title: Identification and characterization of a heat-resistant protease from Serratia liquefaciens isolated from Brazilian cold raw milk.
abstract: The cold storage of raw milk before heat treatment in dairy industry promotes the growth of psychrotrophic microorganisms, which are known for their ability to produce heat-resistant proteolytic enzymes. Although Pseudomonas is described as the main causative genus for high proteolytic spoilage potential in dairy products, Serratia liquefaciens secretes proteases and may be found in raw milk samples as well. However, at the present there is no information about the proteolytic spoilage potential of S. liquefaciens in milk after heat-treatment. The main aim of this research was to assess the proteolytic spoilage potential of S. liquefaciens isolated from Brazilian raw milk and to characterize the involved protease. S. liquefaciens was shown to secrete one heat-resistant spoilage metalloprotease of, approximately, 52 kDa encoded by the ser2 gene. The heat-resistance of Ser2 was similar to the aprX encoded metalloprotease produced by Pseudomonas. Although the ser2 gene was detected in all S. liquefaciens isolates tested in this study, the proteolytic activity of the isolates in milk was highly heterogeneous. Since nucleotide and deduced amino acid sequences of ser2 of all tested isolates are identical, this heterogeneity may be attributed to differences in enzyme expression levels or post-translational modifications.
authors.affiliation: Department of Microbiology, Federal University of Viçosa, Viçosa, MG 36.570-900, Brazil; CAPES Foundation, Ministry of Education of Brazil, Brasília, DF 70.040-020, Brazil; Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, B-9090 Melle, Belgium.
authors.forename: Solimar Gonçalves
authors.initials: SG
authors.lastname: Machado
authors.affiliation: Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, B-9090 Melle, Belgium; Department of Pathology, Bacteriology and Poultry Diseases, Ghent University (UGent), Salisburylaan 133, B-9820 Merelbeke, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Heyndrickx
authors.affiliation: Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, B-9090 Melle, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: De Block
authors.affiliation: Laboratory for Protein Biochemistry and Biomolecular Engineering, Department of Biochemistry and Microbiology, Ghent University (UGent), KL Ledeganckstraat 35, B-9000 Gent, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Devreese
authors.affiliation: Laboratory for Protein Biochemistry and Biomolecular Engineering, Department of Biochemistry and Microbiology, Ghent University (UGent), KL Ledeganckstraat 35, B-9000 Gent, Belgium.
authors.forename: Isabel
authors.initials: I
authors.lastname: Vandenberghe
authors.affiliation: Department of Microbiology, Federal University of Viçosa, Viçosa, MG 36.570-900, Brazil. Electronic address: mvanetti@ufv.br.
authors.forename: Maria Cristina Dantas
authors.initials: MC
authors.lastname: Vanetti
authors.affiliation: Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, B-9090 Melle, Belgium.
authors.forename: Els
authors.initials: E
authors.lastname: Van Coillie
mesh_terms: D000818:Animals; D001938:Brazil; D003080:Cold Temperature; D010450:Endopeptidases / Q000378:metabolism*; D005516:Food Microbiology; D006358:Hot Temperature; D008892:Milk / Q000382:microbiology*; D011549:Pseudomonas / Q000201:enzymology; D044090:Serratia liquefaciens / Q000201:enzymology* / Q000302:isolation & purification
chemical_list: D010450:Endopeptidases
keywords: Metalloprotease; Psychrotrophic; Spoilage; ser2