Aqueous state laccase thermostabilization using carbohydrate polymers: Effect on toxicity assessment of azo dye

Thermostability of laccase from Pleurotus florida was studied at different temperatures (50–65 °C) using various polysaccharide additives (Guar Gum, starch, agarose and agar). The stability of laccase was enhanced with Guar Gum (0.3%), starch (8%), agarose (0.4%) and agar (0.4%). As revealed by PAGE, among two isoenzymes (L1 and L2) of laccase, improvement of enzyme stability observed in the presence of Guar Gum at 60 °C was proved by the appearance of L2 isoenzyme. The analysis of Arrhenius plot for stabilized laccase revealed the break point shifted to 60 °C with activation energy of 2.41 KJmol−1 protected by additive Guar Gum whereas other additives, the break point shifted to 52.5 °C. Stabilized laccase was used for decolorization of azo dye (reactive blue 198). FTIR analysis was performed to confirm the decolorization of dye by laccase. Allium cepa toxicity test was performed which indicate that root growth inhibition was dye concentration dependent.