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.