CELL BEHAVIOUR AND ACCUMULATION OF SELENIUM BY LACTIC ACID BACTERIA

FERNANDO GABRIEL MARTINEZ; LUCIANA RUIZ-RODRIGUEZ; MICAELA PESCUMA; FERNANDA MOZZI

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

CERELA

The traceelement Selenium (Se) is essential for human health; its deficiency isassociated to viral infections, thyroid dysfunction, different types of cancerand aging. The Se content in food is scarce in Argentina and it has been reportedas lower than those for other countries indicating a moderate status of thismicronutrient content in our foods. Se health benefits depend on the form in whichit is consumed; organic and elemental Se are less toxic and have increasedbioavailability than inorganic Se. Some lactic acid bacteria (LAB) are able toaccumulate and bio-transform Se into elemental and organic forms. The abilityof LAB isolated from Argentinean fruits to grow in the presence of and to accumulateSe was studied in this work. Lactococcuslactis subsp. lactis CRL2009, Leuconostoc pseudomesenteroides CRL1997,Lactobacillus brevis 77, L. rhamnosus CRL2031, Enterococcus hirae 90, and Fructobacillustropaeoli CRL2038 were grown in MRS supplemented with 5, 10, and 20 mg/L Na2SeO3at 30 °C for 24 h. Cell growth (OD600, cfu/mL), pH, glucose concentrationand organic acid production (HPLC), and Se accumulation (atomic absorptionspectrophotometry) were determined. All strains were able to grow in the presenceof Se and no significant differences were found when increasing the Seconcentrations except for Lc. lactis CRL2009,which showed a decrease of 0.8 (at 6 h) and 1.0 log U cell growth in thepresence of 5 and 20 mg/L Se, respectively. Consistently, no differences on theacidifying capacity of the strains when Se was added to the growth medium wasobserved except for the Lc. LactisCRL2009 strain, which showed pH values 0.22 and 1.50 higher than the controlswhen grown in presence of 5 and 20 mg/L of Se at 24h incubation. Regarding glucosemetabolism, Leuc. pseudomesenteroidesCRL1997 and L. brevis 77 producedhigher amount of acetic acid (0.13 and 2.93 g/L, respectively) and less ethanol(2.3 and 1.2 g/L, respectively) in the presence of Se respect to the controls.The opposite behavior was observed for F.tropaeoli CRL2038, which produced less acetic acid (0.2 g/L) and moreethanol (1.3 g/L). Atomic absortion spectrophotometry studies, showed that LABstrains were able to accumulate between 1.7 and 39.3% of the added Se to theculture medium at 24 h incubation, being F.tropaeoli CRL2038 and Lc. lactis CRL2009 the strains which showed the highestamounts of intracellular Se (449 and 472 mg Se/kg cell, respectively). Seenrichment of LAB could be an interesting tool for food supplementation to improvethis micronutrient intake in humans.