Abstract: In this study, out of 119 bacterial isolates from duck foods, a novel selenium-enriched probiotic strain, designated as D1-019, was selected for its tolerance to selenite. This strain was obtained after four rounds of screening, which did not cause a red selenium phenomenon. Strain D1-019 was identified as Bacillus pumilus based on its colonial morphology, Gram staining, 16S rDNA analysis, and phylogenic tree analysis. Using an orthogonal experiment design, we obtained the optimum culture conditions for selenium enrichment as follows: pH 5, 30 ℃ for 48 h, and addition of 20 μg/mL selenite at 6 h of cultivation. Under these conditions, B. pumilus D1-019 eliminated selenite in the medium with a conversion rate of 100% and produced (1 327 ± 113) mg/kg of organic selenium, which was superior to the currently available seleniumenriched microbes. Our results indicated that B. pumilus D1-019 can be a promising candidate for selenium-enriched probiotics in the food industry.

Key words: Bacillus pumilus, organic selenium, selenium-enriched, probiotics, selenite, 16S rDNA