Effect of plasmin digest of ？o-casein on survival of some pathogenic and probiotic bacteria

The aim of this work was to evaluate the presence of antibacterial properties in a plasmin digest of bovine ò？-casein. Although native bovine κ-caseinis resistant to plasmin, extensive hydrolysis of this milk protein was observed applying a long incubation period. The antibacterial potential of κ-casein, plasmin, PDò？ was evaluated against pathogenic (Escherichia coli and Staphylococcus aureus) and probiotic (Lactobacillus casei and Lactobacillus acidophilus) bacteria in vitro. Although ò？-casein and plasmin had no antibacterial activity, PDò？ showed antibacterial property against the tested bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PDò？ was determined for the target bacteria. The MIC and MBC of PDò？ against Escherichia coli was considerably higher than Staphylococcus aureus, Lactobacillus casei and Lactobacillus acidophilus bacteria. The growth curves alterations of target bacteria in the presence of PDò？ were monitored by turbidimetry in broth culture. The effect of PDò？ on lag time and maximum absorbance was more significant than slope of tested bacteria. In addition of growth curves, PDò？ has inhibitory effects on the plate count confirmation of tested bacteria. The maximum inhibitory effect of PDò？ was created in MIC concentration