Beetroot juice fermented by Lactobacillus brevis 0944 and Lactobacillus paracasei 0920 bacteria was stored for 180 days at 4^oC. During storage, samples were taken at 7, 14, 30, 90 and 180 days and the following characteristics were determined: betalain content, ability to limit chemical mutations induced by N-methyl, N’nitro, N- nitrosoguanidine in the Ames test, and the size of the population of Lactobacillus bacteria. After 7 days of refrigerated storage of fermented beet juice, betalain content was found to be 88% as against the initial content. For up to 30 days of fermented beet juice storage, betalain content remained at the same level. After 90 and 180 days of storage, the level of betalains falls drastically and amounts to 32% and 25%, respectively, as compared to the initial level. The ability to limit chemical mutations in the Ames test is 57% for Salmonella TA 98 and 58% for Salmonella TA 100 at the starting point. The antimutagenic activity of fermented beet juice is preserved at the same level for 30 days. After 90 and 180 days, antimutagenic activity decreases to 32% and 41% for Salmonella TA 98 and to 41% and 22% for Salmonella TA 100. The population of Lactobacillus bacteria sp. after fermentation is at a level of 9.11 Log₁₀ cfu/mL. After 30 days of storage, the population of bacteria falls to 8.15 Log₁₀ cfu/mL. Further storage leads to a decrease in the population of Lactobacillus sp. bacteria to 6.80 Log10 cfu/mL after 180 days. Fermented beet juice preserves its high biological activity for up to 30 days in refrigerated storage.