Role of calcium content in antibacterial activity of donkeys’ milk toward E. coli

Abstract

© 2014, Springer-Verlag Berlin Heidelberg. The objective of this study was to investigate the effect of calcium content in raw donkeys’ milk (DM) on its antibacterial activity against Escherichia coli. Antibacterial assay was performed in artificially contaminated milk samples (without and with added CaCl 2 and EDTA) incubated at 38 °C (donkeys’ body temperature). The EDTA was added to DM to bind its calcium ions, while CaCl 2 was used as the donor of calcium ions. The content of calcium, lysozyme (LYZ) and lactoferrin (LF) as well as pH value were determined in all of the tested milk samples. DM samples showed varying degrees of antibacterial activity against the tested E. coli strains. The milk samples with higher calcium content possessed stronger antibacterial potential toward the tested bacteria. The determinated calcium-dependant antibacterial activity of DM was proved thorough addition of CaCl 2 and EDTA to DM. Calcium content in tested samples was in the range from 377.1 to 1,231 mg/l. The LYZ and LF in tested DM were present at concentrations between 0.98–3.74 g/l and 2.2–54.3 mg/l, respectively. LF was not detected in five of the tested samples, and pH values of the samples were in range from 7.11 to 7.25.