Decolorization and Detoxification of Textile Dyes with a Laccase from Trametes hirsuta

Abstract

Trametes hirsuta and a purified laccase from this organism were able to degrade triarylmethane, indigoid, azo, and anthraquinonic dyes. Initial decolorization velocities depended on the substituents on the phenolic rings of the dyes. Immobilization of the T. hirsuta laccase on alumina enhanced the thermal stabilities of the enzyme and its tolerance against some enzyme inhibitors, such as halides, copper chelators, and dyeing additives. The laccase lost 50% of its activity at 50 mM NaCl while the 50% inhibitory concentration (IC 50 ) of the immobilized enzyme was 85 mM. Treatment of dyes with the immobilized laccase reduced their toxicities (based on the oxygen consumption rate of Pseudomonas putida) by up to 80% (anthraquinonic dyes). Textile effluents decolorized with T. hirsuta or the laccase were used for dyeing. Metabolites and/or enzyme protein strongly interacted with the dyeing process indicated by lower staining levels (K/S) values than obtained with a blank using water. However, when the effluents were decolorized with immobilized laccase, they could be used for dyeing and acceptable color differences (⌬E*) below 1.1 were measured for most dyes.It is known that 90% of reactive textile dyes entering activated sludge sewage treatment plants will pass through unchanged and will be discharged to rivers (34). Not all dyes currently used could be degraded and/or removed with physical and chemical processes, and sometimes the degradation products are more toxic (40). The traditional textile finishing industry consumes about 100 liters of water to process about 1 kg of textile materials. New closed-loop technologies such as the reuse of microbially or enzymatically treated dyeing effluents could help to reduce this enormous water consumption.Several combined anaerobic and aerobic microbial treatments have been suggested to enhance the degradation of textile dyes (5, 23, 32). However, under anaerobic conditions, azo-reductases usually cleave azo dyes into the corresponding amines, many of which are mutagenic and/or carcinogenic (10,11,32). Furthermore, azo reductases have been shown to be very specific enzymes, thus cleaving only azo bonds of selected dyes (50, 51). By contrast, laccases act oxidatively and less specifically on aromatic rings, thus having potential to degrade a wider range of compounds (43).Laccases are involved in the biodegradation of lignins, which constitute the main noncarbohydrate component in wood and are among the most abundant groups of biopolymers in the biosphere. A great number of white-rot fungi have been reported to produce the lignin-degrading enzymes laccase, lignin peroxidases, and manganese peroxidases, or at least one of these enzymes (15,16,44).Laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) have very broad substrate specificity with respect to the electron donor. They catalyze the removal of a hydrogen atom from the hydroxyl group of ortho-and para-substituted monoand polyphenolic substrates and from aromatic amines by one-electron abstraction to form free radicals...

An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

“…EDTA up to a concentration of 300 mM showed no effect on SRL1. DDC (I 50 = 1.2 mM) strongly inhibited the enzyme like many other fungal laccases such as from P. cinnabarinus [43], from B. cinerea [44], from Pleurotus ostreatus, from Trametes versicolor [2] and T. hirsuta [45] where the I 50 values were below 1 mM. Among the halogens tested, fluoride was the strongest inhibitor as shown previously in the literature [46].…”

“…Consequently, the laccase from S. rolfsii, which is very stable in the acidic pH range, may prove to be successful on an industrial scale. Immobilisation of the laccase could further reduce cost of the enzyme and avoid interaction of the enzyme protein with dyes when the treated effluents are reused in dyeing [45].…”

ENZYMATIC EXTRACT OF Trametes maxima CU1 ON PRODUCTIVE PARAMETERS AND CARCASS YIELD OF RABBITS

“…One unit of enzyme was defined as the amount of enzyme catalyzing the release of 1mmol of glucose or xylose equivalent per minute at 25 °C. The laccase determination was carried out according to the protocol described by Abadulla et al (2000), using 20 mM 2,6-dimetoxyphenol (DMP) as substrate in 200 mM sodium acetate buffer, adjusting pH to 4.5. The measurements were made in a spectrophotometer at 468 nm (ε= 49,600 M -1 cm -1 ; Shimadzu, Japan).…”

Voltammetric monitoring of laccase-catalysed mediated reactions

“…The capability of laccase to degrade chromophore substrates such as triarylmethane, indigoid, azo, and anthraquinonic dyes suggests a potential application of the enzyme in textile dye bleaching processes [4,5]. However, these processes have been hindered due to unfavourable kinetics between the enzyme and the dye.…”