Interaction studies of lead(II) ion with cyclic β-(1→3),(1→6) glucans extracted from Bradyrhizobium japonicum based on 'chelation enhanced fluorescence' (CHEF) effect.

Cyclic β-(1→3),(1→6) glucans (CBGs) isolated from Bradyrhizobium japonicum bacteria are the periplasmic oligosaccharides having cyclic structures. This paper presents the isolation of CBGs from the bacteria cultured using optimized medium that improved yields to 350-450 mg per gram of cellular dry weight along with analytical interaction with lead(II) ions in the range 33.0-2.0 ppm with CBG as a binding ligand, using constant wavelength synchronous fluorescence spectroscopy. The binding ability of CBGs towards lead(II) is clearly evident from the scanning electron microscopy (SEM) images. The theoretical calculations using HEX 8.0 gave an insight about the interaction between CBG and lead(II) to be in the ratio of 3:1. The method displayed the sensitivity and selectivity towards lead(II) ions up to 2.0 ppm. This observed property of CBGs can potentially hold an application in bioremediation of the soil contaminated with lead.