Screening And Identification On Antibacterial Lactic Acid Bacteria And Characteristics Of Antibacterial Substance From Koumiss

For obtaining application potential antibacterial activity strains, lactic acid bacteria(LAB) isolated from traditional koumiss were screened and identified by the double agar diffusion method,and the characteristics of its antibacterial substance were analyzed.21 lactic acid bacteria displayed antibacterial activities against 6 strains food-spoliage microorganism by primary screening. After eliminating the effects of organic acid and catalase,the cell-free fermentation supernatant(CFC) of two strains of 8-1 and G-3 showed strong antibacterial activity to against Listeria monocytogenes and Bacillus subtilis. In the meantime,The two strains 8-1 and G-3 were identified as Enterococcus faecalis by physiological-biochemical test and 16S rDNA sequence analysis. Complete inactivation of the antibacterial compounds produced by E. faecalis 8-land G-3 were observed after treatment with inactivated by trypsin, pepsin, papain and proteinase K,and the result confirmed that the inhibitory compounds produced by the strains were proteinaceous.The antibacterial substance were highly thermalstable over a wide temperature range up to 121 ℃ for 15min and retained its activities at pH range (2-6). The antibacterial substance was also expressed active in the presence of different organic solvents, some surfactants, metal salts, and 120min of exposure UV light.The antibacterial substance produced by E. faecalis 8-1 could against different Gram-positive and Gram-negative bacteria. Antibacterial substance was produced after 8 h of incubation at 37 ℃, with maximum production at 24 h of incubation. Antibacterial substance produced by E. faecalis 8-1 also showed stability for 60 days at-20℃,4℃and room temperature,and its action mode could kill the growth of Listeria monocytogenes, but inhibite the growth of Bacillus subtilis.