Effect of Pretreatments on bioremoval of metals and subsequent exposure to simulated gastrointestinal conditions

Water contamination with heavy metals is increased due to environmental contaminants. Arsenic, cadmium, mercury, and lead are well-known toxic heavy metals for humans. Lactobacillus acidophilus is an ideal absorbent for the removal of metals from drinking water. In this study, the ability of treated and untreated L. acidophilus ATCC 4356 to remove four heavy metals, simultaneously, from multi-metallic contaminated water in 24 h was investigated. In addition, the stability of the bacteria–metal complexes was evaluated in simulated gastrointestinal tract conditions. According to the results, untreated L. acidophilus could remove 99.01% and 92.35% of mercury and lead in water, respectively (initial concentration of 700 µg.L−1; inoculum size of 2.6×1012 CFU.mL−1; pH 4; 37°C; 24 h), whereas removal of arsenic and cadmium, under the same conditions, was 91.28% and 61.91% by heat and NaOH treated cells, respectively. In the digest condition, the complexes of bacteria-metal were reversible and the bond stability of untreated bacteria–Hg complexes was stronger than other complexes. The results suggest that treated or untreated L. acidophilus ATCC 4356 cells have the potential to adsorb heavy metals in contaminated water.