Probiotic potential and resistance to Escherichia coli, Salmonella of Bacillus amyloliquefaciens

Bacillus amyloliquefaciens is a Gram-positive spore-forming bacterium that has superior properties compared to other beneficial bacteria used in probiotic preparations. The purpose of this study was to determine the bacterial biological properties under harsh conditions such as high temperature, low pH, bile salts, artificial gastric juice and test the resistance to two types of gram-negative bacteria including Escherichia coli and Salmonella. The results showed that after 3 h of testing at 85oC, the bacterial density remained at 3.05 ± 0.06 log CFU/mL (corresponding to 35.58% of the initial density). Under pH = 2.5 condition and after 3 h, the bacterial density remained up to 5.34 ± 0.04 log CFU/mL (62,43%). With the bile salt concentration up to 0.6% after 3 h, the bacterial density remained at 5.24 ± 0.07 log CFU/mL (61.34%). Under the decomposition action of the enzyme pepsin and in the artificial gastric fluid environment of piglets (0.3% pepsin, pH = 4.5) at different levels, the bacterial density still remained at the level of 5.82 ± 0.15 log CFU/mL (63.66%), which was higher than that of the test of artificial stomach fluid of adult pigs (pepsin 0.3%, pH = 2.5) corresponding to 4.73 ± 0.04 log CFU/mL (55.21%) after 3 h of testing. In this study, B.amiloliquefaciens also showed resistance to gram-negative bacteria such as Salmonella Typhimurium ATCC 14028, Salmonella Enteritidis WHO 2014, E. coli with F4 factor, E. coli with F18+Stx2e factor, field Salmonella Typhimurium, and field Salmonella Enteritidis.