2. Lignin peroxidases (LiPs, EC 1.11.1.14) are monomeric heme-glycoproteins
(Orth and Tien 1995) that use H 2 O 2 , and at first, they were obtained from a
kind of fungus called Phanerochete chrysosporium (Venkatadri and Irvine 1993).
It catalyzes the oxidation of nonphenolic aromatic compounds (Conesa et al.
2002; Sindhu et al. 2016). These enzymes are shown in Fig. 9.5 (Wong 2009;
Brown et al. 2012).
3. Manganese peroxidases (MnP), (EC 1.11.1.13) are also extracellular glycoproteins like lignin peroxidases, which contain heme group and utilize H 2 O 2 (Asgher
et al. 2008; Sindhu et al. 2016). They exert effect on phenolic and nonphenolic
compounds through lipid peroxidation reactions (Binod et al. 2011; Sindhu et al.
2016).
The basic function of the MnP is oxidizing Mn
2+ ions to Mn
3+ , then later, Mn
(III) complexes that occur as a result of the chelation process carried out by
organic acids (such as malate or oxalate), oxidizes various substrates of the MnP
(Hofrichter 2002). Some examples of microorganisms producing this enzyme can
be seen in Fig. 9.5 (Homma et al. 2007; Romero et al. 2007). Both group of
enzymes (laccases and peroxidases) turn phenolic compounds and aromatic
amines into radicals (Higuchi 1989; Kersten et al. 1990).
However, in addition to the differences in their prosthetic groups, the laccases
differ from the peroxidases also because they have lower oxidation potentials
(Hayashi and Yamazaki 1979; Farhangrazi et al. 1994).
9.4 Other Enzymes
In addition to the basic microbial enzymes involved in the biofuel production
process mentioned above, there are some enzymes that contribute to this process.
Pectinases, LPMOs, amylases, pullulanases, and proteases described below are
among such groups of enzymes (Fig. 9.6).
9.4.1 Pectin and Pectinolytic Enzymes
Pectin has a linear backbone consisting of α-1,4 linked D-galacturonic acid residues
which can be methylated and interchanged with L-rhamnose, arabinose, galactose,
and xylose. Furthermore, apart from celluloses and hemicelluloses, pectin is another
structural polysaccharide that ensures the integrity of the plant tissues that are on the
plant cell wall matrix (Kashyap et al. 2001; Celestino et al. 2006).
Pectinolytic enzymes can be evaluated in two different groups: esterases (pectinesterases, EC 3.1.1.11) and depolymerases (hydrolases: endopolygalacturonase, EC
3.2.1.15; exopolygalacturonase, EC 3.2.1.67 and lyases: pectate-lyase, EC 4.2.2.2;
pectin lyase, EC 4.2.2.10) (Soares et al. 2001; Celestino et al. 2006; Elleuche et al.
9 Microbial and Bioinformatics Approach in Biofuel Production
275
(Orth and Tien 1995) that use H 2 O 2 , and at first, they were obtained from a
kind of fungus called Phanerochete chrysosporium (Venkatadri and Irvine 1993).
It catalyzes the oxidation of nonphenolic aromatic compounds (Conesa et al.
2002; Sindhu et al. 2016). These enzymes are shown in Fig. 9.5 (Wong 2009;
Brown et al. 2012).
3. Manganese peroxidases (MnP), (EC 1.11.1.13) are also extracellular glycoproteins like lignin peroxidases, which contain heme group and utilize H 2 O 2 (Asgher
et al. 2008; Sindhu et al. 2016). They exert effect on phenolic and nonphenolic
compounds through lipid peroxidation reactions (Binod et al. 2011; Sindhu et al.
2016).
The basic function of the MnP is oxidizing Mn
2+ ions to Mn
3+ , then later, Mn
(III) complexes that occur as a result of the chelation process carried out by
organic acids (such as malate or oxalate), oxidizes various substrates of the MnP
(Hofrichter 2002). Some examples of microorganisms producing this enzyme can
be seen in Fig. 9.5 (Homma et al. 2007; Romero et al. 2007). Both group of
enzymes (laccases and peroxidases) turn phenolic compounds and aromatic
amines into radicals (Higuchi 1989; Kersten et al. 1990).
However, in addition to the differences in their prosthetic groups, the laccases
differ from the peroxidases also because they have lower oxidation potentials
(Hayashi and Yamazaki 1979; Farhangrazi et al. 1994).
9.4 Other Enzymes
In addition to the basic microbial enzymes involved in the biofuel production
process mentioned above, there are some enzymes that contribute to this process.
Pectinases, LPMOs, amylases, pullulanases, and proteases described below are
among such groups of enzymes (Fig. 9.6).
9.4.1 Pectin and Pectinolytic Enzymes
Pectin has a linear backbone consisting of α-1,4 linked D-galacturonic acid residues
which can be methylated and interchanged with L-rhamnose, arabinose, galactose,
and xylose. Furthermore, apart from celluloses and hemicelluloses, pectin is another
structural polysaccharide that ensures the integrity of the plant tissues that are on the
plant cell wall matrix (Kashyap et al. 2001; Celestino et al. 2006).
Pectinolytic enzymes can be evaluated in two different groups: esterases (pectinesterases, EC 3.1.1.11) and depolymerases (hydrolases: endopolygalacturonase, EC
3.2.1.15; exopolygalacturonase, EC 3.2.1.67 and lyases: pectate-lyase, EC 4.2.2.2;
pectin lyase, EC 4.2.2.10) (Soares et al. 2001; Celestino et al. 2006; Elleuche et al.
9 Microbial and Bioinformatics Approach in Biofuel Production
275