Lead- and copper-complexing extracellular ligands released by Kirchneriella aperta (Chloroccocales, Chlorophyta)

The freshwater planktonic alga Kirchneriella aperta was grown in batch cult ures to stationary growth phase. Copper and lead complexation properties of the exudate from stationary and exponential growth phases were determined by titrations monitored by ion-selective electrodes. Molecular weight fract ionation (dialysis) and analysis of the titration data (Scatchard Plot) rev ealed that K. aperta releases metal-complexing ligands. Copper is associate d with low and high molecular weight compounds, whereas lead forms complexe s with only high molecular weight compounds. Gas-liquid chromatography show ed that mannose and rhamnose make up 74% of the total high molecular weight organic material, with uronic acids present at 19%.