Purification and characterization of exopolysaccharide bioflocculant produced by heavy metal resistant Achromobacter xylosoxidans

•Exopolysaccharide bioflocculant produced by Achromobacter xylosoxidans TERI L1.•FTIR and NMR and LC–MS confirmed the bioflocculant as an exopolysaccharide heteropolymer, glycoprotein.•First time reports for 90% biosorption of Zn, Pb, Ni, Cd and Cu by A. xylosoxidans.•Maximum lead adsorption (1100 mg L−1) reported till date by this TERI L1 strain.•Bioflocculant composed of 75% sugar and 11.5% protein.

Optimization of process parameters enhanced bioflocculating activity of ‘Achromobacter xylosoxidans strain TERI L1’ from 75% to 83.3% in absence of heavy metals, which decreased to 73% in presence of multi-metals. ‘TERI L1’ could adsorb 90% of multi-metals when grown in presence of 1250 mg L−1 Zn, 2 mg L−1 Cd, 30 mg L−1 Pb, 200 mg L−1 Ni and 90 mg L−1 Cu and could adsorb 1100 mg L−1 of Pb when grown in presence of 1500 ppm lead nitrate. The bioflocculant was purified and characterized. Bioflocculant yield was 5 g L−1. Fourier transform infrared spectrum indicated presence of carboxyl, hydroxyl, amino groups, typical of glycoprotein. Spectroscopic analysis of bioflocculant by nuclear magnetic resonance revealed that it is a glycoprotein. LC–MS analysis confirmed the bioflocculant as a carbohydrate hetero polymer. Bioflocculant was composed of 75% total sugar with 72.9% neutral sugar and 11.5% protein. Scanning Electron Micrography revealed effective flocculation of kaolin clay by purified exopolysaccharide bioflocculant.