Flocculating Property of Extracellular Polymeric Substances Produced by a Biofilm-Forming Bacterium Acinetobacter junii BB1A

Extracellular polymeric substances (EPS) produced by a biofilm-producing bacterium Acinetobacter junii BB1A were characterized. Purified EPS on analysis revealed neutral sugar (73.21 %), uronic acid (10.12 %), amino sugars (0.23 %), alpha- amino acids (11.13 %), and aromatic amino acids (1.23 %). Infrared spectrometry revealed the presence of hydroxyl, carboxyl, and amide groups. The average molecular weight of the polysaccharide (PS) fraction of EPS was similar to 2 x 10(5). Gas liquid chromatography analysis of PS revealed the presence of three main sugar residues, namely, mannose, galactose, and arabinose (molar ratio of 3:1:1). Cation-independent flocculation above 90 % was observed in the pH range of 4-5 with EPS dosage of 30 mg l(-1) at 20 A degrees C. The emulsifying activity of EPS was 66.6 % with toluene, 60 % with n-hexadecane, 53.3 % with olive oil, and least activity of 13.3 % with kerosene. Proteinase K- and trichloroacetic acid-treated EPS showed reduction in flocculation and emulsification, suggesting the significant role of protein component. Energy dispersive X-ray spectroscopy was used to provide direct evidence of biosorption of Co(II), Cd(II), and Hg(II) by EPS.