Preclinical Safety Assessment of Bacillus subtilis BS50 for Probiotic and Food Applications

Abstract

Despite the commercial rise of probiotics containing Bacillaceae spp., it remains important to assess the safety of each strain before clinical testing. Herein, we performed preclinical analyses to address the safety of Bacillus subtilis BS50. Using in silico analyses, we screened the 4.15 Mbp BS50 genome for genes encoding known Bacillus toxins, secondary metabolites, virulence factors, and antibiotic resistance. We also assessed the effects of BS50 lysates on the viability and permeability of cultured human intestinal epithelial cells (Caco-2). We found that the BS50 genome does not encode any known Bacillus toxins. The BS50 genome contains several gene clusters involved in the biosynthesis of secondary metabolites, but many of these antimicrobial metabolites (e.g., fengycin) are common to Bacillus spp. and may even confer health benefits related to gut microbiota health. BS50 was susceptible to seven of eight commonly prescribed antibiotics, and no antibiotic resistance genes were flanked by the complete mobile genetic elements that could enable a horizontal transfer. In cell culture, BS50 cell lysates did not diminish either Caco-2 viability or monolayer permeability. Altogether, BS50 exhibits a robust preclinical safety profile commensurate with commercial probiotic strains and likely poses no significant health risk to humans.

The probiotic Bacillus subtilis BS50 decreases gastrointestinal symptoms in healthy adults: a randomized, double-blind, placebo-controlled trial

“…Bacillus subtilis BS50 (also known as B. subtilis BS8-74) is a gram-positive, spore-forming bacterium that was isolated at BIO-CAT Microbials, LLC (Shakopee, MN, USA) from soil collected from Gallatin County, Montana, USA on 4 July 2015. 44 BS50 has been deposited in the American Type Culture Collection with Accession No. PTA-127287.…”

“…Additionally, BS50 cell lysates do not negatively impact cultured human Caco-2 intestinal epithelial cell viability or monolayer permeability. 44 BS50 spore preparations show robust heat resistance and pH tolerance (unpublished data), which predict strain survival across a wide range of pH across the human gastric and intestinal compartments. BS50 also secretes a suite of extracellular enzymes in its vegetative state, which is likely to support postprandial digestion, nutrient absorption, and GI tolerance.…”

“…The safety of BS50 has been demonstrated utilizing published scientific procedures. 44 , 45 In silico and in vitro analyses of BS50 indicate that the BS50 genome does not encode any known Bacillus toxins. 44 The BS50 genome contains several gene clusters involved in the biosynthesis of secondary metabolites, many of which are antimicrobial metabolites such as fengycins that may confer health benefits related to intestinal microbiota balance.…”

“… 44 , 45 In silico and in vitro analyses of BS50 indicate that the BS50 genome does not encode any known Bacillus toxins. 44 The BS50 genome contains several gene clusters involved in the biosynthesis of secondary metabolites, many of which are antimicrobial metabolites such as fengycins that may confer health benefits related to intestinal microbiota balance. Additionally, BS50 cell lysates do not negatively impact cultured human Caco-2 intestinal epithelial cell viability or monolayer permeability.…”

2,4-Dichlorophenol biotransformation using immobilized marine halophilic Bacillus subtilis culture and laccase enzyme: application in wastewater treatment

“…The hemolytic activity of B. subtilis AAK strain was detected according to the method described by Brutscher et al [20]. The cells were streaked onto blood agar plates to test their ability to lyse blood cells.…”