Isolement de souches bactériennes potentiellement productrices de lipases alcalines, à partir du beurre cru et du beurre fermenté « Dhan »
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Considerable interest is carried currently for lipase, mainly to industrial sectors, as well as for the lipolytic flora of the local traditional products. In this context, settles the goal of our work on isolation of lipolytic strains from raw butter and smen, which are two traditional Algerian dairy products. As well as the screening of the best bacterial isolates producing lipases. To achieve our goals, six samples of varied origin were used for the physicochemical analysis and the isolation of lipolytic bacterial strains. We used several media, all these are supplemented with Of egg yolk or olive oil and / or Tween 80. The strains obtained are classified for its activities on agar medium and then grown on Liquid media. Titration is the method used to estimate free fatty acids or lipase activity. Physicochemical characterization results showed that there was a significant difference between the measured parameters of butter and smen samples. Screening yielded to obtaining of several lipolytic isolates from raw materials rich in fat, namely : raw butter and smen. The test of the lipolytic activity has allowed selecting Forty-nine bacterial strains which are approximated on the basis of the phenetic results of six types : 49% (24) are Gram-positive, Branched filamentous, catalase positive, asporulated and immobile ; 31% (15) are Gram-positive, cocci, catalase positive, asporulated, immobile and degrade mannitol ; 10% (5) are Gram-positive, rod, catalase positive, asporulated and immobile ; 4% (2) are Gram-positive, cocci, Catalase positive, asporulated, immobile, does not degrade mannitol and have a yellow color ; 4% (2) are Gram-positive, rod, catalase positive, sporulated and mobile and 2% (1) are Gramnegative, cocci, catalase positive, asporulated and immobile. The test of production of lipase on liquid medium containing inducers of the production of the enzyme (Tween 80, olive oil with or without Tween 80) yielded to the selection of eight strains (SG (5, 8, 9, 14, 25, 26 ) ; BG (32) ; SS (46)), potentially producing true lipases independently of the nature of the lipid source. This finding reveals the degree of adaptation of these strains to various media, giving it various biotechnological applications.