181
9
of >95% can be achieved by additional alkaline
treatment. The degree of polymerization decreases
with increasing degree of deacetylation, which is
not always desired. Enzymes make it possible to
carry out deacetylation without significant depolymerization. However, the conversion is much
lower compared to alkaline treatment.
9.3 Properties and Applications
of Chitin and Chitosan
Chitin and chitosan are both natural biopolymers (7 Chap. 19) and therefore biocompatible
as well as biodegradable and non-toxic. Both
substances have a wide range of applications. The
majority of these substances are used directly, i.e.
in their native, unmodified form. A small part, in
particular of chitosan, is also derivatized in order
to be used as a cosmetic ingredient for special
applications. Between these two polysaccharides,
chitosan has more applications.
ment astaxanthin is extracted in some processes
with organic solvents such as acetone. However,
it is not UV-stable; therefore, it is often simply
exposed to sunlight in the drying step in order
to obtain a white chitin afterward. The general
routes from raw material to chitin are summarized in . Fig. 9.4.
As already mentioned, chitosan is the
deacetylated form of chitin. In order to produce
chitosan on an industrial scale, the chitin previously isolated from crab shells is deacetylated.
This can be done in different ways: With bases
(sodium hydroxide solution), with special
enzymes (N-deacetylases) or by using microorganisms that release these enzymes (. Fig. 9.5).
Industrially, deacetylation with sodium hydroxide solution is the most important process. In
. Fig. 9.6, this process of chitosan production starting from crab shells is shown schematically in very
simplified form. Base-catalyzed deacetylation provides chitosan with a medium degree of deacetylation; chitosans with almost complete deacetylation
. Fig. 9.4 Routes from
raw material to chitin
Raw material
Crab shells, insects, mushrooms, etc.
Deproteinization
with alkali
Demineralization
with acids
Deproteinization
with proteaseproducing bacteria
Demineralization
with acids
Deproteinization
and
demineralization
with
microorganisms
Chitin
Proteins
Minerals
Chitin
. Fig. 9.5 Possibilities of
chitosan production from
chitin
Chitin
Deacetylation with
bases
Deacetylase
Microorganism
produces
deacetylase
Chitosan
9.2 · Production of Chitin and Chitosan
9
of >95% can be achieved by additional alkaline
treatment. The degree of polymerization decreases
with increasing degree of deacetylation, which is
not always desired. Enzymes make it possible to
carry out deacetylation without significant depolymerization. However, the conversion is much
lower compared to alkaline treatment.
9.3 Properties and Applications
of Chitin and Chitosan
Chitin and chitosan are both natural biopolymers (7 Chap. 19) and therefore biocompatible
as well as biodegradable and non-toxic. Both
substances have a wide range of applications. The
majority of these substances are used directly, i.e.
in their native, unmodified form. A small part, in
particular of chitosan, is also derivatized in order
to be used as a cosmetic ingredient for special
applications. Between these two polysaccharides,
chitosan has more applications.
ment astaxanthin is extracted in some processes
with organic solvents such as acetone. However,
it is not UV-stable; therefore, it is often simply
exposed to sunlight in the drying step in order
to obtain a white chitin afterward. The general
routes from raw material to chitin are summarized in . Fig. 9.4.
As already mentioned, chitosan is the
deacetylated form of chitin. In order to produce
chitosan on an industrial scale, the chitin previously isolated from crab shells is deacetylated.
This can be done in different ways: With bases
(sodium hydroxide solution), with special
enzymes (N-deacetylases) or by using microorganisms that release these enzymes (. Fig. 9.5).
Industrially, deacetylation with sodium hydroxide solution is the most important process. In
. Fig. 9.6, this process of chitosan production starting from crab shells is shown schematically in very
simplified form. Base-catalyzed deacetylation provides chitosan with a medium degree of deacetylation; chitosans with almost complete deacetylation
. Fig. 9.4 Routes from
raw material to chitin
Raw material
Crab shells, insects, mushrooms, etc.
Deproteinization
with alkali
Demineralization
with acids
Deproteinization
with proteaseproducing bacteria
Demineralization
with acids
Deproteinization
and
demineralization
with
microorganisms
Chitin
Proteins
Minerals
Chitin
. Fig. 9.5 Possibilities of
chitosan production from
chitin
Chitin
Deacetylation with
bases
Deacetylase
Microorganism
produces
deacetylase
Chitosan
9.2 · Production of Chitin and Chitosan