Sustainable Decolorization of Synthetic Dyes by Trametes versicolor Laccase: In Vitro Evaluation and In Silico Mechanistic Insights

Abstract

Laccase, a copper-containing enzyme, exhibits remarkable catalytic versatility by oxidizing a wide range of phenolic and non-phenolic substrates. This property makes laccase a promising biocatalyst for bioremediation applications. Textile wastewater, which contains environmentally hazardous dyes such as congo red, indigo carmine, and malachite green, poses a significant environmental challenge. In this study, we investigated the use of laccase from Trametes versicolor for dye decolorization through a combined approach of enzymatic treatment and computational analysis to elucidate the underlying decolorization mechanisms. The decolorization of congo red, indigo carmine, and malachite green was most effective at pH 5, 4, and 7, respectively. Among the tested dyes, malachite green exhibited near complete decolorization, exceeding 90% within 24 h across concentrations of 50, 100, 200 and 400 µM at 0.2 U/mL laccase activity. Kinetic analysis revealed that the Trametes versicolor laccase–malachite green system followed Michaelis–Menten behavior, with a K<inf>m</inf> of 612.11 µM and a V<inf>max</inf> of 0.195 µM/min, respectively. Molecular docking and subsequent molecular dynamics simulations provided predictive insights into potential key binding residues at the T1 copper site of laccase. Binding mode analysis suggested that malachite green may adopt a compact orientation within the T1 copper pocket, potentially interacting with hydrophobic and aromatic residues, including F162, L164, F332, and P391, as well as potentially forming stabilizing interactions with the hotspot residue C453. Furthermore, phytotoxicity assessment using mung bean demonstrated that laccase treatment effectively reduced malachite green toxicity, as evidenced by improved seed germination. Collectively, these findings highlight the effectiveness of Trametes versicolor laccase for dye decolorization under specific conditions and provide insights for developing optimized enzymatic strategies for bioremediation.