Decolorization and degradation of synthetic dyes by Irpex lacteus KUC8958

This study was carried out to evaluate the dye decolorizing and detoxifying abilities of Irpex lacteus. The decolorization abilities of 14 strains of I. lacteus were investigated in agar-plates containing 3 synthetic dyes: Congo Red (CR), Orange II (OII), and Reactive Blue 4 (RB4). In an agar plate test, I. lacteus KUC8958 showed the highest dye decolorizing rate with all 3 dyes. Subsequently, we investigated the decolorizing and detoxifying abilities of I. lacteus KUC8958 on synthetic dyes in liquid media under both shaking and static conditions. I. lacteus KUC8958 showed high decolorization rates for CR and BR4 (more than 95%) under shaking conditions, but only moderate decolorization of OII (up to 53%). The dye decolorizing rates of I. lacteus KUC8958 were approximately 20% to 60% higher under shaking conditions than under static conditions. In a detoxification assay, the toxicities of CR and OII solutions increased, whereas the toxicity of RB4 decreased after decolorization by I. lacteus KUC8958. Subsequently, high-performance liquid chromatography analysis detected 2 compounds in CR and 1 compound in OII that were newly formed during the decolorizing process, and which might be involved in the increased toxicities. Further studies are required to identify these newly formed compounds.