Folate levels in cultures of lactic acid bacteria

The folate levels in cultures of the lactic acid bacteria Bifidobacterium longum B6 and ATCC 15708, Lactobacillus acidophilus N1 and ATCC 4356, Lactobacillus delbrueckii ssp. bulgaricus 448 and 449, and Streptococcus thermophilus MC and 573 was investigated. All lactic acid bacteria had higher folate levels in reconstituted milk than in complex media. B. longum B6 had the highest level of folate and S. thermophilus 573 had the lowest level of folate. The time course curves show that all strains tested had the maximum folate levels in 6 h. These strains varied in their abilities to accumulate tetrahydrofolate (THF), 5-methyltetrahydrofolate (5-MeTHF), and 5-formyltetrahydrofolate (5-FmTHF); however, strains of B. longum, L. bulgaricus, and S. thermophilus accumulated more 5-MeTHF than THF or 5-FmTHF. Folate levels decreased 2-16% for the first week and continued to decrease gradually throughout the 3-week period for fermented milk stored at 4 degrees C. Folate contents of milk fermented with L. acidophilus ATCC 4356 and S. thermophilus MC remained the most stable and decreased only about 8% in 2 weeks and 12% in 3 weeks. However, folate level of milk fermented with L. bulgaricus 449 decreased approximately 27% in 2 weeks and 39% in 3 weeks. (C) 2000 Elsevier Science Ltd. All rights reserved.