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

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 multimetals. 'TERI L1' could adsorb 90% of multi-metals when grown in presence of 1250 mg L-1 Zn, 2 mgL(-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. (C) 2015 Elsevier Ltd. All rights reserved.