Environmental Engineering Reference
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should reach the trinuclear cluster through a channel. However, sodium azide is a
known non-competitive inhibitor of laccase (Mishra and Kumar 2009 ).
It has a broad substrate range, and does not require H 2 O 2 for oxidation reactions
in contrast to other oxidases and peroxidases. Therefore, laccases are very useful in
biotechnological applications, such as paper pulp bleaching, synthetic dye decol-
orization, bioremediation, biosensing, chemical synthesis, and immunoassay
(Champagne and Ramsay 2005 ; Couto and Herrera 2006 ). The decolorization
activity of laccases generally depends on the source of the enzyme and also on the
chemical structure of the dye (Abadulla et al. 2000 ; Rodriguez-Couto 2007 ;
Michniewicz et al. 2008 ). Therefore, laccase enzymes obtained from different
strains and also from different fermentation processes may have differentdye
decolorization potential.
Anthraquinone dyes with fused aromatic rings, such as Acid Blue 80 and RBBR,
are generally used as starting materials for polymeric dyes and hence, represent an
important class of toxic and recalcitrant organopollutants. Laccases are considered
remarkable
catalysts in removing highly toxic phenolic pollutants from the
industrial wastewater. According to Hsu et al. ( 2012 ), Lentinus sp. lcc3 possesses a
novel decolorization ef
green
ciency (1 h reaction at room temperature) for Acid Blue 80
(97 % at 1 U ml 1 lcc3) and RBBR (88 % at 20 U ml 1 ). Similarly BenYounes
et al. ( 2007 ) have observed 91 % decolorization of RBBR by laccase produced from
Perenniporia tephropora after 48 h of the treatment.
Erkurt et al. ( 2007 ) reported that F. trogiiwas found to be an ef
cient fungal
strain that produce laccase for decolorization of dyes. It was found that about 90
mg l 1 of RBBR was decolorized by F. trogii after 48 h of incubation, which was
mediated by the laccase enzyme produced by the fungal strain. Forootanfar et al.
( 2012 ) isolated three laccases from three fungal strains and observed their effect on
anthraquinone RBBR dye decolorization both in the presence and absence of redox
mediator HBT (N-hydroxy benzotriazole). It was observed that in all the cases, the
percent of decolorization increased with an increase in HBT concentration. The
puri
ed laccase of T. versicolor showed the highest (80.5 %) decolorization after
30 min incubation in absence of HBT. In case of laccase from A. oryzae and in
absence of HBT, decolorization was found to be only 28.3 % after 30 min.
However, P. variabile caused only 16.6 % decolorization at the same time in
presence of HBT (5 mM). Similarly, it was also reported that laccase enzymes
produced by both Pycnoporus cinnabarinus and genetically modi
ed Aspergillus,
together with a redox mediator and a nonionic surfactant were able to degrade an
azo and an anthraquinone dye, respectively (Schliephake et al. 2000 ; Soares et al.
2001 ).
Murugesan et al. ( 2006 ) studied the role of crude laccase enzyme both in the
presence and absence of redox mediator (HBT) isolated from a white rot fungus
Ganoderma lucidum KMK2 for the decolorization of different dyes, such as
Remazol Black-5 and anthraquinone dye Remazol Brilliant Blue R (RBBR). It was
found that crude enzyme showed maximum decolorization activity to anthraqui-
none dye Remazol Brilliant Blue R (RBBR) without redox mediator, whereas diazo
dye Remazol Black-5 (RB-5) required a redox mediator. Besides, a concentration of
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