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Article Title

Biosynthesis of Folates by Streptococcus thermophilus and Lactobacillus delbruekii ssp. bulgaricus

Abstract

The folate synthesizing ability of yogurt bacteria, including Streptococcus thermophilus MC and ATCC 19258 and Lactobacillus delbrueckii ssp. bulgaricus 448 and 449, were evaluated. The major effort of this study focused on increasing the folate contents of yogurt bacteria fermented milk by adding lactose or calcium chloride. The addition of 2% lactose in reconstituted non-fat dry milk increased folate synthesis. Although folates increased only about 3 to 7% for yogurt cultures incubated for 6 hr, folates increased 12 to 198% for yogurt bacteria grown for 18 hr. The folate content decreased for reconstituted milk fermented with S. thermophilus MC or L. bulgaricus 448 or 449 when 0.02% calcium chloride was added. The folate level increased only for reconstituted milk fermented with S. thennophilus ATCC 19258 when calcium chloride was added. The addition of 2% lactose increased the cell counts for yogurt bacteria grown for 6 and 18 hr. On the other hand, the results of the cell counts from the addition of 0.02% calcium chloride were not consistent. However, the cell counts increased for both L. bulgaricus strains. The folate levels and cell counts during refrigerated storage at 4°C were determined for reconstituted non-fat dry milk fermented with these bacteria. Folate levels decreased about 9 to 28% at the end of the second week. The viable yogurt bacterial counts remained stable for the 2-week shelf life for all four strains tested in this study. To determine the effect of folate on protecting cells from the cytotoxicity of oxidant H2O2, Intestine 407 was used in this study for evaluation. The cell viability of Intestine 407 was increased due to the inhibition of oxidant H2O2 cytotoxicity by folate and Intestine 407 cells demonstrated higher viability when treated with higher concentration of folate.

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