Immobilization resulted sustained copper transport in nostoc calcicola breb

The uptake pattern of copper by a cyanobacterium, Nostoc calcicola in its freely suspended and immobilized form is comprised of adsorption of Cu2+ followed by subsequent metabolism dependent uptake. Immobilized cyanobacterial cells maintained three times more metal profile (300.82 n mol Cu mg-1 protein) over freely suspended cells (96.89 n mol Cu mg-1 protein) at saturated Cu2+ concentration (60µM Cu). Darkness resulted in drastic reduction of Cu2+ uptake (90%) in freely suspended cells and least 10% in immobilized cells. Exogenously added ATP (10µM) on the other hand enhanced Cu2+ uptake in dark incubated free cells. However, the same ATP concentration fails to bring out any sufficient enhancement in terms of Cu2+ uptake in immobilized cells facing dark incubation, thus indicating that immobilized cells were able to maintain its ATP reserve even in the dark. Metabolic inhibitors such as mercaptoehanol, azide, N N’ Dicyclohexycarbodimide and p-chloromercuribenzoate inhibit the metal uptake at different level. Immobilized cells exhibits remarkable Cu2+ transport rate even at the age of 20 and 30 days at which free living counter part took up insignificant Cu2+. These findings suggest the improved metabolic efficiency of immobilized cells over freely suspended cells in term of Cu2+ accumulation and its use as bioreactor for metal removal in repetitive cycles without any measurable loss.