www.pelagiaresearchlibrary.com t Available online a Pelagia Research Library European Journal of Experimental Biology, 2013, 3(6):489-494 ISSN: 2248 –9215 CODEN (USA): EJEBAU 489 Pelagia Research Library Effect of plasmin digest of κ-casein on survival of some pathogenic and probiotic bacteria Marjaneh Sedaghati 1* , Hamid Ezzatpanah 1 , Massod Mashhadi Akbar Boojar 1 , Maryam Tajabadi Ebrahimi 1 and Mehdi Aminafshar 3 1 Department of Food Science and Technology, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran 2 Department of Biochemistry, University of Kharazmi, Tehran, Iran 3 Department of Science, Faculty of Biology, Islamic Azad University, Tehran Central Branch, Iran 4 Department of Animal Science and Technology, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran _____________________________________________________________________________________________ ABSTRACT The aim of this work was to evaluate the presence of antibacterial properties in a plasmin digest of bovine қ-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, PDқ was evaluated against pathogenic (Escherichia coli and Staphylococcus aureus) and probiotic (Lactobacillus casei and Lactobacillus acidophilus) bacteria in vitro. Although қ-casein and plasmin had no antibacterial activity, PDқ showed antibacterial property against the tested bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PDқ was determined for the target bacteria. The MIC and MBC of PDқ 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 PDқ were monitored by turbidimetry in broth culture. The effect of PDқ on lag time and maximum absorbance was more significant than slope of tested bacteria. In addition of growth curves, PDқ has inhibitory effects on the plate count confirmation of tested bacteria. The maximum inhibitory effect of PDқ was created in MIC concentration. Keywords: Bovine; K-casein; Antibacterial; Plasmin; Growth curve _____________________________________________________________________________________________ INTRODUCTION Milk is naturally antimicrobial. As milk is formed in the mammary glands, it contains immunity factors, such as immunoglobulins, from the mother’s blood [1,2]. These immunoglobulins and non-immunoglobulins proteins affect the neonates fight against microbial infection [3,4]. In addition to naturally occurring antimicrobial proteins present in milk, a variety of antibacterial peptides can be released from their parent molecules such as caseins and whey proteins by hydrolysis of them[5,6,7]. κ-casein consists of a single chain of 169 amino acids and has a theoretical molecular weight of 18 974 Da and a theoretical pI of 5.93. It is amphipathic with very specific hydrophobic and polar domains. This casein plays an important role in the formation and stabilization between caseins in sub-micelles and in the complete micelle[1,8]. Enzymatic hydrolysis of κ-casein may affect human health by improving some of their biological properties, including antithrombotic function, opioid activity and protective properties against different microorganisms and