Note: Descriptions are shown in the official language in which they were submitted.
WO91/05808 2 ~ S 7 7 ~3 ~ PCT/FI90/00247
Method for manufacture of chitosan and other products
from shells of organisms, especially marine organisms
The invention relates to a msthod for manufacture of
chitosan and other products, such as chitin and
proteins, from shells of organisms, especially marine
organisms.
There are methods of manufacturing chitin as well as
chitosan, which subject the shells of marine organisms,
such as crabs, shrimps or krills, to deproteinization,
deminerali~ation and deacetylation in separate reaction
systems. The well-known systems of deproteinization
pxocesses are carried out by means of diluted aqueous
solutions of alkaline metal hydroxides or their salts,
usually in a temperature ranging from 20 to 120C for
a period of 0.5-24 h or by means of an enzymatic
method, in a stirring-disintegrating apparatus or in
a tank without stirring. The demineralization process
for obtaining chitin in well-known methods is carried
out by means of aqueous acidic solutions, also with
additives as hydrosulfite or sulfur dioxide, most
. .
- often at room temperature in mixers or reactors
equipped with rotatory mechanisms.
The deacetylation processes of chitin for obtaining
chitosan in well-known systems are realized by
subjecting the chitin to the action of concentrated
aqueous alkaline metal hydroxide solutions, most
often sodium hydroxide solution with 40-60 wt%
concentration at temperatures of 90~140C. The
deacetylation is carried out in pressure reactors
usually equipped with stirrers.
; 35 The well-known methods are described in a monography
of Chitin, Pergamon Press, 1978; Australian Journal
of Biological Science, volume 7, pages 168-178, 1954;
Journal of Americal Chemical Society, volume 79,
WO91/05~08 PCT/Fl90/00247
?. n ~
pages 5046-5049, 1957; Nature, volume 180, pages 40-41~
1957; Journal of Organic Chemistry, volume 23, pages
1990-1991, 1958; Norisho Suisan Koshusho Kenkyo Hokoku,
volume 11, pages 339-406, 1962; Journal of organic
Chemistry, volume 27, pages 1161-1163, 1962; Methods
of Carbohydrate Chemistry, volume 5, pages 403-406,
1965; Chimica Industrie, Genie Chim., volume 99,
pages 1241-1247, 1968; Fishing Technology, volume 11,
number 1, pages 50-53, 1974; INFOFISH International,
volume 5, pages 31-33, l9B7, and also in the
conference proceedings of I-IV International
Conferences on Chitin/Chitosan in USA, Japan, Italy
and Norway at 1978, 1982, 1985 and 1988 as well as in
U.S. Patents Nos. 2072771, 2040879, 3533940, 3862122,
3922260, 4066735, 4195175, 4199496, in Japanese Patents
Nos. 75,126784 and 78,59700, International Ratent
Application No. W086/06082 as well as Polish Patent
No. 119931.
The well-known methods of manufacture of chitosan and
other products from the shells of marine organisms
require the using of sev~ral apparatuses equipped
with stirrers and also requiring the transport of
solid substances between particular technological
process stages. The technological process is of long
duration resulting at the same time in augmentation
of production costs and in occupational health risk
from the chemical substances used. Moreover, the
chemical processes realized by the well-known methods,
in spite of the use of stirring, do not create
possibilities to obtain products with homogenous
properties because of the heterogenous character of
; above processes.
- 35 The object of this invention is to provide a method
for manufacture of chitosan and other products, such
as chitin and proteins, from the shells of organisms,
especially of marine type, in a single apparatus, by
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WO9l/05808 2 ~ 6 7 7 PCT/FI~0/00247
1,
deproteinization using alkaline solutions,
demineralization using acidic solutions, as well as
by deacetylation using concentrated alkaline solutions.
In accordance with a preferr~d embodiment of the
method of the invention the manufacture of chitosan
and other products from the shells of organisms,
especially marine organisms, by deproteinization,
demineralization and deacetylation, is characterized
in that the shells of organisms, especially marine
organisms, such as crabs or shrimps, are subjected to
the continuous action of reaction liquids in a single
apparatus of perforated type or equipped with
perforated divisions, especially in a circulation
system, whereby the reaction liquids flow through a
reactor with a flow rate of 0.5-10000 volume parts
per 1 weight part of solid product and 1 hour, whereby
:: after each reaction stage the solid product obtained
is optionally washed with water using a continuous
system flowing through the reactor with a flow rate
of 1-20000 volume parts per 1 weight part of solid
product and 1 hour in order to remove the residual
;: reaction liquids, whereafter the chitosan obtained in
- a solid form is eventually dried, preferably in air-
:~ 25 flow conditions at a temperature of 40-100C.
According to a preferred embodiment of the invention,
the manufacture of chitosan and other products is
characterized in that the deproteinization is carried
out by using alkaline solutions, especially aqueous
alkaline metal hydroxide solutions or their salts,
such as sodium hydroxide or sodium carbonate, having
: a concentration of 0.1-10 wt%, at a temperature not
lower than 10C for a time necessary to complete the
removal of proteins, the demineralization is carried
out either before or after the deproteinization stage
by using aqueous acidic solutions, expecially
inorganic acids, such as hydrochloric or sulfuric
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W091/0~08 Q3 PCT/FI90/00247
~a~
acids having a concentration of 0.1-20 wt% for a
time necessary to dissolve the inorganic compounds,
such as calcium and magnesium derivatives, at a
temperature not lower than 10C, especially 20-lOO~C,
whereafter the deacetylation is carried out by using
concentrated alkaline solutions, especially aqueous
alkaline metal hydroxide solutions or their salts,
such as sodium or potassium hydroxides or their salts,
having a concentration of 20-60 wt%, for a time
ranging from 30 minutes to 25 hours at a temperature
ranging from 60 to 140C.
The proteins from the alkaline solutions are recovered ~:
by reduction the pH to 3-6 by means of organic or
~15 inorganic acids, such as acetic, hydrochloric or
sulfuric acids, especially having a concentration of
1-lQ wt%. The chitin obtained after demineralization
is purified and optionally dried.
The fundamental advantage of the method according to
the invention is the realization of all the processes,
startingfrom deproteinizationthrough demineralization
finally to deacetylation, including the purification
as well, in a single apparatus, in which the substrate
in a form of shells of oxganisms such as crabs,
shrimps, krills or insects, constitutes a stationary
phase whereas the reaction liquids as well as the
washing water are acting in a continuous movement
enhancing at the same time the effectivity of the
:30 processes by reduction of the time of an individual
operation as weil as by reduction of the concentration
of the reagents used in comparison to well-known
:~methods. Application of a closed circulation system
reduces considerably the consumption of the reaction
liquids.
.,
The advantaqe of the method according to the invention
is the use of the continuous flow system of liquids
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WO~1/05808 PCT/FI90/00247
2~773~
without a necessity for stirring, which is dif~icult
or even impossible to realize in a case oP raw
materials used in the form of shells of marine
organisms. Due to the flow of the reaction liquids
the deproteinization, demineralization and
deacetylation related to the production o~ proteins,
chitin and chitosan, are facilitated.
As a result of the flow of alkaline solution in the
deproteinization process, a dissolution of proteins
present as a residue on the shells will take place.
In a method according to the invention, the rate o~
removal of the proteins is 2-3 times faster than in a
conventional p~riodical method. At the same time it
is possible to use alkaline solutions having lower
concentration for removing of proteins, or to use a
lower temperature in carrying out the process.
`~ Deproteinization in a method according to the invention
~-allows to obtain the proteins without their superfluous
20 degradation and having homogenous properties.
The demineralization in a method according to the
invention by means of the flow of an acid solution,
resulting in he removal of calcium compounds from
25 the shells, takes place where these compounds are
existing in the shells in a form of insoluble
carbonat~s and their removal takes place through
conversion of these carbonates to suitable soluble
salts. The method according to the invention increases
30 the effectivity of demineralization process by the
order of 2-4 times in comparison to well known methods,
as a result of a better penetration of the
demineralizing liquids causing the acceleration of
reaction, which leads firstly to the reduction of
35 process time and secondly to decreased energy
~consumption. The method according to the invention
tallows to obtain chitin characterized by minimal
content o~ ash, being below 0.5-1.0 wt%o
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wo 91/05~08 PCr/F190/00247
r~ ) 6 _~
The deacetylation process as a result of treatmet
with alkaline solutions having ~ high concentration
ranging from 20 to 60 wt% causes a deacetylation
reaction of acetylamino groups of chitin to amine
groups in chitosan. The process is carried out in
order to obtain a product with homogenous properties
and being soluble in an aqueous acetic acid solution.
A method according to the invention ensures a 2-3
times increment in effectivity of a deacetylation
process as a result of better mass exchange caused by
the continuous f low of the deacetylating solution and
also by the augmentation of the deacetylation rate.
It is possible to obtain chitosan with correct
properties as early as after 4 hours of deacetylation
process by using 30-50 wt% concentrated sodium
hydroxide solution at a temperature of 90-100C.
.
2 0 An advantage of a method according to the invention
is also a possibility for effective purification of
the products, resulting from a continuous washing
f low using water, especially in a circulation system .
A possibility of drying of chitin or chitosan in a
reactor by a pressurized air at higher temperature is
also an advantage af f orded by the method .
A method according to the invention allows to reduce
the production cost at least l. 5-2 times, based on a
lower consumption of energy as well as chemicals and
also on a lower cost of labour.
The chitosan, chitin and proteins obtained by the
- method according to the invention are applied to the
- 35 chemical industry, agriculture, medicine,
pharmaceutical and cosmetic industry, paper industry,
waste water treatment etc.
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W091/05808 PCT/F190/00247
7 ~77~
A method for manufacture of chitosan and other
products from the shells of organisms, especially
marine, is realiz~d in an installatio~ shown
schematically in the accompanying drawings, where
Fig. 1 shows the installation having a reactor
equipped with a perforated basket, and
Fig. 2 shows an installation having a reactor
equipped with perforated divisions.
The installation in Fig. 1 contains a reactor 1 in a
; form of a tank having a heating jacket 4, the reactor
bein~ equipped with an immersed perforated basket 2
in which the shells 3 are located. The reactor 1 is
joined to a draining or outlet pipe 5 located in the
reactor outside the basket and being of a controllable
depth of immersion. The pipe is connected through a
pump 6 and through subsequent valves 7 and 9 to an
inlet or conveying pipe 10 leading back to the reactor
into the basket and having its outlet end near the
bottom of the basket. A draining and supply pipe is
connected through a valve 8 to the outlet pipe 5 from
the reactor 1 and to the inlet pipe 10 leading tc, the
reactor, the junction point being between the valves
7 and-9. A branch supply pipe containing a valve 11 is
connected to the pipe 10 between the valve ~ and ~he
reactor.
: .
The action of tha above installation is as following:
a suitable amount of shells 3 is introduced into the
~ perforated basket 2 and the basket is inserted into the
- reactor 1. The deproteinization liquid is introduced
into the reactor 1 after opening of the valves 8 and
9, and after closing of the valve 8 and opening of
the valve 7 and starting of the pump ~, the removal
of proteins will be carried on by recirculating the
reaction liquid through the pipes 5 and 10 optionally
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WOgl/05~08 ~ PCT/Fl90/00247
~r~
by heating the reactor simultaneously. The inlet end
of the pipe is located close to the liquid surface of
the reactor during the recirculating. The valve 9 is
closed after the deproteinization is completed;
whereafter the valve 8 is opened, and the pip~ 5 is
lowered deeper into the reactor 1 taking away the
proteinaceous solution into a suitable tank. Next the
valve 9 is opened and washing water is introduced
through the valve 8 and valve 9, and after closing of
the valve 8 the purification process is carried on. The
purification process can be carried on also with a
continuous flow of the washing water through the
valve 11. The liguid can be recirculated also partly -
by taking of the liquid through the valve 8 only
partly. A~ter the purification and water removal the
de~ineralization as well as the deacetylation liquids
are introduced in turn followed by an application of
suitable water purification operations.
The installation in Fig. 2 contains a reactor 1 in
the ~orm of a tank equipped with a horizontal
`perforated division or partition 2 restricting the
area of the shells 3 to the upper part of the reactor.
The area outside the shells below the partition 2 is
25 joined to a valve 5 at the bottom of the reactor and
to a draining pipe 6 having a pump 7. In the direction
of flow, the pump is followed by a system of valves
8, 9 and 10, where the valve 9 has the same Punction
as the valve 8 in Fig.9, being situated in a supply
30 and drainage line joined to the recirculation line at
the junction point between the valves 8 and 10. The
pump 7 is joined through the valves 8 and 10 to the
reactor 1, where the shells 3 are located, through a 7
conveying pipe 11 to which is connected a supply
35 branch pipe having a valve 12. The outlet of the pipe
11 is located above the shells 3 in the reactor. The
action of the installation shown in Fig. 2 is analogous
; to the installation in Fig. 1.
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wo91/os808 PCT/Fl90/00247
2 ~ 8 ~
The well-known methods for manufacture of chitosan
and other products from the shells up to now have
comprised a stationary system for recovery of proteins,
chitin and chitosan, as described for example in US.
Pat. No. 4,199,496. The following processes as
- deproteinization
- demineralization
- deacetylation
have always been realized in stationary conditions in
separate apparatuses. Penetration rate by reaction
liquid media, reaction effectivity as well as
properties of products obtained have been low in
these conventional methods. The new method for
; manufacture of chitosan and other products as chitin
and proteins according to the present invention,
utilizes the continuous action of reacting liquid
media penetrating solid wastes with much higher
effectivity of reactions of deproteinization,
demineralization as well as deacetylation. In addition,
the processes of chitosan, chitin and proteins
manufacture need to be realized only in one single
apparatus where the shells are placed in the beginning
and the citosan is removed in the end of the process
` series.
.
The action of reaction media in the new system is
better than in well-known methods. In the following
table is presented some comparative data between the
older method and the method of the present invention.
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WO ~1/05808 PCr/F190/00247
ctJ~J~3 10
Table Comparison of optimal conditions for
- processing of shells
Pro~ Opkimal conditions
Wbll-k~n methods New method
1. ~e~rote~ization NaOH conc. 0,5~ NaOH conc. 0,5%
tEmp. about 100C ~.max. 40-60C
or higher
2. D~Ln~ralization HCl conc. 5-10% HCl c~nc. 5-10%
t~ 10-16h tLme max. 4-6 h
3. Deaoetylation NaOH conc. 40-60% NaOH con~. 40-60%
min. 100-140C, max. 100-110C
pref~ly high withou~ pr~re ?
mLn. 10-20h max. 4-8h
. .
.
The chitin and chitosan obtained according to the new
method is more homogenous in properties in comparison
to products obtained by well~known methods. The ash
content in chitosan obtained by new method is lower
than 1%, usually 0.1-0.5%, whereas the level of 1% of
ash is possible to be obtained by well-known methods
using the drastic conditions mainly in a
demineralization stage, taking usually 10-16h in
comparison to max. 4-6h in the new method.
.
: 30 The invention is explained further in the following
examples which do not restrict the scope of claims.
Example 1
.
12.16 weight parts of Norwegian shrimp shells
containing 1.0 wt% of moisture and 0.88 wt~ ~f
nitrogen, and 400 volume parts of 2.5~ aqueous sodium
hydroxide solution were introduced into the reactor
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WO ~1l/0580~ PCl/F190/00247
7 7 ~ 8
shown in Fig. 1. Deproteinization was carried out at
a temperature of 300c and for a period of 1.5 h in
the circulation system using a flow rate of 4934
volume parts per 1 weight part of shells and 1 hour,
whereafter the alkaline solution containing dissolved
proteins with a red colour, d~ = 1.154 g/cm3 and
pH = 11.6, was continuously taken away. Next the shrimp
shells were continuously washed by water with a flow
rate of 6000 volume parts per 1 weight part of shells
and 1 hour, whereafter 350 volume parts of 10% aqueous
hydrochloric acid solution was introduced into the
installation. The demineralization was carried out
using a continuous flow of hydrochloric acid solution
with a flow rate of 5000 volume parts per l weight
part of shells and 1 hour at a temperature of 40C
for a period of 2 h, then the excess of hydrochloric
acid solution was washed off at a temperature of 20-
300C using a wa~er flow rate of 500 volume parts per
1 weight part of chitin and 1 hour to obtain a neutral
reaction of eluate, whereafter the chitin was dried
at a temperature of 90C.
; 3.1 weight parts of chitin in a solid form with a
light yellow colour was obtained. The product was
characterized by a water retention value (WRV) of
87.6%, nitrogen content of 5.5 wt%, ash content of
0.28 wt%. The chitin was not soluble in 4% aqueous
acetic acid solution. IR studies showed the absorption
band at the frequency of 1650 cm~l characteristic for
amide groups.
2.5 weight parts of chitin obtained was introduced in
a reactor shown in Fig. 1 and on it 200 volume parts
of 35% aqueous sodium hydroxide solution was poured.
The deacetylation was carried on using a continuous
- flow with a flow rate of 15 volume parts per 1 weight
part of chitin and 1 hour at a temperature of 75C
for 20 h~ Next the excess of sodium hydroxide solution
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WO 91/05808~ ~ r~ ~ ~) PCI /F190/00247
12
was washed off continuously at a temperature of 20-
30c using a ~low rate of 500 volume parts per 1
weight part of chitin and 1 hour to obtain a neutral
reaction. After the removal of water, the product was
dried by pressurized air at a temperature of 70c.
2.1 waight parts of chitosan with a white colour was
obtained. The product was characterized by the WRV of
95.5%, average molecular weight Mw of 205000,
deacetylation degree of 69.5% and nitro~en content of
6.9 wt%. IR studies showed the absorption band at the
~raquency of 1570 cm~1 characteristic for amine groups.
Example 2
27.72 weight parts of Norwegian shrimp shells
containing 1 wt% of moisture and 0.88 wt% of nitrogen
and 800 volume parts of 5 wt% aqueous sodium hydroxide
solution were introduced into the reactor as in Example
1. The deproteinization was carried on at a temperature
of 60OC for 1 h in a circulation system having a flow
rate of 2480 volume parts per 1 weight part of shells
and 1 hour, whereafter the alkaline solution of
proteins with red colour, d~ = 1.143 g/cm3, pH =
11.7, was drained out.
The protein solution was treated on continuous stirring
by 5% hydrochloric acid solution to obtain pH = 4Ø
0.6 weight parts of proteins with a light red colour,
containing 1.83 wt% nitrogen, characterized by the
presence of aspartic acid, glutamic acid, alanine,
glycine, tyrosine, fenylalanine, lysine, arinine,
threonine, serine, isoleucine and leucine was obtained.
~ 35 Next the shells were continuously washed by water I!
with a flow rate of 9000 volume parts per 1 weight
part of shells and 1 hour. Subsequently, 600 volume
parts of 10% aqueous sulfuric acid solution was
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WO91/05808 13 2 ~ ~ 7 7 PC~/FI90/00247
introduced into the reactor. Demineralization was
carried out by means of a continuous ~low with a flow
rate of 1210 volume parts per l weight part of shells
and 1 hour at a temperature of 40C for 2 h, whereafter
the excess of sulfuric acid solution was washed out
at a temperature 20-30C using a flow rate of 1200
volume parts per 1 weight part of chitin and 1 hour
to obtain a neutral pH of eluate. Next 50U volume
parts of 30% aqueous potassium hydroxide solution
containing 1.5 wt% of potassium carbonate and 0.5 wt%
of sodium carbonate was introduced. Deacetylation was
carried out at a temperature of 100-105C for a period
of 4 h using a flow rate of 7200 volume parts per 1
weight part of chitin and l hour and then, after
purification, the product was dried by pressurized
air at a temperature of 100C.
'
5.35 weight parts of chitosan with a light yellow
colour was obtained. The chitosan was characterized
20 by nitrogen content of 5.9 wt%, WRV f 73-4%, Mw =
169060, deacetylation degree of 73.4~ and a good
solubility in a 4% aqueous acetic acid solution. IR
studies showed the absorption band at the frequency
of 1560 cm~l characteristic of amine groups.
~xamDle 3
.~ .
21.49 weight parts of Norwegian shrimp shells with
properties as in Example 1 and 900 volume parts of 1%
aqueous sodium hydroxide solution was introduced into
the reactor shown in Fig. 1. Deproteinization at a
temperature of 50C for 1.5 h in a circulation system
using a flow rate of 9800 volume parts per 1 weight
part of shells and 1 hour was carried on, whareafter
~ 35 the proteins containing solution with a red colour,
d~ = 1.112 g/cm3, pH = 1~.05 was drained out. Next
the product obtained was washed by water using a flow
rate of 4200 volume parts per 1 weight part of shells
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W09l/0580~ PCT/Fl90/00247
~r~ 14
and l hour, whereafter 700 volume parts of 10% aqueous
hydrochloric acid solution were introduced.
Demineralization at a temperature of 20-23C for 280
minutes using a flow rate of lo volume parts per l
weight part of shells and 1 hour was carried out.
Next the excess of hydrochloric acid solution was
washed out with water at room temperature using a
flow rate of 1000 volume parts per l weight part of
chitin and 1 hour. After the water had drained out,
600 volume parts of 50% aqueous sodium hydroxide
solution were introduced into the reactor and the
deacetylation was carried out using continuous
circulation at a temperature of 110-120C for 330
minutes using a flow rate of 2400 volume parts per 1
weight part of chitin and 1 hour. The product obtained
after the washing was dried at a temperature of 80C.
:,
3.3 weight parts of chitosan with white colour
characterized by WRV of 87.6%, nitrogen content of
6.2%, Mw of 75690, deacetylation degree of 78.2%, ash
content of 0.93 wt~ and very good solubility in 4%
aqueous acetic acid solution was obtained. IR studies
-~ showed the absorption band at the frequence of 1580
cm~l characteristic of amine groups.
Exam~le 4
:
` 31.73 weight parts of Norwegian shrimp shells with
properties as in Example 1 and 800 volume parts of 5%
aqueous sodium hydroxide solution were introduced
into the reactor presented in Fig. 1. Deproteinization
at a temperature of 50C for 2 h with a flow rate of ~ -
7560 volume parts per 1 weight part of shells and 1
hour was carried on, whereafter the alkaline solution
containing proteins with a red colour, d2~ = 1.159
g/cm3, pH = 11.7 was taken off. Next the product was
washed continuously by water to obtain a pH of 7
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WO9l/05808 PCT/Fl90/00247
20~77~
using a flow rate of 1150 volume parts per 1 weight
part of shells and 1 hour, whereafter the water was
taken out from the reactor.
Demineralization was carried out by means of 800
volume parts of 10% aqueous hydrochloric acid solution
for 2 h at a temperature of 40C using a flow rate of
` 125 volu~e parts per 1 weight part of shells and 1
hour. Next the excess of hydrochloric acid solution
was washed out by water with a flow rate of 15200
volume parts per 1 weight part of chitin and 1 hour
to obtain a pH of 7Ø After water had drained out,
600 volume parts of 40% aqueous sodium hydroxide
solution was introduced into the reactor and the
deacetylation at a temperature of 90c for 6 h as
well as at a temperature of 100C for next 1 h was
carried on. The product obtained after purification
was dried at a temperature of 90C.
6.3 weight parts of chitosan with a white colour
characterized by deacetylation degree of 85.8%, ash
contents of 0.83 Wt4, nitrogen contents of 6.1 wt%,
WRV of 106.6%, Mw of 184800 and a good solubility in
4~ aqueous acetic acid solution was sbtained. IR
studies showed the absorption band at the frequency
of 1560 cm~1 characteristic of amine groups.
Exam~le 5
32.5 weight parts of milled crab shells characterized
by nitrogen contents of 0.7 wt~, and 800 volume parts
of 5~ aqueous hydrochloric acid solution were
introduced into the reactor presented in Fig. 2.
Demineralization at a temperature of 70 for 90 minutes
using a flow rate of 1580 volume parts per l weight
part of shells and 1 hour was carried out, whereafter
the acid solution was taken off and the residues were
continuously washed by water with a flow rate of 5050
WO91/05808 PCT/Fl90/00247
~o~ume parts per 1 weight part of shPlls and 1 hour.
After the water had been taken off 600 volume parts
of 0.5~ aqueous potassium hydroxide solution were
introduced into the reactor and the deproteinlzation
was carried out at a temperature of 50C for 4 h
using a flow rate of 4580 volume parts per 1 weight
part of shells and 1 hour. Next the alkaline solution
containing proteins with a red colour, d~ = 1.112
g/cm3, pH = 12.06, was taken off from the reactor,
and immediatel~i~ thereafter 500 volume parts of 60%
aqueous potassium hydroxide solution were introduced
obtaining a 57.5% aqueous potassium hydroxide solution
- as a result. Deacetylation was carried on at a
temperature of 130C for 3 h. The alkaline solution
was next taken off from the reactor and the product
obtained was purified and dried at a temperature of
80C.
4.5 weight parts of chitosan with light red colour
characterized by deacetylation degree of 75%, ash
, contents of 0.35 wt%, nitrogen contes of 7.4 wt%, WRV
~ of 115% and a good solubility in 4% acetic acid
- solution was obtained. IR studies showed the absorption
band at the frequency of 1570 cm~1 characteristic of ~.
amine groups.
A prolongated deacetylation realized in the above
conditions for the next 14 h allowed to obtain 4
weight parts of chitosan with a light red colour
characterized by WRV of 120%, deacetylation degree of
92.5~, ash contents of 0.32 wt%, nitrogen contents of
7.9 wt% and a very good solubility in 4% aqueous
acetic acid solution.
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