Banwari Lal
The Energy and Resources Institute, India
Title: Production and characterization of exopolysaccharide bioflocculants produced by Acromobacter sp.: Biosorption of heavy metals
Biography
Biography: Banwari Lal
Abstract
Present study highlights isolation of bio-flocculent producing microbes; Achromobacter sp. TERI-IASST N and Achromobacter xylosoxidans TERI L1, capable of biosorption of multi metals (Pb, Zn, Cd, Ni, and Cu). These microbes were isolated from heavy metal contaminated activated sludge samples collected from petroleum refineries. At optimum process parameters (pH 7.5, 37°C temperature, 1% sucrose as feed stock, 120 h incubation period) bioflocculating activity of ‘TERI L1’ strain enhanced (in presence of sucrose as carbon source) to 83.3%. This activity decreased to 73%, when grown in presence of multi-metals. ‘TERI L1’ could adsorb 90% of multi-metals when grown in presence of 1250 mg L−1Zn, 2 mg L−1Cd, 30 mg L−1 Pb, 200 mg L−1Ni and 90 mg L−1Cu and could adsorb 1100 mg L−1 of Pb, when grown in presence of 1500 ppm lead nitrate. ‘TERI-IASST N’ demonstrated 90% flocculation activity (in absence of heavy metals) at optimum condition; ‘pH 6, temperature 37 oC, C/N ratio 1, 1% sucrose as feed stock, 120 h incubation period). In presence of multimetals, flocculation activity of strain N decreased to 84%. ‘TERI-IASST N’ strain revealed 430 mg L−1 Zn and 30 mg L−1 Pb. Bioflocculant yield efficiency of ‘TERI-IASST N’ and ‘TERI L1’ strains were; 10.5 g/L and 5 g/L, respectively. The bioflocculants were thermostable and retained up to 80% flocculating activity after being heated at 90ºC for 30 minutes, which is attributed to the polysaccharide backbone. LC–MS analysis confirmed the bioflocculants as, carbohydrate hetero-polymers. Nuclear magnetic resonance studies revealed that the bioflocculants were glycoproteins. To the best of our knowledge this is the first study that reports the isolation of A. xylosoxidans strain that has significant potential for bioflocculant production as well as for adsorption of multi-metals. The exopolysaccharide bioflocculants produced by ‘TERI L1’ and ‘TERI-IASST N’ strains have good potential for bioremediation of heavy metal contaminated wastewater.