the growth of pathogenic bacteria (including Escherichia coli, staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa) and fungi (Penicillium expansum and Botrytis cinerea).
According to a research on antimicrobial properties of beef-derived peptides, it was found that certain types of ACE (angiotensin converting enzyme) inhibitory peptides from beef meat hydrolysates inhibited the growth of some pathogenic microorganisms. The peptides of interest (GLSDGEWQ, FHG, DFHING and GFHI) were isolated by means of reversed-phase high-performance liquid chromatography. The liberated peptides were examined for Antimicrobial activity against pathogens consisting of E. coli; P. aeruginosa; Salmonella typhimurium (Gram-negative bacteria) and Listeria monocytogenes; S. aureus; B. Cereus (Gram-positive bacteria). It was observed that the growth of S. typhimurium, E. coli, Listeria monocytogenes and B. Cereus was significantly inhibited by the action of peptide GLSDGEWQ (i.e. it was inhibitory against both Gram-negative and Gram-positive bacteria).
Further, the inhibition of P. aeruginosa was detected by the activities of FHG and GFHI. Many in vitro studies have reported the activity of antimicrobial peptides derived from food proteins. Further investigations to determine the bioactivities of antimicrobial peptides in vivo would be worthwhile in order to promote functional food formulation and health benefits.