In vitro assessment of safety and functional probiotic properties of Lactobacillus mucosae strains isolated from Iranian native ruminants intestine

The search for host isolated probiotic bacteria from animal intestine may discover new probiotic candidates with promising health properties. This study evaluated the safety and functional probiotic potential of the lactic acid bacteria (LAB) isolated from the Iranian native ruminants intestine under in vitro assays. The isolates‌ were selected according to criteria including survivability in low pH, bile salts, pancreatic enzymes, different temperatures, NaCl concentrations, antibacterial activities, presence of adhesion genes and safety characteristics. The selected LAB were then identified to species level using 16S rRNA gene sequencing. The results showed that out of one hundred and eighty-seven LAB isolates, only six strains (NABRII50, NABRII51, NABRII52, NABRII53, NABRII54 and NABRII55) were tolerant to low pH, bile salt, pancreatin enzyme, 45 °C temperature and 2% sodium chloride. The six selected isolates belonged to Lactobacillus mucosae. Two of the adhesion genes (mub and map) were detected in all strains except NABRII53. The virulence factors were observed in NABRII50, NABRII53 and NABRII55. The tetracycline resistance gene (tet (S)) was detected in NABRII55. This study was the first effort to select Lb. mucosae strains with the probiotic potential from the Iranian ruminants intestine. These results revealed that the ruminant intestinal ecosystem could be considered as a valuable origin of probiotic candidates and all the selected LAB strains except NABRII50, NABRII53 and NABRII55 could be considered as promising probiotics. HIGHLIGHTS Lactobacillus mucosae strains isolated from Iranian native ruminants intestine including NABRII51, NABRII52 and NABRII54 showed probiotic potential under in vitro assays. The Lb. mucosae strains including NABRII51, NABRII52 and NABRII54 were able to survive in intestinal physiological conditions, and carried the adhesion genes, such as mub and map. In vitro biosafety assays confirmed that Lb. mucosae strains (NABRII51, NABRII52 and NABRII54) were safe to further studies.