Selenium accumulation and selenonanoparticle production by lactic acid bacteria isolated from tropical fruits fromNorthwestern Argentina

FERNANDO GABRIEL MARTINEZ; MICAELA PESCUMA; FERNANDA MOZZI

Cordoba

Congreso; VII CICYTAC; 2018

Selenium accumulation and selenonanoparticle production by lactic acidbacteria isolated from tropical fruits from Northwestern ArgentinaMartínez F G (1), Pescuma M (1), Mozzi F (1)(1) Centro de Referencia para Lactobacilos (CERELA-CONICET), Chacabuco145, San Miguel de Tucumán, Argentina.fmartinez@cerela.org.arSelenium (Se) is an essential micronutrient that is incorporated into the humandiet mainly through vegetable and fruit ingestion. Se is present as selenocysteinin Se-dependent enzymes important to human health such as glutathioneperoxidase, thyoredoxin reductase, and deiodinases. The Se content in food isscarce in Argentina indicating a moderate status of this trace element.Fermented foods bioenriched with Se using microorganisms have receivedmuch attention in the last years. In this sense, lactic acid bacteria (LAB)constitute a relevant biotechnological tool due to their ability to reduce inorganicSe into organic Se forms and Se-nanoparticles (SeNP), which are less toxic andhave increased bioavailability than inorganic Se. In this work we aimed to studythe capability of fruit-derived LAB strains to reduce and accumulate Se and toproduce SeNP. The capacity to reduce Se and the resistance to this metalloidwas evaluated in the fruit origin strains Weissella cibaria 25, Lactobacillusbrevis 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. Selenitecontent in the supernatants, measured by the 2,3-diaminonaphthalene method,showed high removal (81,3 - 97,5%) of the added Se highlighting the reducingcapacity of the tested strains. Five mg/L of Se was used in further studiesfollowing the Se recommended daily intake of the Argentine food code. Cellgrowth (OD600, CFU/ml), pH and Se accumulation (atomic absorptionspectrometry), and SeNP formation (scanning electron microscopy) weredetermined. All strains were able to grow in the presence of Se but a slightdecrease in growth parameters was observed for the Weissella and Lact. brevisstrains. The assayed LAB strains accumulated intracellularly between 61,3 and71,3% 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 after6 h; the increase in the reddish color was due to SeNP formation. All assayedstrains were able to produce spherical nanoparticles without affecting cellmorphology. Our results suggest that these strains display a significantcapability to reduce and accumulate Se and could be used to produce SeNP orto elaborate Se-enriched fermented foods.