Characterization and quantification of folates produced by yeast strains isolated from kefir granules

For the first time to our knowledge, distribution and content of individual folate forms in kefir yeast strains were investigated. This was done using a validated method based on reversed-phase high performance liquid chromatography (HPLC) with fluorescence and diode array (DAD) detection. Eight kefir yeast strains, belonging to different Candida and Saccharomyces species, were isolated from Russian kefir granules. They were grown in synthetic media at standardized conditions before analysis. The average folate content for these yeast strains was 10,780 +/- 550 mu g/100 g dry matter. In all yeast strains tested, the most abundant folate forms as percentages were 5-methyltetrahydrofolate (43-59%), and 5-formyltetrahydrofolate (23-38%), whereas tetrahydrafolate occurred in a lesser proportion (19-23%).