Proteolysis of milk proteins by AprX, an extracellular protease identified in Pseudomonas LBSA1 isolated from bulk raw milk, and implications for the stability of UHT milk. (October 2015)

• Record Type: Journal Article
• Authors: Matéos, A.; Guyard-Nicodème, M.; Baglinière, F.; Jardin, J.; Gaucheron, F.; Dary, A.; Humbert, G.; Gaillard, J.-L.
• Is Part Of: International dairy journal. Volume 49(2015)
• Page Start: 78
• Page End: 88
• Publication Date: 2015-10
• Subjects: Dairying -- Periodicals; Industrie laitière -- Périodiques; Electronic journals; 338.1762142
• DOI: 10.1016/j.idairyj.2015.04.008
• Languages: English
• ISSNs: 0958-6946

Abstract

Abstract: 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 non-casein 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 αS1 -, β- and κ-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.