Screening of lactic acid bacteria for highly producing extra and intracellular folate and their potential use in production of bio-enriched yogurt

In this study, firstly, Microbial Assay (MA) was performed to evaluate the levels of intra and extracellular folate (Quatro folate) produced by 43 lactic acid bacteria strains isolated from traditional Iranian dairy products. The results obtained from strain screening showed that two strains of Lactobacillus delbrueckii subsp. bulgaricus , two strains of Streptococcus thermophilus , two strains of Lactobacillus delbrueckii subsp. lactis and one strain of Lactobacillus helveticus are highly folate producing. However, two strains of Lactobacillus delbrueckii subsp. bulgaricus produced higher amounts of folate (133.23 μg/mL and 102 μg/mL, respectively). In the second phase, eight yogurt samples were produced by using the two highest folate producing strains and compared with the control sample. The folate production in yogurt samples showed that Y8 sample has the highest amount of folate (117.93, 38.81 μg/mL determined by microbial and HPLC assay methods, respectively). It was found that the microbial assay method has the ability to measure different forms of folate derivatives compared to the HPLC method. The results exhibited that the isolates examined in this study showed the ability to produce extracellular folate at higher levels and can be used as bio-enrichment cultures to produce functional foods. • -The highest amount of extracellular folate was produced by NO. 25 & 26 of L. bulgaricus. • -The lowest amount of extracellular folate was produced by NO. 86 L. helveticus. • -The highest amount of folate was produced in Y8 yogurt sample. • -The microbial assay method showed more folate than the HPLC method.