Page 165 - Materials Chemistry, Second Edition

146 Life Cycle Assessment of Wastewater Treatment

enzyme activity by enzyme deactivation. LiPs can oxidize a variety of aromatic
compounds, including some pharmaceuticals (Harms et al., 2011; Falade et al., 2016).
MnPs are extracellular glycoproteins with a molecular weight range of 32–62.5
kDa and optimum activity from pH 4 to 7 and from 40 to 60°C (Ürek and Pazarlioğlu,
2004; Baborová et al., 2006). Fungi secrete multiple isoforms of MnPs in carbon- and
2+
nitrogen-limited media supplemented with Mn , which plays the role of mediator
for MnP and VA (Hakala et al., 2005; Cheng et al., 2007). Immobilization with
sodium alginate, gelatin, or chitosan (as carriers) and glutaraldehyde crosslinking
agent can increase the stability of the enzyme (Cheng et al., 2007). The activity of
MnP increases in the presence of co-oxidants, such as glutathione, unsaturated fatty
acids, and Tween 80, and is inhibited by NaN , ascorbic acid, β-mercaptoethanol,
3
and dithreitol (Hofrichter, 2002; Ürek and Pazarlioğlu, 2005). The MnPs generate
Mn(III) ions, which can act to oxidize and degrade a variety of complex substrates,
including lignin, and specifically oxidize phenolic structures and aromatic amines
(Harms et al., 2011; Falade et al., 2016). Fungal MnPs have been used to break down
a variety of common pharmaceutical wastes (Shin et al., 2007; Wen et al., 2010;
Golan-Rozen et al., 2011; Rodarte-Morales et al., 2011).
VP enzymes are a class of hemoprotein peroxidases with broad substrate specific-
2+
ity, capable of direct oxidization of Mn , methoxybenzenes, phenols, and aromatic
compounds. VPs oxidize both phenolic and nonphenolic lignin model dimers, as
well as the other substrates, in the absence of manganese (Ruiz-Duenas et al., 2007),
due to having multiple active sites and different oxidative abilities with or without
manganese (Knop et al., 2016). These features make them interesting for biotechno-
logical applications and the bioremediation of recalcitrant pollutants (Tsukihara et
al., 2006; Wong, 2009). They have the traits of both LiP (oxidation of non-phenolic
aromatics) and MnP (oxidation of phenolics) (Falade et al., 2016; Eibes et al., 2011).
Some studies have shown their use in treating pharmaceutical waste (Taboada-Puig
et al., 2011; Eibes et al., 2011; Salame et al., 2012).
Dye-decolorizing peroxidases (DyPs) produced by some basidiomycetes have
little sequence similarity to the other peroxidases described in this section. They can
oxidize a variety of dyes, including xenobiotic anthraquinone derivatives that other
peroxidases rarely oxidize (Hofrichter et al., 2010; Harms et al., 2011; Salvachúa
et al., 2013).
Whereas the enzymes described above are all peroxidases requiring H O , lac-
2
2
cases are N-glycosylated extracellular copper-containing oxidases, with a molecular
weight range of 58 to 90 kDa (Wells et al., 2006; Murugesan et al., 2006; Mishra
and Bisaria, 2006; Zouari-Mechichi et al., 2006; Quaratino et al., 2007), that
require O gas but not H O for activity. They are produced by a variety of bacte-
2
2
2
ria, green plants, and fungi (Upadhyay et al., 2016; Yang et al., 2017) with wide-
spread occurrence in ascomycetes and basidiomycetes (Harms et al., 2011). Fungal
laccases’ pH and temperature activity profiles are dependent on the WRF species;
however, optimum activities have been reported between pH 2 and 10 and between
40 and 65°C for laccases from different sources (Lu et al., 2017; Ullrich et al.,
2005; Zouari-Mechichi et al., 2006; D’Souza et al., 2006; Quaratino et al., 2007;
Murugesan et al., 2006). LacI and LacII are two laccase isozymes that have been
identified in different fungal species, including Physisporinus rivulosus, Trametes