Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
emulsifiers in food, pharmaceutical, and cosmetics production, are synthesized by
lipases in organic media, from the fatty acids and mono- or disacharides. An increase
in the degree of polymerization of carbohydrate moieties is achieved in the second
step by using the CGTase preparation, and cyclodextrins, maltooligosaccharides, or
starch as donors.
CGTases and other transglycosylating enzymes of the α-amylase family also
synthesize cyclic molecules of cycloamyloses consisting of over 20 glucose residues.
31 A low yield of synthesis, required low concentration of high-molecularweight
amylose, and high concentration of the enzymes make the larger-scale production
of cycloamyloses economically not feasible.
10.4.1.6 Trehalose
Trehalose, a nonreducing disaccharide, containing two α-1,1-linked glucose residues,
plays an important role in nature and in food, pharmaceutical, and cosmetics
industries, and in tissue engineering (cryopreservation of mammalian cells). The
enzymatic conversion of dextrins to trehalose is more profitable than its extraction
from plants and bakery yeast. The enzymatic process involves concerted action of
an isomerase called malto-oligosyltrehalose synthase (MTS) with malto-oligosyltrehalose
trehalohydrolase (MTH). 33 The first of those biocatalysts (MTS) converts the
first α-1,4 glycosidic linkage from the reducing end of the dextrin to the α-1,1 bond.
This conformational alteration in the sugar molecule facilitates MTH hydrolysis of
the neighboring α-1,4 linkage to the trehalose molecule. A mesophilic strain of
Arthrobacter was the original source of MTS and MTH, but their thermostable
counterparts from the thermophilic archaeon Sulfolobus shibatae appeared to be
superior from the technological standpoint. Trehalose is also available from maltose
by using trehalose synthase. 2
10.4.1.7 Other Starch Conversions
Apart from GHs and GTs, starch processing employs other enzymes, including
isomerases, mainly xylose isomerase for glucose conversion to fructose, and lyases.
The production of 1,5-anhydro-D-fructose by exo-1,4-α-D-glucan lyase from
starch, glycogen, or related oligo- and polymers of D-glucose are examples of a
potential large-scale application of a lyase in starch conversion. 2 Chemical synthesis
of this precursor for antibiotics appeared to be extremely laborious, and therefore
only the enzymatic process can contribute to elucidation of its metabolic role and
potential uses in medicine.
10.4.2 CELLULOSE, CHITIN, AND CHITOSAN
Complete hydrolysis of cellulose, the most abundant natural biopolymer, composed of
β-1,4-linked glucopyranose residues (degree of polymerization up to 15,000), produced
by plants (approximately 10 15 kg per year) and some bacteria, requires common,