70
1
General Principles
relatively labile and is hydrolyzed by mild acid (pH 4) and is the donor of D-glucopyranose
for the biosynthesis of dextrans and related polysaccharides by glucansucrases and the donor
of D-fructofruanose for the biosynthesis of levan and inulin (see > Sect. 11), fructofuranose
polysaccharides by levansucrase and inulinsucrase; (c) it is the sugar of commerce because of
the ease of obtaining it in large quantities in a pure state from sugar cane and sugar beets; (d) it
crystallizes relatively easily; and (e) it has a pleasant sweet taste and has been recognized by
humans for over 10,000 years as a sweet food and a natural sweetening agent. See > Fig. 5 for
the structure of sucrose.
The origin of sucrose is thought to have been in the Indus Valley, where many woody, wild
sugar cane plants that have the fundamental characteristics of the modern cultivated strains can
still be found growing today. Sugar cane grows well in a warm, humid, tropical or semi-tropical
climate. In the late 18th century on the European continent, the sugar beet was found to be an
alternative source of sucrose that did not require a tropical or semi-tropical climate for growth.
Sucrose is hydrolyzed into its component sugars (D-glucose and D-fructose) by the action of
the enzyme, invertase, a β-fructofuranosidase, and by mild acid. In this form it is known as
invert sugar, due to the fact that the direction of rotation of polarized light is inverted from
dextrorotatory to levorotatory on hydrolysis. Honey is usually a mixture of sucrose and invert
sugar. Yeasts also have invertase and can hydrolyze sucrose and then ferment the component
sugars into ethyl alcohol.
In addition to sucrose, several plants also form a series of sucrose-based oligosaccharides with
chains of α-1→6 D-galactopyranose units linked to the D-glucose moiety of sucrose [4]. The
first in the series is the trisaccharide, raffinose, in which D-galactopyranose is linked α-(1→6)
to sucrose; the second is a tetrasaccharide, stachyose, in which D-galactopyranose is linked α(1→6) to the D-galactopyranose unit of raffinose. The next is a pentasaccharide, verbascose,
with D-galactopyranose linked α-(1→6) to the terminal D-galactose unit of stachyose, and the
next is a hexasaccharides, ajugose, with D-galactopyranose linked α-(1→6) to the terminal
D-galactose unit of verbascose.
These D-galactopyranosyl sucrose oligosaccharides are particularly found in the tubers and
seeds of legumes. Raffinose is found in cottonseeds and in sugar beets. Although sugar beets
only contain about 0.05% by weight raffinose as compared with 16–18% sucrose, it has been
isolated and crystallized with a purity of better than 99% from sugar beet syrup, where it
accumulates during the processing of sucrose.
Soybeans are a good source of stachyose, where it is found to the extent of 2–3% by weight.
In general, legume seeds and the mullein root are sources of verbascose. The enzyme invertase
and mild acid specifically hydrolyze the oligosaccharides to give D-fructose and the corresponding reducing oligosaccharides that are terminated at the reducing-end with D-glucose.
For example, raffinose is hydrolyzed to give D-fructose and the reducing disaccharide, melibiose [α-D-galactopyranosyl-(1→6)-D-glucose].
Another series of galacto-sucrose oligosaccharides involves the attachment to the D-fructofuranose moiety of sucrose [4]. The attachment of α-D-galactopyranose 1→6 to the fructose moiety gives the nonreducing trisaccharide, planteose. It is found primarily in the
seeds of the Plantago family of plants, for example, the common weed and herb, plantain. Mild acid hydrolysis gives D-glucose and the reducing keto-disaccharide, planteobiose
[α-D-galactopyranosyl-(1→6)-D-fructose]. Another nonreducing trisaccharide, melezitose,
has α-D-glucopyranosyl linked (1→3) to the D-fructofuranose moiety of sucrose. It is found
1
General Principles
relatively labile and is hydrolyzed by mild acid (pH 4) and is the donor of D-glucopyranose
for the biosynthesis of dextrans and related polysaccharides by glucansucrases and the donor
of D-fructofruanose for the biosynthesis of levan and inulin (see > Sect. 11), fructofuranose
polysaccharides by levansucrase and inulinsucrase; (c) it is the sugar of commerce because of
the ease of obtaining it in large quantities in a pure state from sugar cane and sugar beets; (d) it
crystallizes relatively easily; and (e) it has a pleasant sweet taste and has been recognized by
humans for over 10,000 years as a sweet food and a natural sweetening agent. See > Fig. 5 for
the structure of sucrose.
The origin of sucrose is thought to have been in the Indus Valley, where many woody, wild
sugar cane plants that have the fundamental characteristics of the modern cultivated strains can
still be found growing today. Sugar cane grows well in a warm, humid, tropical or semi-tropical
climate. In the late 18th century on the European continent, the sugar beet was found to be an
alternative source of sucrose that did not require a tropical or semi-tropical climate for growth.
Sucrose is hydrolyzed into its component sugars (D-glucose and D-fructose) by the action of
the enzyme, invertase, a β-fructofuranosidase, and by mild acid. In this form it is known as
invert sugar, due to the fact that the direction of rotation of polarized light is inverted from
dextrorotatory to levorotatory on hydrolysis. Honey is usually a mixture of sucrose and invert
sugar. Yeasts also have invertase and can hydrolyze sucrose and then ferment the component
sugars into ethyl alcohol.
In addition to sucrose, several plants also form a series of sucrose-based oligosaccharides with
chains of α-1→6 D-galactopyranose units linked to the D-glucose moiety of sucrose [4]. The
first in the series is the trisaccharide, raffinose, in which D-galactopyranose is linked α-(1→6)
to sucrose; the second is a tetrasaccharide, stachyose, in which D-galactopyranose is linked α(1→6) to the D-galactopyranose unit of raffinose. The next is a pentasaccharide, verbascose,
with D-galactopyranose linked α-(1→6) to the terminal D-galactose unit of stachyose, and the
next is a hexasaccharides, ajugose, with D-galactopyranose linked α-(1→6) to the terminal
D-galactose unit of verbascose.
These D-galactopyranosyl sucrose oligosaccharides are particularly found in the tubers and
seeds of legumes. Raffinose is found in cottonseeds and in sugar beets. Although sugar beets
only contain about 0.05% by weight raffinose as compared with 16–18% sucrose, it has been
isolated and crystallized with a purity of better than 99% from sugar beet syrup, where it
accumulates during the processing of sucrose.
Soybeans are a good source of stachyose, where it is found to the extent of 2–3% by weight.
In general, legume seeds and the mullein root are sources of verbascose. The enzyme invertase
and mild acid specifically hydrolyze the oligosaccharides to give D-fructose and the corresponding reducing oligosaccharides that are terminated at the reducing-end with D-glucose.
For example, raffinose is hydrolyzed to give D-fructose and the reducing disaccharide, melibiose [α-D-galactopyranosyl-(1→6)-D-glucose].
Another series of galacto-sucrose oligosaccharides involves the attachment to the D-fructofuranose moiety of sucrose [4]. The attachment of α-D-galactopyranose 1→6 to the fructose moiety gives the nonreducing trisaccharide, planteose. It is found primarily in the
seeds of the Plantago family of plants, for example, the common weed and herb, plantain. Mild acid hydrolysis gives D-glucose and the reducing keto-disaccharide, planteobiose
[α-D-galactopyranosyl-(1→6)-D-fructose]. Another nonreducing trisaccharide, melezitose,
has α-D-glucopyranosyl linked (1→3) to the D-fructofuranose moiety of sucrose. It is found