Evaluation of lactobacilli from human sources for uptake and accumulation of selenium

The trace mineral selenium (Se) is currently in demand for health supplements for human and animal nutrition. In the present study, 25 isolates of Lactobacillus species of human origin from Indian population were screened for their ability to uptake and accumulate Se in a more bioavailable form. Total Se accumulated by cells was measured by inductively coupled plasma emission spectrometry (ICPES) after wet digestion of Se-enriched cultures. Ten out of 25 isolates grew luxuriantly, as red pigmented colonies, on medium amended with different concentrations of sodium selenite. All the strains when grown in a culture medium supplemented with 10 μg/mL sodium selenite (corresponding to 4.5 μg/mL Se) resulted in Se accumulation in the range of 129.5 to 820.0 μg/g of dry weight (d.w.) as measured using the ICPES method. Elemental Se produced due to reduction of sodium selenite by bacteria was seen as irregular globules under the scanning electron microscope (SEM). Out of all the tested cultures, Lactobacillus reuteri NCDC77 was found to have the greatest ability to uptake Se (28.8% of inorganic Se in medium) and total Se accumulated was up to 820 μg/g d.w., significantly higher than that of control (742.5 μg/g d.w.). The findings of present study indicate that lactobacilli from human sources have the ability for uptake and accumulation of Se, and the prolific strain has the potential to be explored as an alternative source of organic dietary Se.