4 Biotechnological Application of Alkaline-Active
Starch-Modifying Enzymes
Alkaline-active starch-modifying enzymes have a diverse range of properties in
terms of reaction conditions for activity, substrate and product specificity. For
instance, they act on starch, amylose, amylopectin and pullulan to produce a wide
range of products including glucose, maltose, maltooligosaccharides, cyclodextrins
and branched dextrins. The optimum temperature of activity of these enzymes varies
from moderate to high, while others are stable in the presence of various additives.
These properties make these enzymes promising in industrial applications.
4.1 Detergent Industry
Detergents have been formulated to contain enzymes in order to enhance their
performance in the removal of tough stains and also make the detergents environment friendly. Amylases are the second most important enzymes used in detergent
industries, and about 90% of all liquid detergents are containing these enzymes
[9, 10, 19]. The enzymes in the detergents aid in degrading starchy food residues
from potato, custard, gravies, chocolate and so forth to dextrins and other smaller
oligosaccharides, thereby facilitating dirt removal [20, 21]. Amylases from
alkaliphiles that are active at lower temperatures and alkaline conditions are most
suited for this application. In addition, they are also required to be stable against
chelating agents, surfactants and the prevailing oxidizing washing environment
[13, 22]. As metalloenzymes, most α-amylases contain at least one calcium ion per
enzyme molecule, which is essential for activity and stability [23]. The amount of
bound calcium may vary from one to about ten [6, 24]. As such, these enzymes
are generally inhibited by chelating agents such as zeolites, EDTA and EGTA
[25]. Several amylases from alkaliphiles have been reported to exhibit stability
under these conditions, including stability in the presence of ionic and non-ionic
surfactants such as sodium dodecyl sulphate, Triton X-100 and Tween 20 as
well as in the presence of EDTA and oxidizing agents such as hydrogen peroxide
and sodium perborate. These amylases are from Bacillus licheniformis MTCC1483
[26], Bacillus licheniformis NH1 [9], thermophilic Bacillus sp. A3-15 [27],
Bacillus sp. PN 5 [28], Bacillus sp. ANT-6 [29], Bacillus sp. TS-23 [30], Bacillus
sp. KSM-1378 [31], Bacillus sp. L1711 [32] and Bacillus sp. KSM-K38, which were
found to have remarkable properties such as stability in the presence of up to
100 mM EDTA and EGTA and excess (1.8 M) of H 2 O 2 [25].
Alkaline-active debranching enzymes in combination with α-amylases have been
proposed to be very effective for the removal of starch stains [33]. This is because
these enzymes can catalyse hydrolysis of both α-1-6 and α-1-4 bonds in starch,
thereby complementing the α-amylase activity and enhancing the efficiency of
breakdown of starch-based stains. Alkaline-active debranching enzymes that have
been described include alkaline-active pullulanases from Bacillus sp. 202-1 [34],
Starch-Modifying Enzymes
227
Starch-Modifying Enzymes
Alkaline-active starch-modifying enzymes have a diverse range of properties in
terms of reaction conditions for activity, substrate and product specificity. For
instance, they act on starch, amylose, amylopectin and pullulan to produce a wide
range of products including glucose, maltose, maltooligosaccharides, cyclodextrins
and branched dextrins. The optimum temperature of activity of these enzymes varies
from moderate to high, while others are stable in the presence of various additives.
These properties make these enzymes promising in industrial applications.
4.1 Detergent Industry
Detergents have been formulated to contain enzymes in order to enhance their
performance in the removal of tough stains and also make the detergents environment friendly. Amylases are the second most important enzymes used in detergent
industries, and about 90% of all liquid detergents are containing these enzymes
[9, 10, 19]. The enzymes in the detergents aid in degrading starchy food residues
from potato, custard, gravies, chocolate and so forth to dextrins and other smaller
oligosaccharides, thereby facilitating dirt removal [20, 21]. Amylases from
alkaliphiles that are active at lower temperatures and alkaline conditions are most
suited for this application. In addition, they are also required to be stable against
chelating agents, surfactants and the prevailing oxidizing washing environment
[13, 22]. As metalloenzymes, most α-amylases contain at least one calcium ion per
enzyme molecule, which is essential for activity and stability [23]. The amount of
bound calcium may vary from one to about ten [6, 24]. As such, these enzymes
are generally inhibited by chelating agents such as zeolites, EDTA and EGTA
[25]. Several amylases from alkaliphiles have been reported to exhibit stability
under these conditions, including stability in the presence of ionic and non-ionic
surfactants such as sodium dodecyl sulphate, Triton X-100 and Tween 20 as
well as in the presence of EDTA and oxidizing agents such as hydrogen peroxide
and sodium perborate. These amylases are from Bacillus licheniformis MTCC1483
[26], Bacillus licheniformis NH1 [9], thermophilic Bacillus sp. A3-15 [27],
Bacillus sp. PN 5 [28], Bacillus sp. ANT-6 [29], Bacillus sp. TS-23 [30], Bacillus
sp. KSM-1378 [31], Bacillus sp. L1711 [32] and Bacillus sp. KSM-K38, which were
found to have remarkable properties such as stability in the presence of up to
100 mM EDTA and EGTA and excess (1.8 M) of H 2 O 2 [25].
Alkaline-active debranching enzymes in combination with α-amylases have been
proposed to be very effective for the removal of starch stains [33]. This is because
these enzymes can catalyse hydrolysis of both α-1-6 and α-1-4 bonds in starch,
thereby complementing the α-amylase activity and enhancing the efficiency of
breakdown of starch-based stains. Alkaline-active debranching enzymes that have
been described include alkaline-active pullulanases from Bacillus sp. 202-1 [34],
Starch-Modifying Enzymes
227