Preparation of Buttermilk Peptide Extract That Has Antimicrobial Activity against Avian Pathogens

Introduction: Antibiotics are commonly used in poultry production as growth promoters. This practice has been called into question given the growing problem of antibiotic resistance. Antimicrobial peptides may hold promise as effective alternatives to antibiotics. To this end, large amounts of active preparations of antimicrobial peptides need to be produced, at low cost, from inexpensive food substrates using large-scale commercially viable processes.

Purpose: The objective was to develop a rapid and efficient method for preparing buttermilk cationic peptide extract and to test the antimicrobial activity against specific enteric avian pathogens.

Methods: Buttermilk was digested with pepsin. The ultrafiltered peptide extract (<10 kDa) was fractionated according to the charges through high-capacity cation-exchange adsorptive membrane. Using the microdilution technique on microplates, antimicrobial activity was assessed against four avian pathogens: Salmonella enterica var. Enteritidis, Salmonella enterica var. Typhimurium, two strains of Escherichia coli and again Staphylococcus aureus.

Results: The yield of buttermilk cationic peptide extract accounted for 6.5 ± 1.8% (n=3) of the total buttermilk extract. The buttermilk cationic peptide extract showed bactericidal activity against the selected avian strains, with bacterial losses of 1.7 log CFU/ml (Salmonella Typhimurium) to 3 log CFU/ml (E. coli O78:H80) at < 5 mg/ml; the effectiveness of cationic peptide extract varied with the strains. Using the same method of preparation, cationic peptide extract from lactoferrin hydrolysate showed bactericidal activity at 0.6 mg/ml (E. coli O78:H80) and 2.5 mg/ml (Salmonella Typhimurium).

Significance: These results demonstrate that membrane adsorption chromatography is an effective way to prepare cationic peptide extracts from buttermilk that have antimicrobial activity against avian pathogens.