saccharide between soils under different land management regimes. As a result, we
suggest that forest soils have accumulated more abundantly microbe-derived polysaccharides than plant-derived ones in comparison to non-forest soil. Finally, considering ectomycorrhrizal (ECM) fungal sclerotia, a type of microbial biomass
typical of forest soils as a source of microbial polysaccharides, we discuss how
sclerotia contribute to forest soil polysaccharides based on a recent study by Sugiura
et al. (2017).
6.2 Determination of Neutral Saccharides in Soil, and Data
Collection
6.2.1 Methods for Neutral Saccharide Determination of Soil
and Plant Materials
The release of neutral sugars from soil polysaccharides depends on the hydolytic
conditions, the nature and concentration of the acid used, and temperature and
heating time (Oades et al. 1970; Cheshire 1979). For example, pentose is more
labile to sulfuric acid than hexose (Oades et al. 1970; Cheshire 1979). Pretreatment
such as soaking soil with strong sulfuric acid at room temperature for hydrolysis
poses a considerable risk of underestimating the total saccharide content (Oades
et al. 1970). Therefore we collected data obtained by the same hydrolysis procedure
of Oades et al. (1970) to compare content and composition of neutral saccharides
between different soils. Neutral saccharides of plant materials were also analyzed by
the same hydrolysis procedure of soil analysis, unless otherwise noted.
The hydrolysis procedure is briefly as follows: Soil and plant material samples
were refluxed for 20 min in a glycerin/oil bath with 2.5 mol L
À1 H 2 SO 4 solution
(primary hydrolysis). The air-dried residues of primary hydrolysis were soaked for
16 h at a room temperature in 13 mol L
À1 H 2 SO 4 and refluxed for 5 h after addition
of water to being the concentration to 0.5 mol L
À1 H 2 SO 4 (secondary hydrolysis).
Qualitative and quantitative determination of released sugar monomer was carried
out by gas-liquid chromatography of alditol acetate derivatives using myo-inoshitol
as an internal standard (Oades et al. 1970; Cheshire et al. 1973), unless otherwise
noted.
The sugars in the primary and secondary hydrolysates are designated as easily
hydrolysable saccharides (EH-saccharides or EH-glucose for glucose) and as
non-easily hydrolysable saccharides (NEH-saccharides or NEH-glucose), respectively. EH-saccharides and NEH-saccharides are equivalent in hydrolysability to
non-cellulosic or hemicellulosic saccharides, and to cellulosic saccharides, respectively, in the analysis of soil and plant materials (Oades et al. 1970; Murayama 1980,
1984a). We avoid here to use the terms hemicellulosic (or non-cellulosic) or
cellulosic, as these terms refer originally to plant polysaccharides, even when we
refer to saccharides of plant materials.
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S. Murayama and Y. Sugiura
suggest that forest soils have accumulated more abundantly microbe-derived polysaccharides than plant-derived ones in comparison to non-forest soil. Finally, considering ectomycorrhrizal (ECM) fungal sclerotia, a type of microbial biomass
typical of forest soils as a source of microbial polysaccharides, we discuss how
sclerotia contribute to forest soil polysaccharides based on a recent study by Sugiura
et al. (2017).
6.2 Determination of Neutral Saccharides in Soil, and Data
Collection
6.2.1 Methods for Neutral Saccharide Determination of Soil
and Plant Materials
The release of neutral sugars from soil polysaccharides depends on the hydolytic
conditions, the nature and concentration of the acid used, and temperature and
heating time (Oades et al. 1970; Cheshire 1979). For example, pentose is more
labile to sulfuric acid than hexose (Oades et al. 1970; Cheshire 1979). Pretreatment
such as soaking soil with strong sulfuric acid at room temperature for hydrolysis
poses a considerable risk of underestimating the total saccharide content (Oades
et al. 1970). Therefore we collected data obtained by the same hydrolysis procedure
of Oades et al. (1970) to compare content and composition of neutral saccharides
between different soils. Neutral saccharides of plant materials were also analyzed by
the same hydrolysis procedure of soil analysis, unless otherwise noted.
The hydrolysis procedure is briefly as follows: Soil and plant material samples
were refluxed for 20 min in a glycerin/oil bath with 2.5 mol L
À1 H 2 SO 4 solution
(primary hydrolysis). The air-dried residues of primary hydrolysis were soaked for
16 h at a room temperature in 13 mol L
À1 H 2 SO 4 and refluxed for 5 h after addition
of water to being the concentration to 0.5 mol L
À1 H 2 SO 4 (secondary hydrolysis).
Qualitative and quantitative determination of released sugar monomer was carried
out by gas-liquid chromatography of alditol acetate derivatives using myo-inoshitol
as an internal standard (Oades et al. 1970; Cheshire et al. 1973), unless otherwise
noted.
The sugars in the primary and secondary hydrolysates are designated as easily
hydrolysable saccharides (EH-saccharides or EH-glucose for glucose) and as
non-easily hydrolysable saccharides (NEH-saccharides or NEH-glucose), respectively. EH-saccharides and NEH-saccharides are equivalent in hydrolysability to
non-cellulosic or hemicellulosic saccharides, and to cellulosic saccharides, respectively, in the analysis of soil and plant materials (Oades et al. 1970; Murayama 1980,
1984a). We avoid here to use the terms hemicellulosic (or non-cellulosic) or
cellulosic, as these terms refer originally to plant polysaccharides, even when we
refer to saccharides of plant materials.
94
S. Murayama and Y. Sugiura