Use of Fungal Laccases and Peroxidases for Enzymatic Treatment of Wastewater Containing Synthetic Dyes - Green Chemistry for Dyes Removal from Wastewater - page 230

In addition, by using isolated enzymes in a more defined mixture, the
reaction mechanisms of synthetic dye decolorization and possible degra-
dation pathways may be explored in a more controlled fashion.
In fact, the use of purified and crude phenol oxidizing enzymes for
industrial wastewater treatment has been investigated extensively since the
early 1980s using various plant and fungal enzymes, including horseradish
peroxidase (HRP), soybean peroxidase (SBP), LiP, MnP, chloroperoxidase,
non-ligninolytic fungal peroxidases (such as Coprinopsis cinerea peroxi-
dase), laccase, and tyrosinase [15-17,136-140]. These phenol-oxidizing
enzymes have broad substrate specificity and are capable of oxidizing
many substituted phenols and aromatic amines. Among these phenol oxi-
dizing enzymes, those enzymes secreted by lignin-degrading, white rot
fungi such as P. chrysosporium are characterized by their exceptional abil-
ity to degrade non-phenolic, more complex aromatic compounds of natu-
ral or xenobiotic origins as mentioned earlier. Many research papers have
been published on the enzymatic treatment of synthetic dyes over the last
15 years. This section reviews and discusses these research works.
6.6.1 LigninPeroxidases
The literature concerning the use of purified LiP in dye decolorization is
limited to several earlier works reported in the early 2000s or before. The
requirement of veratryl alcohol for the substantial decolorization activity
by LiP might have discouraged the researchers. Ollikka et al. [141] reported
the decolorization of various azo, triarylmethane, heterocyclic and poly-
meric dyes by three purified LiP isozymes (0.1 U/mL) from P. c h r y s o s p o -
rium . Veratryl alcohol (2 mM) was essential to decolorization of most of the
dyes tested, but one of the LiP isozymes could decolorize certain dyes such
as Acid Orange 52, Basic Blue 9, and Basic Blue 17 without the addition of
veratryl alcohol. Young and Yu [142] investigated a LiP-catalyzed oxidation
of azo (Acid Violet 7, Acid Orange 74, Reactive Black 5, and Acid Black 24),
indigoid (Acid Blue 74), phthalocyanine (Reactive Blue 15), anthraquinone
(Acid Green 27 and Acid Blue 25) dyes in the presence of 1 mM of veratryl
alcohol. Among the dyes tested, the triazo dye Acid Black 23 was the most
resistant to decolorization by the purified LiP, although fungal treatment
with P. chrysosporium and T. versicolor could decolorize this dye by >96%.
Ferreira et al. [143] reported N -demethylation of a heterocyclic dye, Basic
Blue 9, that yielded azure B and azure A (see Figure 6.8) using LiP from
P. chrysosporium. N -Demethylation of a triarylmethane dye, Basic Violet 3,
with purified LiP from P. chrysosporium was also demonstrated by Bumpus