to degrade the chain of this carbohydrate polymer into sugar monomers via microbial action. Starch is made up of amylose and amylopectin polysaccharides that are
assembled from glucose unit (Madihah et al. 2001). Their relative amount/ratio of
amylose and amylopectin varies with biomass type and source of starch.
Amylose is made up of a long linear polymer consisting of more than a few
thousands of glucose units through an α-1,4 glycosidic bond (de Souza and de
Magalhaes 2010). Amylose contributes to the helical shape of starch polymer
(Minteer 2011). Their content in starch is commonly between 14 and 27%. Amylose
with roughly around 4000 to 340,000 in molecular weight has a hydrophobic inner
surface that acts similarly to the cyclodextrins and able to withstand spiral molecules
of water (Singhal et al. 2008). This is due to the substitution by aromatic molecules
or hydrophobic lipid. Amylopectin appears like a root-like structure as it possesses
α-1,4 linked linear chain consisting of 10–60 glucose units and α-1,6 linked side
chains with 15–45 glucose units. Amylopectin consists of two chains, namely
A-chain and B-chains. The A-chain is generally made of 13–23 residues while
B-chain are composed of 235 residues (Bertoft et al. 2008). There are two fractions
that exist in B-chain which are short and long chains.
Lignocellulosic-based biomass is a plant-based material and its component
consists of three basic structures specifically cellulose, hemicellulose, and lignin
(Balat et al. 2008; Ibrahim et al. 2017). This type of biomass includes wood and
fibrous materials from agricultural wastes, organic sources, organic municipal
wastes, and organic industrial wastes. Recently, this class of biomass have been
abundantly produced by the agricultural industries, which has led to serious environmental problems. In order to overcome this problem, lignocellulosic biomass has
been used as a substrate for biofuel production and to date, it has been recognized as
one of the valuable source. In average, lignocellulosic biomass is composed of
38–50% of cellulose, 23–32% hemicellulose, and 15–25% of lignin (Abd-aziz
2002). The content between cellulose, hemicellulose, and lignin varies between
one plant species to another dependent on age and soil (Table 4.2).
Cellulose is made up of long, linear homopolymers of β-1,4 linked D-glucose
units and forms a crystalline amorphous structure. The rigid cellulose structure
which requires harsh treatment to break down, is caused by the bonded hexoses by
β-1,4 glycosidic bond in linear arrangement (Balat 2011; Saini et al. 2015). Cellulose
can be found in the cell wall of plants, particularly in the stalks, stems, and in all the
Table 4.2 Various biomass with their constituents
Biomass
Cellulose
(%)
Hemicellulose
(%)
Lignin
(%)
References
Sago pith residue
37.0
20.0
6.0
Linggang et al.
(2013)
Oil palm fibre
40.0
39.0
21.0
Hassan et al. (2010)
Wheat straw
27.1
21.1
22.5
Adapa et al. (2011)
Sugarcane
bagasse
41.6
25.1
20.3
Kim and Day (2011)
4 Biobutanol Production from Agricultural Biomass
73
assembled from glucose unit (Madihah et al. 2001). Their relative amount/ratio of
amylose and amylopectin varies with biomass type and source of starch.
Amylose is made up of a long linear polymer consisting of more than a few
thousands of glucose units through an α-1,4 glycosidic bond (de Souza and de
Magalhaes 2010). Amylose contributes to the helical shape of starch polymer
(Minteer 2011). Their content in starch is commonly between 14 and 27%. Amylose
with roughly around 4000 to 340,000 in molecular weight has a hydrophobic inner
surface that acts similarly to the cyclodextrins and able to withstand spiral molecules
of water (Singhal et al. 2008). This is due to the substitution by aromatic molecules
or hydrophobic lipid. Amylopectin appears like a root-like structure as it possesses
α-1,4 linked linear chain consisting of 10–60 glucose units and α-1,6 linked side
chains with 15–45 glucose units. Amylopectin consists of two chains, namely
A-chain and B-chains. The A-chain is generally made of 13–23 residues while
B-chain are composed of 235 residues (Bertoft et al. 2008). There are two fractions
that exist in B-chain which are short and long chains.
Lignocellulosic-based biomass is a plant-based material and its component
consists of three basic structures specifically cellulose, hemicellulose, and lignin
(Balat et al. 2008; Ibrahim et al. 2017). This type of biomass includes wood and
fibrous materials from agricultural wastes, organic sources, organic municipal
wastes, and organic industrial wastes. Recently, this class of biomass have been
abundantly produced by the agricultural industries, which has led to serious environmental problems. In order to overcome this problem, lignocellulosic biomass has
been used as a substrate for biofuel production and to date, it has been recognized as
one of the valuable source. In average, lignocellulosic biomass is composed of
38–50% of cellulose, 23–32% hemicellulose, and 15–25% of lignin (Abd-aziz
2002). The content between cellulose, hemicellulose, and lignin varies between
one plant species to another dependent on age and soil (Table 4.2).
Cellulose is made up of long, linear homopolymers of β-1,4 linked D-glucose
units and forms a crystalline amorphous structure. The rigid cellulose structure
which requires harsh treatment to break down, is caused by the bonded hexoses by
β-1,4 glycosidic bond in linear arrangement (Balat 2011; Saini et al. 2015). Cellulose
can be found in the cell wall of plants, particularly in the stalks, stems, and in all the
Table 4.2 Various biomass with their constituents
Biomass
Cellulose
(%)
Hemicellulose
(%)
Lignin
(%)
References
Sago pith residue
37.0
20.0
6.0
Linggang et al.
(2013)
Oil palm fibre
40.0
39.0
21.0
Hassan et al. (2010)
Wheat straw
27.1
21.1
22.5
Adapa et al. (2011)
Sugarcane
bagasse
41.6
25.1
20.3
Kim and Day (2011)
4 Biobutanol Production from Agricultural Biomass
73