Abstract:To screen lactic acid bacteria with strong selenium-enriching capacity for the development of selenium-enriched foods. Taking lactic acid bacteria isolated from fermented foods as the research objects， strains with high selenium tolerance and high conversion rate were obtained through primary screening and re-screening， and their species were identified. Optimize the conditions for selenium-enriched fermentation （sodium selenite concentration， addition time， shaker rotation speed， and fermentation time）. Determine the tolerance of the strain to artificial gastrointestinal fluid and its antioxidant activity （clearance rates of hydroxyl radicals and superoxide anion radicals）. Pediococcus pentosaceus S2 strain was screened out. Its optimal selenium-enriched conditions were as follows： sodium selenite concentration of 50 μg/mL， addition time of 6 h， shaker speed of 100 r/min， fermentation time of 24 h， and the selenium conversion rate reached up to 89.94% at the highest.In the simulated gastrointestinal digestion， the initial viable bacterial count of the selenium-enriched strain was 8.98 lg （CFU/mL）， and the survival rate after digestion was 0.21%， and it was significantly higher than that of the non-selenium-enriched group. The DPPH free radical scavenging rate （20.90%）， hydroxyl radical scavenging rate （64.61%） and superoxide anion radical scavenging rate （53.72%） of the selenium-enriched strain were significantly higher than those of the inorganic selenium group. Pediococcus pentosaceus S2 has a highly efficient selenium-enriching ability. After selenium-enrichment， its gastrointestinal tolerance and antioxidant activity are significantly improved， making it a potential strain for the development of selenium-enriched foods.