Studies On Isolation And Antibacteria Characterization Of Lactic Acid Bacteria In The Koumiss

Forty-seven strains of lactic acid bacteria in this study were isolated from ten samples of koumiss collected from the heardsman's home in Inner Mongolia-XiLinGuoLe region, and their antibacterial characterization were also studied. They respectively belonged to Lactobacittus L.lactis subsp.lactis E.faecalis, E.durans Rpseudoaviwn and Lc.mesenteroides subsp.dextranicum by identification. A total of forty-seven strains of lactic acid bacteria were screened for antagonistic activities under conditions that eliminated the effects of organic acids and hydrogen peroxide. Twelve strains of lactobacilli and eight strains of entercocci were only shown to inhibit the growth of indicator organism-Listeria through plate diseases test. Among them, the supernatants of fermented liquor from six of the eight strains of entercocci exhibited inhibitory activity against indicator organism-Listeria. And the bodies of twelve strains of lactocilli and two strains of entercocci also exhibited inhibitory activity against indicator organism-Listeria. But all the strains were not shown to inhibit the growth of indicator oigamsm-StaphylococcusaureuswdE.coli. Two of the six strains , 4-3-2 and 3-3-2, were chosen for further study. Maximum production of antibacterial substances were obtained in the late log period in MRS medium. The antibacterial substances were shown to be heat stable(12rC,30min)in acid conditions(pH2.0). Furthermore, the 4-3-2 strain was shown to be equally active at pH values ranging from 4.5 to 12, and the 3-3-2 strain was from 4.5 to 8.5. The antibacterial substances from cell-free culture liquor were extracted by the methods of amnonium sulfate salting-out or acetone precipitation.