Testing the Antimicrobial Properties of Casein from Bovine Milk

Abstract

Casein proteins are the main proteins found in milk and make up 80% of milk proteins. They are shown to contain peptides which exhibit antibacterial properties. Caseins are composed of alpha, beta, and kappa subunits, which prior research has shown are effective in inhibiting bacterial growth. This project tests how well different concentrations of a mix of these caseins, as well as the three caseins separately, can inhibit the growth of E. coli ATCC 25922. Disk diffusion assays were carried out and the results have found that a crude casein isolate shows inhibition at 50 mg/mL and 25 mg/mL concentrations, while the three separate caseins showed no signs of inhibition at any concentration up to 50 mg/mL. One possible explanation is that the individual caseins may have lost their antimicrobial properties during the separation process carried out by the manufacturer. Prior research has also shown that the presence of gastric enzymes in the casein solution can be important in breaking down the caseins to release the more bioactive peptides in it. In the future, better separation methods of the caseins can be done where the inhibitory properties are retained, and the addition of an enzyme would help the caseins inhibit bacteria more effectively.