International Dairy Journal, 49, pp. 78-88.
Matéos, A., Guyard-Nicodème, M., Baglinière, F., Jardin, J., Gaucheron, F., Dary, A., Humbert, G., Gaillard, J.-L.
2015
UHT milk made from milk contaminated by Pseudomonas LBSA1 destabilised during storage. Sedimentation of UHT milk was observed; zeta potential of casein micelles decreased, while contents of noncasein nitrogen and non-protein nitrogen increased. Pseudomonas LBSA1 produced an extracellular
protease that hydrolysed caseins but not whey proteins; this was identified as AprX, a thermoresistant
protease belonging to the serralysin family. This protease showed a broad range of pH activity (pH 6 to
pH 10) and an optimal temperature of activity of 40°C. Peptides released from purified alpha-s1-, beta- and kappa-caseins were determined by tandem mass spectrometry. The identified cleavage sites did not reveal a strong specificity of the extracellular protease. However, the presence of basic or aromatic amino acid residues in the P1 position had a positive influence on cleavage in comparison with acidic amino acid residues or proline.