After the last incubation, 2 samples were
taken to determine the concentration of extracellular and intracellular
folates. A sample (500 mL) of LAB-containing vitamin-free
media was taken, and 500 mL of folate protecting buffer (0.1 mol/L
phosphate buffer, pH 6.8, containing 1.5% (w/v) ascorbic acid) to
prevent vitamin oxidation and degradation was added, mixed and
centrifugated for 5 min at 5000 g.