Effect of some complex nutrients on improvement of bioaccumulation of lead by Rhizopus arrhizus

The present study indicated that a few complex nutrients enhanced bioaccumulation of lead by Rhizopus arrhizus M1 from chemically defined medium containing 1 mg/L of the metal. Amongst them, yeast extract showed most prominent effect. Highly significant increment (p < 0.001) of lead accumulation of about 67% [from. 147.8 mu g/g (control) to 247.78 mu g/g cell dry weight] was observed when the culture medium was supplemented with yeast extract at a concentration of 10 mg/ml. Specific composition of a complex nutrient was found to influence lead accumulation, when a commercial peptone preparation enriched with tryptophan showed improved bioaccumulation of lead, in comparison to other peptone. A few amino acids and water-soluble vitamins were also found to stimulate lead uptake in similar cultural conditions, although not to the extent of the complex nutrients. The present study indicated that lead removal from aqueous systems with the use of commercially available complex nutrients as composite sources of amino acids, vitamins and other useful macromolecules for Rhizopus arrhizus M1, would definitely provide cost-effectiveness when applied in large-scale industrial processes.