Isolation, Characterization, and Assessment of Probiotic Properties of Bacillus clausii Isolated from Children’s Stools in a Northern Province of Vietnam

Bacillus clausii is a widely utilized human probiotic in various commercial products; however, there has been limited research on the isolation from diverse sources and evaluation of probiotic characteristics of Bacillus clausii. For the first time in this study, Bacillus clausii strains were isolated and evaluated from stool samples obtained from healthy volunteer children in a northern province of Vietnam. The inherent biological properties of the isolated Bacillus clausii strains were specifically examined to explore their potential application as probiotics. Thirteen colonies underwent screening through morphological and biochemical analyses, along with protein Maldi Tof MS. Among these isolates, Bacillus M23 and M31 were identified. In the preliminary safety screening, both strains exhibited negative hemolytic activity. Additionally, in vitro characteristics, such as spore formation, resistance to acid and bile salts, resistance to pathogenic microorganisms, assessment of extracellular enzyme production, and antibiotic sensitivity testing were determined for these strains, falling within the observed range for other probiotic strains. The 16S rRNA gene sequencing revealed that Bacillus M31 shared 97% similarity with Bacillus clausii DSM 8716 in the Genbank database. These findings suggest that the Bacillus clausii M31 shows promise as a probiotic candidate, although further extensive in vitro/vivo studies are necessary to validate its efficacy and safety.