Release of antimicrobial peptides through bromelain hydrolysis of leatherjacket (Meuchenia sp.) insoluble proteins

Antibacterial peptides have been found to be a natural part of animal and plant defence systems. In some cases, antimicrobial peptides have been found to be released by hydrolysis of food proteins. In the present study, two antibacterial peptide fractions (fractions 9 and 12) had been isolated from bromelain hydrolysate of leatherjacket (Meuchenia sp.) insoluble muscle proteins. Assay for antimicrobial activity showed that fraction 12 had a minimum inhibition concentration (MIC) value of 4.3 mg/ml against Bacillus cereus and Staphylococcus aureus, while fraction 9 only showed some activity against Bacillus cereus without a MIC being reached at a 5.35 mg/ml peptide concentration. Further fractionation, on an analytical C-18 column, indicated that the fractions contained many other peptides that could account for the high MIC value relative to the cationic antibiotic polymyxin.