Abstract
Cadmium (Cd) and lead (Pb) are heavy metals, important environmental pollutants, and potent toxicants to organism. Lactic acid bacteria (LAB) have been reported to remove Cd and Pb from solutions and therefore represent a useful tool for decontamination of food and beverages from heavy metals. Heavy metal ion binding by LAB was reported as metabolism-independent surface process. In this work ten Lactobacillus strains were investigated with respect to hydrophobicity, Lewis acid-base, and electrostatic properties of their outer cell surface in order to characterize their Cd and Pb removal capacity. Seven L. plantarum and L. fermentum strains were shown to remove Cd from culture medium. The metabolism-dependent accumulation mechanism of Cd removal was proposed based on extended character of Cd binding and lack of correlation between any of the surface characteristics and Cd removal. The results of this study should be considered when selecting probiotic strains for people at risk of Cd exposure.
Highlights
Lead (Pb) and cadmium (Cd) are the two most abundant toxic heavy metals in the environment, reported in the Priority List of Hazardous Substances on the 2nd and 7th places, respectively [1]
The following Lactobacillus strains were used in this study: Lactobacillus plantarum 8PA3 (“Lactobacterin dry”, Biomed, Russia), Lactobacillus plantarum B-578 (All-Russian Collection of Microorganisms, VKM), Lactobacillus plantarum S1 (Silage, Chistopolsky region, Tatarstan Rep., Russia), Lactobacillus plantarum Ga (“Gastropharm,” Biovet, Bulgaria), Lactobacillus fermentum Na (“Narine,” Narex, Armenia), Lactobacillus fermentum 3-2, Lactobacillus fermentum 3-3, Lactobacillus brevis DSM-20054, Lactobacillus buchneri DSM-20057 (German Collection of Microorganisms and Cell Cultures, DSMZ), and Lactobacillus rhamnosus I2L (Russian National Collection of Industrial Microorganisms, VKPM)
Application of 10 mg/L Cd resulted in reduced optical density at 600 nm (OD600) values in the stationary phase of L. plantarum 8PA3, L. plantarum j-578, and L. fermentum 3-2 cultures and totally inhibited growth of L. brevis 20054, L. buchneri 20057, and L. rhamnosus I2L
Summary
Lead (Pb) and cadmium (Cd) are the two most abundant toxic heavy metals in the environment, reported in the Priority List of Hazardous Substances on the 2nd and 7th places, respectively [1]. They are biologically nonessential and nondegradable and tend to accumulate in exposed organisms. Pb exposure induces neurologic and hematological dysfunctions, cardiovascular, hepatic, and renal damage, and reproductive disorders in the human body. Cd toxicity is associated primarily with renal, skeletal, and pulmonary dysfunctions [3]; hepatic, reproductive, and cardiovascular disorders are described [4]. International Agency for Research on Cancer (IARC) classifies Cd as a group I human carcinogen
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