Utilização de fungos resistentes na redução da concentração de cromo hexavalente em efluente de curtume

Abstract

Heavy metals are some of the most persistent and potent anthropogenic environmental contaminants, representing a high ecological and health risk, mainly leading to toxic effects and the ability to bioaccumulate along the food chain. As industrialization progresses, the amount of chromium in aquatic and terrestrial ecosystems has increased, becoming a global concern due to the various toxic effects even at low concentrations. Due to this, the removal of this heavy metal from wastewater is extremely important for the protection of health and the environment. In this sense, searching for an alternative to physical-chemical treatments for the removal of hexavalent chromium from tannery effluent, we propose in this study bioremediation using strains of the fungi Penicillium commune, Fusarium equiseti and Paecilomyces lilacinus. The fungal strains were submitted to tests of tolerance to Cr6+ through exposure to 150 mg.L-1, later optical microscopy analysis and possible structural alterations caused by the presence of the toxic compound were identified, where it was possible to observe some changes as swelling of the cell wall and formation of vacuoles. In addition, fungal strains were submitted to different concentrations of Cr (VI) in order to evaluate the behavior of fungal cell defense mechanisms, which were identified as extracellular, by biosorption and intracellular processes, by formation of vacuoles, biotransformation, chelation by proteins, among others. Considering the results obtained, tests were carried out to substitute the glucose source of the fermentation medium for sugarcane hydrolysate, seeking an alternative to the use of commercial glucose. The results were satisfactory, since even in the presence of interferences, the fungi were able to metabolize glucose from the medium, increasing the biomass. Finally, the bioremediation of the tannery effluent was carried out by three experiments, the first in the presence of glucose and salts, the second only the effluent, and a third with hydrolysate. Although the concentration of Cr (VI) in the effluent decreased, the concentrations that remained were still toxic, being 3.40 ± 0.61 mg Cr6+.L-1 for the fungus FE and 3.14 ± 0, 31 mg Cr6+.L-1 for the fungus PL in the presence of hydrolysate, and 2.56 ± 0.08 mg Cr6+.L-1 for the PC fungus in the absence of nutrients, being toxic to the environment and not provided for by Brazilian law. In this sense, process improvement studies are proposed through continuous flow of nutrients, since intracellular defense mechanisms, dependent on metabolism, are activated in the process of reducing the concentration of toxic compounds, and the increase of fungal biomass causes that the biosequestration of the metallic ions in the medium occurs more effectively.