Biosorption of copper by Paenibacillus polymyxa cells and their exopolysaccharide

Biosorption of heavy metals by gram-positive, non-pathogenic and non-toxicogenic Paenibacillus polymyxa P13 was evaluated. Copper was chosen as a model element because it is a pollutant originated from several industries. An EPS ( exopolysaccharide)- producing phenotype exhibited significant Cu(II) biosorption capacity. Under optimal assay conditions (pH 6 and 25 degrees C), the adsorption isotherm for Cu(II) in aqueous solutions obeyed the Langmuir model. A high q value (biosorption capacity) was observed with whole cells (q(max)= 112 mgCu g(-1)). EPS production was associated with hyperosmotic stress by high salt (1 M NaCl), which led to a signi. cant increase in the biosorption capacity of whole cells (q(max)= 150 mgCu g(-1)). Biosorption capacity for Cu(II) of the purified EPS was investigated. The maximum biosorption value (q) of 1602 mg g(-1) observed with purified EPS at 0.1 mg ml(-1) was particularly promising for use in field applications.