Diversity and in Vitro Probiotic Characteristics of Culturable Lactic Acid Bacteria from Goat's Raw Milk

This study was to assess the probiotic attributes, technological properties and safety profiles of lactic acid bacteria isolated from local raw goat milk in Xinjiang, and built a cornerstone of exploitation of functional dairy products. Isolates were analyzed the genetic differences by 16S rRNA gene sequence combined Rep-PCR fingerprint typing technology. Preliminary screening under acid and bile salt base conditions were conducted and before the following experiments, including simulated gastrointestinal fluid tolerance, cell surface properties (hydrophobicity and autoaggregation), antimicrobial activity, processing stress tolerance (lysozyme and heat), and antibiotic sensitivity. Principal component analysis (PCA) was used to identify and screen the strains with optimal probiotic properties. This study found that the 23 lactic acid bacteria strains were isolated from 15 goat milk samples, including Leuconostoc mesenteroides (9 isolates), Lactiplantibacillus plantarum (6 isolates), Latilactobacillus curvatus (4 isolates), Enterococcus faecium (2 isolates) and Enterococcus durans (2 isolates). Seven strains were able to maintain considerable viable bacterial counts under pH2.0 and 0.3% bile salt conditions, indicating their high tolerance to acid and bile salt. Among them, strain SY43-10 and strain SY43-4 possessed a high tolerance towards simulated gastrointestinal fluid with over 5 lg CFU/mL after treatment, high self-agglutination rates of over 27% after 24 h and high hydrophobicit. Meanwhile, the viable counts after heat and lysozyme treatment of these two strains were more than 7 lg CFU/mL. Both of the two strains were susceptible to ampicillin and chloramphenicol, and were intermediate or susceptible to cefoxitin, erythromycin, and penicillin. In conclusion, strains Lactiplantibacillus plantarum SY43-10 and Lactiplantibacillus plantarum SY43-4 can be used as potential beneficial strains for further development of fermented dairy and functional products.