A green approach to Azo dye C.I. Disperse blue 291 treatment: mitigating ecotoxicological effects through enzymatic and adsorptive strategies using endophytic fungi

Textile dyes are persistent pollutants that pose significant risks to the environment and living organisms. Before being released into aquatic ecosystems, these dyes require effective treatment. Among these dyes, the azo dye Disperse Blue 291 exhibits relevant toxicological and mutagenic activity. However, a scarcity of studies has been identified that evaluate the effects of the DB291 dye before and after decolorization. Endophytic fungi have shown promising potential in bioremediation, particularly through biosorption and biodegradation. This study aimed to evaluate the ability of endophytic fungi to decolorize the textile dye Disperse Blue 291 (DB291). Seven fungal strains were screened in a minimal medium containing 10 µg/mL of DB291 for seven days. Aspergillus flavus CL07 and Alternaria alternata PL75 showed decolorization rates above 90% and were selected for further analysis. Both fungi achieved complete decolorization, A. flavus CL07 within 48 h and A. alternata PL75 within 168 h. Spectroscopic and enzymatic analyses suggested that biosorption was the main mechanism for A. flavus CL07, while A. alternata PL75 also employed extracellular laccase activity in dye degradation. Infrared spectroscopy analysis indicated chemical interactions between dye molecules and fungal biomass. Ecotoxicity assays using Artemia salina revealed that the original dye was highly toxic, causing developmental arrest and complete lethality. In contrast, the decolorization product from A. alternata PL75 exhibited no significant toxicity, supporting normal development in all tested stages. These results suggest that endophytic fungi, particularly A. alternata PL75, offer an effective and environmentally safe approach to the bioremediation of textile dye-contaminated environments.