Screening Of Bacillus Subtilis And Probiotic Potential Evaluation

Antibiotics are widely used as feed additives to feed animals in farming, aiming to inhibiting the intestinal pathogenic bacteria infection and promoting animal growth. But the use of antibiotics can cause pathogenic bacteria resistance increase, and these resistant bacteria can be transmitted between animals or get into the environment to give rise to environmental pollution and the infection threat to humans, and the difficulty of clinical medication chosen medicine. Which we cannot ignore is that adding antibiotics in animals feed may cause antibiotic secondary infection. Professionals and farmers have realized the use of antibiotics may cause many problems and in breeding industry in China has entered the post-antibiotic era, probiotics is the preferred alternative. As it possesses the effect of the inhibit bacteria and promote growth, probiotics becomes a good substitute for antibiotics,while it is green and will not result in bacterial drug resistance. So probiotics have really broad prospects.In this research, we made horizontal comparisons on several strains of bacillus subtilis.Firstly we compare their probiotic potential in vitro from several aspects such as the growth performance, the tolerance of acid and bile, the bacteriostatic test, the antibiotic resistance test and the blood clotting test. Then we put the strain with good performance into animal test to inspect the growth promoting active effect as potential probiotics in vivo.The results showed that bacillus subtilis B5 grows well, the survival rate under the condition of pH = 3.0 is over 90% and the survival rate under the condition of pH =1.5 is still higher than 70%. More than 60% of the B5 strains survived after 1h in 0.3% of the high concentration of bile salts environment. The strain showed significant inhibitory effect to many pathogenic bacterias, but showed no resistance to common antibiotics. B5 significantly increased the experimental rabbit’s growth performance after being made into powder and added to the diet. So bacillus subtilis B5 is identified as a good probiotic strain.In this research one outstanding strain was screened from multiple strains of bacillus subtilis strains, and the animal experiment was carried out. This laid the foundation for the strains of bacillus subtilis to the application to Rabbit keeping.