CONICET | Buscador de Institutos y Recursos Humanos

Selenium accumulation and selenonanoparticle production by lactic acid bacteria isolated from tropical fruits from Northwestern ArgentinaMartínez F G (1), Pescuma M (1), Mozzi F (1)(1) Centro de Referencia para Lactobacilos (CERELA-CONICET), Chacabuco 145, San Miguel de Tucumán, Argentina.fmartinez@cerela.org.arSelenium (Se) is an essential micronutrient that is incorporated into the human diet mainly through vegetable and fruit ingestion. Se is present as selenocystein in Se-dependent enzymes important to human health such as glutathione peroxidase, thyoredoxin reductase, and deiodinases. The Se content in food is scarce in Argentina indicating a moderate status of this trace element. Fermented foods bioenriched with Se using microorganisms have received much attention in the last years. In this sense, lactic acid bacteria (LAB) constitute a relevant biotechnological tool due to their ability to reduce inorganic Se into organic Se forms and Se-nanoparticles (SeNP), which are less toxic and have increased bioavailability than inorganic Se. In this work we aimed to study the capability of fruit-derived LAB strains to reduce and accumulate Se and to produce SeNP. The capacity to reduce Se and the resistance to this metalloid was evaluated in the fruit origin strains Weissella cibaria 25, Lactobacillus brevis 73, Lact. plantarum CRL 2030 and Fructobacillus tropaeoli CRL 2034. The strains were grown in MRS or MRS-Fructose (Fructobacillus strain) supplemented with 20 mg/L of sodium selenite at 30 °C for 24 h. Selenite content in the supernatants, measured by the 2,3-diaminonaphthalene method, showed high removal (81,3 - 97,5%) of the added Se highlighting the reducing capacity of the tested strains. Five mg/L of Se was used in further studies following the Se recommended daily intake of the Argentine food code. Cell growth (OD600, CFU/ml), pH and Se accumulation (atomic absorption spectrometry), and SeNP formation (scanning electron microscopy) were determined. All strains were able to grow in the presence of Se but a slight decrease in growth parameters was observed for the Weissella and Lact. brevis strains. The assayed LAB strains accumulated intracellularly between 61,3 and 71,3% of the Se present in the medium after 24 h of incubation. Moreover, pellets displayed a time-dependent color change turning from white to red after 6 h; the increase in the reddish color was due to SeNP formation. All assayed strains were able to produce spherical nanoparticles without affecting cell morphology. Our results suggest that these strains display a significant capability to reduce and accumulate Se and could be used to produce SeNP or to elaborate Se-enriched fermented foods.Key words: Lactic acid bacteria, Selenium, Nanoparticles