Simultaneous biosorption of chromium and zinc from aqueous solution by Lactobacillus plantarum exopolysaccharides and biofilm characterized by structural and functional analysis

Heavy metals represent significant environmental pollutants in today's world. The primary sources of human exposure to these heavy metals are through food and water, which can lead to various life-threatening diseases. Therefore, it is imperative to focus on the removal of these contaminants to safeguard human health. The study describes the optimization of biosorption conditions of chromium [Cr(III)] and zinc [Zn(II)] through biofilm and exopolysaacharides (EPS) of Lactobacillus plantarum. The strain was tested for minimum inhibitory concentration and assessed at 100–350 ppm for Cr (III) and Zn (II) in terms of log cfu/mL. Metal adsorption capacity of biofilm was slightly higher as compared to EPS. Biosorption of Cr (III) at pH 2 showed 90% biosorption through biofilms and 88% through EPS. Zn (II) showed maximum binding of about 86% and 78% by biofilm and EPS, respectively, at pH 8 at 37°C for 24 h. The binding of metal is mostly dependent upon the functional group present, the surface morphology of biofilm, and the EPS of strain.