Characterization of lactic acid bacteria-based probiotics as potential heavy metal sorbents

To isolate and characterize lactic acid bacteria (LAB) and determine whether they could potentially be used as heavy metal (cadmium and lead) absorbing probiotics.The study used 53 environmental (mud and sludge) samples to isolate cadmium- and lead-resistant LAB, by following spared plate technique. A total of 255 cadmium- and lead-resistant LAB were isolated from these samples. The survival of 26 of the LAB was found after passing through sequential probiotic characterizations. These 26 probiotic LAB exhibited remarkable variations in their metal-resistant and metal-removal abilities. Of 26, seven (Cd54-2, Cd61-7, Cd69-12, Cd70-13, Pb82-8, Pb96-19 and Cd109-16) and four (Pb71-1, Pb73-2, Pb85-9 and Pb96-19) strains displayed relatively elevated cadmium- and lead-removal efficiencies from water, respectively, compare with that of the remaining strains. Strains Cd70-13 and Pb71-1 showed the highest cadmium (25%) and lead (59%) removal capacity from MRS (De Man, Rogosa and Sharpe) culture medium, respectively, amongst the selected strains and showed a good adhesive ability on fish mucus. A phylogenetic analysis of their 16S rDNA sequences revealed that the strains Cd70-13 and Pb71-1 belong to Lactobacillus reuteri.Excellent probiotic, metal sorption and adhesive characteristics of newly identified Lact. reuteri strains Cd70-13 and Pb71-1 were isolated, which indicated their high potential abilities to survive in the intestinal milieu and to uptake the tested metals from the environment.To our knowledge, this is the first study that has aimed to isolate, characterize and identify metal-resistant LAB strains that have potential to be a probiotic candidate for food and in vivo challenge studies in the intestinal milieu of fish for the uptake and control of heavy metal bioaccumulation.