Tolerancia de Aspergillus flavus y Aspergillus nidulans a metales tóxicos

Introduction: Metals are found naturally in the environment, but their indiscriminate use has caused serious pollution problems. Objective: Two species of Aspergillus were isolated and identified from tailings, then their tolerance index at different concentrations of several metals was evaluated. Materials and methods: Fungi were isolated from tailings located in the Sonoran Desert. Fungal growth was evaluated in the presence of Cr⁶⁺, Pb²⁺, Zn²⁺, Ag⁺, Cd²⁺, Cu²⁺ and Hg²⁺ metals using the tolerance index and minimum inhibitory concentration (MIC). Results and discussion: A. flavus had very high tolerance indices to Cr⁶⁺, Pb²⁺ and Zn²⁺ at all concentrations evaluated (>20 mM); it also had a high tolerance index to the other metals at lower concentrations. The MIC for this fungus in the presence of Cd²⁺, Hg²⁺ and Ag⁺ was recorded between 5 and 10 mM. The growth of A. nidulans was not inhibited with 20 mM of Cr⁶⁺. The MIC of A. nidulans in presence of Hg²⁺, Ag⁺ and Cu²⁺ is in the range 1-5 mM; with Cd²⁺, Pb²⁺ and Zn²⁺ it is in the range between 15 and 20 mM. The dose-response curves display a characteristic sigmoidal shape. With Ag⁺ and Cu²⁺ A. flavus displayed a hermetic behavior. Conclusion: High metal tolerance of these fungi suggests their potential use in the removal of metals.