Abstract: Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 were used as the materials to prepare a selenium-enriched yogurt starter. The optimal conditions for selenium enrichment with Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 were explored by single-factor and Box-Behnken design methods. The optimal conditions for selenium enrichment were fructooligosaccharide of 1%, Se4+ concentration of 6.83μg/mL, initial pH 6.0, inoculation ratio between Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 of 2:1, inoculation amount of 3.8%, incubation temperature of 42 ℃, selenium addition time point at the 24 h of cultivation, and cultivation period of 60 h. Under the optimal conditions, the content of selenium in the mixture of Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 was (551 ± 4.6)μg/g and the conversion rate of selenium was (42.2 ± 3.6)%. In addition, an excellent fermentation performance of selenium-enriched yogurt starter prepared by Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 was achieved. The content of organic selenium in the yogurt prepared by this starter was (17 ± 4.5)μg/kg.

Key words: Bifidobacterium adolescentis, Lactobacillus casei, selenium enrichment, yogurt