Screening, Identification, and Biological Characteristics of Potentially Probiotic Lactic Acid Bacteria
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Abstract:
197 strains of lactic acid bacteria isolated from sour horse milk were screened and identified, and their biological characteristics were studied. In acid tolerance assays and bile salt tolerance assays, ten strains with relatively high tolerance were preliminarily selected. The survival rates of the ten strains after three hours of treatment with artificial gastric juice were between 46.48% and 95.86%. Among them, three strains with survival rates higher than 80% were selected and subjected to artificial intestinal fluid treatment for four and eight hours. After that, the numbers of live bacteria were determined: 1.65×109 to 1.81×1010 colony-forming units per milliliter. Furthermore, the three strains all exhibited certain hydrophobicity. Among them, the survival rates of strain 2-33 in artificial gastric juice and artificial intestinal fluid reached 95.86% and 80.80%, respectively, with cell surface hydrophobicity of 42.61%. Thus, strain 2-33 was identified as the target strain (a potential probiotic). An antibiotic sensitivity assay showed that strain 2-33 is resistant to norfloxacin, cefradine, gentamicin, vancomycin, and streptomycin; moderately sensitive to clindamycin; and sensitive to tetracycline, chloramphenicol, erythromycin, and ampicillin. Finally, the 16S ribosomal DNA gene sequence of strain 2-33 was determined by a molecular biological method; this gene’s length was found to be 1432 bp. The accession number in NCBI is MN611708. Stain 2-33 showed 100% homology with Lactobacillus plantarum JCM1149, and sugar fermentation assay results on this strain are consistent with those of GB 4789.35-2016; therefore, the strain was identified as L. plantarum. The results of this study provide data for further research on probiotics and the development of functional foods in the future.
