Cadmium biosorption by lactic acid bacteria Weissella viridescens ZY-6

Cadmium in food and drinking water poses a serious threat to human health. In this study, a strain of lactic acid bacteria (LAB), namely, Weissella viridescens ZY-6 was utilized to remove Cd2+ from aqueous solution. Its Cd2+ binding capacity was assessed in different conditions, the underlying mechanism was investigated, and its use for removal of Cd2+ from vegetable and fruit juices was also evaluated. Results showed that Cd2+ binding ability of ZY-6 was influenced by Cd2+ concentration, biomass dosage, incubation time, temperature, and pH. Cd2+ adsorption could be improved by pretreatments of boiling and ultrasonication. In binary metal systems, the Cd2+ removal rate by ZY-6 decreased in the presence of other metal cations such as Mg2+, Mn2+, and Fe2+. Binding experiments using different cellular components showed that Cd2+ was mainly adsorbed on the bacterial cell walls, and only small amount accumulated inside the cells. Scanning electron microscopy proved that after adsorption, the cells appeared crumpled, wrinkled, and longer. Fourier transform infrared spectroscopy revealed negatively charged functional groups such as –OH, –NH2, COO-, and PO on the surface of the cells reacting with Cd2+ in the solution mainly through electrostatic reaction. ZY-6 treatment removed 69.45%–79.91% of the Cd2+ from three kinds of vegetable and fruit juices. Therefore, W. viridescens ZY-6 may be used as an effective biosorbent for cadmium in the environment, human diet, and animal feed due to its detoxification properties. •Cd2+ binding ability of ZY-6 was influenced by Cd2+ concentration, biomass dosage, incubation time, temperature, and pH.•Cd2+ binding ability of biomass could be improved by boiling and ultrasonication treatment.•Cd2+ binding ability decreased in the presence of other heavy metals.•Binding of Cd2+ resulted in the changes in the cell morphology.•Functional groups on the cell wall reacted with Cd2+ during binding.