Degradation of textile polyazodyes by Polyporus ciliatus laccase produced in peanut shell solid medium: purification and characterization

Abstract

This study describes decolorization of reactive sulfonated azoic dye Direct Blue 71, one of the recalcitrant and highly used industrial dyes, by Polyporus ciliatus derived laccase. Agro-industrial wastes are increasingly used as substrates for laccase production from white rot fungi through solid-state fermentation (SSF). Peanut shell (PS) is an attractive substrate for laccase production, and SSF is an adequate strategy for that purpose. It has been employed as a novel support-substrate for laccase production by Polyporus ciliatus under solid-state fermentation. The highest laccase yield of 1260 U/ml was attained using PS after 13 days of incubation at 30°C. The purified laccase (55 kDa) showed maximum activity at pH 3 and 60°C. The extracellular laccase enzyme was purified 67.6-fold to a specific activity of 1466 U/mg by a Mono-Q anion-exchange column. The purified enzyme Km value was found to be 24 µM, while the Vmax value was observed to be 0.96 µM s-1 with ABTS as a substrate. It had high thermotolerance and pH stability and was resistant to several metal ions including copper, cadmium, and iron. P. ciliatus pure laccase showed high potential for the decolorization and detoxification of the reactive sulfonated azoic dye Direct Blue 71, which suggested that this enzyme could be used for textile effluent treatment.