Faraco 2016). Pretreatment by these organisms
has been shown to reduce the energy required
in refining wood chips in mechanical pulp production and to improve certain strength and
brightness properties of paper. White rot
fungi such as Phanerochaete chrysosporium,
Phanerochaete crassa, and Pleurotus pulmonarius have been studied as potential bio-bleaching
agents for both Kraft pulp and sulfite pulp. The
CAZymes and lignin-degrading enzymes from
these fungi, and others discussed earlier in this
chapter, have been studied and cloned into
yeast and bacterial vectors for use in biorefinery applications. Further advances in this area
with the application of enzyme suites, including
the use of lytic polysaccharide monooxygenase
(LPMO) enzymes from decay fungi to enhance
sugar and phenolic yield from biomass is
expected in the future (Bissaro et al. 2018).
Given the need for sustainable production
of a wide range of products beyond pulp and
paper however, interest in the past 5 years has
also been on the conversion of biomass, including lignin, to produce platform chemicals for
biopolymers. The use of lignin as an “economic
pull-through” product to provide additional
high-value products over and above the holocellulose-derived products is of increasing
interest in the field. This has opened up potential for the use of white rot fungi, as well as
brown rot fungi, in these applications.
B. Brown Rot Fungi
Less information is available relative to the use
of brown rot fungi in biotechnological applications. In part this is because the removal of
lignin from wood pulp was the primary focus
of microbial/enzymatic conversion of lignocellulose in the 1970s and 1980s, and white rot
fungi with peroxidases and laccases were the
most appropriate biotechnological tools for
this task. It was thought that brown rot fungi
had no enzymes useful in this regard; however,
more recent studies on delignification have
showed that some types of LMPOs may interact
with lignin degrading enzymes to promote the
degradation and release of lignin (Li et al.
2019), suggesting that cellulase enzymes from
either white rot or brown rot fungi may have a
broader role in lignin deconstruction than was
previously thought. Because of historical
carry-over, white rot fungi have continued to
be better studied, and their use as the primary
agents in biotechnology processing has
continued even as the field has shifted to the
use of lignocellulose biomass in the production
of platform chemicals (from both holocellulose
and lignin) to produce downstream bio-based
chemicals.
Brown rot fungal activity was previously
demonstrated to be effective for use in activating lignin for production of laminated wood
(Jin et al. 1991) and composite panels (Jin
et al. 1990b). Additional research also demonstrated the feasibility of using brown rotted
lignin as a high-quality, formaldehyde-free
adhesive (Li and Geng 2005). The chelatormediated Fenton (CMF) mechanism, derived
from the brown rot fungi, has been considered
for application in the activation of lignin on
fiber surfaces to provide enhanced bonding of
fiber-based products and has been patented for
use in those applications (Qian et al. 2002, 2004;
Goodell and Jellison 2008; Yelle et al. 2004).
Relative to pollutant and xenobiotic remediation, Serpula spp. brown rot was found to be
effective in the removal of copper from preservative-treated wood as a remediation treatment
(Kartal et al. 2015). Similarly CMF chemistry
was demonstrated to be significantly more
effective than Fenton chemistry alone in the
degradation of complex pollutants like pentachlorophenol (Goodell et al. 1997) and DDT
(Purnomo et al. 2008) and also in the decolorization of recalcitrant dyes (Goodell et al. 2002,
2004).
Brown rot CAZymes have been little
explored for biorefinery applications, but a
powerful LMPO has been isolated from the
brown rot Gloeophyllum spp. and cloned into
yeast for expression (Kojima et al. 2016). The
combination of brown rot enzymatic and nonenzymatic mechanisms may lead to future biorefinery applications, particularly where nonfiber products are of primary interest, and
downstream platform chemicals produced
from oligosaccharides and modified lignin can
be produced (Goodell et al. 2017).
390
B. Goodell
has been shown to reduce the energy required
in refining wood chips in mechanical pulp production and to improve certain strength and
brightness properties of paper. White rot
fungi such as Phanerochaete chrysosporium,
Phanerochaete crassa, and Pleurotus pulmonarius have been studied as potential bio-bleaching
agents for both Kraft pulp and sulfite pulp. The
CAZymes and lignin-degrading enzymes from
these fungi, and others discussed earlier in this
chapter, have been studied and cloned into
yeast and bacterial vectors for use in biorefinery applications. Further advances in this area
with the application of enzyme suites, including
the use of lytic polysaccharide monooxygenase
(LPMO) enzymes from decay fungi to enhance
sugar and phenolic yield from biomass is
expected in the future (Bissaro et al. 2018).
Given the need for sustainable production
of a wide range of products beyond pulp and
paper however, interest in the past 5 years has
also been on the conversion of biomass, including lignin, to produce platform chemicals for
biopolymers. The use of lignin as an “economic
pull-through” product to provide additional
high-value products over and above the holocellulose-derived products is of increasing
interest in the field. This has opened up potential for the use of white rot fungi, as well as
brown rot fungi, in these applications.
B. Brown Rot Fungi
Less information is available relative to the use
of brown rot fungi in biotechnological applications. In part this is because the removal of
lignin from wood pulp was the primary focus
of microbial/enzymatic conversion of lignocellulose in the 1970s and 1980s, and white rot
fungi with peroxidases and laccases were the
most appropriate biotechnological tools for
this task. It was thought that brown rot fungi
had no enzymes useful in this regard; however,
more recent studies on delignification have
showed that some types of LMPOs may interact
with lignin degrading enzymes to promote the
degradation and release of lignin (Li et al.
2019), suggesting that cellulase enzymes from
either white rot or brown rot fungi may have a
broader role in lignin deconstruction than was
previously thought. Because of historical
carry-over, white rot fungi have continued to
be better studied, and their use as the primary
agents in biotechnology processing has
continued even as the field has shifted to the
use of lignocellulose biomass in the production
of platform chemicals (from both holocellulose
and lignin) to produce downstream bio-based
chemicals.
Brown rot fungal activity was previously
demonstrated to be effective for use in activating lignin for production of laminated wood
(Jin et al. 1991) and composite panels (Jin
et al. 1990b). Additional research also demonstrated the feasibility of using brown rotted
lignin as a high-quality, formaldehyde-free
adhesive (Li and Geng 2005). The chelatormediated Fenton (CMF) mechanism, derived
from the brown rot fungi, has been considered
for application in the activation of lignin on
fiber surfaces to provide enhanced bonding of
fiber-based products and has been patented for
use in those applications (Qian et al. 2002, 2004;
Goodell and Jellison 2008; Yelle et al. 2004).
Relative to pollutant and xenobiotic remediation, Serpula spp. brown rot was found to be
effective in the removal of copper from preservative-treated wood as a remediation treatment
(Kartal et al. 2015). Similarly CMF chemistry
was demonstrated to be significantly more
effective than Fenton chemistry alone in the
degradation of complex pollutants like pentachlorophenol (Goodell et al. 1997) and DDT
(Purnomo et al. 2008) and also in the decolorization of recalcitrant dyes (Goodell et al. 2002,
2004).
Brown rot CAZymes have been little
explored for biorefinery applications, but a
powerful LMPO has been isolated from the
brown rot Gloeophyllum spp. and cloned into
yeast for expression (Kojima et al. 2016). The
combination of brown rot enzymatic and nonenzymatic mechanisms may lead to future biorefinery applications, particularly where nonfiber products are of primary interest, and
downstream platform chemicals produced
from oligosaccharides and modified lignin can
be produced (Goodell et al. 2017).
390
B. Goodell