Isolement, purification et identification des bactéries lactiques à partir de lait cru de chèvre

Abstract

Lactic acid bacteria have acquired great importance by their presence in the food industry and for a longtime. Isolation of lactic strains from three samples of raw goat's milk from three regions in the wilaya of Mostaganem, allowed us to obtain 20 strains to Gram positive and catalase negative. For identified the bacterial genera, we are use this tests : Growth in the presence of NaCl 6.5%; growth at pH = 5, pH = 6.5 and pH 9.6; growth test different temperatures (22C°, 30C°, 45C°); study of heat resistance; growth test in mid milk Sherman; test hydrolysis of arginine (ADH); test production of acetoin; fermentative type of test. The fermentation test sugars using the gallery 20 Strep identified 20 isolates. These isolates were affiliated to seven bacterial genera as follows alleged: Lactobacillus delbrueckii (6) Lactobacillus fermentum (2) Streptococcus thermophilus (1) Streptococcus mitus (4) Enterococcus durans (4) Lactococcus lactis subsp lactis diacetylactis biovae (2) Pediococcus faecalis (1) The results of technological test are satisfactory for industrial use. The strains present a good proteolytic activity. However, they do not produce dextrane on MSE medium. Strains have a kinetics growth and acidification in skim milk at 37°C.