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Identification d'une souche de Pseudomonas, bactérie psychrotrophe isolée de lait cru : Caractérisation de sa protéase extracellulaire et des sites d'hydrolyses sur les caséines bovines

Abstract : Milk storage at refrigeration temperature permits the growth of psychrotrophic microorganisms, mainly belonging to the genus Pseudomonas that can generally produce heat-resistant extracellular proteases, causing milk proteolysis during storage. The proteolytic psychrotrophic strain isolated from raw milk, Pseudomonas sp. LBSA1 produces a unique caseinolytic extracellular protease with an apparent molecular mass of 49 kDa with milk addition. Different factors, such as temperature, agitation, and addition of many components can affect its production. A polyphasic taxonomic study of the LBSA1 strain reveals that it is phylogenetically related to the species P. poae, but, it has an original siderovar and then it could belong to a new Pseudomonas species. The protease of the strain LBSA1 was purified, the corresponding gene was sequenced; the enzyme is identified as a zinc metalloprotease of the serralysin family (E.C. 3.4.24.40). It is active under broad pH values and that optimal temperature for activity is nearly 40°C. The protease presented a low temperature inactivation around 45°C but it showed a greater stability around 60-80°C. The bovine caseins are rapidly hydrolysed by the enzyme without a real specificity but whey proteins are resistant to the action of the protease.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2006_0056_NICODEME.pdf
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Submitted on : Thursday, March 29, 2018 - 10:40:06 AM
Last modification on : Thursday, May 28, 2020 - 2:19:13 PM

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Muriel Nicodème. Identification d'une souche de Pseudomonas, bactérie psychrotrophe isolée de lait cru : Caractérisation de sa protéase extracellulaire et des sites d'hydrolyses sur les caséines bovines. Microbiologie et Parasitologie. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10056⟩. ⟨tel-01746549⟩

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