amount and size of large ring cyclodextrins formed was found to depend on the
enzyme CGTase used, reaction time and type of substrate used. These large ring
cyclodextrins have unique structures and geometry of their cavities, which are more
flexible and have been proposed to find applications as novel host compounds in
molecular recognition processes [89].
CGTases have also been applied in the synthesis of alkyl glycosides with
long carbohydrate groups for use as surfactants. Surfactants with long-carbohydratechain alkyl groups are generally preferred due to their attractive properties.
However, they are difficult to synthesize. Several studies have shown the possibility
of using CGTase for the production of surfactants with longer carbohydrate chains.
In one study, the commercially available surfactant, dodecyl-β-d-maltoside (DDM),
was converted to dodecyl-β-d-maltooctaoside (DDMO), in a single step by using
B. macerans CGTase as catalyst and α-cyclodextrin (α-CD) as glycosyl donor,
resulting in high yields of up to 80% of the DDMO [90]. In a follow-up study,
the enzyme was immobilized on Eupergit C and used in a packed-bed reactor
for continuous production of long-carbohydrate-chain alkyl glycosides from
α-cyclodextrin and n-dodecyl-(1,4)-beta-maltopyranoside (C(12)G(2)beta), a commercially available surfactant [91]. Yields of up to 50% of the product, n-dodecyl(1,4)-beta-maltooctaoside (C(12)G(8)beta), were achieved with the immobilized
enzyme. An investigation of the transglycosylation reaction between an alkyl
polyglycoside and α-cyclodextrin by the Bacillus macerans CGTase resulted
in production of alkyl glucopyranosides glycosylated with 6 (primary coupling
products) or 12 (secondary coupling products) glucose residues, with glycosylation
of both α- and β-anomers [92]. Thus CGTases have shown to be important
enzymes for synthesis and biotransformation applications such as in the production
of surfactants with superior properties.
4.4 Food Industry
Starch is an important constituent of the human diet. It contributes greatly to
the textural properties of many foods and is widely used in food and industrial
applications as a thickener, colloidal stabilizer, gelling agent, bulking agent and
water retention agent. It is chemically and enzymatically processed into a variety of
products such as starch hydrolysates, glucose syrups, fructose, maltodextrin and
cyclodextrin derivatives for use in the food industry.
Industrial starch processing involves three stages, gelatinization, liquefaction
and saccharification. In gelatinization, starch slurry consisting of 30–40% dry solids
is injected with pressurized steam (jet cooking) at 105
C for 5 min, resulting in a
highly viscous suspension of dissolved starch. After gelatinization, the starch slurry
is cooled to the desired temperature for liquefaction. Liquefaction is the partial
hydrolysis of the starch slurry and results in reduced viscosity of the starch
hydrolysate. It is carried out using amylases which hydrolyse the starch slurry to
produce dextrins. Liquefaction is typically carried out at 95–100
C for 1–2 h, in the
Starch-Modifying Enzymes
233
enzyme CGTase used, reaction time and type of substrate used. These large ring
cyclodextrins have unique structures and geometry of their cavities, which are more
flexible and have been proposed to find applications as novel host compounds in
molecular recognition processes [89].
CGTases have also been applied in the synthesis of alkyl glycosides with
long carbohydrate groups for use as surfactants. Surfactants with long-carbohydratechain alkyl groups are generally preferred due to their attractive properties.
However, they are difficult to synthesize. Several studies have shown the possibility
of using CGTase for the production of surfactants with longer carbohydrate chains.
In one study, the commercially available surfactant, dodecyl-β-d-maltoside (DDM),
was converted to dodecyl-β-d-maltooctaoside (DDMO), in a single step by using
B. macerans CGTase as catalyst and α-cyclodextrin (α-CD) as glycosyl donor,
resulting in high yields of up to 80% of the DDMO [90]. In a follow-up study,
the enzyme was immobilized on Eupergit C and used in a packed-bed reactor
for continuous production of long-carbohydrate-chain alkyl glycosides from
α-cyclodextrin and n-dodecyl-(1,4)-beta-maltopyranoside (C(12)G(2)beta), a commercially available surfactant [91]. Yields of up to 50% of the product, n-dodecyl(1,4)-beta-maltooctaoside (C(12)G(8)beta), were achieved with the immobilized
enzyme. An investigation of the transglycosylation reaction between an alkyl
polyglycoside and α-cyclodextrin by the Bacillus macerans CGTase resulted
in production of alkyl glucopyranosides glycosylated with 6 (primary coupling
products) or 12 (secondary coupling products) glucose residues, with glycosylation
of both α- and β-anomers [92]. Thus CGTases have shown to be important
enzymes for synthesis and biotransformation applications such as in the production
of surfactants with superior properties.
4.4 Food Industry
Starch is an important constituent of the human diet. It contributes greatly to
the textural properties of many foods and is widely used in food and industrial
applications as a thickener, colloidal stabilizer, gelling agent, bulking agent and
water retention agent. It is chemically and enzymatically processed into a variety of
products such as starch hydrolysates, glucose syrups, fructose, maltodextrin and
cyclodextrin derivatives for use in the food industry.
Industrial starch processing involves three stages, gelatinization, liquefaction
and saccharification. In gelatinization, starch slurry consisting of 30–40% dry solids
is injected with pressurized steam (jet cooking) at 105
C for 5 min, resulting in a
highly viscous suspension of dissolved starch. After gelatinization, the starch slurry
is cooled to the desired temperature for liquefaction. Liquefaction is the partial
hydrolysis of the starch slurry and results in reduced viscosity of the starch
hydrolysate. It is carried out using amylases which hydrolyse the starch slurry to
produce dextrins. Liquefaction is typically carried out at 95–100
C for 1–2 h, in the
Starch-Modifying Enzymes
233