Abstract:To identify lactic acid bacteria with excellent antibacterial properties, 39 strains of lactic acid bacteria from traditional fermented food products were screened using the Oxford cup method. The growth curve, acid production ability, bile salt tolerance, osmotic tolerance, acid and alkali tolerance, and antibacterial spectrum of each of the selected strains were investigated. Then, the stability of the metabolites of each of the chosen strains was studied. Finally, three strains with good antibacterial properties were identified. They are Lactobacillus plantarum HS011, Lactobacillus delbrueckii HS023, and Streptococcus thermophilus HS033. The pH values of their fermentation supernatants decreased from 5.44, 5.44 and 5.42 to 3.55, 3.54 and 3.57, respectively, after cultivation for 20 h. The three lactic acid bacteria can tolerate less than 0.1% bile salt and 14% NaCl, and grow well within the pH range of 5.0~8.0. All three strains have abroad bacteriostatic spectrum and can effectively suppress the growth of Escherichia coli O157:H7, Bacillus cereus, Listeria monocytogenes, and Enterobacter sakazakii. However, the chosen L. plantarum strains have no inhibitory effects on molds and yeasts. The metabolites of these strains retained their antibacterial activity even after various treatments such as temperature (20~121 ℃), pH (2.0~8.0), papain, trypsin, pepsin, proteinase K, and catalase treatments. The lactic acid bacteria isolated from traditional fermented food products have good probiotic properties, and their metabolites are stable, and can, therefore, be used as starters in fermented products and can be further developed and utilized.
