P19: Bioremoval of Se(IV) from Aqueous Medium: a potential strategy for production of probiotic Se-enriched lactic acid bacteria biomass

Selenium (Se) is an essential micronutrient for humans and animals. Lactic acid bacteria such as Lactobacillus, Lactococcus, Enterocococcus, Streptococcus and Bifidobacterium species are currently under intensive research because of their probiotic properties and other essential roles in most fermented foods. We screened thirty-six Enterococcus species for Se(IV) bioremoval. Several isolates grew luxuriantly and significantly removed Se(IV) from Se(IV) amended medium. Two isolates, LAB 14 and LAB 18, respectively identified by 16S rRNA gene sequence analysis as Enterococcus faecalis (98% similarity) and Enterococcus faecium (97% similarity) were further studied. The two isolates grew optimally and removed selenium at initial pH 7.0. Optimum removal of Se(IV) from the medium was recorded at 25ºC. Time course studies showed that after 8 hours of incubation, LAB 14 and LAB 18 cultures displayed the highest biomass production and Se(IV) bioremoval and most selenite in culture depleted in 24 h. At initial concentrations of 10 mg L^-1 and 60 mg L^-1, E. faecium (LAB 18) removed 9.91 mg L^-1 and 59.70 mg L^-1, respectively after 24 h. Similar Se(IV) bioremoval capacity was recorded with E. faecalis (LAB 14). Substantial amount of Se was detected in biomass of E. faecium (0.4599 mg g^-1 of dry weight) and E. faecalis (0.4759 mg g^-1 of dry weight). The significant uptake and transformation of Se(IV) suggest that Se(IV)-enriched Enterococcus biomass can be used to deliver dietary Se through feed augmentation.