Decolorization of azo and anthraquinone dyes by crude laccase produced by Lentinus crinitus in solid state cultivation.

Abstract

White-rot basidiomycetes such as Lentinus crinitus produce laccases with potential use in dye biodegradation. However, high productivity and enzymes with specific properties are required in order to make viable laccase production. We aimed to produce laccase from Lentinus crinitus grown in sugarcane bagasse for dye decolorization. Solid state cultivation medium had sugarcane bagasse added with a nutrient solution of 10g/L glucose, 1g/L KH2PO4, 0.5g/L MgSO4, 0.001g/L FeSO4, 0.01g/L ZnSO4, and 0.01g/L MnSO4. The addition of different nitrogen sources (peptone, urea, or peptone plus urea) and different nitrogen concentrations (0, 0.4, 0.6, 0.8, 1.0, and 1.2g/L) were evaluated. Enzymatic extract was used in the decolorization of azo dyes, reactive blue 220 (RB220) and reactive black 5 (RB5), and anthraquinone dye, Remazol brilliant blue R (RBBR). The greatest laccase activity (4800U/g dry mass) occurred when the peptone and urea mixture was added to the solid state cultivation medium. When the nitrogen concentration was 1g/L, the laccase activity increased to 6555U/g dry mass. The laccase activity peak occurred on the 10th day, and the maximum decolorization within 24h was observed with enzymatic extracts obtained on different cultivation days, i.e., 6th day for RB220, 10th day for RB5, and 9th day for RBBR. Manganese and lignin peroxidases were not produced when nitrogen was added to the cultivation medium. The crude enzymatic extract was more effective in the decolorization of azo dyes (RB220 and RB5), more than 90% of decolorization, than anthraquinone dye with 77% decolorization.