Preliminary in vitro assessment of probiotic properties of Bacillus subtilis GM1, a spore forming bacteria isolated from goat milk

Document Type : Full paper (Original article)


1 Ph.D. Student in Microbiology, Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Iran

2 Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Iran


Background: Species of the Bacillus genus have a long history of use in biotechnology. Some Bacillus strains have recently been identified for food applications and industrial as safe bacteria, which mostly have been recognized as probiotic strains. Aims: The primary purpose of the current study was to evaluate the probiotic characteristics of Bacillus subtilis strains isolated and identified from the goat milk samples. Methods: After sampling from 40 goat milk and cultivation, suspected colonies were subjected to biochemical and molecular identification. Then, the confirmed isolate was assessed for in vitro probiotic tests, including hemolysis and lecithinase properties, bile salt, acid, and artificial gastric juice resistance, antioxidant activity, antibiotics susceptibility, enterotoxin genes detection, and attachment capacity to the HT-29 cells. Results: Among 11 suspected isolates evaluated, only one isolate was identified as B. subtilis. In vitro tests for this strain showed similar results to other probiotic strains. The B. subtilis strain was susceptible to various antibiotics. The enterotoxin genes were not detected based on PCR assay. Concerning its probiotic characteristics assessment, especially tolerance to bile salts and acidic conditions, the Bacillus strain could have the potential to consider as a probiotic. Conclusion: Goat milk can be recommended as a source of Bacillus isolates. Also, the isolated strain showed high adaptability to the gastrointestinal environment, relatively equal percentages of adhesion properties, and some safety aspects, having the potential to be considered as an appropriate probiotic.


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