The laccase from the newly isolated Trametes cubensis was investigated for its potential to degrade malachite green (MG) dye. Optimized solid-substrate fermentation enhanced laccase production by 8.8-fold, reaching an activity of 6577.0 ± 14.3 U/g. Proteomic characterization identified enzyme with 4 % sequence coverage, molecular weight of 43.1 kDa, and alignment with multicopper oxidases. Using one-factor-at-a-time optimization, MG decolorization was maximized at 89 % under optimal conditions: 20 U/mL enzyme dose, 0.1 mg/mL dye concentration, pH 5.0, and 2 h incubation at 50 °C. Crosslinking the laccase onto chitosan beads resulted in 82 % immobilization efficiency, with high recyclability and reusability, retaining over 52 % activity after 7 cycles and demonstrating similar (p < 0.05) dye degradation potential. MG degradation products exhibited significantly reduced phyto-, cyto-, and microbial toxicity. The degradation pathway was elucidated using gas chromatography-mass spectrometry analysis. Thus, both free and immobilized laccase from T. cubensis offer sustainable tool for effective MG degradation with reduced toxicity.
Keywords: Bioremediation; Dye decolorization; Enzyme immobilization; OFAT optimization; White rot fungi.
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