86
1
General Principles
11 Properties and Occurrence of D-Fructose in Polysaccharides
Polysaccharides that exclusively contain D-fructose are known as fructans and there are two
known kinds, inulin and levan. Inulin is a polysaccharide containing β-D-fructofuranose linked
(2→1) [118]. Inulins are found in the roots and tubers of the family of plants known as the
Compositae, which includes asters, dandelions, dahlias, cosmos, burdock, goldenrod, chicory,
lettuce, and Jerusalem artichokes. Other sources are from the Liliacae family, which includes
lily bulbs, onion, hyacinth, and tulip bulbs. Inulins are also produced by certain species of
algae [119]. Several bacterial strains of Streptococcus mutans also produce an extracellular
inulin from sucrose [120].
Levan is a polysaccharide containing β-D-fructofuranose residues linked (2→6) with (2→1)
branch linkages. They are primarily found in grasses [119] and are produced extracellularly
by several bacterial strains of Bacillus subtilis, Aerobacter levanicum (syn. Erwinia herbicola) [121], and Streptococcus salivarius [122]. They are of higher molecular weight than the
inulins, having 100–200 D-fructofuranose residues per molecule. The branch chains are relatively short, containing 2–4 D-fructofuranose residues.
12 Properties and Occurrence of Sugar Alcohols
12.1 Glycerol
When aldoses or ketoses are reduced, sugar alcohols are formed. For example, glycerol is
a simple, three carbon sugar alcohol, formed by the reduction of glyceraldehydes. It is found
as a major component in two types of lipids, triacylglycerol (triglyceride fats and oils) and
phospholipids. In the former, the three hydroxyl groups of glycerol are esterified by fatty
acids. In the latter, glycerol is esterified by two fatty acids at the first two carbons and by
phosphoric acid at the third carbon. The phosphoric acid is further esterified by the hydroxy
groups of ethanolamine, N,N,N-trimethyl ethanolamine (choline), or by the hydroxy group of
L-serine. The triglycerides make up the well-known fat deposits found in adipose tissue and
the phospholipids are major components found in the lipid bilayers of membranes of cells and
organelles and play important roles in nerve transmission. Glycerol is also a common component in the teichoic acids (see > Sect. 12.3).
Free glycerol is obtained from the saponification of fats and oils. It is a slightly sweet, highly
water-soluble liquid. It has the ability to absorb water, making it a valuable humectant and an
emollient for skin conditioners. It is also used as a plasticizer in the formation of polymeric
materials and is used in the manufacture of pharmaceuticals and the explosive, trinitroglycerine.
12.2 Properties and Occurrence of Free Sugar Alcohols,
D-Glucitol, D-Mannitol, Ribitol, Xylitol, and D-Arabinitol
D-glucose can be reduced either chemically or enzymatically to give D-glucitol (frequently
called D-sorbitol). It was first obtained from the fresh juice of the berries of the mountain
ash [123]. D-Glucitol occurs widely in plants, being found in algae and higher plants. It is
especially prevalent in red seaweed, where it occurs to the extent of 10–14% by weight [124]
1
General Principles
11 Properties and Occurrence of D-Fructose in Polysaccharides
Polysaccharides that exclusively contain D-fructose are known as fructans and there are two
known kinds, inulin and levan. Inulin is a polysaccharide containing β-D-fructofuranose linked
(2→1) [118]. Inulins are found in the roots and tubers of the family of plants known as the
Compositae, which includes asters, dandelions, dahlias, cosmos, burdock, goldenrod, chicory,
lettuce, and Jerusalem artichokes. Other sources are from the Liliacae family, which includes
lily bulbs, onion, hyacinth, and tulip bulbs. Inulins are also produced by certain species of
algae [119]. Several bacterial strains of Streptococcus mutans also produce an extracellular
inulin from sucrose [120].
Levan is a polysaccharide containing β-D-fructofuranose residues linked (2→6) with (2→1)
branch linkages. They are primarily found in grasses [119] and are produced extracellularly
by several bacterial strains of Bacillus subtilis, Aerobacter levanicum (syn. Erwinia herbicola) [121], and Streptococcus salivarius [122]. They are of higher molecular weight than the
inulins, having 100–200 D-fructofuranose residues per molecule. The branch chains are relatively short, containing 2–4 D-fructofuranose residues.
12 Properties and Occurrence of Sugar Alcohols
12.1 Glycerol
When aldoses or ketoses are reduced, sugar alcohols are formed. For example, glycerol is
a simple, three carbon sugar alcohol, formed by the reduction of glyceraldehydes. It is found
as a major component in two types of lipids, triacylglycerol (triglyceride fats and oils) and
phospholipids. In the former, the three hydroxyl groups of glycerol are esterified by fatty
acids. In the latter, glycerol is esterified by two fatty acids at the first two carbons and by
phosphoric acid at the third carbon. The phosphoric acid is further esterified by the hydroxy
groups of ethanolamine, N,N,N-trimethyl ethanolamine (choline), or by the hydroxy group of
L-serine. The triglycerides make up the well-known fat deposits found in adipose tissue and
the phospholipids are major components found in the lipid bilayers of membranes of cells and
organelles and play important roles in nerve transmission. Glycerol is also a common component in the teichoic acids (see > Sect. 12.3).
Free glycerol is obtained from the saponification of fats and oils. It is a slightly sweet, highly
water-soluble liquid. It has the ability to absorb water, making it a valuable humectant and an
emollient for skin conditioners. It is also used as a plasticizer in the formation of polymeric
materials and is used in the manufacture of pharmaceuticals and the explosive, trinitroglycerine.
12.2 Properties and Occurrence of Free Sugar Alcohols,
D-Glucitol, D-Mannitol, Ribitol, Xylitol, and D-Arabinitol
D-glucose can be reduced either chemically or enzymatically to give D-glucitol (frequently
called D-sorbitol). It was first obtained from the fresh juice of the berries of the mountain
ash [123]. D-Glucitol occurs widely in plants, being found in algae and higher plants. It is
especially prevalent in red seaweed, where it occurs to the extent of 10–14% by weight [124]