manganese peroxidases produce Mn3+and act mainly on phenolic units; both were
discovered inPhanerochaete chrysosporium (Martínez et al. 2005 ).Pleurotus
eryngiiproduces versatile peroxidase that shows catalytic properties similar to
lignin and manganese peroxidases (Ruiz Dueñas et al. 1999 ). On the other hand,
oxidades, such as glyoxal and aryl-alcohol oxidases described inPhanerochaete
chrysosporiumand P. eryngii, respectively (Guillén et al. 1992 ), produce the
hydrogen peroxide necessary for the catalytic action of the peroxidases (Kersten
1990 ), Finally, to avoid the repolymerization of the derived phenols produced
during lignin oxidation, aryl-alcohol dehydrogenases and quinone reductases cat-
alyze their reduction (Guillén et al. 1997 ).
Laccases oxidize several phenolic and nonphenolic substrates using four Cu
+ions on the active site. Type 1 copper acts as an electron acceptor from substituted
phenols or amines and is liable for the development of blue color. While type 2
copper transfer electrons to the molecular oxygen which further reduces water
molecule (Martínez et al. 2005 ). Laccases also generate radicals, and then nonen-
zymatic reactions were also produced, such as polymerization and hydrogen
abstraction. Although they have been isolated from ascomycetes and deuter-
omycetes, lignin degradation studies have not been a focus as much on the ba-
sidiomycetes (Madhavi and Lele 2009 ). Most common laccase producers are
Fig. 12.1 Overview of the place of lignin in cellulosic biomass and the reactions catalyzed by
lignoenzymes. Figure extracted from Alcalde ( 2015 )
264 Ú. Fillat et al.