The present study aimed to evaluate the safety of Bacillus subtilis (BS) IDCC1101, newly isolated from Cheonggukjang in Korea. Genome sequencing of BS IDCC1101 was performed to investigate the presence of secondary metabolites, virulence, antibiotic resistance, and mobile elements. Its phenotypic safety analyses included antibiotic susceptibility, enzyme activity, carbohydrate utilization, production of biogenic amines (BAs) and D-/L-lactate, hemolytic activity, and toxicities in HaCaT cells and rats. The genome of BS IDCC1101 consisted of 4,118,950 bp with 3077 functional genes. Among them, antimicrobial and antifungal secondary metabolites were found, such as fengycin, bacillibactin, and bacilysin. Antibiotic resistance and virulence genes did not exhibit transferability since they did not overlap with mobile elements in the genome. BS IDCC1101 was susceptible to almost all antibiotics suggested for assessment of BS’s antibiotic susceptibility by EFSA guidelines, except for streptomycin. BS IDCC1101 showed the utilization of a wide range of 27 carbohydrates, as well as enzyme activities such as alkaline phosphatase, esterase, esterase lipase, naphthol-AS-BI-phosphohydrolase, α-galactosidase, β-galactosidase, α-glucosidase, and β-glucosidase activities. Additionally, BS IDCC1101 did not exhibit the production of D-/L-lactate and hemolytic activities. Its toxicity in HaCaT cells and rats was also not detected. Thus, these genotypic and phenotypic findings indicate that BS IDCC1101 can be safely used for industrial applications.

Irritable bowel syndrome is a chronic disorder affecting the gastrointestinal tract, negatively impacting patients’ quality of life. Here, we aimed to evaluate the effects of Lacticaseibacillus rhamnosus IDCC 3201 (RH 3201) on irritable bowel syndrome with constipation (IBS-C). In this randomised, double-blind, placebo-controlled trial, a total of 30 subjects with IBS-C were randomly assigned (1:1) to receive 8 weeks of probiotics administration or placebo. Concerning bowel activities, both irritant bowel movements and discomfort caused by constipation showed significant improvement with RH 3201 at 8 weeks. Symptoms including severity of abdominal bloating, frequency of abdominal bloating, and satisfaction of bowel habits based on the irritable bowel syndrome-severity scoring system also ameliorated in the probiotic group. Analysis of the fecal microbiome revealed that the abundance of Bacteroides cellulosilyticus and Akkermansia muciniphila was higher during the period of RH 3201 administration compared to the placebo. Untargeted metabolome analysis further suggested a correlation between specific metabolites, such as N-acetylornithine, xanthine, and 3-phenylpropionic acid, and the improvement of clinical symptoms. These results indicate that RH 3201 was effective in ameliorating IBS-C, potentially by enriching beneficial microbes and associated metabolites in the gut environment.

Probiotic Lactobacillus species are known to exert health benefits in hosts when administered in adequate quantities. A systematic safety assessment of the strains must be performed before the Lactobacillus strains can be designated as probiotics for human consumption. In this study, we selected Lactobacillus fermentum IDCC 3901, L. gasseri IDCC 3101, L. helveticus IDCC 3801, and L. salivarius IDCC 3551 as representative Lactobacilli probiotic strains and investigated their probiotic properties and potential risks through phenotypic and genomic characterization. Various assays including antimicrobial resistance, biogenic amine production, L-/D-lactate production, acute oral toxicity, and antipathogenic effect were performed to evaluate the safety of the four Lactobacillus strains. Genomic analysis using whole genome sequencing was performed to investigate virulence and antibiotic resistance genes in the genomes of the selected probiotic strains. The phenotypes of the strains such as enzymatic activity and carbohydrate utilization were also investigated. As a result, antibiotic resistances of the four Lactobacillus species were detected; however, neither antibiotic resistance-related genes nor virulence genes were found by genomic analysis. Moreover, the four Lactobacillus species did not exhibit hemolytic activity or β-glucuronidase activity. The biogenic amine production and oral acute toxicity were not shown in the four Lactobacillus species, whereas they produced D-lactate with minor ratio. The four Lactobacillus species exhibited antipathogenic effect to five pathogenic microorganisms. This study provides a way to assess the potential risks of four different Lactobacillus species and validates the safety of all four strains as probiotics for human consumption.

Lactic acid bacteria (LAB) are probiotic microorganisms widely used for their health benefits in the food industry. However, recent concerns regarding their safety have highlighted the need for comprehensive safety assessments. In this study, we aimed to evaluate the safety of L. bulgaricus IDCC 3601, isolated from homemade plain yogurt, via genomic, phenotypic, and toxicity-based analyses. L. bulgaricus IDCC 3601 possessed a single circular chromosome of 1,865,001 bp, with a GC content of 49.72%, and 1910 predicted coding sequences. No virulence or antibiotic resistance genes were detected. Although L. bulgaricus IDCC 3601 exhibited antibiotic resistance to gentamicin and kanamycin, this resistance is an intrinsic feature of this species. L. bulgaricus IDCC 3601 did not produce biogenic amines and did not exhibit hemolytic activity. Phenotypic analysis of enzyme activity and carbohydrate fermentation profiles revealed the metabolic features of L. bulgaricus IDCC 3601. Moreover, no deaths or abnormalities were observed in single-dose oral toxicity tests, suggesting that L. bulgaricus IDCC 3601 has no adverse effect on human health. Finally, L. bulgaricus IDCC 3601 inhibited the growth of potential carbapenem-resistant Enterobacteriaceae. Therefore, our results suggest that L. bulgaricus IDCC 3601 is a safe probiotic strain for human consumption.

This study aimed to explore the safety and properties of Lacticaseibacillus paracasei IDCC 3401 as a novel probiotic strain via genomic and phenotypic analyses. In whole-genome sequencing, the genes associated with antibiotic resistance and virulence were not detected in this strain. The minimum inhibitory concentration test revealed that L. paracasei IDCC 3401 was susceptible to all the antibiotics tested, except for kanamycin. Furthermore, the strain did not produce toxigenic compounds, such as biogenic amines and D-lactate, nor did it exhibit significant toxicity in a single-dose acute oral toxicity test in rats. Phenotypic characterization of carbohydrate utilization and enzymatic activities indicated that L. paracasei IDCC 3401 can utilize various nutrients, allowing it to grow in deficient conditions and produce health-promoting metabolites. The presence of L. paracasei IDCC 3401 supernatants significantly inhibited the growth of enteric pathogens (p < 0.05). In addition, the adhesion ability of L. paracasei IDCC 3401 to intestinal epithelial cells was found to be as superior as that of Lacticaseibacillus rhamnosus GG. These results suggest that L. paracasei IDCC 3401 is safe for consumption and provides health benefits to the host.