THESIS

Table 8 Characteristics of enzyme β-amylase (E.C. 3.2, 1.2)
Origin of Enzyme Molecular weight pH Optimum Temperature Optimum
Plant - Barley 56,000 5.2 -
Microbial
( o C)
- Wheat 64,200 5.2-6.2 55
- Soya 57,000 5.4 55
- Sweet potato 50,000 5.6 50-55
- Bacillus cereus
- B. polymyxa
- B. megaterium
Source: Ray and Nanda (1996)
58,000
42,000
58,000
7.0
7.5
6.5
4.1.2 Enzymes specific for the α-(1,6) linkage
40
40
40-50
Debranching enzymes specifically hydrolyze alpha-(1,6) linkages of
branched α-glucan (amylopectin, glycogen) and their degradation products. They are
present essentially in higher plants and microorganisms, where they play an important
role in the total hydrolysis of starch. These enzymes are divided into two groups,
based on their action pattern (Fogarty, 1983). Enzymes that can directly hydrolyze α-
(1,6) linkages of native amylopectin and glycogen. This group includes the
pullulanases (glycogen 6-glucanohydrolase, E.C. 3.2.1.41) and the isoamylases
(glycogen 6-glucanohydrolase, E.C. 3.2.1.68), which are distinguished by their
respective aptitudes to hydrolyze pullulan (poly α-(1,6)-maltotriose) and glycogen.
These enzymes are produced exclusively by microorganisms. More recently, a
pullulanase derived from Bacillus acidopullulyticus has been found to be sufficiently
stable for use at 60 o C and the enzyme has been commercialized. The use of this
enzyme in saccharification provides an increase in dextrose yield of 0.5 to 1.5%
(Jensen and Norman, 1984).
51