In vitro remobilization of Cd immobilized by fungal biomass

The capacity of Trichoderma koningii and Fusarium culmorum mycelia (strains isolated from the rhizosphere of a healthy rye plant) for immobilization of Cd from solution and remobilization of this metal from the mycelia by soil extracts and defined chemical solutions (0.02 M Na-EDTA, 0.1 M NaNO3, 0.1 M CaCl2) were studied. The amounts of Cd immobilized by live mycelia of the two tested fungi were significantly different. However, these differences were not found when the autoclaved mycelia were used in the experiments. The identity of the fungus, the composition of the reaction solution and its pH, as well as the duration of contact with the solution had a significant effect on metal remobilization from live mycelia. The amounts of cadmium released were dependent on a combination of these factors. The amounts of Cd remobilized by 0.1 M NaNO3 and by autoclaved soil extract were nearly in the same range. Filtered soil extract and 0.1 M CaCl2 were much more effective than either 0.1 M NaNO3 or than autoclaved soil extract. Enrichment of the soil extract with spent medium from either of the tested fungi affected Cd remobilization by the soil extract in different way. This finding indicates that fungal extracellural metabolites added together with the spent media were involved in the remobilization processes.