title: Milk-deteriorating exoenzymes from Pseudomonas fluorescens 041 isolated from refrigerated raw milk.
abstract: The practice of refrigerating raw milk at the farm has provided a selective advantage for psychrotrophic bacteria that produce heat-stable proteases and lipases causing severe quality problems to the dairy industry. In this work, a protease (AprX) and a lipase (LipM) produced by Pseudomonas fluorescens 041, a highly proteolytic and lipolytic strain isolated from raw milk obtained from a Brazilian farm, have been purified and characterized. Both enzymes were purified as recombinant proteins from Escherichia coli . The AprX metalloprotease exhibited activity in a broad temperature range, including refrigeration, with a maximum activity at 37 °C. It was active in a pH range of 4.0 to 9.0. This protease had maximum activity with the substrates casein and gelatin in the presence of Ca (+2) . The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from 7.0 to 10. It exhibited the highest activity, in the presence of Ca (+2) , on substrates with long-chain fatty acid residues. These results confirm the spoilage potential of strain 041 in milk due to, at least in part, these two enzymes. The work highlights the importance of studies of this kind with strains isolated in Brazil, which has a recent history on the implementation of the cold chain at the dairy farm.
authors.affiliation: Departamento de Ciência e Tecnologia de Alimentos, Instituto Federal do Sudeste de Minas Gerais, Rio Pomba, MG, Brazil.
authors.forename: Maurilio L
authors.initials: ML
authors.lastname: Martins
authors.affiliation: Departamento de Ciência de Alimentos, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil.
authors.forename: Uelinton M
authors.initials: UM
authors.lastname: Pinto
authors.affiliation: Institute of Microbiology, Ernst-Moritz-Arndt University of Greifswald, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Riedel
authors.affiliation: Departamento de Microbiologia, Universidade Federal deViçosa, Viçosa, MG, Brazil.
authors.forename: Maria C D
authors.initials: MC
authors.lastname: Vanetti
mesh_terms: D000818:Animals; D001938:Brazil; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008892:Milk / Q000382:microbiology*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000302:isolation & purification*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012034:Refrigeration; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D011994:Recombinant Proteins; D008049:Lipase; D010447:Peptide Hydrolases
keywords: Pseudomonas fluorescens; extracellular lipase; extracellular protease; food deterioration; raw milk