Copper Ion Sorption Ability of the Micromycetes Alternaria alternata (Fr.) Keissl. and Fusarium oxysporum Schltdl.

Our analysis of the metabolic and ecological features of fungi indicates a high bioremediation potential of the fungal mycelium. The relevance of the problems solved in this work is conditioned by the insufficiently of the mechanisms studied and the conditions of micromycetal activity on heavy metal detoxication. The effect of copper on the development of two micromycete species, namely, melanized Alternaria alternata (Fr.) Keissl., 1912 and hyaline Fusarium oxysporum Schltdl., 1824 cultivated on Czapek agar (with 2 or 3% sucrose), was compared; the ability of the mycelium to sorb copper cations when grown in a liquid culture with 0, 0.05, 0.1, 0.25, and 0.5 mg Cu²⁺/L was evaluated. F. oxysporum had noticeable advantages in terms of the growth rate, tolerance, and conidia production on a medium with Cu²⁺. The effective concentration of copper (EC₅₀), indicating the resistance of the fungus, increased for F. oxysporum by 1.5 times with increasing sucrose content in the medium. The melanized culture of A. alternata was superior to F. oxysporum in terms of the sorption capacity. The percentage of Cu²⁺ extraction by the fungal mycelium from the medium reached 40% in the case of F. oxysporum and twice as much in the case of A. alternata. The vast majority of copper was sorbed by the cell walls of hyphae and washed away by water. A small amount (a maximum of 0.16 µg Cu²⁺/g dry mycelium of A. alternata) penetrated inside the mycelial cells. F. oxysporum, which had no intracellular protective melanins, accumulated Cu²⁺ (two to 14 times) less. The results show that the mechanisms of resistance to Cu²⁺ and sorption are different in the species studied: in Fusarium they are determined mainly by the barrier functions of the hyphae cell walls, while in Alternaria melanin plays a significant role in protection against the toxic action of Cu.