Resumo

Selenium (SeIV) is an essential micronutrient for several organisms, and there is an increased interest about adequate sources for dietary selenium supplementation. Also, selenium is found in food plants mostly as selenomethionine and in animal tissues as selenocysteine and other unidentified forms. In animals, amendment of food with selenium can increase the carcass weight. So, the aim of this study was to evaluate the selenium bioaccumulation capacity of an Enterococcus strain for feed implementation. The isolate LAB18s was identified as Enterococcus durans by the VITEKŪ 2 system and analysis of both 16S rDNA gene sequence (JX503528) and the 16S-23S rDNA intergenic spacer (ITS). After 24 hours of incubation, the isolate Enterococcus durans LAB18s bioaccumulated high Se(IV) concentrations, reaching 2.60 and 176.97 mg g-1 of biomass in media containing initial amounts of 15 and 240 mg/l sodium selenite, respectively. The isolate grew optimally and had high selenium bioaccumulation at initial pH of 7.0 and 30°C. Time course studies showed that Enterococcus durans LAB18s displayed the highest bioaccumulation of Se(IV) after 6 hours of incubation. Analyses from scanning electron microscopy (SEM) demonstrated the presence of filaments connecting the cells of Enterococcus durans LAB18s cultivated in the presence of sodium selenite. It was demonstrated that a considerable amount of Se(IV) was absorbed by Enterococcus durans LAB18s. Therefore, this strain may represent an alternative source of organic dietary selenium. Also, an excess of inorganic selenium (e.g., Na2SeO3) can cause toxic reactions in living organisms, and therefore, attention has been given to organic selenium, due to its good characteristics such as lower toxicity, better palatability, higher absorption and bioavailability, and less environmental pollution.