Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to the purification of long-
chain dicarboxylic acids, s~ecifically, dicarboxylic acids
having 10 to 18 carbon atoms.
Recently, a method for producing long-chain
dicarboxylic acids from hydrocarbon such as normal paraffin
as a substrate by fermentation using a microorganism such as
yeast, fungi or bacteria has been developed.
Heretofore, long-chain dicarboxylic acids ~hereinafter
called dicarboxylic acids) produced by fermentation as
described above, have been generally recovered through the
following steps:
~1) the cells in the fermentation broth are removed by
means of solid-liquid separation method such as centrifugation
or ~iltration;
(2) dicarboxylic acids or their salts are allowed to
precip;tate by acidifying or basifying the aforesaid broth
containing dicarboxylic acids; and
13~ the precipitated dicarboxylic acids or their salts
are separated from the broth and dried and recovered.
In the production of dicarboxylic acids by fermentation,
however, forming of 0.2 to 6.0wt% of impurities cannot be
prevented though the amount varies depending on the properties
of the microorganism in use and cultural conditions. These
impurities are presumed to be metabolic wastes excreted by
the microorganism and substances emitted by the cells themselves.
Moreover, such impurities cannot b~ removed by the process of
recovery of dicarboxylic acids from the fermentation broth
described above. Accordingly, purification is a great problem
in the production of dicarboxylic acids by means of fermentation.
a~
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For analysis of dicarboxylic acids in the broth,
separation of the products from the broth or from the same
after removing cells has been conventionally employed. When
said technique is applied to the purification of said
dicarboxylic acids, however, problems such as low solubility
of dicarboxylic acids in ethylether, low flash point of
ethylether and requirement for a large-scale extraction
equipment arise. Viewing from the economical as well as
operational standpoint (for the prevention of disaster), said
method is unsuitable to be employed on a commercial basis.
In the light of the situation as described above,
this invention has been accomplished. Therefore, the purpose
of this invention is to offer an advantageous method for
purifying dicarboxylic acids produced by means of fermentation.
Thus according to the present invention, there is
provided a method for the purification of long-chain dicarbox-
ylic acids having from 10-18 carbon atons and produced by
fermentation, wherein said long-chain dicarboxylic acids or
their salts are dissolved in lower aliphatic alcohol or
tetrahydrofuran or the aqueous solution of either of the
aforesaid, and insoluble matters are removed from the solution.
Dicarboxylic acids produced by fermentation which
are to be purified by the method of this invention have 10 to
18 carbon atoms.
In this invention, concentrated or dried fermentation
broth containing dicarboxylic acids from which cells have been
removed or crude dicarboxylic acids or their salts obtained by
acidifying or basifying said cell-free fermentation broth are
dissolved in low aliphatic alcohol or tetrahydrofuran or
aqueous solution of either of them in order to purify dicarbox-
ylic acids ~y removing impurities. Of the above mentioned, use
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of crude dicarboxylic acids or their salts precipitated by
means of acidification or salting-out technique is desirable.
Regarding salts of dicarboxylic acids, it is necessary that
these salts be soluble în low aliphatic alcohol or tetra-
hydrofuran. For example, potassium salt of tridecanedioic
acid can be purified by the method of this invention but the
salts of calcium and magnesium are not appropriate to be used
for purification by this invention because of their low
solubility in said solvents.
As the lower aliphatic alcohol employed in this
invention, there can be employed methylalcohol, ethylalcohol,
n-propyl alcohol and isopropyl alcohol. The solubility of
dicarboxylic acids, the target products, in these lower
aliphatic alcohols or tetrahydrofuran or their aqueous solutions
is high while impurities described above dissolve little in
these solvents. In addit;on, said solvents possess following
merits: giving ~ood filterbîlity to the dissolved dicarbox-
ylic acids, safe in treatment, no corrosive action on the
equipment and no influence on the quality of the products even
2~ if a trace amount remains in dicarboxylic acids after purification.
On the basis of solubility alone, methyl ketone,
acetic acid, furfural, dioxane, lauric acid and dimethyl
sulfoxide could be used, but being deficient in the above
mentioned merits, that is, good filterbility, safety, non-
corrosiveness and little influence on the quality of the
purified products remaining as residue, said solvents are not
practical.
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Of said lower aliphatic alcohols, especially
methylalcohol and ethylalcohol possess not only the above
described merits but also facilitate evaporation of the solvent
after purification of the products and fractional distillation
for recovery of the products. When methylalcohol or ethyla~x~ol
is employed in aqueous solutîon lOOwt portion against 40wt
portion or less of water for the former and lOOwt portion
against 67wt portion or less of water for the latter are desirable.
In order to dissolve the concentrated or dried broth
from which cells have been removed or the crude dicarboxylic
acids or their salts obtained by precipitation in said alcohol
or its aqueous solution, 2.5~g to lOkg of methyl alcohol
~lSkg for 70% alcohol aqueous solution) and 3.8kg to 7.Skg of
ethylalcohol (12kg for 60% alcohol a~ueous solution) can be
used. It is desirable to ~arm said mixture at 40C to 50C in
order to accelerate dissolving speed.
The alcohol solution containing dicarboxylic acids
obtained by dissolution as described above is allowed to pass
through a cylindrical vessel filled with sands and diatomaceous
2Q earth to filter ou,t impurities contained in said solution. The
resultant solution is filtered further through an industrial
~ilter paper followed by washing said filter layer and the
filter paper with alcohol, thereafter mixing said alcohol
with the filtered solution and finally evaporating alcohol and
water from the mixed solution by the conventional method in
order to o~tain purified dicarboxylic acids.
The method o~ removing said impurities is not limited
to the filtration described above. Conventional solid~ uid
separation methods can be applied.
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In this invention, besides the above described
evaporation of alcohol and water for recovering dicarbox-
ylic acids, there can be employed another method in which
water or diluted solution of mineral acid, for example,
aqueous solution of l.Okg of methyl alcohol containing 0.2kg
of dicarboxylic acids (methyl alcohol:water - 9:1) is added
with 3.6 to 7.2kg of water to precipitate dicarboxylic acids
by degrading the solubility and then separating the products
from said aqueous solutio~.
This method has a merit in that it prevents a
danger of explosion at dryi~g dicarboxylic acids because the
products separated from the solution are made alcohol-free by
washing with water prior to drying, and on the other hand,
alcohol is easily recovered since there is no solid matter
remaining in the solution.
The present invention will now be described specifically
wit~ reference to preferred embodiments in the following specific
but non-limiting examples.
Example 1
Ten kilograms of crude tridecanedioic acid ~containing
2.1wt% water) produced by means of fermentation was dissolved
in 50 L of methylalcohol (containing 3.5wt~ water) at 45C.
Said solution was passed through a sand layer which was filled
in a cylindrical vessel with 20cm of internal diameter and Scm
in depth followed by filtration through an industrial filter
paper in order to remove insoluble matters. Said sand layer
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and the filter paper wer~ ~ashed with lOL of met~lalc~h~`l
(containing 3.5wt% water). The filtrate described above
and said wash solution were mixed and then water and methyl
alcohol in said mixture were evaporated by heating the mixture.
The weight of the resultant purified tridecanedioic acid
(with 0.3wt% water) was 9.2kg. Nitrogen contents in the crude
tridecanedioic acid and the purified tridecanedioic acid were
measured using Kjeldahl analytical method. It was found that
nitrogen content of the crude tridecanedioic acid was 0.49wt~
~3.3% as protein) and that of the purified tridecanedioic acid
0.02wt% (below 0.13% as protein) respectively against the dry
weight of the sample.
Example 2
In 8.lL of ethylalcohol ~7.9wt% water) 2.Okg of crude
tridecanedioic acid ~4.6~t~ water~ produced by means of
fermentation was dissolvea at 48C. The resultant solution
was passed through a sand layer filled in a cylindrical vessel
with 6cm internal diameter and 5cm deep. The filtered solution
was further filtered through an industrial filter paper. Said
sand layer and the filter paper were washed with 2.5L of
ethylalcohol containing 7.9wt% water, followed by mixing said
wash alcohol with the filtrate mentioned above in order to
evaporate ethylalcohol. As a result, 1.81kg (0.2wt% water
content) of purified tridecanedioic acid was obtained. Nitrogen
contents of the crude tridecanedioic acid and purified
tridecanedioic acid were ~.37wt~ and below 0.02wt% respectively
against the dry weight of the sample.
Example 3
Ten kg of tridecanedioic acid ~43.8wt~ water) obtained
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from the fermentation broth which was acidified and filtered
through a filter press after cells were removed was dissolved
in 25L of methylalcohol ~elow 2wt% water) in order to remove
insoluble matters with the method in Example 1. To 34L of
the mixture of the wash alcohol and the filtrate 60L of water
was added to precipitate tridecanedioic acid. Said precipitate
was filtered by pressure at room temperature, washed with water
and dried at 60C. As a result, 4.9kg of purified tridecanedioic
acid (below 0.4wt% water) was obtained. Nitrogen contents
of the crude tridecanedioic acid and the purified tridecanedioic
acid were 0.32wt% and below 0.02wt% respectively.
