Note: Descriptions are shown in the official language in which they were submitted.
CA 02472246 2009-10-07
METHOD FOR THE RECOVERY OF SUGARS
BACKGROUND OF THE INVENTION
The present invention relates to a chromatographic separation
method of separating carbohydrates, especially sugars, from a mixture includ-
ing the same. The mixture to be treated in accordance with the present inven-
tion is typically a biomass-derived solution including carbohydrates/sugars.
Especially, the invention provides a chromatographic separation method of
recovering mannose with high purity from biomass-derived solutions, such as
spent sulphite pulping liquors. Mannose can be recovered in a crystalline form
or in the form of a solution. The claimed process of recovering mannose is
based on the use of a combination of a Ba2+ form resin and a resin in other
than Ba2+ form as the separation resin, whereafter mannose is crystallized, if
desired. In connection with the separation process of the invention, xylose
and
arabinose products can also be obtained as by-products, depending on the
composition of the starting biomass-derived solution.
Mannose is useful e.g. for various pharmaceutical applications. It
can be used as a starting material or raw material for various pharmaceutical
products. Mannose is also therapeutically useful in the treatment of urine in-
fections and intravenous inflammation conditions. In food technology, man-
nose is useful e.g. for so-called PositechTM applications (GMO-testing of food
products).
Mannose is also useful as the raw material for the production of
mannitol, which has various pharmaceutical applications.
Mannose can be recovered from wood resources, where mannose
is present as a mixture with other carbohydrates and lignin components. In
wood and other plant-based material, mannose typically occurs in polymeric
form, such as hemicellulose, most frequently as a heteropolymer with glucose
and/or galactose in glucomannans, galactoglucomannans and galactoman-
nans. Spent liquors obtained from conifer wood-pulping processes are espe-
cially rich in mannose. Mannose has also been recovered from vegetable ivory
nuts and specific seaweeds.
The recovery of mannose with high purity from plant-based material
has presented a problem in the state of the art.
CA 02472246 2009-10-07
2
= Jones, J.K.N & Wall, R.A. (Canadian Journal of Organic Chemistry
38 (1960), pp. 2290 to 2294) have described a process for the separation of
sugars from synthetic sugar mixtures and plant extracts using ion-exchange
resins. The process relates to the separation of monosaccharide mixtures,
including D-mannose and D-mannitol, using neutral salt forms of sulphonic
acid type ion-exchange resins. The resin DowexTM 50W X8 in Ba2+ form has
been used as the separation resin.
Larsson, L.I & Samuelsson, O. (Acta Chemica Scandinavica 19
(1965), pp. 1357 to 1364) describe an automatic procedure for the separation
of monosaccharides present in wood hydrolysates using ion exchange resins.
The separation of 16 monosaccharides, including D-mannose, has been stud-
ied by partition chromatography on strongly basic anion exchange resins in the
sulphate form using ethanol as the eluant.
Furthermore, the utilization of ion exchangers for the isolation of
monosaccharides has been studied with the aim to examine the behaviour of
sugars on columns containing a bisulfite saturated resin. For example, an an-
ion exchanger (AmberliteTM IRA-400) in the bisulphite form has been used to
separate fructose, glucose and mannose. As a practical result of this study,
an
improved method for the determination of reducing sugars in sulphite waste
liquor is proposed.
The interactions occurring between aluminium oxide and aqueous
solutions of monosaccharides, including D-mannose have also been studied. It
is suggested that by proper choice of alumina, separation of sugars can be
easily and quickly achieved on a preparative as well as analytical scale.
It is also known to recover mannose from various sources through
mannose derivatives. Fujita, T & Sato,T in Bull. Chem. Soc. Japan 33 (1960)
353 disclose the recovery of D-mannose through N-phenyl-D-
mannopyranosylamine. It is recited that N-phenyl-D-mannopyranosylamine is
so stable and insoluble in water that it was recommended for the isolation of
D-mannose even from very impure raw materials.
Herrick, F.W., Casebier, R.L., Hamilton, J.K. & Wilson, J.D. ("Man-
nose chemicals", Applied Polymer Symposium No. 28 (1975), pp. 93 to 108)
disclose a study relating to the development of an economic process for re-
covering mannose or its derivatives from wood resources, such as a spent
sulphite liquor, where mannose is a major component of mixtures containing
other carbohydrates and lignin fragments. The main achievement of this work
CA 02472246 2009-10-07
3
t
was the development of processes for recovering sodium mannose bisulphite
and methyl mannoside from several raw materials. Processes were developed
for recovering mannose from crude mixtures via two routes: (1) formation of
the sodium bisulphite adducts of monomeric wood sugar mixtures, crystalliza-
tion and separation of sodium mannose bisulphite and regeneration of man-
nose from this intermediate, and (2) anhydrous methanolysis concurrent with
glycosidation of crude mixed-sugar polymers or monomers, crystallization and
separation of methyl a-D mannoside and regeneration of mannose from this
intermediate. These procedures for recovering mannose have the drawback
that they are very cumbersome to carry out in practice.
Sinner, M, Simatupang, M.H. & Dietrichs, H.H. ("Automated Quanti-
tative Analysis of Wood Carbohydrates by Borate Complex Ion Exchange
Cromatography", Wood Science and Technology, 1975, pp. 307 to 322) de-
scribe a simple automated analytical method for the separation and quantita-
tive determination of sugars from acidic and enzymatic hydrolysates of wood
polysaccharides via borate complex ion exchange chromatography. The sug-
ars separated in this way include mannose, fructose, arabinose, galactose,
xylose, glucose and disaccharides like xylobiose, cellobiose and sucrose.
GB 1 540 556 (ICI Americas, publ. 14 February 1979) relates to a
method of separating mannose from glucose present in aqueous solutions.
The starting mixture of glucose and mannose is typically obtained by epimeri-
zation of glucose in an aqueous solution. The separation of mannose from
glucose is typically carried out using a cation exchange resin in the form of
an
alkaline earth metal salt, such as in Cat+, Srz+ or Ba2+ form. The cation ex-
change resin is preferably a strongly acid cation exchange resin, typically a
resin based on styrene divinylbenzene.
The separation of sugars from lignosulphonates has been de-
scribed by Hassi, R., Tikka, P. & Sjostrom, E. ("Recovery of Lignosulphonates
and Sugars from Spent Sulphite Liquors by Ion Exclusion Chromatography,
1982 International Sulfite Pulping Conference, Sheraton Centre Hotel, To-
ronto, Ontario, October 20-22, pp. 165 to 170). Ion exclusion chromatography
on a strongly acid cation exchange resin has been applied to the fractionation
of lignosulphonates and sugars, including mannose, present in a spent sul-
phite liquor. The resin used in the tests was a strongly acid gel-type polysty-
rene cation exchange resin (AmberliteTM IR-120, Ca 2+ form). It is proposed
that
the sugar fraction might be used as a raw material source for mannitol produc-
CA 02472246 2004-06-30
WO 03/056038 PCT/FI02/01059
4
tion.
Finnish Patent 78734 (Suomen Sokeri Oy, publ. 5 April 1987) re-
lates to a multi-step process of separating sugars and lignosulphonates from a
spent sulphite pulping liquor. This process comprises introducing a spent sul-
phite pulping liquor into a chromatographic column including a separation
resin
in a metal salt form, typically a strongly acid cation exchange resin in a
Ca2+
form, eluting the column with water to recover a fraction rich in lignosulpho-
nates and a fraction rich in sugars, introducing the fraction rich in sugars
thus
obtained into another chromatographic column including a separation resin in
a monovalent metal salt form, typically in Na+ form. A sugar fraction free
from
lignosulphonates is obtained.
WO 96/27029 (Xyrofin Oy, publ. 6 September 1996) relates to a
method of recovering an organic compound, such as sugars, from solutions by
crystallizing the compound substantially by way of nucleation. It is proposed
that mannose can be recovered by the nucleation crystallization process, for
example.
Finnish Patent 97 625 (Xyrofin Oy, publ. 5 March 1996) discloses a
process for crystallizing xylose. In this process, xylose is recovered by
crystal-
lization from solutions in which the xylose purity is relatively low.
Especially,
this process concerns recovering xylose from biomass-derived solutions.
WO 99/10542 (Cultor Corporation, publ. 4 March 1999) discloses a
process of recovering L-arabinose from sugar beet pulp by a chromatographic
separation method using a cation exchanger in a monovalent metal form as
the separation resin. The L-arabinose solution thus obtained is purified by
means of cation and anion exchangers and adsorbent resins.
WO 01/21271 Al (Sohkar Oy, publ. 29 March 2001) discloses a
method of recovering pectin, arabinose and salts from vegetable material us-
ing a cation exchange resin, which is preferably in the form of a multivalent
metal.
Biomass-derived raw materials used for the recovery of mannose
are typically complex multicomponent mixtures. Separation of mannose with
sufficient purity from these complex mixtures has presented a problem. One of
the problems associated with the above-described known processes is that
they provide mannose as a mixture with other closely-related sugars or that
they do not provide mannose with a sufficient degree of purity. On the other
hand, the production of mannose from mannans and other mannose deriva-
CA 02472246 2009-10-07
tives is technically very cumbersome. Furthermore, it has been problematical
to prepare suitable starting mannose solutions for the crystallization of man-
nose to obtain a crystalline mannose product.
It has now been found that mannose with high purity can be effec-
5 tively recovered from biomass-derived carbohydrate-containing solutions
using
a novel chromatographic separation method. With the chromatographic
method of the invention, a mannose fraction having a purity of 45 to 80% or
more can be obtained. The mannose fraction obtained from the chroma-
tographic separation can then be further purified by crystallization. The
crystal-
lization provides a crystalline mannose product having a purity of up to 99%
or
more. In connection with the method of the invention, various other sugars,
such as xylose and arabinose can be recovered as by-products, depending on
the composition of the starting biomass-derived raw material.
BRIEF DESCRIPTION OF THE INVENTION
It is thus an object of the present invention to provide a method of
recovering a mannose product with high purity from carbohydrate mixtures
containing the same. As by-products, various other sugars, such as xylose and
arabinose can be recovered.
In accordance with one aspect of the present invention, there is pro-
vided a method of recovering mannose from a solution derived from biomass,
comprising subjecting said solution to a chromatographic separation process
using at least one chromatographic separation resin bed which is substantially
in a Ba2+ form and at least one chromatographic separation resin bed, where
the resin is a cation exchange resin in other than Ba2+ form; and recovering
at
least one mannose fraction.
In an embodiment of the invention the chromatographic separation
process of the method comprises at least two chromatographic separation
steps, whereby at least one of these steps is carried out with a chroma-
tographic separation resin bed which is substantially in a Ba2+ form and at
least one of these steps is carried out with a chromatographic separation
resin
bed, where the resin is a cation exchange resin in other than Ba2+ form.
In another embodiment of the invention, the method comprises feeding
a solution derived from biomass into a first chromatographic column including
a chromatographic separation resin bed which is substantially in a Ba2+ form,
eluting said column with an eluant, recovering a first mannose fraction, and
CA 02472246 2009-10-07
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then feeding said first mannose fraction into a second chromatographic col-
umn including a chromatographic separation resin bed, where the resin is a
cation exchange resin in other than Ba2+ form, eluting said column with an
eluant, and recovering a second mannose fraction.
In a further embodiment of the invention, the chromatographic separa-
tion process comprises two separation steps with a chromatographic separa-
tion resin bed which is substantially in a Ba2+ form and one separation step
with a chromatographic separation resin bed, where the resin is a cation ex-
change resin in other than Ba2+ form.
In another embodiment of the invention, the method comprises feeding
a solution derived from biomass into a first chromatographic column including
a chromatographic separation resin bed which is substantially in a Ba2+ form,
eluting said column with an eluant, recovering a first mannose fraction,
feeding
said first mannose fraction into a second chromatographic column including a
chromatographic separation resin bed which is substantially in a Ba2+ form,
eluting said column with an eluant, recovering a second mannose fraction, and
then feeding said second mannose fraction into a third chromatographic col-
umn including a chromatographic separation resin bed, where the resin is a
cation exchange resin in other than Ba2+ form, eluting said column with an
eluant, and recovering a third mannose fraction.
In another embodiment of the invention, the cation exchange resin in
other than Ba2+ form is in the form of a cation selected from hydrogen, NH4,
alkali metal cations and alkaline earth metal cations.
In another embodiment of the invention, the cation is selected from
NH4, Na+, K+, Mg2+ and Cat+.
In another embodiment of the invention, the chromatographic separa-
tion process is carried out with a strongly acid cation exchange resin.
In another embodiment of the invention, the purity of the at least one
mannose fraction is 45 to 80% mannose on RDS.
In another embodiment of the invention, the purity of the second man-
nose fraction is 45 to 80% mannose on RDS.
In another embodiment of the invention, the purity of the third mannose
fraction is 45 to 80% mannose on RDS.
In another embodiment of the invention, the chromatographic separa-
tion process provides a mannose fraction having a purity of more than 80% on
RDS.
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In another embodiment of the invention, the purity of the second man-
nose fraction is more than 80% on RDS.
In another embodiment of the invention, the purity of the third mannose
fraction is more than 80% on RDS.
In another embodiment of the invention, the method further comprises
one or more purification steps selected from membrane filtration, ion ex-
change, evaporation, filtration and derivatization carried out before, after
or
between said chromatographic separation step or steps.
In another embodiment of the invention, the derivatization comprises
forming N-phenyl-D-mannopyranosylamine as a mannose derivative.
In another embodiment of the invention, the method further comprises
crystallization of mannose to obtain a crystalline mannose product.
In another embodiment of the invention, the crystallization is carried out
with a solvent selected from water, alcohol and a mixture of alcohol with
water.
In another embodiment of the invention, the crystallization is carried out
with a mixture of ethanol and water.
In another embodiment of the invention, the crystallization is carried out
with water.
In another embodiment of the invention, the crystallization provides
crystalline mannose having a purity of more than 90% on RDS.
In another embodiment of the invention, the crystallization provides
crystalline mannose having a purity of more than 95% on RDS.
In another embodiment of the invention, the crystallization provides
crystalline mannose having a purity of more than 99% on RDS.
In another embodiment of the invention, the method further comprises
separation of other sugars.
In another embodiment of the invention, the method comprises separa-
tion of xylose as a pre-treatment step.
In another embodiment of the invention, the separation of xylose is car-
ried out through crystallization.
In another embodiment of the invention, the method further comprises
separation of arabinose.
In another embodiment of the invention, the method further comprises
separation of xylose by precipitation crystallization as a pre-treatment step
and
the separation of arabinose is carried out before the precipitation
crystalliza-
tion of xylose.
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8
In another embodiment of the invention, the separation of arabinose is
carried out by a chromatographic separation process to recover an arabinose
fraction.
In another embodiment of the invention, the chromatographic separa-
tion is carried out using a chromatographic separation resin bed in the form
of
a monovalent cation.
In another embodiment of the invention, the monovalent cation is se-
lected from hydrogen, ammonium and alkali metal cations.
In another embodiment of the invention, the cation is selected from H+,
NH4, Na+ and K+.
In another embodiment of the invention, the method further comprises
chromatographic purification of said arabinose fraction.
In another embodiment of the invention, the chromatographic purifica-
tion of said arabinose fraction comprises at least one step using a chroma-
tographic separation resin bed in the form of an alkaline earth metal cation.
In another embodiment of the invention, the alkaline earth metal is Cat+.
In another embodiment of the invention, the separation of arabinose is
carried out with a strongly acid cation exchange resin.
In another embodiment of the invention, the method further comprises
separation of rhamnose as a pretreatment step.
In another embodiment of the invention, the separation of rhamnose is
carried out before the separation of arabinose.
In another embodiment of the invention, the solution derived from bio-
mass is a biomass hydrolysate containing mannose and further sugars se-
lected from xylose, arabinose, rhamnose, galactose, glucose and fructose.
In another embodiment of the invention, the solution derived from bio-
mass is a biomass hydrolysate containing mannose and further sugars se-
lected from xylose, arabinose and rhamnose.
In another embodiment of the invention, the solution derived from bio-
mass is a hydrolysate derived from mannose-containing vegetable material.
In another embodiment of the invention, the solution derived from bio-
mass is a hydrolysate derived from lignocellulosic material.
In another embodiment of the invention, the solution derived from bio-
mass is a hydrolusate derived from softwood or hardwood.
In another embodiment of the invention, the solution derived from bio-
mass is a spent sulphite pulping liquor.
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= In another embodiment of the invention, the spent sulphite pulping liq-
uor is a spent sulphite pulping liquor recovered after the separation of rham-
nose.
In another embodiment of the invention, the spent sulphite pulping liq-
uor is a spent sulphite pulping liquor recovered after the separation of
xylose.
In another embodiment of the invention, the mannose is D-
mannose.
The invention is based on the idea of purifying the mannose-
containing carbohydrate mixture chromatographically using at least two sepa-
ration resins, one of which is Ba2+-based resin.
With the method of the invention, a mannose product with high pu-
rity can be obtained.
DEFINITIONS RELATING TO THE INVENTION
In the specification and throughout the examples and the claims,
the following definitions have been used:
SAC refers to a strongly acid cation exchange resin.
DS refers to a dry substance content measured by Karl Fischer ti-
tration, expressed as % by weight.
RDS refers to a refractometric dry substance content, expressed as
% by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
The following drawings are illustrative embodiments of the invention
and are not meant to limit the scope of the invention as defined in the claims
in
any way.
Figure 1 is a graphical presentation of the concentration profile of
the mannose-arabinose separation with Na+ form SAC resin (separation A) of
Example 1.
Figure 2 is a graphical presentation of the concentration profile of
the mannose separation with Ba2+ form SAC resin (separation C.1) of Exam-
ple 1.
Figure 3 is a graphical presentation of the concentration profile of
the repeated mannose separation with Ba2+ form SAC resin (separation C.2)
CA 02472246 2009-10-07
of Example 1.
Figure 4 is a graphical presentation of the concentration profile of
the mannose separation with Ca 2+ form SAC resin (separation C.3) of Exam-
ple 1.
5 Figure 5 is a graphical presentation of the concentration profile of
the arabinose separation with Ca 2+ form SAC resin (separation E.1) of Exam-
ple 1.
Figure 6 is a graphical presentation of the concentration profile of
the repeated arabinose separation with Ca 2+ form SAC resin (separation E.2)
10 of Example 1.
Figure 7 is a process scheme describing one embodiment of the in-
vention for recovering mannose and xylose. The process also includes separa-
tion of arabinose as a pre-treatment step.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a method of recovering mannose from a so-
lution containing the same. The method of the invention is characterized in
that said mixture is subjected to a chromatographic separation process using
at least one chromatographic separation resin bed which is at least partly in
a
Ba2+ form and at least one chromatographic separation resin bed which is in
other than Ba2+ form and recovering at least one mannose fraction.
The chromatographic separation process of the invention typically
comprises at least two chromatographic separation steps, whereby at least
one of these steps is carried out with a chromatographic separation resin bed
which is at least partly in a Ba2+ form and at least one of these steps is
carried
out with a chromatographic separation resin bed which is in other than Ba2+
form.
One embodiment of the invention is typically carried out by feeding
a solution containing mannose into a first chromatographic column including a
chromatographic separation resin bed which is at least partly in a Ba2+ form,
eluting said column with an eluant, recovering a first mannose fraction, and
then feeding said first mannose fraction into a second chromatographic col-
umn including a chromatographic separation resin bed in other than Ba2+ form,
eluting said column with an eluant, and recovering a second mannose fraction.
In another embodiment of the invention, said chromatographic
separation process comprises two separation steps with a chromatographic
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= separation resin bed which is at least partly in a Ba2+ form and one
separation
step with a chromatographic separation resin bed in other than Ba2+ form.
This embodiment of the invention is typically carried out by feeding
a solution containing mannose into a first chromatographic column including a
chromatographic separation resin bed which is at least partly in a Ba2+ form,
eluting said column with an eluant, recovering a first mannose fraction,
feeding
said first mannose fraction into a second chromatographic column including a
chromatographic separation resin bed which is at least partly in a Ba2+ form,
eluting said column with an eluant, recovering a second mannose fraction, and
then feeding said second mannose fraction into a third chromatographic col-
umn including a chromatographic separation resin bed in other than Ba2+ form,
eluting said column with an eluant, and recovering a third mannose fraction.
In the above-mentioned embodiment of the invention, some other
separation may be carried out before the Ba2+ separation. In the same way,
some other separation may be carried out between the Ba2+ separations. Fur-
thermore, between two ion exchange operations, equilibration of the ions or
the ion composition is typically carried out, for example by ion exchange.
In one embodiment of the invention, said resin (resin bed) which is
at least partly in a Ba2+ form is substantially in a Ba2+ form. During the
chroma-
tographic separation process, balancing of the chromatographic column oc-
curs, whereby said resin bed which is at least partly in a Ba2+ form may even
contain other ions, such as H+, alkali metal cations, such as Na+ and K+, and
alkaline earth metal cations, such as Ca 2+ and Mgt+.
Said resin which is at least partly in a Ba2+ form refers to a cation
exchange resin.
Said resin (resin bed) in other than Ba2+ form refers to a resin,
which is in the form of a cation other than Ba2+. Said resin is typically a
cation
exchange resin, where the cation is in the hydrogen form (H+), in NH4+ form or
in the form of a metal selected from alkaline metals and alkaline earth
metals,
such as Na+, K+, Mg2+ and Ca2+. An especially preferred metal is Ca2+.
The chromatographic separation for obtaining mannose in accor-
dance with the present invention is typically carried out with a strongly acid
cation exchange resin. A preferred resin is a cross-linked styrene-
divinylbenzene based resin. A suitable cross-linking degree of the resin is 1
to
20% by weight, preferably 3 to 8% by weight. The average particle size of the
resin is normally 10 to 2000 m, preferably 100 to 400 m. Zeolite-based mo-
I i 1 r i .r. i Irru it i I ii r
CA 02472246 2009-10-07
12
= lecular sieves can also be used.
The eluant used in the chromatographic separation according to the
present invention is either water, a solvent, e.g. an alcohol, or a mixture
thereof. A preferred eluant is water.
The elution is preferably carried out at a temperature from 10 to
95 C, more preferably from 30 to 95 C, most preferably from 55 to 85 C.
The chromatographic separation method of the invention provides a
mannose fraction where mannose is in a solution form. The mannose product
obtained from the chromatographic separation has a typical purity of 45 to
80% mannose on RDS.
To improve the yield of the chromatographic separation, recycle
fractions of the chromatographic separation can also be used.
The chromatographic separation method of the invention may fur-
ther comprise one of more purification steps selected from membrane filtra-
tion, ion exchange, evaporation, filtration and derivatization. These
purification
steps may be carried out before, after or between said chromatographic sepa-
ration step/steps.
Ion exchange is typically carried out to purify the mannose-
containing solution from SO4- ions, for example.
In the derivatization method, a mannose derivative is formed,
whereafter mannose is regenerated from the derivative thus obtained. One
example of useful mannose derivatives is N-phenyl-D-mannopyranosylamine.
The mannose solution obtained from the chromatographic separa-
tion can be further purified by crystallization to obtain a crystalline
mannose
product. The crystallization is typically carried out using a solvent selected
from water, alcohol and a mixture of water and alcohol. In a preferred em-
bodiment of the invention, the crystallization is carried out with a mixture
of
ethanol and water.
The crystallization is carried out by evaporating the mannose solu-
tion or mannose syrup obtained from the chromatographic separation to an
appropriate dry substance content (e.g. to RDS of about 85%). The boiling
syrup may be seeded with mannose seed crystals. The seeds, if used, are
suspended in a crystallization solvent, which may be either water, a solvent ,
e.g. an alcohol, or a mixture thereof. A typical crystallization solvent is
ethanol.
After cooling the crystallization mass to room temperature, the
crystallization
solvent is added. The crystallization mass may then be allowed to stand for a
I i I I i , i wi it 1
CA 02472246 2009-10-07
13
= period of time, preferably for 3 to 6 days, typically at room temperature,
whereafter the crystals are filtered off. The filtration cake is washed with
the
crystallization solvent. Mannose crystals with a high purity are obtained.
The crystallization provides crystalline mannose having a purity of
over 90%, preferably over 95% and most preferably over 99% on RDS.
The method of the invention may also comprise separation of other
sugars, such as xylose, rhamnose and arabinose, depending on the composi-
tion of the starting mannose-containing solution. The separation of other sug-
ars is typically carried out before the separation of mannose.
The method of the invention may thus comprise separation of xy-
lose as a pretreatment step. The recovery of xylose may be carried out by
various methods, e.g. through precipitation crystallization.
The xylose precipitation crystallization is preferably carried out im-
mediately before the chromatographic separation of mannose.
In the xylose precipitation crystallization, the solution containing
mannose and some xylose is subjected to a crystallization step. The precipita-
tion crystallization of xylose is typically carried out by evaporating the
solution
to a desired dry substance content, seeding the solution with xylose seed crys-
tals, and then cooling the crystallization mass according to a desired cooling
program. The crystallization mass is filtered to obtain a xylose cake and man-
nose-containing crystallization run-off. Xylose is recovered from the
crystalli-
zation cake and the run-off containing mannose is subjected to the chroma-
tographic purification described above for obtaining mannose with high purity
in accordance with the present invention.
The method of the invention may also comprise separation of ara-
binose, preferably as a pretreatment step. The separation of arabinose may
be carried out before the precipitation crystallization of xylose. Chroma-
tographic separation is typically used for the recovery of arabinose. The chro-
matographic separation of arabinose is preferably carried out using a chroma-
tographic separation resin bed in the form of a monovalent cation, which is
selected from hydrogen, ammonium and alkali metal cations. Said monovalent
cation is typically selected from H+, Na+, K+ and NH4. An arabinose fraction
is
recovered. The chromatographic separation resin is preferably a strongly acid
cation exchange resin.
The arabinose fraction may be subjected to further chromatographic
purification. The chromatographic purification of the arabinose fraction
typically
CA 02472246 2009-10-07
14
comprises at least one step using a chromatographic separation resin bed in
the form of an alkaline earth metal, preferably Cat+. The arabinose fraction
thus obtained may also be crystallized.
The method of the invention may also comprise separation of
rhamnose as a pretreatment step. The separation of rhamnose is typically car-
ried out before the separation of arabinose.
For xylose-rich raw materials, the method of the invention may also
comprise separation of xylose as a pretreatment step. The separation of xy-
lose it typically carried out before the separation of arabinose.
The method of the invention may also include further purification
steps, such as membrane filtration, e.g. ultrafiltration and nanofiltration,
ion
exchange, evaporation and filtration to remove e.g. lignosulphonates, acids
(organic acids and inorganic acids) and salts.
The starting solution containing mannose is typically a mixture con-
taining carbohydrates, such as sugars. The solution may contain, in addition
to
mannose, e.g. xylose, galactose, glucose, rhamnose, arabinose and fructose.
The mixture may also contain disaccharides and higher saccharides.
The material containing a mixture of carbohydrates is typically de-
rived from a biomass, typically mannose-containing vegetable material, such
as softwood or hardwood, straw, corn husks, corn cops, corn fibers and sugar
beet. The starting material is as a rule used in the form of a hydrolysate ob-
tained e.g. by prehydrolysis, total hydrolysis, steam hydrolysis, enzymatic hy-
drolysis or acid hydrolysis.
The biomass hydrolysate used for the recovery of mannose in ac-
cordance with the present invention is typically a spent liquor obtained from
a
pulping process. The spent liquor is especially a spent sulphite pulping
liquor,
which may be obtained by acid, basic or neutral sulphite pulping. If the bio-
mass hydrolysate, e.g. the spent liquor contains mannose in polymeric form,
the polymeric mannose can be hydrolysed by acids or enzymes before the
chromatographic separation steps.
A typical spent liquor useful in the present invention is a mannose-
containing spent liquor, which is preferably obtained from acid sulphite
pulping.
The spent liquor may be obtained directly from sulphite pulping. It may also
be
a concentrated sulphite pulping liquor or a side-relief obtained from sulphite
cooking. It may also be a mannose-containing fraction chromatographically
obtained from a sulphite pulping liquor.
iIrr it Ir
CA 02472246 2009-10-07
In the present invention, the liquor to be treated may also be any
other liquor obtained from the digestion or hydrolysis of biomass, typically a
hydrolysate obtained from acid hydrolysis of lignocellulosic material. Such a
hydrolysate may be obtained from lignocellulosic material for example by
5 treatment with an inorganic acid, such as hydrochloric acid, sulphuric acid
or
sulphur dioxide, or by treatment with an organic acid, such as formic acid or
acetic acid. A spent liquor obtained from solvent-based pulping, such as phe-
nol-based pulping and ethanol-based pulping may also be used.
The starting solution containing mannose may be e.g. a spent sul-
10 phite pulping liquor recovered after the separation of rhamnose. The
starting
solution may also be a spent sulphite pulping liquor recovered after the sepa-
ration of xylose.
The mannose product obtained in accordance with the present in-
vention typically comprises D-mannose.
15 The following examples illustrate the invention. The examples are
not be construed to limit the claims in any manner.
In the following examples, the following definitions are used:
DS refers to the dry substance content measured by Karl Fischer ti-
tration, expressed as % by weight, unless otherwise indicated.
The contents (expressed in % on DS) of various components of the
fractions obtained from the chromatographic and other separations have been
measured using the HPLC method.
Example 1
A process scheme describing the multistep separation process of
Example 1 is presented in Figure 7.
The starting liquor used in the first step of the process was a man-
nose-containing side stream separated from Ca2+ based sulphite spent liquor
after the recovery of xylose and rhamnose. Birch had been used as raw mate-
rial for the sulphite pulping.
The mannose-containing side stream recovered after the separation
of rhamnose was subjected to chromatographic separation to obtain a man-
nose fraction and an arabinose fraction (chromatographic separation A). The
mannose fraction was subjected to separation B (xylose precipitation crystalli-
zation) to obtain a xylose cake and a crystallization run-off containing man-
nose. The mannose-containing run-off from the crystallization of xylose was
CA 02472246 2009-10-07
16
subjected to three successive chromatographic separations (C.1), (C.2) and
(C.3). The mannose fraction from the last chromatographic separation was
subjected to mannose crystallization.
The arabinose fraction from separation (A) was subjected to two
successive chromatographic separations (E.1) and (E.2) for recovering purified
arabinose.
The starting mannose-containing liquor obtained after the separa-
tion of rhamnose had the following composition:
Component Content % on DS
Xylose 36
Mannose 15
Galactose 13
Glucose 4.8
Rhamnose 0.6
Arabinose 4.9
Fructose 1.4
Others 24.6
(A) Separation of arabinose using Na+-form SAC resin
A strongly acid cation exchange resin in Na+ form was used to re-
move the salts from the feed and to collect arabinose from the end of the elu-
tion profile. The separation was done using the following separation condi-
tions:
Column diameter 0.6 m
Bed height 5.3 m
Feed size 108.51
Feed RSD 35 /100
Temperature 65 OC
Flow rate 170 I/h
Resin Finex CS 11 GC, 5.5% DVB,
average particle size 0.35 mm
The composition of the mannose and arabinose fractions collected
from separation (A) are set forth in Table 1.
CA 02472246 2009-10-07
17
Table 1.
Composition of the mannose and arabinose fractions in % on DS
Component Mannose fraction Arabinose fraction
Xylose 43 34
Mannose 19 13
Galactose 16 10
Glucose 6.3 0.2
Rhamnose 1.1 0.1
Arabinose 1.8 17
Fructose 1.2 2.2
Others 8.9 23.5
The mannose yield was 38% for mannose purity of 19 % on DS and
xylose purity of 43 % on DS.
The concentration profile of separation (A) is presented in Figure 1.
(B) Xylose precipitation crystallization
The mannose fraction obtained from separation (A) and having a
xylose content of about 43 % on DS was subjected to precipitation crystalliza-
tion to separate xylose.
The precipitation crystallization of xylose was carried out in pilot
scale with one crystallizer of about 200 liters. The feed liquor was
evaporated
to a final DS of 87.5%. The batch was seeded in a boiling pan with xylose
seed crystals. The mass was cooled down from 60 C to 31 C in 48 hours and
then the mass was held at 31 C for 24 hours. No dilutions were made. The
mass was dropped down to a mingler and then filtrated.
The results of the xylose precipitation crystallization are set forth in
Table 2. The table shows the contents of various components in the crystalli-
zation feed, cake and run-off in % on DS.
Table 2.
Analysis results of the xylose precipitation crystallization
Component Feed Cake Run-off
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18
Glucose 5.9 2.9 7.0
Xylose 42.7 73.8 29.8
Arabinose 3.5 1.0 2.9
Mannose 19.5 7.2 23.7
The mannose purity of the crystallization run-off inreased to about
24 % on DS and the xylose purity decreased to about 30%.
(C) Mannose separations
(C.1.) Mannose separation with Ba2+ form SAC resin
The run-off fraction obtained from the xylose precipitation crystalli-
zation was subjected to chromatographic separation using a Ba2+ form SAC
resin. The separation was done using the following separation conditions:
Column diameter 0.225 m
Bed height 5.3 m
Feed size 11.91
Feed RSD 32 g/1
Temperature 65 OC
Flow rate 25 I/h
Resin Finex CS 08 GC, 4 % DVB,
average particle size 0.38 mm
The mannose fraction was collected with a mannose yield of 70%
and the total purity of 49 % on DS was obtained. The composition of the man-
nose and xylose fractions is presented in Table 3.
Table 3.
Composition of the mannose and xylose fractions from the first
separation with Ba2+ form SAC resin in % on DS
Component Xylose fraction Mannose fraction
Xylose 47 9.2
Mannose 9.6 49
Galactose 23 13
Glucose 12 0.2
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19
Rhamnose 1.8 0.8
Fructose 0.1 4.0
Others 6.5 24.2
The concentration profile of separation (C.1) is presented in Figure
2.
(C.2.) Ba2+ form SAC resin separation
A second Ba2+ form SAC resin separation was used to purify the
mannose fraction obtained from the previous step (separation C.1). The same
separation conditions were used as in separation (C.1) above.
The mannose fraction obtained from the separation had a purity of
63 % on DS with a mannose yield of 68%. The compositions of the mannose
and xylose fractions in % on DS are set forth in Table 4.
Table 4.
Composition of the mannose and xylose fractions from the second
separation with Ba2+ form SAC resin
Component Xylose fraction Mannose fraction
Xylose 19 1.1
Mannose 41 63
Galactose 24 3.5
Glucose 0.5 -
Rhamnose 1.4 0.2
Fructose 0.7 7.8
Others 13.9 24.3
The xylose fraction still contained 40% mannose.
The concentration profile of separation (C.2) is presented in Figure
3.
(C.3.) Separation with Ca 2+ form SAC resin
The mannose fraction obtained from separation (C.2) was sub-
jected to a further chromatographic separation using Ca 2+ form SAC resin. The
separation was done using the following separation conditions:
CA 02472246 2009-10-07
Column diameter 0.225 m
Bed height 4.8 m
Feed size 11 I
Feed RSD 30.7 100 g
Temperature 65 OC
Flow rate 30 I/h
Resin Finex CS 11 GC, 5.5 % DVB,
average particle size 0.35 mm
The composition of the mannose fraction in % on DS is set forth in
Table 5.
5
Table 5.
Composition of the mannose fraction obtained from the separation
with a Ca2+ form SAC resin
Component Mannose fraction
Xylose 1.8
Mannose 80
Galactose 5.1
Glucose -
Rhamnose 0.2
Fructose 2.6
Others 10.3
Mannose fraction purity of 80 % on DS was obtained with a man-
nose yield of 70%. The concentration profile of separation (C.3) is presented
in
Figure 4.
D. Mannose crystallization
(D.1.) Mannose crystallization using water-ethanol solvent (batch 1)
2924 g of mannose syrup having a DS of 51 % and a mannose con-
tent of 78%, based on the refractometric dry solids content of pure mannose,
was evaporated to RDS of 86.2% and moved to a 2-liter reaction vessel at a
temperature of 30 C. Seeding (30 C, RDS 86.2%) was made to the boiling
CA 02472246 2009-10-07
21
syrup with 0.03% seeds on DS. The seeds were suspended with 10 ml etha-
nol.
The mass was cooled down from a temperature of 30 C to a tem-
perature of 25 C. 800 g ethanol was added slowly to the mass.
After 5 days from seeding, the crystals were filtrated with a pressure
filter. The filtration gave a cake purity of 93.0% (including solvent ethanol
as
impurity) and a mother liquor purity of 52.5% (including solvent ethanol as im-
purity). This corresponds to a mannose yield of 41%. The crystal size was in
the range of 10 to 20 m.
The filtration cake was washed twice with ethanol. The crystals
were centrifuged and dried at 40 C for 24 hours. The crystals had a crystal
water content of 0.3% and a mannose content of 99.9%.
(D.2). Mannose crystallization using water-ethanol solvent (batch 2)
1230 g of a mannose syrup having a DS of 50% and a mannose
content of 93%, based on the refractometric dry solids content of pure man-
nose, was evaporated to an RDS of 84.1% and moved to a 2-liter reaction
vessel at a temperature of 30 C. Seeding (30 C, RDS 84.1 %) was made to the
boiling syrup with 0.03% seeds on DS. The seeds were suspended with 10 ml
ethanol.
The mass was cooled down from a temperature of 30 C to a tem-
perature of 20 C. 300 g ethanol was added slowly to the mass.
After 3 days from seeding, the crystals were centrifuged. The centri-
fuging gave a cake purity of 96.0% (including solvent ethanol as impurity).
The
centrifuging result corresponds to a 50% mannose yield. The crystal size was
in the range of 30 to 50 gm.
The centrifuging cake was washed twice with ethanol. The crystals
were centrifuged and dried at 40 C for 24 hours. The crystal water content was
analyzed to be 0.2%, and the crystal mannose content to be 99.7%.
(D.3.) Mannose crystallization using water as the solvent
1552 g of a mannose syrup having a DS of 50% and a mannose
content of 80%, based on the refractometric dry solids content of pure man-
nose, was evaporated to an RDS of 86.7% and moved to a 1-liter reaction
vessel at a temperature of 60 C. Seeding (60 C, RDS 86.7%) was made to the
boiling syrup with 0.07% seeds on DS.
CA 02472246 2009-10-07
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The mass was cooled down from a temperature of 60 C to a tem-
perature of 25 C. After 6 days from seeding, the centrifuging cake gave a pu-
rity of 99.5%. The centrifuging result corresponds to a mannose yield of 30%.
The crystal size was in the range of 30 to 50 m.
(E) Purification of the arabinose fraction
The arabinose fraction obtained from separation (A) had a purity of
% on DS. This fraction was further purified with a Ca 2+ form SAC resin.
10 (E.1.) Purification of the arabinose fraction with a Ca 2+ form SAC
resin.
The separation was done under the following separation conditions:
Column diameter 0.225 m
Bed height 4.9 m
Feed size 18.81
Feed RSD 30.2 /100
Temperature 65 C
Flow rate 30 I/h
Resin Finex CS 11 GC, 5.5% DVB,
average particle size 0.40mm
The compositions of the feed, xylose and arabinose fractions in %
on DS are set forth in Table 6.
Table 6.
Composition of the feed, xylose and arabinose fractions from the
first separation with Ca 2+ resin
Component Feed Xylose fraction Arabinose frac-
tion
Xylose 39 50 21
Mannose 16 16 14
Galactose 13 15 9.2
Glucose 1.1 1.5 0.3
Rhamnose 0.3 0.3 0.3
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23
Arabinose 9.7 3.5 19
Fructose 0.1 0.6 1.3
Others 20.8 13 35.4
The concentration profile of separation (E.1) is presented in Figure
5.
(E.2.) Repeated purification of the arabinose fraction with a Ca 2+
form SAC resin
The arabinose fraction obtained from separation (E.1) was sub-
jected to another purification with a Ca 2+ form resin. The separation was
done
using the following separation conditions:
Column diameter 0.225 m
Bed height 4.9 m
Feed size 20 I
Feed RSD 30.6 /100
Temperature 65 C
Flow rate 30 I/h
Resin Finex CS 11 GC, 5.5% DVB,
average particle size 0.40mm
The composition of the feed, xylose and arabinose fractions in % on
DS is set forth in Table 7.
Table 7.
Composition of the feed and xylose and arabinose fractions from
the second separation with a Ca 2+ form resin
Component Feed Xylose fraction Arabinose frac-
tion
Xylose 27 43 14
Mannose 16 20 13
Galactose 11 15 7
Glucose 0.2 0.6 0.0
Rhamnose 0.4 0.4 0.3
CA 02472246 2009-10-07
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= Arabinose 18 6.2 26
Fructose 3.8 1.5 5.3
Others 23.6 13.6 34.7
The arabinose was collected with an 85% yield.
The concentration profile of separation (E.2) is presented in Figure
6.
It will be obvious to a person skilled in the art that, as the technol-
ogy advances, the inventive concept can be implemented in various ways. The
invention and its embodiments are not limited to the examples described
above but may vary within the scope of the claims.
