Bioremediation of selenite by selenite-resistant Lactococcus raffinolactis seD2b under laboratory scale

The accumulation of selenium oxyanions in the form of selenite (SeO3-2) in soil and water resources created increasingly worrying on human health and environment. The current project directed toward screening of selenite-resistant lactic acid bacteria for their potential use as safe biocatalysts in the selenite bio-remediation.
Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of selenite against isolated strains were evaluated using agar dilution method. Inhibitory effects of selenite against isolated strains were calculated employing well diffusion agar method. Turbidity testing was used to investigate bacterial growth. Identification of the potent bacterium strain was carried out based on bio-chemical tests and phylogenetic analysis. A colorimetric method using 3, 3-Diaminobenzidine hydrochloride has been developed for the microbial selenite removal.
Results indicated that Lactococcus raffinolactis strain seD2b exhibited the highest MIC (110 mM) and MBC (140 mM) values and also the lowest inhibitory effect with the average diameter of the inhibition zone (26.6 mm) in the presence of selenite. After 72 h incubation of the reaction medium containing 10mM of initial selenite concentration with resting cells of Lactococcus raffinolactis seD2b, the concentration of toxic selenite in the reaction medium decreased by 90.2% .
Discussion and Given the ability of Lactococcus raffinolactis strainseD2b in the remove and reduce selenite, screening of lactic acid bacteria as green bio-catalysts for their application in the bio-remediation of selenite and their economic importance on synthesis of selenium has been proposed.