Capsular Polysaccharides Are Crucial for the Biosorption of Aqueous Pb(II) Ions by Limosilactobacillus fermentum B44
Wenhui Yu1,2, Yitian Wang1,3, Jin Han1
1State Key Laboratory of Dairy Biotechnology, Shanghai Engineering Research Center of Dairy Biotechnology, Dairy Research Institute, Bright Dairy & Food Co., Ltd, Shanghai, 201103, China.
Abstract:
Lead (Pb) is a widespread heavy metal pollutant that presents substantial risks to ecological systems and human health. The utilization of probiotic lactic acid bacteria (LAB) for the detoxification of Pb(II) in the host has aroused great interest. However, few studies had focused on the roles of capsular polysaccharide (CPS) in the bacteria adsorption of Pb(II). In the present study, L. fermentum B44 was selected out of nine lactobacilli for its superior absorption capacity of Pb(II) in vitro. The adsorbed Pb(II) ions by B44 cells were predominantly enriched on the capsule. Removal of the CPS from cells of strain B44 by 1 mol/L guanidine hydrochloride (GuHCl) would decrease the adsorption capacity of the host cells. The CPS showed a high capacity for Pb(II) adsorption, and its adsorption behaviour was more accurately described by the Langmuir isotherm model (R2 = 0.97) than by the Freundlich isotherm model (R2 = 0.907). Adsorption of Pb(II) ions would lead the CPS transforming from stacked, porous flakes to rough, condensed ones, with Pb(II) sediment on the CPS surface. Amide groups in B44 CPS were crucial in the adsorption of Pb(II). Our results provided intuitive evidence of the Pb(II) adsorption site on B44 cells and the protection of CPS to the bacterial cells.
