Decolorization of Synthetic Dyes and Textile Effluents by Basidiomycetous Fungi

Decolorization of six synthetic dyes and two raw textile effluents (A and B) by eight basidiomycetous fungi was investigated. Among eight basidiomycetous fungi, fungal isolate RCK-1 decolorized textile effluent A maximally (42%), while fungal isolate RCK-3 was found to decolorize more of Congo Red (69%), Xylidine Ponceau 2R (100%), Poly R-478 (96%), Indigo Carmine (99%), Lissamine Green B (90%), Toluidine Blue (57%) and textile effluent B (54%), than the rest of fungi. Percentage decolorization of all synthetic dyes and textile effluents by the new fungal isolates RCK-1 and RCK-3 was higher compared to the most widely studied simultaneous lignin degrader, Phanerochaete chrysosporium and selective lignin degrader, Pycnoporus cinnabarinus, when tested in liquid cultures. A statistically significant positive correlation between laccase production and decolorization of dyes and effluents was obtained as compared to other ligninolytic enzymes (lignin peroxidase and manganese peroxidase) production. This showed the importance of the differential contribution of the different ligninolytic enzymes towards the decolorization of the synthetic dyes and textile effluents. The substantially higher ligninolytic enzyme production by the fungal isolates RCK-1 and RCK-3 also suggested their potential use for textile effluent treatment and other possible biotechnological applications.     

Effects and Interactions of Medium Components on Laccase from a Marine-Derived Fungus Using Response Surface Methodology

The effects of various synthetic medium components and their interactions with each other ultimately impact laccase production in fungi. This was studied using a laccase-hyper-producing marine-derived basidiomycete, Cerrena unicolor MTCC 5159. Inducible laccases were produced in the idiophase only after addition of an inducer such as CuSO₄. Concentration of carbon and nitrogen acted antagonistically with respect to laccase production. A combination of low nitrogen and high carbon concentration favored both biomass and laccase production. The most favorable combination resulted in 917 U L⁻¹ of laccase. After sufficient growth had occurred, addition of a surfactant such as Tween 80 positively impacted biomass and increased the laccase activity to around 1,300 U L⁻¹. Increasing the surface to volume ratio of the culture vessel further increased its activity to almost 2,000 U L⁻¹.     

A Rapid Two-Step Bioremediation of the Anthraquinone Dye, Reactive Blue 4 by a Marine-Derived Fungus

A rapid two-step technique for bioremediation of the anthraquinone dye, the Reactive Blue 4 (RB4) by a marine-derived fungus is reported here. In the first step, 1,000?mg?l^?1 of this dye treated with partially purified laccase of this fungus resulted in 61?% color removal and twofold decrease in chemical oxygen demand by 12?h. The metabolites formed during the enzymatic degradation were characterized by mass spectrometry, ultra performance liquid chromatography, and UV/visible spectroscopy. These analyses confirmed changes in the aromatic character of the parent dye and formation of low molecular weight phenolic compounds as the final products of the enzymatic degradation. Based on these results, the probable degradation products of RB4 were 2-formylbenzoic acid, 1,2,4,5-tetrahydroxy-3-benzoic acid, 2,3,4-trihydroxybenzenesulfonic acid, and 1,2,3,4-pentahydroxybenzene. In the second step, the enzyme-transformed dye solution subjected to sorption on the powdered fungal biomass resulted in a further reduction in color up to 93?% within 10?min. Sorption of the degraded dye was confirmed by the changes in the pattern of Fourier transform infrared spectroscopy spectrum. The two-step treatment resulted in a decrease of 29?% in total carbon accompanied by twofold decrease in toxicity. This is the first report on decolorization, detoxification, and mineralization of RB4 by laccase from a marine-derived fungus.