Abstract:The thermal resistance, acid resistance, bile salt resistance, adhesion ability, antibiotic susceptibility, and other biological characteristics of Brevibacillus laterosporus strain S62-9 were studied in vitro. Strain S62-9 exhibited good thermal tolerance, with a survival rate of 86.20% after incubation in an 85 ℃ water bath for 5 min. It had the lowest survival rate (85.70%) after exposure to simulated gastric juices at pH 2.0 for 4 h, whereas the survival rates at pH 3.0 and 4.0 were both higher than 95.00%. The survival rates after 4-h treatments in 0.1%, 0.2%, and 0.3% bile-salt-stimulated intestinal fluids were 93.30%, 91.70%, and 88.30%, respectively. Strain S62-9 showed high tolerance to simulated gastrointestinal transit, where its survival rate was 96.00% after being treated with gastric juice at pH 2.0 for two hours followed by a three-hour treatment in intestinal fluid containing 0.3% bile salt. The bacterium in the trophozoite stage showed an adhesion ability of 20.70 CFU per Caco-2 cell, which was higher than that of the control strain (Bacillus subtilis K1). Strain S62-9 had no observable resistance to 10 types of antibiotics tested and was thus considered to be a biosafe strain. These excellent probiotic characteristics of B. laterosporus S62-9 meet the standards and requirements of a good probiotic, laying a theoretical basis for its development and application as a probiotic strain.
