Detection of the Cholera Toxin-binding Activity of κ-Casein Macropeptide and Optimization of Its Production by the Response Surface Methodology

The cholera toxin (CT)-binding activity of purified κ-casein macropeptide (CMP) from bovine κ-casein was detected. In addition, a statistical model was developed to optimize the production of CMP. CMP was prepared by chymosin hydrolysis of κ-casein and a subsequent 3% trichloroacetic acid treatment. CMP was further fractionated in an ion-exchange column by FPLC. CT binding activity was eluted at 0.18 M NaCl and was a single 8.9 kDa peptide without tyrosine and arginine residues. The CT binding activity was rapidly lost by a carbohydrase treatment. The conditions for CMP production with chymosin were optimized by using the response surface methodology (RSM). The estimated optimum levels of the factors were as follows: reaction temperature, 38.5°C; pH, 6.44; and time, 35.9 min. A validation experiment was performed in which CMP was prepared under the predicted parameters, and it was ascertained that the estimated optimum conditions gave better production of CMP than any other conditions.