Screening of Lactic Acid Bacteria from Donkey Milk in Xinjiang for Use as Starter Culture and Their Probiotic Characteristics

Thirty-eight strains suspected of being lactic acid bacteria were isolated from 15 donkey milk samples collected in Hami, Xinjiang, of which seven strains were found to have obvious milk coagulation characteristics. The strains were identified by 16S rRNA gene sequencing as Pediococcus acidilactici HL12-21, Pediococcus pentosaceus HL29-5, Enterococcus mundtii HL30-3, Lactobacillus plantarum HL21-44, Lactobacillus coryniformis HL26-24, Lactobacillus curvatus HL29-1 and Leuconostoc lactis HL13-23. They were screened for their milk coagulation time, acid-producing capacity, post-acidification capacity, aroma-producing capacity, sensory characteristics and viable counts during cold storage, of which HL12-21, HL29-5, HL21-44 and HL29-1 possessed better acid-producing and aroma-producing capacity and weaker post-acidification capacity, and the single culture fermented milk had the highest comprehensive scores for color, texture and flavor. The number of viable bacteria still remained above 10⁶ CFU/mL after storage at 4 ℃ for 20 days. In addition, the tolerance of the seven strains and the probiotic bacterium Lactobacillus rhamnosus GG to simulated gastrointestinal fluid, as well as their antimicrobial spectra, antibiotic resistances and antioxidant activities were compared. The results showed that HL29-5 and HL30-3 were superior to the other strains in terms of all above probiotic properties, with special reference to the highest scavenging rates against hydroxyl, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion free radicals (over 30%). Based on our results, Pediococcus pentosaceus HL29-5 holds great potential as a probiotic starter culture for developing specialty yogurt.