Congo Red removal and toxicity reduction by lichen endophytic fungi: A multi-trophic evaluation

Abstract

The discharge of toxic, carcinogenic, and genotoxic dyes, such as Congo Red, commonly used in the food, textile, cosmetic, and pharmaceutical industries, into soil and water represents a major environmental problem that adversely affects ecosystems. Microbial treatment has emerged as a promising strategy for the removal of Congo Red from contaminated environments. In this study, Congo Red removal was evaluated using fungi isolated from lichens inhabiting rocks in extreme environments, and HPLC was used to assess changes in the chromatographic profile following fungal treatment. The toxic effects of untreated and fungal-treated Congo Red solutions were assessed using terrestrial (Triticum aestivum and Drosophila melanogaster), aquatic (Daphnia magna), and mammalian (L929 mouse fibroblast cell line) biological models. The highest Congo Red removal efficiencies were achieved with Aspergillus flavus, Cladosporium limoniforme, and Fusarium redolens. While untreated Congo Red exhibited pronounced toxic effects, the fungal-treated solutions showed markedly reduced acute toxicity under the tested experimental conditions. Similar results were obtained in the cell culture assays. This study demonstrates that lichen-associated fungi effectively removed Congo Red from the culture medium under the tested conditions, accompanied by a marked reduction in toxicity. However, the relative contributions of biotransformation and biosorption require further investigation.