Assessment of Heteroporus biennis secretion extracts for decolorization of textile dyes

In the present study, the dye-decolorizing properties of soluble extracts from the indigenous fungus Heteroporus biennis IOC4581 were determined. Decolorizing activity was associated with the secretion of a 45-kDa laccase. Laccase expression was extremely sensitive to carbon and nitrogen contents in culture media. Supplementation with metal ions and aromatic compounds resulted in extremely variable protein secretion profiles, although enzyme yields were not improved. Kinetic parameters of the soluble crude extract were promising, destaining seven out of nine textile dyes without the need of redox mediators. The extract was insensitive to Ca2+, Mg2+, Mn2+, and Zn2+ ions, and catalysis was enhanced in the presence of Cu2+ and Al3+ ions. The soluble fungal extract retained its maximal decolorizing activity at a wide range of pH (2.0-9.0) and temperature (4-50 °C), indicating potential application to dye biodegradation.