Efficient Decolorization of Textile Dye by Immobilized Thermotolerant Laccase from Bacillus subtilis CFB-09

The widespread discharge of textile dyes into aquatic environments has led to a growing public health concern, as a result of their toxicity in water bodies. Hence, there is urgent need for sustainable dye removal strategies. Enzyme-based bioremediation has emerged as a promising eco-friendly approach, with laccase, a multicopper oxidase, gaining attention due to its ability to oxidize a wide range of phenolic compounds including lignin-mimicking dyes. Therefore, this study explores the degradation of methyl blue dye using laccase from Bacillus subtilis CFB-09. The physicochemical properties of free and immobilized laccase were characterized, and their decolorization efficiency was evaluated across varied dye concentration (25-200 mg/L). Results showed that free and immobilized laccase exhibited optimal activity at 30 °C, pH 5.0 and 40 °C, pH 6.0, respectively. Free laccase demonstrated high thermal stability by retaining over 80% residual activity up to 70 °C for 180 min of incubation, while immobilized laccase exhibited a gradual decline in activity yet retained over 50% residual activity at 30-70 °C for 90 min. Decolorization studies of methyl blue showed that both free and immobilized laccase achieved maximum decolorization at lower dye concentrations. Remarkably, at 125 mg/L, immobilized laccase exhibited slightly higher decolorization (81.28%) than free laccase (78%) after 120 h, indicating enhanced stability and prolonged activity, while at higher concentration (200 mg/L), both free and immobilized laccase showed reduced efficiency (~6.87%). These findings suggest that both free and immobilized laccase hold promise as cost-effective and eco-friendly solutions for mitigating the environmental and health hazards associated with textile dye pollution.