Integrated Enzymatic and Spectroscopic Evaluation of Congo Red Dye Decolorization by White Rot Fungal Isolates

Abstract

Aims: To evaluate the Congo red dye decolorization and biodegradation potential of native fungal isolates. Study Design: Fungal isolates were obtained from naturally occurring fruiting bodies on tree trunks and agricultural field soil. The isolates were screened for their Congo Red degradation potential using both qualitative (plate assay) and quantitative (broth decolorization) methods. Enzymatic activity and spectral analyses were performed to elucidate the mechanisms of dye removal. Place and Duration of Study: Soil sample and fungal fruiting bodies were collected from the Agro-Forestry Research Centre (AFRC), Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India. All experiments were conducted in the Department of Microbiology, Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, from January 2025 to March 2025. Methodology: Two fungal isolates, WFP 1 and WDP 2, were selected based on their decolorization zones on low nitrogen basal medium plates supplemented with 100 mg/L Congo Red and ligninolytic enzyme production on mineral salt medium agar plates supplemented with specific substrates. Enzyme assays were performed to quantify laccase, azo-reductase, and lignin peroxidase (LiP) under dye-free and dye-induced conditions. Quantitative decolorization was evaluated in liquid medium over 24 hours. Structural modifications in the dye were analyzed using UV-Visible and Fourier Transform Infrared (FTIR) spectroscopy. Results: Both WFP 1 and WDP 2 exhibited high decolorization efficiency, achieving 89.20 ± 1.028% and 89.96 ± 0.904% decolorization within 24 hours, respectively. Enzymatic profiling revealed higher laccase production in WDP 2, indicating superior oxidative capacity. UV-Visible spectra showed significant absorbance reduction in the 200–300 nm range, suggesting degradation of azo and aromatic structures. FTIR analysis revealed alterations in hydroxyl, amine, and aromatic functional groups, confirming both biosorption and enzymatic degradation. Conclusion: White-rot fungi isolated from fruiting bodies on tree trunks demonstrate significant potential for Congo Red decolorization through combined biosorption and enzymatic mechanisms. These findings support their application in eco-friendly treatment of industrial dye effluents.