| Use of antimicrobial polymers in foods, biomedical and other applications hold long-term promise. In food applications, such polymers would maintain their antimicrobial efficacy by reducing the amount of antimicrobials added directly to the foods. The limited scope of action of most antimicrobials calls for finding new antimicrobials that have wide spectra of activity and functionality. Synthetic antimicrobial peptides that are amphipatic, cationic and form α-helixes have been shown antimicrobial at low levels (μg/ml) against several microorganisms. Among these, peptides composed of lysine and leucine and 14 amino acid residues in length have been previously immobilized and reported little toxic against human erythrocytes.; In this study, an amphipatic cationic peptide composed of 8 leucine and 6 lysine amino acid residues was synthesized by solid phase peptide synthesis (SPPS). The same peptide was attached to polystyrene resin beads by the same method. The soluble peptide and the modified polystyrene (MPS) were microcidal against the food-borne microorganisms Bacillus subtilis, Escherichia coli O157:H7, Kluyveromyces marxianus, Listeria monocytogenes, Pseudomonas fluorescens, Serratia liquefaciens, Staphylococcus aureus and Salmonella typhimurium in buffer. The soluble peptide was 200–7000 more potent than the MPS and reduced more than 3 log 10 the cells within 10 min at concentrations less than 10 μg/ml. In addition, the soluble peptide caused the decrease of E. coli O157:H7 intracellular ATP, K+ and UV-absorbing materials.; Soluble peptide and MPS inhibited E. coli O157:H7 growth in trypticase soy broth in a concentration-dependent manner. They also reduced E. coli O157:H7 survival in apple juice and microflora present in meat exudate liquid. The peptides reduced E. coli O157:H7 at pH 3.5–7, showing highest antimicrobial activity at pH 3.5. Activity of the MPS was retained after it was sterilized at 120°C, heated in a dry oven at 120 and 200°C and washed 40 times. |
