171
p-menthen-8-thiol is also found responsible for pineapple and grapefruit types of
flavors, respectively. However, the role of sulfur-containing compounds in imparting smell to dried shiitake mushroom is not established (Nishikawa et al. 1967;
Wada et al. 1967a, b; Yasumoto et al. 1971; Hiraide et al. 2004).
The carbohydrates and glycoproteins of shiitake mushroom such as lentinan and
LEM and LAP are very good source of nutrition. The lentinans are polysaccharides
[(C 6 H 10 O 5 )n] of high molecular weight 5 × 10
5
Da present in the cell wall of fruiting
bodies. It is soluble in water and free from phosphorus and sulfur. It is present as a
triple helix structure which is composed of glucose molecules linked to branched
backbone via β-(1-3)-linkages and β-(1-6)-glucose side chain (Wasser and Weis
1997; Wasser 2002). The structural orientation of glucose moieties in a helix is
known to play important biological and pharmacological roles (Mizuno 1999). The
other biological molecules known as glycoproteins such as L. edodes mycelia
(LEM) and LAP have been obtained from mushroom mycelia and culture media,
respectively. The LEM contains nucleic acid derivatives, vitamin B and ergosterol
compounds and is found to have an antitumor activity. The immune-active molecule
EP3 has been obtained from LEM fractionation (Suzuki et al. 1990). The other peptide–polysaccharide-based complex known as KS-2-α-mannan peptide KS-2 has
been obtained from the extraction of L. edodes mushroom upon treatment with hot
water and precipitation with ethanol. It is found effective against Sarcoma 180 and
Ehrlich’s carcinoma (Fujii et al. 1978). The other molecule known as eritadenine, a
secondary metabolite isolated from L. edodes mycelia (400–700 mg/kg of dry matter), is identified for its role in lowering cholesterol level (Chibata et al. 1969). It
was formerly assigned as lentinacin (Chibata et al. 1969) and lentysine (Kamiya
et al. 1969; Rokujo et al. 1970; Saito et al. 1975). Additionally, sugars such as trehalose, arabitol, glycerol, mannose, mannitol, and arabinose have been reported.
The water-soluble material dietary fibers composed of β-glucan and protein along
with heteropolysaccharides, lignin and chitin, are also reported in the cell wall
(Bisen et al. 2010).
10.5 Genome Organization and Gene Mining for Unique
Aroma of Shiitake and Shelf-Life Enhancement
The genome of monokaryotic L. edodes sequenced on Illumina HiSeq 2000 and
2500 platform is 41.8–46.1 Mb in size. The complete genome encodes 13,028–14,889
predicted genes (Chen et al. 2016; Shim et al. 2016). Of these, only 11.5% of the
depicted proteins in L. edodes are found to share orthologs with other fungal species, whereas about 22% of the proteins were unique to L. edodes (Chen et al. 2016;
Shim et al. 2016). The enzymes γ-glutamyl transpeptidase and C-S lyase are
involved in the formation of lenthionine; a main volatile flavor is produced from
lentinic acid (a γ-L-glutamyl-cysteine sulfoxide precursor) (Chen et al. 2016). The
enzymes γ-glutamyl transpeptidase and C-S lyase are involved in the formation of
10 Recent Developments in Shiitake Mushrooms and Their Nutraceutical Importance
p-menthen-8-thiol is also found responsible for pineapple and grapefruit types of
flavors, respectively. However, the role of sulfur-containing compounds in imparting smell to dried shiitake mushroom is not established (Nishikawa et al. 1967;
Wada et al. 1967a, b; Yasumoto et al. 1971; Hiraide et al. 2004).
The carbohydrates and glycoproteins of shiitake mushroom such as lentinan and
LEM and LAP are very good source of nutrition. The lentinans are polysaccharides
[(C 6 H 10 O 5 )n] of high molecular weight 5 × 10
5
Da present in the cell wall of fruiting
bodies. It is soluble in water and free from phosphorus and sulfur. It is present as a
triple helix structure which is composed of glucose molecules linked to branched
backbone via β-(1-3)-linkages and β-(1-6)-glucose side chain (Wasser and Weis
1997; Wasser 2002). The structural orientation of glucose moieties in a helix is
known to play important biological and pharmacological roles (Mizuno 1999). The
other biological molecules known as glycoproteins such as L. edodes mycelia
(LEM) and LAP have been obtained from mushroom mycelia and culture media,
respectively. The LEM contains nucleic acid derivatives, vitamin B and ergosterol
compounds and is found to have an antitumor activity. The immune-active molecule
EP3 has been obtained from LEM fractionation (Suzuki et al. 1990). The other peptide–polysaccharide-based complex known as KS-2-α-mannan peptide KS-2 has
been obtained from the extraction of L. edodes mushroom upon treatment with hot
water and precipitation with ethanol. It is found effective against Sarcoma 180 and
Ehrlich’s carcinoma (Fujii et al. 1978). The other molecule known as eritadenine, a
secondary metabolite isolated from L. edodes mycelia (400–700 mg/kg of dry matter), is identified for its role in lowering cholesterol level (Chibata et al. 1969). It
was formerly assigned as lentinacin (Chibata et al. 1969) and lentysine (Kamiya
et al. 1969; Rokujo et al. 1970; Saito et al. 1975). Additionally, sugars such as trehalose, arabitol, glycerol, mannose, mannitol, and arabinose have been reported.
The water-soluble material dietary fibers composed of β-glucan and protein along
with heteropolysaccharides, lignin and chitin, are also reported in the cell wall
(Bisen et al. 2010).
10.5 Genome Organization and Gene Mining for Unique
Aroma of Shiitake and Shelf-Life Enhancement
The genome of monokaryotic L. edodes sequenced on Illumina HiSeq 2000 and
2500 platform is 41.8–46.1 Mb in size. The complete genome encodes 13,028–14,889
predicted genes (Chen et al. 2016; Shim et al. 2016). Of these, only 11.5% of the
depicted proteins in L. edodes are found to share orthologs with other fungal species, whereas about 22% of the proteins were unique to L. edodes (Chen et al. 2016;
Shim et al. 2016). The enzymes γ-glutamyl transpeptidase and C-S lyase are
involved in the formation of lenthionine; a main volatile flavor is produced from
lentinic acid (a γ-L-glutamyl-cysteine sulfoxide precursor) (Chen et al. 2016). The
enzymes γ-glutamyl transpeptidase and C-S lyase are involved in the formation of
10 Recent Developments in Shiitake Mushrooms and Their Nutraceutical Importance