Biosorption, bioaccumulation and bioreduction of hexavalent chromium by Trichoderma koningiopsis LBM 253

TATARIN AS; SADAÑOSKI MA; POLTI MA; FONSECA, MI.

Congreso; LIX Annual Meeting SAIB 2023; 2023

Chromium (Cr) is one of the most toxic metals that cause the pollution of soil and groundwater. Cr(III) and Cr(VI) are the moststable forms of this metal. The high toxicity of Cr(VI) poses a significant threat to human health due to its potent oxidizing,mutagenic, and carcinogenic properties. Mycoremediation is an eco-friendly and effective technology to clean Cr contaminatedsites. Fungal exposure to heavy metals can induce the development of mechanisms that allow them to metabolize and reduce theconcentration of these pollutants through mostly involving biosorption, bioaccumulation and/or bioreduction. Based on thisbackground, the aim of this work was to determine the main mechanisms implicated in Cr mycoremediation. Biosorption,bioaccumulation and bioreduction assays were carried out with 4, 8, and 12 days of fresh fungal mycelia cultured in presence of200 mg L-1 of Cr(VI). Controls were carried out with fungal mycelia cultured without Cr(VI). Mycelia were fixed, dehydrated,dried, and gold metalized to analyze using a scanning electron microscope coupled with an energy-dispersive X-rayspectrophotometer (SEM-EDX) to biosorption assays. Fresh mycelia were disrupted with liquid nitrogen, and the supernatantwas used for Cr(VI) bioaccumulation and intracellular chromate reductase (ChrR) activity determinations. Metal bioaccumulationcapacity was calculated based on Cr(VI) intracellular concentration. SEM-EDX analysis confirmed biosorption mechanismthrough the presence of Cr on the mycelial surface of T. koningiopsis LBM 253. EDX analysis did not detect Cr on fungalsurfaces from the control assays. The determination of Cr(VI) bioaccumulation revealed values of 3.47 ± 0.28; 4.82 ± 0.14 and6.63 ± 0.45 μg g-1 at 4, 8, and 12 days of incubation, respectively. These results demonstrate that T. koningiopsis LBM 253 wasable to bioaccumulate Cr(VI) inside the cell which could be attributed to the high level of tolerance of this fungus. T. koningiopsisLBM 253 showed both extracellular and intracellular ChrR activity indicating their involvement in Cr(VI) bioreduction. Cr(VI)presence in culture media induced changes in both intracellular and extracellular ChrR activity. Notably, higher titers ofextracellular ChrR activity were observed in absence of Cr(VI), and the peak of ChrR activity was detected at 4 d of incubation.In the presence of Cr(VI), the highest extracellular ChrR titers were detected at 4 and 12 d of incubation. Intracellular fractions ofculture medium containing Cr(VI) exhibited the highest titers of ChrR activity at 8 d of incubation. Based on our findings, wepropose that T. koningiopsis LBM 253 utilizes biosorption, bioaccumulation, as well as extracellular and intracellularbioreduction, which occur simultaneously and dynamically, enhancing the overall remediation process. This response highlightsthe ability of T. koningiopsis LBM 253 to remove Cr(VI) by employing different intracellular and extracellular responsemechanisms.Keywords: Biosorption, Bioaccumulation, Bioreduction, Hexavalent ChromiumMethods: Spectroscopy, Electronic microscopy