Biosorption of lead by Gram-ve capsulated and non-capsulated bacteria

Abstract

The biosorption of lead by two Gram-ve bacteria, either non-capsulated (Citrobacter freundii ) or capsulated (Klebsiella pneumoniae) was characterised. Lead biosorption was found to be influenced by the pH of the solution, initial metal concentration, and amount of the dried powdered cells and contact time. Thus, the optimum biosorption capacity, by the two tested bacteria, was attained at pH 4, initial lead concentration of about 481.2 mg/ℓ and contacted with 2 g dried cells/ℓ for 100 min. However, the dried powdered cells of both organisms can be safely stored for long periods (125 d) at room temperature (25 ± 2°C) without any loss of their biosorption efficiency, i.e. their binding sites not affected by storage. The results revealed that the presence of capsule (K. pneumoniae) increased the biosorption efficiency of the bacterium.