and other industrial areas. To provide the bioconversion of starch, a variety of
enzyme combinations are required. These combinations consist of α-amylase,
β-amylase, glucoamylase, isoamylase, and pullulanase (Haki and Rakshit 2003).
Some microorganisms that biosynthesize amylase (Somda et al. 2011; de Barros
Ranke 2020) and pullulanase (Awg-Adeni et al. 2013; Orhan et al. 2014) are
indicated in Fig. 9.6.
9.4.2.1 α-Amylases (EC 3.2.1.1)
α-amylases are extracellular enzymes also known as α-1,4-glucan-4glucanohydrolase or glycogenase (Cherry et al. 2004). The members of
α-amylases are in GH families of 13, 57, and 119 (Elleuche and Antranikian
2013). This endo-acting amylolytic enzyme produces some oligosaccharides such
as maltose, maltotriose, and dextrins by randomly hydrolyzing the α-1,4 linkages of
starch and similar long-chain carbohydrates (Sivaramakrishnan et al. 2006;
Amoozegar et al. 2019).
Microbial α-amylases are the most preferred among the industrial α-amylases
(De Souza 2010; Zhang et al. 2017).
9.4.2.2 β-Amylases (EC 3.2.1.2)
β-amylases are known as α-1,4-D-glucan maltohydrolase or saccharogen amylase.
They are exo-acting enzymes that allow the constitution of β-maltose by hydrolyzing
the second α-1,4 glycosidic linkage at the non-reducing end of the starch. All the
known isozymes are in GH14 family (Vaidya et al. 2015; Saini et al. 2017) with the
exception of ß-amylase [GH57] from Pyrococcus furiosus (Elleuche and
Antranikian 2013).
9.4.2.3 Glucoamylases (EC 3.2.1.3)
Glucoamylases are also named γ-amylase, amyloglucosidase, and glucan
1,4-α-glucosidase. It enables the formation of the glucose units by hydrolyzing the
α-1,4 glycosidic links at the non-reducing ends in the amylose and amylopectin. At
the same time, they also hydrolyze α-1,6 glycosidic links, and they produce glucose
as the final product (Xu et al. 2016; Saini et al. 2017). Seldomly, they hydrolyze
α-1,3 glycosidic linkages (Kumar and Satyanarayana 2009).
These enzymes are categorized in GH15 family (Bourne and Henrissat 2001).
Apart from the other amylase forms (α-amylase, β-amylase), glucoamylases are very
active and stable in acidic environments (Saini et al. 2017).
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277
enzyme combinations are required. These combinations consist of α-amylase,
β-amylase, glucoamylase, isoamylase, and pullulanase (Haki and Rakshit 2003).
Some microorganisms that biosynthesize amylase (Somda et al. 2011; de Barros
Ranke 2020) and pullulanase (Awg-Adeni et al. 2013; Orhan et al. 2014) are
indicated in Fig. 9.6.
9.4.2.1 α-Amylases (EC 3.2.1.1)
α-amylases are extracellular enzymes also known as α-1,4-glucan-4glucanohydrolase or glycogenase (Cherry et al. 2004). The members of
α-amylases are in GH families of 13, 57, and 119 (Elleuche and Antranikian
2013). This endo-acting amylolytic enzyme produces some oligosaccharides such
as maltose, maltotriose, and dextrins by randomly hydrolyzing the α-1,4 linkages of
starch and similar long-chain carbohydrates (Sivaramakrishnan et al. 2006;
Amoozegar et al. 2019).
Microbial α-amylases are the most preferred among the industrial α-amylases
(De Souza 2010; Zhang et al. 2017).
9.4.2.2 β-Amylases (EC 3.2.1.2)
β-amylases are known as α-1,4-D-glucan maltohydrolase or saccharogen amylase.
They are exo-acting enzymes that allow the constitution of β-maltose by hydrolyzing
the second α-1,4 glycosidic linkage at the non-reducing end of the starch. All the
known isozymes are in GH14 family (Vaidya et al. 2015; Saini et al. 2017) with the
exception of ß-amylase [GH57] from Pyrococcus furiosus (Elleuche and
Antranikian 2013).
9.4.2.3 Glucoamylases (EC 3.2.1.3)
Glucoamylases are also named γ-amylase, amyloglucosidase, and glucan
1,4-α-glucosidase. It enables the formation of the glucose units by hydrolyzing the
α-1,4 glycosidic links at the non-reducing ends in the amylose and amylopectin. At
the same time, they also hydrolyze α-1,6 glycosidic links, and they produce glucose
as the final product (Xu et al. 2016; Saini et al. 2017). Seldomly, they hydrolyze
α-1,3 glycosidic linkages (Kumar and Satyanarayana 2009).
These enzymes are categorized in GH15 family (Bourne and Henrissat 2001).
Apart from the other amylase forms (α-amylase, β-amylase), glucoamylases are very
active and stable in acidic environments (Saini et al. 2017).
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277