Acceleration of Anthraquinone-Type Dye Removal by White-Rot Fungus Under Optimized Environmental Conditions

The decolorization of the recalcitrant dye Remazol Brilliant Blue R (RBBR) by the culture filtrate of Polyporus sp. S133 and the effect of various environmental factors were investigated. Both biodegradation and biosorption were playing an important role in bioremoval mechanisms. The highest biosorption of RBBR in Polyporus sp. S133 was shown by all carbon sources such as sucrose, glucose, fructose, and starch. No biosorption was shown by the addition of aromatic compounds and metal ions; 97.1?% RBBR decolorization was achieved in 120-rpm culture for 96?h, as compared to 49.5?% decolorization in stationary culture. Increasing the shaking rotation of the culture to more than 120?rpm was proven to give a negative effect on decolorization. The highest production of laccase was shown at pH 4 and constantly decreases when the pH level increases. The addition of glucose, ammonium tartrate, Cu²⁺, and protocatechuic acid was the suitable environmental condition for RBBR decolorization. There was a positive relationship between all environmental conditions and laccase production in the decolorization of RBBR.     

Decolorization of Azo,Triphenylmethane and Anthraquinone Dyes by Laccase of a Newly Isolated <Emphasis Type="Italic">Armillaria</Emphasis> sp. F022

A newly isolated white-rot fungus, Armillaria sp. strain F022, was isolated from the decayed wood in a tropical rain forest. Strain F022 was capable of decolorizing a variety of synthetic dyes, including azo, triphenylmethane, and anthraquinone dyes, with an optimal efficiency of decolorization obtained when dyes added after 96 h of culture, with the exception of Brilliant Green. All of the tested dyes were decolorized by the purified laccase in the absence of any redox mediators, but only a few were completely removed, while others were not completely removed even when decolorization time was increased. The laccase, with possible contributions from unknown enzymes, played a role in the decolorization process carried out by Armillaria sp. F022 cultures, and this biosorption contributed a negligible part to the decolorization by cultures. The effect of dye to fungal growth was also investigated. When dyes were added at 0 h of culture, the maximum dry mycelium weight (DMW) values in the medium containing Brilliant Green were 1/6 of that achieved by the control group. For other dyes, the DMW was similar with control. The toxic tolerance of dye for the cell beads was excellent at least up to a concentration of 500 mg/l. The optimum conditions for decolorization of three synthetic dyes are at pH 4 and 40°C.     

Biodegradation Mechanism of Phenanthrene by Halophilic <Emphasis Type="Italic">Hortaea</Emphasis> sp. B15

This aim of the study is to investigate a halophilic bacterium Hortaea sp. B15, isolated from petroleum-contaminated soil for biodegradation of phenanthrene. Hortaea sp. B15 has the ability to completely degrade phenanthrene (100 mg/L) under salinity 10% within 1-week incubation. The metabolitic product of phenanthrene was identified and assayed by using ultraviolet-visible spectrophotometer and mass spectral analysis. Result revealed that Hortaea sp. B15 metabolized phenanthrene to form 9,10-phenanthrene quinone, salicylic acid, and gentisic acid. Hortaea sp. B15 has an efficient utilization of phenanthrene in high-saline liquid medium. All the results indicated that the fungus has a promising application for the study of high-molecular-weight PAH biodegradation and contaminated saline-alkali soil bioremediation.     

Decolorization and Metabolism of Anthraquionone-Type Dye by Laccase of White-Rot Fungi Polyporus sp. S133

Utilization of microbes including white-rot fungi and bacterial strains for decolorization of synthetic dyes is one promising strategy of an environmentally friendly and cost-competitive alternative to physico-chemical decomposition processes for treating industrial effluents. In this study, the biodegradation ability of the white-rot fungi Polyporus sp. S133 that produce high laccase was investigated in order to decolorize anthraquinone-type dye. Parameter including pH, temperature, and non-ionic surfactant were used to comparatively study the decolorizing effects on Remazol Brilliant Blue R (RBBR). The purified laccase totally decolorized 200 mg L⁻¹ initial concentration of RBBR dye when only 1.5 U L⁻¹ of laccase was used in the reaction mixture. The optimal decolorization rates were achieved at pH 5 and at a temperature of 50°C. N-hydroxybenzotriazole, a small molecular weight redox mediator, was found to accelerate the decolorization. Tween 20 inhibited the decolorization while Tween 80 and Brij 35 showed no inhibition effect. Two compounds were identified as the intermediates (m/z 304.3 and m/z 342.2). These results suggest that laccase from Polyporus sp. S133 is a powerful tool for the decolorization of anthraquinone dyes. A pathway for the metabolism of the RBBR by laccase of Polyporus sp S133 was proposed. These proposed pathways could contribute to a better comprehension of the mechanisms used by oxidative enzymes to transform organic compounds.