Casesidin-like anti-bacterial peptides in peptic hydrolysate of camel milk β-casein

The antibacterial activity of camel milk β-casein and its peptic hydrolysate was investigated. The hydrolysate was fractionated by ultrafiltration successively through membranes with a 10 kDa and a 1 kDa cut-off, sequentially. Antibacterial activity assays against Staphylococcus aureus CNRZ 3, Listeria innocua ATCC 33090 and Escherichia coli ATCC 25922 were performed. The growth of S. aureus and L. innocua strain was not inhibited by β-casein; E. coli strain growth was slightly inhibited. All fractions of hydrolysates exhibited some anti-bacterial activity and molecular mass fraction <1 kDa was the most active against both Gram-positive bacterial strains. Mass spectrometry analysis revealed that this fraction contained 129 peptides. Interestingly, 2 of them, f(193-204) and f(193-213), presented at least 50% homology with casecidins 15 and 17 from bovine β-casein. This is the first study reporting the presence of two putative antibacterial fragments in camel β-casein peptic hydrolysate.