Environmental Engineering Reference
In-Depth Information
described a peroxidase isolated from
P. ostreatus
that can decolorize a vari-
ety of triarylmethane and azo dyes, including Basic Violet 3, Basic Green 4,
bromophenol blue, Acid Orange 52, Direct Red 28, as well as Poly R-478.
Shrivastava
et al.
[150] produced MnP and manganese-independent per-
oxidase (MIP), which is presumably versatile peroxidase, by
P. ostreatus
in
solid-state fermentation and compared their activities on the decoloriza-
tion of seven related triarylmethane dyes. They found that MnP preferred
the dyes that have free phenolic group on the chromophore, such as phe-
nol red,
o
-cresol red and
m
-cresol purple, while MIP could catalyze the
oxidation of brominated dyes, such as bromocresol green (see Figure 6.8).
Mohorčič
et al.
[151] conducted a fungal strain screening for decolorizing
diazo dye Reactive Black 5. Among the 25 strains tested, only two, namely
B. adusta
and
Geotrichum candidum
, could effectively decolorize this
diazo dye. Subsequently, they used purified MnP from
B. adusta
to decol-
orize various azo and anthraquinone dyes, including Reactive Black 5,
Acid Red 111, Acid Orange 7, Disperse Yellow 211, Reactive Blue 19, and
Disperse Blue 354. Two disperse dyes were apparently more resistant to
decolorization.
6.6.3 Laccases
Laccases are by far the most studied enzymes for decolorization of syn-
thetic dyes. This subsection is organized into three parts: treatability
studies, kinetics and reaction mechanisms, and toxicity. Many laccase
preparations from various white rot fungi, such as
Pleurotus
spp. (
P. ostea-
tus
and
P. s a j o r - c a j u
),
Trametes
spp. (
T. versicolor
,
T. hir s ut a
,
T. modesta
,
and
T. t ro g ii
),
Sclerotium rolfsii
,
L. edodes
, and
Pycnoporus sanguineus
, as
well as a laccase produced by genetically modified
Aspergillus niger
, have
been evaluated.
6.6.3.1 TreatabilityStudies
Rodríguez
et al.
[152] performed the screening of 16 strains of white rot
fungi for the production of ligninolytic enzymes and decolorization of
23 synthetic dyes. They selected laccases from
P. ostreatus
and
Trametes
hispida
for enzymatic treatment. The laccase from
T. hispida
was able to
decolorize a wider variety of dyes than that from
P. ostreatus
. Abadulla
et al.
[153] also conducted a screening study to compare laccase prepara-
tions from
P. ostreatus
,
Schizophyllum commune
,
N. crassa
,
Polyporus
sp.,
S. rolfsii
,
Trametes villosa
, and
Myceliophtora thermophile
for the decolor-
ization of 11 structurally different dyes.
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