Biosorption of Cadmium by Fungi

Abstract

The aim of this study was to investigate Cadmium removal potential of two different fungal biomass namely Paecilomyces variotii and Cladosporium resinae. Experiments were carried out under shake flask conditions i.e at different pH, temperature of 28°C and agitation rate of 120 rpm. The effect of biomass concentration, pH and metal concentration on the ability of dried biomass to remove metal from solution was investigated. Optimization of pH and biomass dosage for maximum removal was carried out. Non-living cells of Paecilomyces variotii were superior to Cladosporium resinae. P.variotii was found to be superior in metal uptake. Removal potential of cadmium by live cells of P.variotii was also superior to those of C.resinae at different metal concentrations and 96 hrs of incubation. Maximum adsorption was at 10-20 ppm after 96 hr. Column studies for metal removal from 50 ppm cadmium containing solution with non-living biomass of both the organisms were carried out till complete saturation. P.variotii showed saturation in 33 hrs whereas C.resinae showed saturation in 28 hours. For the same metal ion different adsorbents had different removal rates. Residual metal concentration decreased with time whereas metal uptake showed an increasing trend, which followed Langmuir and Freunlich isotherm. SDS-PAGE analysis of cells grown with (test) and without (control) metal stress showed the presence of extra bands in the tracks, which were loaded with test samples. This confirmed the release of certain extracellular proteins by the cells when exposed to metal ions in the media, which may help in adsorption process. Out of live and dead cells for cadmium removal studies, use of dead cells is economical because it does not require any maintenance of sterile conditions and the dead biomass can be regenerated. Therefore there is plenty of scope for large-scale application of nonliving biomass for metal ion removal.