Use of Fungal Laccases and Peroxidases for Enzymatic Treatment of Wastewater Containing Synthetic Dyes - Green Chemistry for Dyes Removal from Wastewater - page 234

azo (Direct Blue 71 and Reactive Black 5), indigoid (Acid Blue 74), and
bifunctional (Reactive Blue 221) dyes were tested. They noted a significant
difference in substrate specificity of laccase preparations from these four
fungi. For example, laccases from T. versicolor and S. rolfsii could decolor-
ize triarylmethane dyes better than the ones from T. modesta and T. hir-
suta . The effect of redox mediators was also confirmed. Abadulla et al. [54]
used purified T. hir s ut a laccase in an ultrafiltration reactor and immobi-
lized enzyme on alumina in a packed column reactor to decolorize seven
dyes, including Reactive Blue 221, Reactive Black 5 (diazo), Direct Blue
71 (triazo), Basic Red 9 (triarylmethane), Reactive Blue 19, Acid Blue 225
(anthraquinone), and Acid Blue 71 (indigoid). They found that anthraqui-
none dyes and Acid Blue 71 could be decolorized twice as fast as azo dyes.
They also found that the laccase immobilization improved its thermal sta-
bility and reduced the susceptibility to known laccase inhibitors such as
sodium chloride, diethyldithiocarbamate, and sodium fluoride.
Zouari-Mechichi et al. [162] purified two isozymes of laccase from a
T. t for g ii strain isolated in Tunisia and tested them for decolorizing six
dyes (chemical structures unknown, likely acid metal complex dyes). They
found that crude and purified enzymes performed similarly in the decol-
orization test and that certain dyes were resistant to decolorization even
in the presence of HBT. Trupkin et al. [163] also used a strain of T. t ro g ii
to evaluate the extracellular enzymes for decolorization of various dyes,
including Acid Red 26, Basic Green 4, Acid Blue 74, Reactive Blue 19, Poly
R-478, and azure B. They found MnP and laccase in the liquid culture fil-
trate, but laccase was more predominant. The dye decolorization efficiency
was higher when a whole broth with mycelium was used, suggesting that
biosorption and other mechanisms are involved. Crude laccase from
T. t for g ii was also used to evaluate the decolorization of three anthraqui-
none (anthraquinone blue, Reactive Blue 19, and Poly R-478), three azo
(Direct Red 28, Acid Red 26, and Janus Green), two triarylmethane (Basic
Violet 3 and Basic Green 4), one heterocyclic (azure B), and one indigoid
(Acid Blue 74) dyes [84]. Poly R-478 and azure B were most resistant to
decolorization by the crude T. t ro g g i laccase, followed by Janus Green and
Direct Red 28. A majority (>80%) of Acid Blue 74 and two anthraquinone
dyes could be decolorized within 30 min.
Nagai et al. [164] reported the use of purified laccase from L. edodes
for the decolorization of an azo (Acid Red 2 and Reactive Orange 16),
a diazo (Acid Black 1), a triarylmethane (bromophenol blue), and two
anthraquinone (Reactive Blue 19 and Poly R-478) dyes. Reactive Orange
16 and Poly R-478 were resistant to the decolorization by L. edodes lac-
case alone, although these dyes could be decolorized in the presence of a