INDUSTRIAL-SCALE D-MANNOSE EXTRACTION FROM D-MANNOSE BISULFITE ADDUCTS
20200102338 · 2020-04-02
Inventors
Cpc classification
C13K13/007
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention relates to a process for the selective isolation of highly purified, crystalline D-mannose from complex sugar mixtures, in particular from mixed wood sugars, more particularly from spent sulfite liquor (SSL). The process of the present invention is based on converting mannose into essentially pure mannose bisulfite adducts. Subsequent oxidative recovery of mannose from the mannose bisulfite adducts renders crystalline mannose in improved yields and purities.
Claims
1. Process for the isolation of purified D-mannose, comprising at least the following steps: (a) providing a feed of mixed sugars, which feed comprises D-mannose, including D-mannose in the form of polymers or copolymers; (c) optionally concentrating the feed of mixed sugars of step (a) to a predetermined dry matter content, wherein said dry matter content is from 1% to 70%; (d) adding at least one sulfite to the feed of mixed sugars of step (a) or to the mixture of step (c), resulting in a D-mannose-bisulfite adduct; (e) regenerating or recovering D-mannose from the D-mannose-bisulfite adduct of step (d) by treating said D-mannose-bisulfite adduct with at least one oxidant and at least one base.
2. Process according to claim 1, wherein the feed of mixed sugars in step (a) comprises or consists of a spent sulfite liquor (SSL).
3. Process according to claim 2, wherein the feed of mixed sugars is subjected, after step (a) and before step (d), to a pretreatment step (b), wherein said pretreatment step (b) comprises the separation, preferably by ultrafiltration, of at least a portion of the high molecular weight lignosulfonates present in the feed of mixed sugars.
4. Process according to any of the preceding claims, additionally comprising the following step (f), after step (e): (f) crystallizing D-mannose from the mixture of D-mannose and sulfate of step (e) by first precipitating sulfate.
5. Process according to any of the preceding claims, wherein the feed of mixed sugars is or comprises a hydrolysate or a prehydrolysate of biological material with mannose containing polymers such as mannan, xylomannan, glucomannan, galactomannan or galactoglucomannan, or a glucose epimerization mixture.
6. Process according to claim 5, wherein the raw material for the feed is selected from annual plants, corms, in particular konjac, yeast and fungi cell walls, in particular Saccharomyces cerevisiae, agricultural residues or food residues, in particular copra meal, palm kernel meal, spent coffee grounds or orange peel, or wood, in particular softwood.
7. Process according to any of claims 2 to 6, wherein, prior to step (a), a lignocellulose-based raw material is cooked with a sulfite, preferably a sodium, calcium, ammonium, sodium or magnesium sulfite under acidic, neutral or basic conditions.
8. Process according to any one of the preceding claims, wherein the sulfite added in step (d) is selected from the Na.sup.+, Ca.sup.2+, NH.sub.4.sup.+, K.sup.+-salts of either sulfite, bisulfite and/or metabisulfite, including SO.sub.2 as a liquid or a gas, or any combination thereof.
9. Process according to any one of the preceding claims, wherein at least one solvent is added to the reaction mixture of (d).
10. Process according to any one of the preceding claims, wherein the D-mannose bisulfite product resulting from step (d) has a dry matter content of 30 to 70 wt.-% and/or a D-mannose content of 50 to 60 wt.-%, based on the overall dry mass.
11. Process according to any one of the preceding claims, wherein the D-mannose bisulfite product resulting from step (d) preferably has a dry matter content of 30 to 80 wt.-%, preferably 40 to 70% (based on the overall weight) and/or a D-mannose content of 50 to 70 wt.-%, preferably 55% to 60 wt % (based on the overall dry mass).
12. Process according to any one of the preceding claims, wherein the oxidant of step (e) is selected from peroxides, organic peroxides, ozone, hypochlorite (and its derivatives), air, oxygen, or any combination thereof, wherein H.sub.2O.sub.2 is preferred as oxidant.
13. Process according to any one of the preceding claims, wherein, in step (e), the pH at no time exceeds the value of 7, preferably wherein during the addition of the oxidant and base, the pH preferably is controlled to be in the range of from 1 to 5.
14. Process according to any one of the preceding claims, wherein the feed of mixed sugars from step (a), or the aqueous phase comprising D-mannose from step (b) or the mixture from step (c), is subjected to a sodium source, preferably to sodium sulfate, to exchange anions for sodium, or is subjected to a potassium source, preferably to potassium sulfate, to exchange anions for potassium.
Description
BRIEF DESCRIPTION OF THE FIGURES
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[0091]
[0092]
[0093]
DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION
Raw Materials
[0094] In respect to the raw material to be used as feedstock for D-mannose extraction, no limitations exist, in principle, as long as the material contains D-mannose in some form (e.g. as polymers or as co-polymers), for instance as mannan, xylomannan, galactomannan, glucomannan or galactoglucomannan.
[0095] Mannan is abundant in nature, and is present, for example, in the endosperm of the monocotyledonous (e.g. Arecaceae family), such as ivory nuts (Phytelephas sp.), dates (Phoenix dactylifera), oil palm kernels (Elaeis guineensis) and coconut (Cocos nucifera). Mannan is also found in the cell walls of several green algae belonging to the Codiaceae and Dasycladaceae families. It is also distributed within some species from Apiaceae, Rubiaceae (Coffea sp.) and Asteraceae. Furthermore, mannan is found to be a major constituent of Mycobacteriae and yeast cell walls. Xylomannan is found in red seaweed (Nothogenia fastigiata).
[0096] Galactomannan is mainly found in leguminous seeds such as Fenugreek (Trigonella foenum-graecum), Guar (Cyamopsis tetragonoloba), Tara (Caesalpinia spinosa) and Carob (Ceratonia siliqua). Galactomannan is also a component of the cell wall of the mold Aspergillus.
[0097] Glucomannan is found in the roots of the konjac plant (Amorphophallus konjac). It is also a hemicellulose that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledons.
[0098] Galactoglucomannan are prominent components of coniferous woods (almost 20% of dry matter from softwoods are hemicellulosic galactoglucomannan). These are also found in other wood species as well as in the primary cell walls of other plants, fruits, and seeds, such as flax, tobacco plants, or kiwifruit.
[0099] A suitable feed of mixed sugars may be or comprise a hydrolysate or a prehydrolysate in particular of biological material with mannose containing polymers such as mannan, xylomanna, glucomannan, galactomannan or galactoglucomannan, or a glucose epimerization mixture.
[0100] The raw material for the feed is selected from annual plants, corms, in particular konjac, yeast and fungi cell walls, in particular Saccharomyces cerevisiae, agricultural residues or food residues, in particular copra meal, palm kernel meal, spent coffee grounds or orange peel, or wood, in particular softwood.
[0101] Preferred raw materials that are suited for the process of the present invention are energy crops, annual plants, agricultural residues and wood. One advantage of such materials is that not only that D-mannose may be extracted, but that the cellulose pulp can be further processed to valuable products, for example by way of converting the lignocellulosic biomass in a biorefinery process (biomass conversion).
Sulfite Pulping
[0102] Unlike the sodium based Kraft process that is performed at a pH of the fresh cooking liquor of about 13, sulfite cooking is characterized in that it covers the whole pH range. The pH may range from <1 (using sulfur dioxide solutions in water) to >13 (using sulfur dioxide or sodium sulfite or sodium bisulfite together with sodium hydroxide).
[0103] Sulfite cooking may be divided into four main groups: acid, acid bisulfite, weak alkaline and alkaline sulfite pulping.
[0104] In embodiments of the present invention and prior to step (a), the lignocellulosic biomass is cooked with a sulfite, preferably a sodium, calcium, ammonium or magnesium sulfite, further preferably calcium sulfite under acidic, neutral or basic conditions.
[0105] This sulfite cook dissolves most of the lignin as sulfonated lignin (lignosulfonate) together with parts of the hemicellulose, if present. This dissolved or liquid phase (pulping liquor) is the liquid SSL phase. The cellulose is left almost intact in the pulp, together with parts of the hemicellulose.
Separation of Pulp and SSL
[0106] Prior to step (a), the pulp (solid phase; cellulose and hemicellulose) is preferably separated from the spent sulfite liquor (liquid SSL phase; SSL, sulfonated lignin and hemicellulose) by any separation method known to the person skilled in the art; in particular pressing, filtration, sedimentation or centrifugation.
EXAMPLES
Example 1
Preparation of a Spent Sulfite Liquor
[0107] Spent Sulfite Liquor (SSL) was derived from the digestion of softwood chips with calcium sulfite, in a pulping step (Ca-based SSL).
[0108] The sulfite spent liquor stream was then subjected to a pretreatment step of ultrafiltration (UF, 2-100 KDa MWCO), in which the high molecular weight lignosulfonates (LS), and any other substances retained by the membrane were separated from the aqueous permeate containing the D-mannose (see Scheme 1 in
[0109] Some of the water was then stripped off the D-mannose rich Ca-SSL-permeate solution under vacuum, in order to obtain a Ca-SSL concentrate. This brown Ca-SSL concentrate was then used to prepare the mannose-sulfite adduct.
Example 2
Preparation and Working-Up of the Mannose-Sulfite Adduct
[0110] The aqueous Ca-SSL concentrate obtained with pre-treatment by ultrafiltration was contacted with an excess of sulfite, in an aqueous solution (see Scheme 3,
[0111] The resulting solution was then stirred and the pH was adjusted to pH4. A short chain alcohol was then added to the reaction as an anti-solvent, while maintaining a reaction temperature of 60 C. The resulting solution was then held at 60 C. for 30 hours before being cooled to 20 C. for a time period of 5 to 7 hours.
[0112] The mixture was left to crystallize under a set temperature program for 18 to 24 hours, in which time period a thick beige/white slurry of solids developed. The solid was then filtered off using vacuum filtration to provide a wet filter cake. The so-obtained D-mannose-bisulfite adduct was essentially free from other sugars. The filter cake was then washed with a solvent consisting of water and ethanol (25-50 vol % water in ethanol). After the washing procedure, the essentially colorless white solid was centrifuged/pressure dried to remove most of the mother liquor from the wet filter cake. The wet D-mannose bisulfite product typically had a dry matter content of 30 to 80 wt.-% and a D-mannose content of 50 to 60 wt.-% (based on dry mass).
Example 3
Oxidation of the Mannose-Sulfite Adduct (Laboratory Scale)
[0113] 1.0 kg of mannose-bisulfite adduct (equivalent to 500 g D-mannose) were added into a 5 L reactor, followed by the addition of 2.0 L of water. The slurry was agitated using a mechanical overhead stirrer and the reactor was fitted with a thermometer, pH-probe and a 500 mL addition funnel. The reaction temperature (jacket) controlled using a temperature controlled thermostat.
[0114] 330 to 340 mL of H.sub.2O.sub.2 (35% aq.) were added to the slurry of D-mannose bisulfite adduct, via the addition funnel over the course of 15-20 minutes. 50% aq. NaOH was simultaneously added to the solution in such fashion that the temperature of the reaction did not exceed 40 to 45 C., while the pH was kept <4.5. In total, 250 to 260 g of 50%, aq. NaOH was needed for the transformation. The NaOH addition time was typically 20 to 40 minutes. After addition of approximately of the volume (or mass) of 50% aq. NaOH, the mixture had become an essentially clear solution. At this point, the pH also rose slowly from pH 1.5 to 2.5 to pH 3 to 4. Addition of NaOH was stopped at pH=5. After complete addition of both H.sub.2O.sub.2 and 50% aq. NaOH, the solution was cooled to 20 to 25 C. (at pH=5) and left to stir at this temperature for 1 hour. At this time a sample was collected and filtered through a 0.45 m syringe filter. The residual H.sub.2O.sub.2 content at this point was <250 ppm, as determined by peroxide sticks (Quantostix).
[0115] Two drops of the filtrate were diluted with D.sub.2O and subjected to .sup.1H-NMR spectroscopy to determine if all of the D-mannose bisulfite adduct had reacted. D-mannose bisulfite adduct has a characteristic signal at 4.14 ppm (d, J=9.5 Hz), readily traceable in the .sup.1H-NMR-spectrum.
Optional De-Colorization Step
[0116] In an optional step, 5 g of charcoal (1 wt % based on dry D-Mannose in D-mannose bisulfite adduct) is added to the oxidized solution obtained after addition of H.sub.2O.sub.2 and NaOH. The resulting slurry was stirred for 1 hour at pH 4.5-5 (20-23 C.). After this time, the charcoal was filtered off under vacuum (fiber glass filter) to give a charcoal free de-colorized solution. This operation has only a limited effect on the sugar content and sugar distribution in the solution.
[0117] The lightly yellow solution (before or after de-colorization with charcoal) was filtered and water was evaporated off (rotary evaporator, 60 C., water-suction) until a syrup like residue containing approx. 20-30 wt % water obtained (determined by Karl Fischer titration). This step provided a syrup/slurry containing large amounts of Na.sub.2SO.sub.4 and D-mannose.
Example 4
Salt Precipitation
[0118] 500 wt.-% EtOH (with respect to the total amount of D-mannose in the starting adduct) was added to the syrup containing D-mannose from Example 3. The slurry was heated to 50 C. and maintained at this temperature for 1 hour to dissolve the sugars and precipitate the Na.sub.2SO.sub.4 (under mechanical-overhead stirring). The solids were then filtered off at 40 to 50 C. (vacuum filtration, blue-ribbon filter paper) and the filter cake was washed with 100 wt % EtOH (with respect to the total amount of D-mannose in the starting adduct, EtOH/H.sub.2O, 95:5 by wt. at 20 C.) to provide a combined filtrate. The water content (Karl Fischer titration) was determined to be 7 to 10 wt.-% in the filtrate. On the basis of sugar analysis (ion chromatography), conversion/recovery of D-mannose from the D-mannose bisulfite adduct was found to be within the range of 95 to 100% (i.e. quantitative).
Example 5
Crystallization
[0119] The warm filtrate obtained in example 4 (45 C.) was seeded at 45 C. with crystalline D-mannose and allowed to cool down slowly (0.8 C./h) from 45 C. to 10 C. Crystallization was allowed to proceed for 48 hours before the solid mass of product was filtered of at 10 C. The resulting filter cake was washed with a solution comprised of 95:5 EtOH/Water (by volume) cooled to 5 C. to give a white crystalline solid. The solid was dried under vacuum at 45 C. to provide crystalline D-mannose in 50 to 55% yield based on D-mannose found in the starting D-mannose bisulfite adduct. The dry product contained <0.15 wt.-% EtOH and <0.10 wt.-% residual water. The purity of the solid was 98-99% by ion chromatography and no other sugars than D-mannose could be detected (by ion chromatography). The ash content was typically <0.25 wt.-%.
Example 6: Pilot Scale Isolation of D-Mannose from a Na-Permeate Concentrate
Ultrafiltration and Concentration of Permeate
[0120] Ca-spent sulfite liquor (Ca-SSL) was ultra-filtrated (UF) at 45 C. over 24 modules of PU120 membranes having a 20 kDa molecular cut-off (MWCO). The total dry matter content of the permeate was roughly 4.3%. The permeate was continuously collected during UF-operations and finally concentrated to 45-50% dry matter (DM), using a circulation evaporator. The pressure during distillation was maintained between 90-100 mbar. After this procedure the brown, Calcium rich permeate concentrate obtained was used for further processing.
Ion-Exchange from Calcium to Sodium
[0121] The Calcium permeate concentrate was ion-exchanged from Ca-form to Na-form using solid Na.sub.2SO.sub.4. 1848 L of Ca-permeate concentrate (47.8% DM) was treated with 148 kg of Na.sub.2SO.sub.4 at pH=1.3 and stirred for 1 hour. The solid CaSO.sub.4 as formed was subsequently decanted off to provide 1780 L of essentially particle free Na-permeate concentrate having a D-mannose concentration of 180-190 g/L and a dry matter content of 49%. The residual Calcium level of this sample was 0.04% (of DM).
Na-D-Mannose Bisulfite Adduct Formation
[0122] 238 kg of ion-exchanged permeate concentrate containing 180-190 g/L D-mannose, and 159 L water were loaded into a suitable reactor. The pH of the resulting brown solution was adjusted to 4.5 using 50% aq. NaOH. After pH-adjustment, 111 kg of absolute Ethanol were added and the resulting solution was heated to 30 C. 33 kg of Sodium metabisulfite (Na.sub.2S.sub.2O.sub.5) was then added in one portion at 30 C. with sufficient mixing to allow the solids to dissolve. After complete dissolution, the agitation rate was lowered and the batch was seeded with pure Na-D-Mannose bisulfite adduct to facilitate crystallization. The reaction was then cooled from 30 C. to 20-21 C. over the course of 7 hours and maintained at 21 C. for 13 hours before the solids were filtered off using a Nutsche filter. The resulting filter cake was washed with 5*53 L of EtOH/Water (50/50 by vol.) to give an essentially colorless solid. The washed solid had a D-mannose content of 62% (Ion-chromatography, dry matter) and 49% loss on drying (LOD). The filter cake was then converted into a slurry in water (100-150 L) and transferred to the oxidation reactor.
Na-D-Mannose Bisulfite Adduct Oxidation
[0123] In total, 4 batches of Na-D-Mannose bisulfite adduct were pooled (slurry, telescoped) before being oxidized. One oxidation batch contained roughly 100 kg D-mannose. To the slurry of Na-D-Mannose bisulfite adduct, 48-49 kg H.sub.2O.sub.2 (30-35% aq.) and 45 kg NaOH (50% aq.) was added at such a rate that the reaction temperature did not exceed 45 C. and reaction pH was 6. The total addition time was roughly 2.5 hours. After complete addition of H.sub.2O.sub.2 and NaOH, the pH was adjusted to 6 and the reaction was allowed to stir for 2-3 hours before the residual peroxide content was determined using peroxide sticks (Macherey Nagel Quantofix peroxide 1000). After the oxidation was deemed complete, water was evaporated off under vacuum (30-50 mbara, jacket temp 85 C.) until the residual volume was ca 150 L determined both visually and by radar measurement. The water content in the residue at this point was determined by Karl-Fisher titration to be in the region of 25 wt %.
Precipitation of Na.sub.2SO.sub.4 and Crystallization of D-Mannose
[0124] 491 kg absolute ethanol (pre-heated to 60 C.) was added to the 150 L residue containing roughly 25 wt % water and the resulting slurry was heated to 60 C. and stirred at this temperature for 1-2 h to dissolve all D-mannose and precipitate Na.sub.2SO.sub.4. After this time, Na.sub.2SO.sub.4 was filtered off (filter Nutsche heated to 55 C.) and the filtrate was transferred to a crystallization reactor pre-heated to 55 C. The filtrate was seeded with pure D-mannose at 55 C. and subsequently cooled from 55 C. to 20 C. over the course of 12 hours. After cooling, the crystallization was maintained at 20 C. for 6 hours to complete the crystallization. The solids were then filtered off and washed two times with 118 L Ethanol/Water (95:5 by wt.) before the solid D-mannose was dried under vacuum (jacket temp. 60 C.) with periodical stirring, until the loss on drying (LOD) was observed to be lower than 0.5%. In total 61.2 kg of a white solid was isolated and the dry crystalline product showed a D-Mannose HPLC assay of 99% (HPLC-RI) and a residual ash-level of 0.3%.
Example 7: Isolation of D-Mannose from K-Permeate Concentrate
[0125] Ion Exchange from Calcium to Potassium
[0126] The Calcium permeate concentrate from Example 6 (5 L, 180 g/L mannose) was ion exchanged into the K-form using solid K.sub.2SO.sub.4. The pH adjusted to 1.3 using KOH (50% aq. KOH). K.sub.2SO.sub.4 (425 g (85 g/L permeate concentrate)) was added and the reaction mixture was stirred at 20 C. for 1 hour. The grey precipitate was filtered off to provide a permeate concentrate in potassium (K) form.
K-D-Mannose-Bisulfite Adduct Formation
[0127] 5 L Ion exchanged permeate concentrate (180 g/L D-mannose) was loaded in to a 10 liter jacketed reactor. The pH was adjusted to pH 4.5 using KOH (50% aq.). EtOH (0.5 vol. eq., 2.5 L) was added and the reaction mixture was heated to 30 C. Potassium disulfite (K.sub.2S.sub.2O.sub.5) (1.0 kg) was added in one portion and the reaction was stirred at 70 rpm for 10 minutes before the agitation rate was reduced to 47 rpm and the reaction was stirred at 30 C. for 1 hour. The heat was turned off and the mixture was cooled down to 21 C. overnight (18 h). The resulting solid mass was filtered and the filter cake was washed with a mixture of EtOH and Water (50/50 by vol.) The resulting white granular solid was slurred in 0.5 L water and transferred to a 5 L 3-necked flask.
K-D-Mannose-Bisulfite Adduct Oxidation
[0128] H.sub.2O.sub.2 (0.3 kg, 30-33% aq) was added slowly to the slurred K-D-mannose bisulfite adduct (containing approx. 56% D-mannose) in a 5 L 3-necked flask. During addition of H.sub.2O.sub.2 the pH of the reaction mixture was maintained between pH 4 and pH 6 by addition of KOH (50 wt %, 0.42 kg). The temperature of the reaction was not allowed exceed 45 C. After addition was completed the residual H.sub.2O.sub.2-level was measured with peroxide strips (Macherey Nagel Quantofix peroxide 1000) and H.sub.2O.sub.2-level was adjusted (if necessary) by adding more H.sub.2O.sub.2 (in case too little H.sub.2O.sub.2 was added) or more K.sub.2S.sub.2O.sub.5 (in case too much H.sub.2O.sub.2 was added) so that the residual H.sub.2O.sub.2-level was 800 ppm. The reaction mixture was stirred for one hour before .sup.1H NMR was performed to confirm completion of the reaction. The K-D-mannose bisulfite adduct has a characteristic signal at 4.14 ppm (d, J=9.5 Hz), readily traceable in the .sup.1H-NMR-spectrum. After completion, the reaction mixture was filtrated to remove any residual solid.
Precipitation of K.sub.2SO.sub.4 and D-Mannose Crystallization
[0129] The oxidized solution was divided over 3 round bottom flasks and the water was partially evaporated off using a rotary evaporator until the water content in the residue was 22-30 wt % (Karl Fisher) EtOH, preheated to 58 C. (0.9 L) was added slowly to the thick syrup and the reaction mixture was stirred at 60 C. for 1 hour. The precipitated salt (K.sub.2SO.sub.4) was filtered off over preheated filter (preheated in oven at 60 C.). The filtrate was then allowed to cool down (after seeding with 1 g D-mannose at 50 C.) from 55 C. to 20 C. over 16-18 hours to crystallize the D-Mannose. The formed D-Mannose crystals were filtered off and dried under vacuum (60 C., water suction) to provide 226 g D-mannose. The observed purity was 98.6% (HPLC-RI) and an ash level of 0.3%.