120
and making other nutrients available to the animal. As cited by Jalc (2002), the
enzymes secreted by fungi had strong affinity to metabolize lingo-celluloses and
these are biological agents in treating rice straw to improve its nutritional value
through the selective action of delignification. Nevertheless, its current use in developing countries is still a big question due to limitation in technical skills and the
availability of resources to produce and handle large quantities of fungi or their
enzymes for practical and field application. Biological treatment of straw brings
some concerns and problems to be addressed and overcome (Schiere and Ibrahim
1989). For example, there are fungi species that are not edible and produce toxic
substances both to human and animals. Fungi also require an environment for them
to grow and reproduce, such as pH, temperature, pressure, and O 2 , and CO 2 concentrations before, during, and after the treatment period. With the current development
in mycology, there are now simple protocols or guides to be used in growing fungi
as well in enzyme production or purification for rice straw treatment. There are
commercially available enzyme inoculants or additives available in the market such
that the costs to purchase these substrates will continuously decline and can be used
by ruminant raisers to increase their production efficiency as well as their farm
income (Beauchemin et al. 2004).
7.3.3.1 White-Rot Fungi Treatment
White-rot fungi are known to have degrading or decaying properties by acting
ligno-cellulolytic components of farm byproducts including wood. These have the
capacity to decompose and metabolize cellulose, hemicellulose, and lignin under
favorable environments through enzymatic reactions to their substrates (Eriksson
et al. 1990). Some of the significant characteristics of many white-rot fungi species
involve their ability to effectively hydrolyze lignin hence they are considered to be
lignin degraders. These species can improve the nutritive value of fodder by tendering more degradable carbohydrates for rumen microbial fermentation (Yamakava
and Okamnto 1992; Howard et al. 2003). White-rot fungi secrete varieties of extracellular lignin-modifying enzymes that consist of lignin-peroxidase (LiP),
manganese- dependent peroxidase (MnP), laccase (phenol oxidase), and H 2 O 2 -
producing oxidase (aryl-alcohol oxidase; AAO and glyoxaloxidase) (Kirk and
Farrell 1987; Arora et al. 2002; Novotny et al. 2004; Arora and Gill 2005; Lechner
and Papinutti 2006).
Researchers have observed that some fungi species can decompose or directly
act on free phenolic monomers to break the bonds or cross-links between lignin and
polysaccharides of rice straw (Chen et al. 1996). Other fungal species improve the
IVDMD of treated straw (Karunanandaa et al. 1995; Karunanadaa and Varga 1996a,
b; Fazaeli et al. 2006). Karunanandaa et al. (1995) also reported that incubation of
rice straw with 8–10% w/w for 30 days using three white-rot fungi species. Pleurotus
sajor-caju enhanced IVDMD in both rice leaves and stems. However, results
obtained using Cyathus stercoreus gave the highest IVDMD compared to other
fungi species (Karunanandaa et al. 1992). The sequence by which the white-rot
D. Aquino et al.
and making other nutrients available to the animal. As cited by Jalc (2002), the
enzymes secreted by fungi had strong affinity to metabolize lingo-celluloses and
these are biological agents in treating rice straw to improve its nutritional value
through the selective action of delignification. Nevertheless, its current use in developing countries is still a big question due to limitation in technical skills and the
availability of resources to produce and handle large quantities of fungi or their
enzymes for practical and field application. Biological treatment of straw brings
some concerns and problems to be addressed and overcome (Schiere and Ibrahim
1989). For example, there are fungi species that are not edible and produce toxic
substances both to human and animals. Fungi also require an environment for them
to grow and reproduce, such as pH, temperature, pressure, and O 2 , and CO 2 concentrations before, during, and after the treatment period. With the current development
in mycology, there are now simple protocols or guides to be used in growing fungi
as well in enzyme production or purification for rice straw treatment. There are
commercially available enzyme inoculants or additives available in the market such
that the costs to purchase these substrates will continuously decline and can be used
by ruminant raisers to increase their production efficiency as well as their farm
income (Beauchemin et al. 2004).
7.3.3.1 White-Rot Fungi Treatment
White-rot fungi are known to have degrading or decaying properties by acting
ligno-cellulolytic components of farm byproducts including wood. These have the
capacity to decompose and metabolize cellulose, hemicellulose, and lignin under
favorable environments through enzymatic reactions to their substrates (Eriksson
et al. 1990). Some of the significant characteristics of many white-rot fungi species
involve their ability to effectively hydrolyze lignin hence they are considered to be
lignin degraders. These species can improve the nutritive value of fodder by tendering more degradable carbohydrates for rumen microbial fermentation (Yamakava
and Okamnto 1992; Howard et al. 2003). White-rot fungi secrete varieties of extracellular lignin-modifying enzymes that consist of lignin-peroxidase (LiP),
manganese- dependent peroxidase (MnP), laccase (phenol oxidase), and H 2 O 2 -
producing oxidase (aryl-alcohol oxidase; AAO and glyoxaloxidase) (Kirk and
Farrell 1987; Arora et al. 2002; Novotny et al. 2004; Arora and Gill 2005; Lechner
and Papinutti 2006).
Researchers have observed that some fungi species can decompose or directly
act on free phenolic monomers to break the bonds or cross-links between lignin and
polysaccharides of rice straw (Chen et al. 1996). Other fungal species improve the
IVDMD of treated straw (Karunanandaa et al. 1995; Karunanadaa and Varga 1996a,
b; Fazaeli et al. 2006). Karunanandaa et al. (1995) also reported that incubation of
rice straw with 8–10% w/w for 30 days using three white-rot fungi species. Pleurotus
sajor-caju enhanced IVDMD in both rice leaves and stems. However, results
obtained using Cyathus stercoreus gave the highest IVDMD compared to other
fungi species (Karunanandaa et al. 1992). The sequence by which the white-rot
D. Aquino et al.