9.4.5 Non-hydrolytic Cellulose-Degrading Enzymes (LPMOs:
Lytic Polysaccharide Monooxygenases)
Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent redox enzymes
that require oxygen (Mohanram et al. 2013; Laurent et al. 2019) and help to increase
the degradation of some persistent polysaccharides such as crystalline cellulose
(Quinlan et al. 2011) and chitin (Langston et al. 2011).
LPMOs are very important for the pretreatment of the biomass (Levasseur et al.
2013). LPMOs known to act on cellulose and chitin in the beginning have later been
identified to react also with a series of polysaccharides such as starch (Leggio et al.
2015), xyloglucan, cellodextrins, and glucomannan (Borisova et al. 2015; BennatiGranier et al. 2015; Johansen 2016).
The discovery of this enzyme group has been started in 2010 when VaageKolstad et al. introduced the oxidative enzyme (CBP21) that is located in the
backbone of chitin and can break glycosidic bonds (Vaaje-Kolstad et al. 2010). In
the beginning, the LPMOs obtained only from the fungi were classified in the
GH61 family. Later, when GH61 family was designated as oxidative enzymes,
this enzyme group was reclassified and placed into the auxiliary activity families
(AA) (Quinlan et al. 2011; Beeson et al. 2012; Hemsworth et al. 2015). LPMOs can
be accessed via CAZy database [www.cazy.org] (Levasseur et al. 2013; Lombard
et al. 2014).
Similar to glycosidic hydrolase enzyme producers, the LPMOs can be predominantly obtained from certain fungi (Vaaje-Kolstad et al. 2010; Hemsworth et al.
2015), bacteria (Forsberg et al. 2014; Zhang et al. 2015; Eijsink et al. 2019), and
viruses (Chiu et al. 2015; Johansen 2016; Filiatrault-Chastel et al. 2019) (Fig. 9.6).
The strength of the LPMOs to increase the activity of the GHs has been one of the
driving forces which made the investigations on LPMOs press forward. In the
presence of an external e
À donor (oxygen), LPMOs (special oxidoreductases)
oxidize the glycosidic bonds (Vaaje-Kolstad et al. 2010; Quinlan et al. 2011;
Forsberg et al. 2014) and give way to the cleavage of the polysaccharide chain,
which in turn significantly contributes to the accessibility of the hydrolytic enzymes
(hydrolases) to the substrate (Vermaas et al. 2015; Laurent et al. 2019).
In the pretreatment with LPMO, compared to cellulases, it has been determined
that the degradation of the highly resistant crystalline cellulose is completed faster
and entirely (Eibinger et al. 2014).
It was observed that the yield from different celluloses (such as bacterial cellulose, microcrystalline cellulose, cellulose pretreated with phosphoric acid) increased
6–8 times in the combination of AA9 (AA: auxiliary activity) and CDH (cellobiose
dehydrogenase) (Langston et al. 2011; Hemsworth et al. 2015). These tremendous
activities of the LPMOs are significant development in biomass conversion. However, there are some points that need to be solved or considered in industrial
applications:
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281
Lytic Polysaccharide Monooxygenases)
Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent redox enzymes
that require oxygen (Mohanram et al. 2013; Laurent et al. 2019) and help to increase
the degradation of some persistent polysaccharides such as crystalline cellulose
(Quinlan et al. 2011) and chitin (Langston et al. 2011).
LPMOs are very important for the pretreatment of the biomass (Levasseur et al.
2013). LPMOs known to act on cellulose and chitin in the beginning have later been
identified to react also with a series of polysaccharides such as starch (Leggio et al.
2015), xyloglucan, cellodextrins, and glucomannan (Borisova et al. 2015; BennatiGranier et al. 2015; Johansen 2016).
The discovery of this enzyme group has been started in 2010 when VaageKolstad et al. introduced the oxidative enzyme (CBP21) that is located in the
backbone of chitin and can break glycosidic bonds (Vaaje-Kolstad et al. 2010). In
the beginning, the LPMOs obtained only from the fungi were classified in the
GH61 family. Later, when GH61 family was designated as oxidative enzymes,
this enzyme group was reclassified and placed into the auxiliary activity families
(AA) (Quinlan et al. 2011; Beeson et al. 2012; Hemsworth et al. 2015). LPMOs can
be accessed via CAZy database [www.cazy.org] (Levasseur et al. 2013; Lombard
et al. 2014).
Similar to glycosidic hydrolase enzyme producers, the LPMOs can be predominantly obtained from certain fungi (Vaaje-Kolstad et al. 2010; Hemsworth et al.
2015), bacteria (Forsberg et al. 2014; Zhang et al. 2015; Eijsink et al. 2019), and
viruses (Chiu et al. 2015; Johansen 2016; Filiatrault-Chastel et al. 2019) (Fig. 9.6).
The strength of the LPMOs to increase the activity of the GHs has been one of the
driving forces which made the investigations on LPMOs press forward. In the
presence of an external e
À donor (oxygen), LPMOs (special oxidoreductases)
oxidize the glycosidic bonds (Vaaje-Kolstad et al. 2010; Quinlan et al. 2011;
Forsberg et al. 2014) and give way to the cleavage of the polysaccharide chain,
which in turn significantly contributes to the accessibility of the hydrolytic enzymes
(hydrolases) to the substrate (Vermaas et al. 2015; Laurent et al. 2019).
In the pretreatment with LPMO, compared to cellulases, it has been determined
that the degradation of the highly resistant crystalline cellulose is completed faster
and entirely (Eibinger et al. 2014).
It was observed that the yield from different celluloses (such as bacterial cellulose, microcrystalline cellulose, cellulose pretreated with phosphoric acid) increased
6–8 times in the combination of AA9 (AA: auxiliary activity) and CDH (cellobiose
dehydrogenase) (Langston et al. 2011; Hemsworth et al. 2015). These tremendous
activities of the LPMOs are significant development in biomass conversion. However, there are some points that need to be solved or considered in industrial
applications:
9 Microbial and Bioinformatics Approach in Biofuel Production
281