Sugar – starch – and carbohydrates – Processes – Carbohydrate manufacture and refining
Reexamination Certificate
2000-01-11
2002-09-17
Brunsman, David (Department: 1755)
Sugar, starch, and carbohydrates
Processes
Carbohydrate manufacture and refining
C127S046300
Reexamination Certificate
active
06451123
ABSTRACT:
This invention pertains to processes for separating sugars and sugar alcohols, such as xylose, mannose, galactose, arabinose, glucose, xylitol, arabitol, sorbitol, galactitol, or mannitol from mixtures with other sugars or sugar alcohols, mixtures such as hardwood or softwood liquors.
Most industrial xylose production is currently based on recovery from hardwood liquors (USA, Russia, Finland, Norway, Austria), with smaller quantities from sugarcane bagasse (China), and possibly other hemicellulose-rich feedstocks. Most industrially produced xylose is hydrogenated to produce xylitol, a specialty sweetener with outstanding properties as a component of oral hygiene products, diabetic foods and other specialty products. Alternate routes to xylitol are via fermentation of glucose with osmiophilic yeast and enzymatic isomerization, or via xylonic acid by oxidation of glucose, fructose, or galactose.
Mannitol, another specialty sweetener widely used in sugarless chewing gums, is produced industrially by simultaneous chemical isomerization and hydrogenation of fructose, or by enzymatic isomerization of fructose and hydrogenation of the purified mannose. Fermentations of sugars to mannitol are known, and some biomass feedstocks high in mannose do exist. It has been reported that coffee extraction residues and ivory nut meal are good sources of mannose, as are the softwood liquors. Mannitol is also produced by direct extraction from seaweed in China. In chemical isomerization processes, the product mix may contain 60-70% sorbitol and 30-40% mannitol, depending on the hydrogenation conditions; the two are then typically separated by fractional crystallization.
After polysaccharides from biomass hemicellulose, such as arabinoxylan, galactomannan, glucomannan, etc., are hydrolyzed to the corresponding monosaccharides, such as arabinose, galactose, glucose, etc., the separation of the monosaccharides from one another or from sugar alcohols is difficult because of their chemical similarity. Some prior separation processes have been used, including several that rely on chromatography; but only limited efficiencies have been achieved with these prior separation processes.
After plant tissues are hydrolyzed, the resulting “hemicellulose hydrolysates” typically contain mixtures of five- and six-carbon sugars, the pentoses and hexoses. The sugar xylose predominates in hydrolysates from hardwoods and annual plants, while softwood liquors typically comprise primarily mannose, with smaller quantities of xylose, glucose and other sugars. Typical sugar profiles are shown in Table I, whose data are taken from U.S. Pat. No. 5,084,104 and U.S. Pat. No. 3,677,818.
TABLE I
Typical sugar profiles in hardwood and softwood liquors, expressed as
percentages of total sugars.
Hardwood - Sulfuric
Softwood - Southern
acid hydrolysate of
Pine prehydrolysis
Birch
liquor
Xylose
71.5
20.6
Mannose
7.1
37.4
Glucose
10.1
16.5
Galactose
7.7
21.2
Arabinose
3.6
4.3
From hydrolyzed and properly de-ashed and de-lignified hardwood liquors (or other biomass hydrolysates with an excess of xylose), xylose can be recovered by crystallization. After crystallization a non-crystallizing syrup remains, “xylose molasses,” which is a mixture of xylose, glucose, mannose, and other sugars. On the other hand, hydrolyzed and purified softwood liquors, rich in mannose, do not crystallize readily, even where the liquors are nearly free of non-sugar constituents. The reason may be that xylose, glucose, and possibly other sugars inhibit mannose crystallization. Although crystallization can be induced with ethanol or methanol, sugar recovery from such non-crystallizing syrups may be best achieved by chromatography. Separation media such as zeolites and ion exchange resins have been tested for their ability to separate the various sugar constituents. See Table II.
TABLE II
Processes for industrial sugar separations described in the literature.
(Note: Glucose/fructose separation, practiced on a large scale in the
corn sweetener industry, is excluded as it is not considered pertinent to
the separation of biomass-based sugar liquors.)
Sugar Pair
System
Reference
Glucose/
cation/Ca++
Caruel et al., 1991; Caruel, 1991
Mannose
cation/Pb++
Caruel et al., 1991; Caruel, 1991
anion/aryl borate
U.S. Pat. No. 3,864,166
cation/Ca++
U.K. Patent 1,540,556
zeolites
Eur. Pat. Appl. 115,631, 1983
zeolites
Eur. Pat. Appl. 302,970, 1987
zeolites
U.S. Pat. No. 4,471,114
cation/
U.S. Pat. No. 4,837,315
Ca++NH4+
mannose-bisulfite
U.S. Pat. No. 3,677,818
complex
Glucose/Xylose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
anion/aryl borate
U.S. Pat. No. 3,864,166
anion/sulfate
U.S. Pat. No. 5,084,104
Glucose/Arabinose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
Glucose/Galactose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
cation/hydrazine
U.S. Pat. No. 3,471,329
Xylose/Mannose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
mannose-bisulfite
U.S. Pat. No. 3,677,818
complex
anion/sulfate
U.S. Pat. No. 5,084,104
Xylose/Arabinose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
anion/sulfate
U.S. Pat. No. 5,084,104
Xylose/Galactose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
anion/sulfate
U.S. Pat. No. 5,084,104
Mannose/
cation/Ca++
Caruel et al., 1991; Caruel, 1991
Arabinose
cation/Pb++
Caruel et al., 1991; Caruel, 1991
Mannose/Galactose
cation/Ca++
Caruel et al., 1991; Caruel, 1991
cation/Pb++
Caruel et al., 1991; Caruel, 1991
Mannose/Fructose
zeolites
Eur. Pat. Appl. 302,970, 1987
cation/Ca++
U.S. Pat. No. 5,466,795
Non-Patent References cited in Table II
H. Caruel et al., “Carbohydrate separation by ligand-exchange liquid chromatography: correlation between the formation of sugar-cation complexes and the elution order.” J. Chromatogr. 1991, 558(1), 89-104.
Caruel, H., “Procede de Separation Continu d'Hydrates de Carbone par Chromatographie Liquide en Simulation de Lit Mobile,” Ph.D. Dissertation, National Polytechnic Institute of Toulouse, France, June 1991.
In addition to chromatographic techniques, precipitation of mannose as an insoluble bisulfate complex from softwood liquors was also disclosed in U.S. Pat. No. 3,677,818.
On the analytical scale, with the exception of gas chromatography of volatile sugar derivatives, modern methods rely nearly exclusively on liquid chromatography. Historically, borate buffers and borate forms of anion exchange resins have been used with some success, although their use appears to have been discontinued with the proliferation of high performance HPLC “sugar” columns in the 1980's. See J. Khym et al., “The separation of sugars by ion-exchange,” J. Amer. Chem. Soc., 74, 2090-2094, 1952; R. Kesler, “Rapid quantitative anion-exchange chromatography of carbohydrates,” Analytical Chemistry, 1967, 39(12), 1416-1422; A. Floridi, “An improved method for the automated analysis of sugars by ion-exchange chromatography,” Journal of Chromatography. 59, 61-70, 1971; and J. Kennedy et al., “The fully automatic ion-exchange and gel-permeation chromatography of neutral monosaccharides and oligosaccharides with Jeolco JLC-6AH analyzer,” Carbohydr. Res. 54, 13-21, 1977.
The interaction of sugars with the borate anion is strong, and elution times tend to be long. The use of a starch-packed column with an n-butanol:n-propanol:water mobile phase has been described for the separation of xylose, mannose, and other monosaccharides (S. Gardell, “Chromatographic separation and quantitative determination of monosaccharides,” Acta Chemica Scandinavica, 1953, 7, 201-206); as have anion exchange resins in the bisulfate form (Y. Takasaki, “On the separation of sugars,” A
Chen Feng
Saska Michael
Board of Supervisors of Louisiana State University and Agricultu
Brunsman David
Runnels John H.
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