title: Ser2 from Serratia liquefaciens L53: A new heat stable protease able to destabilize UHT milk during its storage.
abstract: The heat-stable protease Ser2 is secreted by the species Serratia liquefaciens, a psychrotrophic bacteria frequently found in raw milk. To understand the physicochemical modifications of casein micelles induced by Ser2 and to confirm its implication in UHT milk destabilization, the enzyme was purified and added to microfiltered raw milk before UHT treatment. UHT milk destabilization was investigated during 90days of storage. A visual destabilization appeared after 8days of storage with the presence of sediment. Zeta potential increase and formation of aggregates were observed during the storage. Using tandem mass spectrometry, numerous released peptides from the four caseins were identified at the end of storage. Caseins were hydrolyzed in the preferential order β->αs1->κ->αs2. No specific peptidic hydrolysed bond was detected. The present study confirmed that the presence of the protease Ser2 in raw milk can be one of the main causes of UHT milk destabilization.
authors.affiliation: Department of Microbiology, Universidade Federal de Viçosa, Viçosa, MG 36.570-900, Brazil; CAPES Foundation, Ministry of Education of Brazil, Brasília DF 70.040-020, Brazil.
authors.forename: François
authors.initials: F
authors.lastname: Baglinière
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Tanguy
authors.affiliation: Department of Biochemistry, Universidade Federal de Viçosa, Viçosa, MG 36.570-900, Brazil.
authors.forename: Rafael Locatelli
authors.initials: RL
authors.lastname: Salgado
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Jardin
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Rousseau
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Robert
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France.
authors.forename: Marielle
authors.initials: M
authors.lastname: Harel-Oger
authors.affiliation: Department of Microbiology, Universidade Federal de Viçosa, Viçosa, MG 36.570-900, Brazil.
authors.forename: Maria Cristina Dantas
authors.initials: MC
authors.lastname: Vanetti
authors.affiliation: STLO, Agrocampus Ouest, INRA, 35000 Rennes, France. Electronic address: frederic.gaucheron@inra.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Gaucheron
mesh_terms: D000818:Animals; D061353:Food Storage / Q000379:methods*; D006358:Hot Temperature; D008892:Milk / Q000737:chemistry*; D010447:Peptide Hydrolases / Q000737:chemistry*; D044090:Serratia liquefaciens / Q000737:chemistry*
chemical_list: D010447:Peptide Hydrolases
keywords: Casein micelles; Proteolysis; Ser2; Stability; UHT treatment