CA1237086A - Glucose or maltose from starch - Google Patents
Glucose or maltose from starchInfo
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- CA1237086A CA1237086A CA000466548A CA466548A CA1237086A CA 1237086 A CA1237086 A CA 1237086A CA 000466548 A CA000466548 A CA 000466548A CA 466548 A CA466548 A CA 466548A CA 1237086 A CA1237086 A CA 1237086A
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- maltose
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Abstract
"GLUCOSE OR MALTOSE FROM STARCH"
ABSTRACT
A process for obtaining glucose from thinned starch by par-tially hydrolyzing the latter to give from 50% to 92% glucose followed by separation of the hydrolysis product to afford a glucose-enriched product with recycling of the glucose-depleted stream affords benefits unattainable by conventional commercial processes. Substantial reduc-tions in process time and reversion products and a substantial increase in productivity are among some of the benefits.
ABSTRACT
A process for obtaining glucose from thinned starch by par-tially hydrolyzing the latter to give from 50% to 92% glucose followed by separation of the hydrolysis product to afford a glucose-enriched product with recycling of the glucose-depleted stream affords benefits unattainable by conventional commercial processes. Substantial reduc-tions in process time and reversion products and a substantial increase in productivity are among some of the benefits.
Description
~3~7~
BAC~CGROUND OF 'rho INVENTION
Naturally occurring carbohydrates in the form oE starch are renewable sources of commerically important sugars ineluding the mono-saccharido glucose and disaccharide maltose. glucose and maltose are useful food sweeteners and nutrients. Maltose is even usefu:L in culture media.
Glucose is especially useful because it can be isomerized to form the even sweeter monosaccharide, fructose. this invention relates to a two step process for obtaining high purity glucose or maltose from a feedstock comprising starch derived from such plants as cassava, maize, potatoes, rice, tapioca, taro and wheat.
Figures 1 and 2 are flow diagrams for the conventional process and the process of this irvention, respeetively.
The conventional scheme for glueose production from thinned stareh is depieted in Figure 1. In Figure 1, and throughout the specificatioll, the term "thinned stareh" refers to a liquified stareh partially hydrolyzed by an alpha-amylase enzyme. Different types of alpha-amylase enzymes are often used to produce thinned starch with different, but analogous properties depending upon whether maltose or glucose is desired. lhinned starch has a dry solids (DS) level of 30-45% and contains a minor proportion of monosaccharides, up to lOg but usually less than 4%, 20% to 70g disaccharides through heptasaeeharides (DP2-DP7), and 30% to 80% oeta8aeeharides and the higher moleeular weight polysaeeharides. One measure of its degree of hydrolysis is the dextrose equivalent. A thinned stareh is said to have an inereased dextrose equivalent, that is, an increased proportion of de~tro-rotatory glueose when eompared to untreated stareh. Untreated starch contains no or few free units of dextrose; thinned starch may have the dextrose concentration increased to a low value of from 5 to 25.
In the conventional process of Figure 1, thinned starch 1 enters a saccharifieation or hydrolysis reactor zone, 2, where it undergoes enzyme-catalyzed hydrolysis using a glucose-forming enzyme, for example, .~ I, amyloglucosidase (glucoamylase), hereafter referred Jo as AG. An essential feature of present processes is that hydrolysis is continued in one step until maximum glucose formation is attained, which corresponds to about 34-96% glucose in the product stream, 3, when using a feed-stock containing about 30 dry solids. Although only one reactor zone isdepicted or saccharification, this is but one embodiment, and a plurality of reactor zones in series may be used in other embodiments.
Effluent, 3, from 2 containing more than about 94% glucose (on a dry solids basis) is then concentrated, where necessary, in an evapora-tion zone, 4, to afford a product stream, 5, containing from about 35%to about 50% dry solids. This product stream, 5, is typically the feed-stock entering an isomerization reactor zone, 6, in which glucose is enzymatically converted to fructose by glucose isomerase.
The conventional preparation of maltose from starch is analogous to that depicted in Figure 1, the major difference being that the thinned starch is hydrolyzed with a maltose-producing enzyme. Beta-amylase is largely or exclusively the maltose-producing enzyme used.
Our invention is directed toward both glucose and maltose produc-tion. However, solely for the sake of brevity this description following will be directed toward glucose production, with it being clearly under-stood that a similar description directed toward maltose production is contemplated.
Several disadvantages attach to the conventional process. One disadvantage, generic to any run to maximum conversion, is the increased cost consequent to the process time requirements for attaining maximum conversion: the longer the time for such conversion to be established, the more costly, hence more disadvantageous, is the process. Because glucose represses enzyme activity by complexing with AG, the hydrolysis rate is decreased as glucose accumulates and further increases process time. Another disadvantage characteristic of the relatively lony residence time associated with the AG-catalyzed hydrolysis of thinned starch, .3'7~
is that the glucose, a monosaccharide, reverts to disaccharides, among which is iso~maltose. Because isomaltose is a refractory disac-charide, that is, it is not readily hydrolyzed, and because it is bitter, it is a highly undesirable component of a glucose feedstock used for fructose production. The longer the reaction time, the higher the glucose level and a higher isomaltose concentration in the product results.
A still further disadvantage, at least where a soluble enzyme is used in the saccharification zone, is that the enzyme must be con-tinuously replaced as it is lost during production. Cost rises directly as the amount of glucose formed per unit of enzyme decreases.
Because present commercial processes for production of high fructose corn syrup by isomerization of glucose utilize a glucose feed-stock containing at least 94% glucose, a constraint of any new or modified process for production of glucose is that it afford comparable glucose levels.
The more efficient process of our invention can provide a product stream haYing at least g4% glucose and avoiding the aforementioned disadvantages of conventional processes. 0ur invention is a process whereby a feedstock of thinned starch is hydrolyzed to afford glucose (maltose) below maximum formation levels, the effluent is separated into a glucose (maltose)-depleted stream, the glucose (maltose)-enriched stream is recovered9 and the glucose (maltose)-depleted stream is recycled to the hydrolysis step.
By carrying out hydrolysis to a state substantially short of maximum glwcose formation, the invention herein achieves a considerable saving time and affords glucose with substantially lower levels of rever-sion products.
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Therefore an advantage oF our invention is that it affords a substantial reduction in process time. Another advantage accompany-ing a reduction in time is that the process of our invention affords glucose with less reversion products than the prior art pro-cesses.
Still other advantages accrue from the characteristics of enzyme-catalyzed hydrolysis of thinned starch of which presently used commercial processes cannot take advantage. When a feedstock for AG-catalyzed hydrolysis is increased in dry solids, it is found that enzyme stability, as measured by its half-life, also increases. It is also found that the rate of glucose formation increases with increasing dry solids. Both of these characteristics are quite favorable, yet cannot be used in present commercial processes because ;ncreasing dry solids also leads to a lower maximum glucose level accompanied by increased reversion products.
In contrast to the prior art methods, the process of the instant invention is able to advantageously utilize the favorable characteristics of increased enzyme stability and increased glucose formation rate without any accvmpanying disadvantage of increased reversion products. Thus, in this sense our invention is truly synerg;st;c; it incorporates the benefic;al effects without incorporating the detrimental ones.
he characteristic of using immobilized AG in hydrolyzing thinned starch is that it typically affords less than 94% glucose at equilibrium and the heretofore relatively long residence time has re-sulted in the appearance of unwanted reYersion products. Thus, immobili ed AG can be used only with difficulty in present commercial processes.
Therefore, yet another advantage of the instant invention is that it readily permits the use of an immobilized AG. One oharacteristic of using soluble (or unimmobilized) AG in hydrolyzing thinned starch is that ;t is necessary to continuously replace the enzyme which is lost during the production of glucose. Therefore, still another advantage of the process 7~
described herein ls that it affords a substantial increase in productivity, defined as the amount of glucose formed per unit of enzyme. Thls pro-ductivity increase results, in part, from recycling the enzyme incidental to the recycle stage of the process (where soluble AG is used), as well as a longer half-life (where either a soluble or immobilized AG is used).
The glucose level in our process product stream as described is at least 90%. However, glucose levels of greater than 99% may be readily achieved by suitably varying process variables. Thus, still another advantage of our process is that it may be tailored to continually produce high-purity glucose, with a glucose purity greater than 99%
being attainable.
Yet another advantage of the process which is our invention is that it can afford virtually complete conversion of starch to glucose.
It should be readily apparent from the multitude of the aforementioned advantages that our invention represents a substantial advance in the art of producing glucose at levels of about 94% and greater by enzyme-catalyzed hydrolysis of thinned starch.
SUMMARY OF THE INVENTION
One embodiment of our invention comprises a process for selectively obtaining a sugar which is either glucose or maltose from thinned starch.
A feedstock of thinned starch is hydrolyzed under the action of a glucose- or maltose-producing enzyme to form an effluent stream containing 50% to 92% of the sugar. The effluent stream is separated into a sugar-enriched product stream and a sugar-depleted stream. The sugar-enriched product stream is recovered and the sugar-depleted stream is recycled to the hydrolysis step.
In a more specific embodiment, the effluent from the hydrolysis step contains 70% to 80% sugar. In a still more spec;fic embodiment, the sugar-enriched product stream contains at least 90% sugar.
~3~7~6 DESCRIPTION OF THE INVENTIO'I
This invention is a process for obtaining glucose or maltose from thinned starch which represents a radical departure from prior art methods. One point of departure is the partial hydrolysis of thinned starch. That is to say, whereas the prior art methods hydrolyzed thinned starch for a time sufficient to attain maximum formation of glucose, the process herein continues hydrolysis or a substantially lesser period of time, thereby affording an effluent which contains less than maximum levels of glucose. Yet another point of departure is the separation of the hydrolysis product into a glucose-enriched product stream and a glucose-depleted stream with recycling of the latter to the hydrolysis step. The process herein is conveniently summarized by the flow diagram depicted in Figure 2.
In Figure 2, a thinned starch, 11, as defined within, usually containing from about 30% to about 45% dry solids, is the feedstock for a saccharification reactor zone, 12. Although only one reactor zone is depicted, this is but one embodiment. Embodiments where a plurality of reactor zones are used in the saccharification step are contemplated and are to be considered within the scope of the claimed invention. Ef~lu-ent stream 13, from the saccharification zone contains glucose at levels based on total solids from about 50~ to about ~2%, and this is used as the feedstock for the separation step, 15. Separation is here depicted as a single stage, but embodiments employing multistage separation are variants within the scope of this invention.
The effluent from the separation zone is in two streams, one being product enriched in glucose, 16, to contain at least 90% glucose (on a total solids basis), the other being a glucose-depleted stream, 14.
This latter is then recycled to the saccharification reactor zone, 12.
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Where the glucose-enriched product stream 16 is ultimately to be used as the Feedstock for a glucose isomerase reactor, it is then sent to an evaporation zone, 17, where necessary to afford stream 18 containing from about 35% to about 50% dry solids. Said stream 18 then is utilized as the feedstock for an isomerization reactor zone 19 converting glucose to fructose. However, it is to be clearly under- 1 stood that the glucose-enriched product stream may serve as the glucose source for purposes other than use as a feedskock or isomer;zation to fructose. Other purposes to which the glucose may be put include hdyrogen-ation to sorbitol, fermentation to ethanol, and a sweetener in food.
Where the product is maltose there is no isomerization reactor zone 19 as depicted in Figure 2. The maltose-enriched product stream corresponding to 16 is either used as is or sent to an evaporation zone 17 to afford more concentrated solutions of maltose9 or even dry maltose.
In the initial step of our process, a feedstock of thinned starch is selectively enzymatically hydrolyzed by a glucose-prbducing enzyme, chiefly AG, to an effluent containing from about 50% to about 92% glucose. This selective hydrolysis step often is referred to as a saccharification step. The AG used nay be soluble, in which case it is recycled with the glucose-depleted stream, or it may be an immobilized AG.
In either case pullulanase or alpha-amylase, or both, may be present in the thinned starch feedstock to aid hydrolysis. The temperature at which the enzymatic hydrolysis is conducted depends upon the thermal stability of the enzyme used, but generally the temperature is between about 40 and 80C, with the temperature of about 60C being the most usual one.
however, the AG from at least one microorganism is known to be sufficiently thermostable to allow the process to be run at temperatures even up to about 100C. The pressure at which enzymatic hydrolysis is conducted is from 1 to 1000 pounds per square inch. the residence time during which the 23~7~-3~
starch is in contact with lmmobilized enzyme is relatively short, that is, in a range of from 4 minutes to 1.6 hours and is in correlation with liguid hourly space velocities which may range from about 2 to about S0.
The space velocity and residence time are correlated in such a manner, i.e., short resiclence time and high space velocity within the ranges hereinbefore set forth so as to provide a conversion rate within the desired range. Conversely, it is also contemplated that long residence times and low space velocities with the aforesaid range may also be employed to effect the desired result.
The residence time during which the starch is in contact with soluble enzyme is relatively short in comparison to conYentional processes, that is, in a range of from 2 hours to 48 hours.
A desirable consequence of hydrolyzing thinned starch to an effluent containing from 50% to 92% glucose is a substan-tial reduction in reaction $ime. Thus, hydrolysis to a product con-taining 50% glucose may take less than one-fourth of the time needed to attain 94% glucose, hydrolysis to 90~ glucose may take only one-half the time, and even hydrolysis to 92% glucose may take only three-fifths the time. Another desirable consequence is a decided improve-ment in organoleptic characteristics through substantial reduction of the bitter principal, isomaltose9 hydrolysis to 50~ glucose may be accompanied by only about one-fourth as much isomaltose as accompanies the 94% glucose product.
A feedstock of thinned starch containing from about 30% to about 45% dry solids is conventional in the industry, although our pro-cess is not limited thereto. However, a dry solids level from about35% to about 45% is preferred in the practice of this invention to obtain the full advantage of the salutary effect of higher dry solids on enzyme stability and the rate of glucose formation.
Prior art methods continue the hydrolysis to maxlmum flu-cose formation, which corresponds to glucose leYels of about 94%. How-ever, an essential feature of our process is continuation of hydrolysis to an effluent containing from 50% to 92%, but usually not more than 90% glucose. An effluent containing from about 60% to about 85%
glucose is deisrable, and one containing from aout 70% to about 80 glucose is particularly preferred.
The hydrolysis effluent recovered from this saccharification step is then separated into a glucose-enriched product stream and a glucose-depleted stream in a separation step. Where the glucose-enriched product stream is used as the feedstock for isomerization to fructose, the stream will c.ontain at least about 94% glucose since present processes for forming fructose from glucose require a feedstock containing a least about that level of glucose purity.
Where a feedstock of less Han 94% glucose is acceptable, a less stringent separation to afford 10wer purity glucose may be effected. As a practical matter9 the glucose-enriched product stream generally will contain at least about 90X glucose. It also must be understood that separation may be performed to obtain higher purity glucose, i.e., 94~ glucose. In fact, our invention may be used to continually produce glucose of greater than 99% purity where such high purity material is desired.
Generally, this separation step will comprise a single stage.
Hohever, multi-stage separation may be advantageous in some circumstances, and these are considered to be within the scope of our invention. In any event, the glucose-enriched product stream from the separation step is recovered for subsequent use or processing.
Any method of separation which is selectiYe for glucose rel-ative to disaccharides and higher polysaccharides is suitable. where maltose, a disaccharide. is formed the separation needs to be selec-tive relatiYe only to higher polysaccharides. For example, a membrane-based separation may be effectively utili2ed. As another example, a separation based on solid adsorbents may be utilized. Examples of _g_ the latter include aluminas, silicas, various clays, zeolites, and so forth. Still another method of separation is selective crystalliza-tion of glucose prom the saccharide mixture. Still other methods r of separation which may be used in the process herein include solvent extraction and supercritical extraction, to cite but two further exemplary methods.
An integral part of this invention is the recycling of the glucose-depleted stream to the hydrolysis step. When a plurality of hydrolysis zones connected in series flow are used in the hydrolysis or saccharification step, the particular hydrolysis zone which is the entry point for the recycled stream will depend on process parameters such as reactor configuration, the activity of the particular enzyme, the concentration of reactants and/or products in the recycle stream, whether the enzyme is soluble or immobilized, the enzyme concentration if soluble, desired purity of the product, the particular means of separation, and so forth. Under many process conditions the location of the recycle point may be varied broadly without substantial impact.
or instance, where the enzyme i5 immobilized, a portion of the glucose-depleted stream may be recycled to join the feed prior to entering the hydrolysis zone. But in any eYent it should be clear that the determina-tion of a suitable entry point will depend upon the specific parameters utilized in any particular process with its determinat;on well within the capability of the skilled worker.
As heretofore set forth, the enzymes which are utilized in the process of this invention most often comprise amyloglucosidase or betaamylase which may be composited on a solid support. By utilizing enzymes which are immobilized on a support, it is possible to stabilize the enzyme in a relative manner and therefore to permit effective use of enzyme which otherwise might be lost in the reaction medium. Such immobilized or insolubilized enzymes may be employed in various reactor 3t~ Ç~
systems such as in packed columns, stirrinq tank reactors, etc., depend--ing upon the nature of the substrhte which is utilized therein. By per mitting the reuse of the enzymes which are in a relatively stable condi-tion and thus may be utilized for a relatively lengthy period of time, it is possible to operate the process in a commercially attractive and economical manner.
The particular enzyme may be immobilized on a solid support in any manner known in the art. One such method of immobilizing the enzyme which may be used as an illustration of a method for immobilizing the enzyme is taught in U.S. Patent 4,141,~57.
As hereinbefore set forth, it is also contemplated withir, the scope of this invention that ultra-filtration membranes may be used to recover glucose or maltose from a partially hydrolyzed reaction mixture resulting from the treatment of a liquid starch feedstock with an enzyme. Any membrane which possesses an appropriate molecular weight as well as pore sizes capable of yielding the desired high glucose or maltose content as the permeate while retaining the rejected material which contains unhydrolyzed oligosaccharides is suitable. The ultra-filtration membrane will possess a molecular weight cut-off in the range of from about 100 to about 5000 and will also possess pore sizes in the range of from about 5 to about 125 Angstroms. Some speci-fic examples of these membranes which may be utilized will include cellulose acetates such as cellulose diacetate, cellulose triacetate or mixtures thereof, a membrane resulting from polyethyleneimine cross-linked with a dialdehyde, a diacidchloride, or a diisocyanate9 polyacrolein, chitosan cross-linked with a dialdehyde such as glutaraldehyde9 polystyrene-sulfonates, etc. It is to be understood that these ultra-filtration membranes are only representative of the class of membranes which may be employed and that the present invention is not necessarily limited thereto.
The two-step process o the present invention may be effected in any sultable manner and may comprise either a batch or contlnuous type operation. For example, when a batch type operation it cmployed, a qunntlty of the feedstock comprisiug a liquid starch which ha been previously treated with alpha-amylase to increase the dextrose equivalent is contacted wlth an lmmobillzed amyloglucoslda~e9 in the event that a syrup high ln glucose content ls desired, for a predetermined period of time while employing reaction conditions which include a temperature of from about 45 to about 70C and a pressure which may range from about 1 to about 1000 psl. In addition, the resldence time during which the feed6tock ~B in contact with the immobilized enzyme iB correlated wlth the liquid hourly space velocity at which the feed is introduced Jo as to produce a conversion of the liquid starch to glucose within the desired range. After passage over the immobllized enzyme, the effluent iB recovered and the partially hydrolyzed starch is then subjected to an ultrafiltration step. In thls step, the reactlon mixture is psssad through sn ultrafiltration membrane o the type hereinbefore set forth whereby the permeate which possesses a high glucose or maltose content is recovered as the permeate upon separation from the retentate.
The latter may then also be recycled, a portion of the recycle stream belng ndmixed with the ef1uent from the enzyme trea~me~t while another poFtion of the retentate iB admixed with the ieed stream to the immobllized enzyme treatment zone. It is also contemplated that a third portion, if BO desired, may be recycled back to the zone ln which the feedstock i8 pretreated wlth alpha-amylase.
It is also contemplated within the scope of thih in~entlon that the process may be effected in a continuous manner of operation.
When this type of operation is employed, the feedstock compri~lng the treated liquified starch i8 continuously charged to a reaction vessel such as a column which contains the desired immobilized enzyme, said column being maintained at the proper operating condi-,~:
rm~
tions of temperature and pressure. After passage over the enzyme at a predetermined liquid hourly space velnclty which ls sufficiently high so as to only partially hydrolyze the feedstock, with a con-comitant low or nonexistent production of reversion products such as isomaltose, the effluent is continuously withdrawn and charged to an ultrafiltration apparatus which contains a membrane of the type hereinbefore set forth. After passage through this apparatus, which is also maintained at the proper operating cond;t;ons of temperature and pressure, the pen~eate comprising syrup which has a high glu-cose or maltose content, l.e., above 90X, is recovered. The reten-tate material which contains unhdydrolyzed oligosaccharides such as those which have a DP rating of DP7, DP8, DPg+ (the designation DP
being the degree of polymer kation) is also recovered and a portion thereof recycled back to the column containing the immobilized enzyme for further use as a portion of the feedstock, another portion admixed with the effluent from the immobilized enzyme treatment and, if so desired, a portion to the alpha-amylase step for pretreatment.
Each of the heretofore mentioned membrane separations may be performed using solid adsorbents as well. One such adsorbent is dis-c10sed in U.K. Patent No. 1,585,369, and comprises X or Y zeolites containing one or more selected cations at the exchangeable cationic sites.
Potassium -X zeol;te 7S a particularly preferred adsorbent exhibiting selectivity for glucose with respect to disaccharides and higher ol;gosaccharides and the polysaccharides.
The following eleven examples are given for the purpose of thus trating the present inYention. However, it ;s to be understood that these examples are given merely for purposes of illustration and that the present process us not necessarily limited thereto.
I, , ~L~J~7~3 EXAMPLE I
To illustrate the process of the present invention, a starch feedstock was treated with alpha-amylase to adjust the dextrose equivalent to 15 DE. In this case, the enzyme was immobilized and comprised amylglucosidase composited on a solid alumina support. The treated starch feedstock was passed through a column of 40 cc of the immobilized enzyme, said starch feedstock con-taining 0.1% benzoate and 50 ppm of sodium omadine at a pH of 4.2.
The starch was treated at a temperature of 45C, and a pressure greater than atmospheric at a liquid hourly space velocity of 3.21.
The effluent from this column was analyzed by means of liquid chroma-tography. The analysis showed the following area in which DP is the degree of polymerization (or examp1e, DP7 = seven ~7) monomers of glucose in the oligosaccharide):
9+ 8 7 DP6 DP~ DP4 DP3 DP2 Glucose 19.1 0.2 0.1 - - - 0.3 3.1 77.2 l The e~luent in an amount ox 200 cc which was recovered from this column was then passed through a cellulose acetate membrane, 1~0.7 cc out ox the original 200 cc being obtained and constituting the permeate. Analysis of the permeate aFter passage through the mem-brane at a temperature of 22C and a pressure of 9~ psi showed that said penmeate contained 94.2% glucose, 3.6% maltDse and only 1.7% of the oligosaccharides having a DP of 9~.
The retentate which is recovered from the treatment with the cellulose acetate membranes may then be recycled and utilized as a portion of the feedstock which is charged ts the zone containing the immobilized enzyme comprising amyloglucosidase composited on the treated alumina support.
7~
EXAMPLE II
In a manner similar to that hereinbefore set forth in Ex-ample I, a treated liqui~ied starch ~eedstock was again passed through an lmmobilized amyloglucosidase column under conditions sim-ilar to those in Example I. The effluent from this column, which contained 77.2% glucose as well as minor amounts of maltose, DP3, DP7, DP8 and a major amount of DPg+oligosaccharides, was passed through a membrane comprising polystyrenesulfonate and sold under the trade mark Amicon UM2. The volume ox the effluent which passed through the membrane was 122.8 cc. Analysis of the permeate by means of liquid chromatography showed 97.6~ glucose, 2.3 maltose, and only 0.1% of DPg+ oligosaccharides.
When the above experiment was repeated using a membrane comprising cellulose acetate sold under the trade name Nuclepore and the effluent from the immobilized amyloglucosidase column was passed over this membrane at a temperature of 22C and a pressure of 90 psi, the penmeate was found to contain 97.5% glucose, 2.3% maltose, and 0.2% DP9~ oligosaccharides.
Likewise, the retentate which may be recovered from the treatment of the effluent with the cellulose acetate membrane may be recovered and recycled a portion of the retentate being admixed with the effluent from the immobilized enzyme treatment while the other portion is recycled to form a portion of the ~eedstock which is charged to the inmobilized enzyme treatment zone.
EXAMPLE I_ TD illustrate the ability Do the process of the present in-~L~3~7q~
vention to recover a product containing a high maltose concentration, a liquified starch feedstock which had been pretreated with alpha-amylase to adjust the dextrose equivalent to the desired level was passed through a column containing 100 cc of beta-amylase immobilized on a solid matrix similar to that set forth in Example I above. The feedstock which had a pH of 5.0 contained 0.1 mole ox acetate and 0.2 mole of benzoate which acted as a buffer. The feedstock was passed over the enzyme at a temperature of 55C, a pressure greater than atmo-spheric, at a liquid hcurly space velocity of 5. The effluent which was recovered from this column was subjected to liquid chromatography analysis with the following result:
HPLC ANALYSIS: (AREA %) 9~ B 7 DP6 DP5 DP4 DP3 DP2 Glucose 36.9 0.9 0.3 , 0.3 0.1 0.5 11.1 50.2 O5 The effluent from this column in an amount of 100 cc was passed through a cellulose acetate membrane while maintaining the mem-brane apparatus at a temperature of 22C and a pressure of gO psi.
Analysis of the permeate by means of liquid chromatography showed the presence of 79.0% maltosep 16.3% of a DP3 product and 2.4% of a DPg+
oligosaccharide.
When the aboYe experiment was repeated using an ultraf;l-tration membrane sold under the trade mark of Amicon UM2, the permeate was found to contain 90.1% maltosep 9.7~ of a DP3 oligosaccharide and only 0.2X of a DP9~ oligosaccharide.
In a similar manner the retentate which is recovered from the treatment with the ultrafiltration membrane of the above paragraph may be recycled, a port;on being admixed with the effluent withdrawn from the treatment with the immobilized beta-amylase while another portion may be admixed with the feedstock comprising the liquified starch prior to passage over the immobilized enzyme.
EXAMPLE IV
In this example, a liquified starch feedstock which may be pretreated with alpha-amylase Jo adjust the dextrose equivalent of said starch to a predetermined level may be passed through an immobilized amyloglucosidase column at a temperature of 45C and a pressure greater than atmospheric. The effluent from the column may be withdrawn after having been in contact with the immobilized enzyme for a predetermined period of time sufficient to permit a conversion to glucose of about 75% and may then be passed through an ultrafiltration membrane compris-ing polyacrolein, said passage over the membrane being effected at con-ditions which Jill include ambient temperature and a pressure of about
BAC~CGROUND OF 'rho INVENTION
Naturally occurring carbohydrates in the form oE starch are renewable sources of commerically important sugars ineluding the mono-saccharido glucose and disaccharide maltose. glucose and maltose are useful food sweeteners and nutrients. Maltose is even usefu:L in culture media.
Glucose is especially useful because it can be isomerized to form the even sweeter monosaccharide, fructose. this invention relates to a two step process for obtaining high purity glucose or maltose from a feedstock comprising starch derived from such plants as cassava, maize, potatoes, rice, tapioca, taro and wheat.
Figures 1 and 2 are flow diagrams for the conventional process and the process of this irvention, respeetively.
The conventional scheme for glueose production from thinned stareh is depieted in Figure 1. In Figure 1, and throughout the specificatioll, the term "thinned stareh" refers to a liquified stareh partially hydrolyzed by an alpha-amylase enzyme. Different types of alpha-amylase enzymes are often used to produce thinned starch with different, but analogous properties depending upon whether maltose or glucose is desired. lhinned starch has a dry solids (DS) level of 30-45% and contains a minor proportion of monosaccharides, up to lOg but usually less than 4%, 20% to 70g disaccharides through heptasaeeharides (DP2-DP7), and 30% to 80% oeta8aeeharides and the higher moleeular weight polysaeeharides. One measure of its degree of hydrolysis is the dextrose equivalent. A thinned stareh is said to have an inereased dextrose equivalent, that is, an increased proportion of de~tro-rotatory glueose when eompared to untreated stareh. Untreated starch contains no or few free units of dextrose; thinned starch may have the dextrose concentration increased to a low value of from 5 to 25.
In the conventional process of Figure 1, thinned starch 1 enters a saccharifieation or hydrolysis reactor zone, 2, where it undergoes enzyme-catalyzed hydrolysis using a glucose-forming enzyme, for example, .~ I, amyloglucosidase (glucoamylase), hereafter referred Jo as AG. An essential feature of present processes is that hydrolysis is continued in one step until maximum glucose formation is attained, which corresponds to about 34-96% glucose in the product stream, 3, when using a feed-stock containing about 30 dry solids. Although only one reactor zone isdepicted or saccharification, this is but one embodiment, and a plurality of reactor zones in series may be used in other embodiments.
Effluent, 3, from 2 containing more than about 94% glucose (on a dry solids basis) is then concentrated, where necessary, in an evapora-tion zone, 4, to afford a product stream, 5, containing from about 35%to about 50% dry solids. This product stream, 5, is typically the feed-stock entering an isomerization reactor zone, 6, in which glucose is enzymatically converted to fructose by glucose isomerase.
The conventional preparation of maltose from starch is analogous to that depicted in Figure 1, the major difference being that the thinned starch is hydrolyzed with a maltose-producing enzyme. Beta-amylase is largely or exclusively the maltose-producing enzyme used.
Our invention is directed toward both glucose and maltose produc-tion. However, solely for the sake of brevity this description following will be directed toward glucose production, with it being clearly under-stood that a similar description directed toward maltose production is contemplated.
Several disadvantages attach to the conventional process. One disadvantage, generic to any run to maximum conversion, is the increased cost consequent to the process time requirements for attaining maximum conversion: the longer the time for such conversion to be established, the more costly, hence more disadvantageous, is the process. Because glucose represses enzyme activity by complexing with AG, the hydrolysis rate is decreased as glucose accumulates and further increases process time. Another disadvantage characteristic of the relatively lony residence time associated with the AG-catalyzed hydrolysis of thinned starch, .3'7~
is that the glucose, a monosaccharide, reverts to disaccharides, among which is iso~maltose. Because isomaltose is a refractory disac-charide, that is, it is not readily hydrolyzed, and because it is bitter, it is a highly undesirable component of a glucose feedstock used for fructose production. The longer the reaction time, the higher the glucose level and a higher isomaltose concentration in the product results.
A still further disadvantage, at least where a soluble enzyme is used in the saccharification zone, is that the enzyme must be con-tinuously replaced as it is lost during production. Cost rises directly as the amount of glucose formed per unit of enzyme decreases.
Because present commercial processes for production of high fructose corn syrup by isomerization of glucose utilize a glucose feed-stock containing at least 94% glucose, a constraint of any new or modified process for production of glucose is that it afford comparable glucose levels.
The more efficient process of our invention can provide a product stream haYing at least g4% glucose and avoiding the aforementioned disadvantages of conventional processes. 0ur invention is a process whereby a feedstock of thinned starch is hydrolyzed to afford glucose (maltose) below maximum formation levels, the effluent is separated into a glucose (maltose)-depleted stream, the glucose (maltose)-enriched stream is recovered9 and the glucose (maltose)-depleted stream is recycled to the hydrolysis step.
By carrying out hydrolysis to a state substantially short of maximum glwcose formation, the invention herein achieves a considerable saving time and affords glucose with substantially lower levels of rever-sion products.
~,~?J~ 7~3~.D
Therefore an advantage oF our invention is that it affords a substantial reduction in process time. Another advantage accompany-ing a reduction in time is that the process of our invention affords glucose with less reversion products than the prior art pro-cesses.
Still other advantages accrue from the characteristics of enzyme-catalyzed hydrolysis of thinned starch of which presently used commercial processes cannot take advantage. When a feedstock for AG-catalyzed hydrolysis is increased in dry solids, it is found that enzyme stability, as measured by its half-life, also increases. It is also found that the rate of glucose formation increases with increasing dry solids. Both of these characteristics are quite favorable, yet cannot be used in present commercial processes because ;ncreasing dry solids also leads to a lower maximum glucose level accompanied by increased reversion products.
In contrast to the prior art methods, the process of the instant invention is able to advantageously utilize the favorable characteristics of increased enzyme stability and increased glucose formation rate without any accvmpanying disadvantage of increased reversion products. Thus, in this sense our invention is truly synerg;st;c; it incorporates the benefic;al effects without incorporating the detrimental ones.
he characteristic of using immobilized AG in hydrolyzing thinned starch is that it typically affords less than 94% glucose at equilibrium and the heretofore relatively long residence time has re-sulted in the appearance of unwanted reYersion products. Thus, immobili ed AG can be used only with difficulty in present commercial processes.
Therefore, yet another advantage of the instant invention is that it readily permits the use of an immobilized AG. One oharacteristic of using soluble (or unimmobilized) AG in hydrolyzing thinned starch is that ;t is necessary to continuously replace the enzyme which is lost during the production of glucose. Therefore, still another advantage of the process 7~
described herein ls that it affords a substantial increase in productivity, defined as the amount of glucose formed per unit of enzyme. Thls pro-ductivity increase results, in part, from recycling the enzyme incidental to the recycle stage of the process (where soluble AG is used), as well as a longer half-life (where either a soluble or immobilized AG is used).
The glucose level in our process product stream as described is at least 90%. However, glucose levels of greater than 99% may be readily achieved by suitably varying process variables. Thus, still another advantage of our process is that it may be tailored to continually produce high-purity glucose, with a glucose purity greater than 99%
being attainable.
Yet another advantage of the process which is our invention is that it can afford virtually complete conversion of starch to glucose.
It should be readily apparent from the multitude of the aforementioned advantages that our invention represents a substantial advance in the art of producing glucose at levels of about 94% and greater by enzyme-catalyzed hydrolysis of thinned starch.
SUMMARY OF THE INVENTION
One embodiment of our invention comprises a process for selectively obtaining a sugar which is either glucose or maltose from thinned starch.
A feedstock of thinned starch is hydrolyzed under the action of a glucose- or maltose-producing enzyme to form an effluent stream containing 50% to 92% of the sugar. The effluent stream is separated into a sugar-enriched product stream and a sugar-depleted stream. The sugar-enriched product stream is recovered and the sugar-depleted stream is recycled to the hydrolysis step.
In a more specific embodiment, the effluent from the hydrolysis step contains 70% to 80% sugar. In a still more spec;fic embodiment, the sugar-enriched product stream contains at least 90% sugar.
~3~7~6 DESCRIPTION OF THE INVENTIO'I
This invention is a process for obtaining glucose or maltose from thinned starch which represents a radical departure from prior art methods. One point of departure is the partial hydrolysis of thinned starch. That is to say, whereas the prior art methods hydrolyzed thinned starch for a time sufficient to attain maximum formation of glucose, the process herein continues hydrolysis or a substantially lesser period of time, thereby affording an effluent which contains less than maximum levels of glucose. Yet another point of departure is the separation of the hydrolysis product into a glucose-enriched product stream and a glucose-depleted stream with recycling of the latter to the hydrolysis step. The process herein is conveniently summarized by the flow diagram depicted in Figure 2.
In Figure 2, a thinned starch, 11, as defined within, usually containing from about 30% to about 45% dry solids, is the feedstock for a saccharification reactor zone, 12. Although only one reactor zone is depicted, this is but one embodiment. Embodiments where a plurality of reactor zones are used in the saccharification step are contemplated and are to be considered within the scope of the claimed invention. Ef~lu-ent stream 13, from the saccharification zone contains glucose at levels based on total solids from about 50~ to about ~2%, and this is used as the feedstock for the separation step, 15. Separation is here depicted as a single stage, but embodiments employing multistage separation are variants within the scope of this invention.
The effluent from the separation zone is in two streams, one being product enriched in glucose, 16, to contain at least 90% glucose (on a total solids basis), the other being a glucose-depleted stream, 14.
This latter is then recycled to the saccharification reactor zone, 12.
~L2~ 3~
Where the glucose-enriched product stream 16 is ultimately to be used as the Feedstock for a glucose isomerase reactor, it is then sent to an evaporation zone, 17, where necessary to afford stream 18 containing from about 35% to about 50% dry solids. Said stream 18 then is utilized as the feedstock for an isomerization reactor zone 19 converting glucose to fructose. However, it is to be clearly under- 1 stood that the glucose-enriched product stream may serve as the glucose source for purposes other than use as a feedskock or isomer;zation to fructose. Other purposes to which the glucose may be put include hdyrogen-ation to sorbitol, fermentation to ethanol, and a sweetener in food.
Where the product is maltose there is no isomerization reactor zone 19 as depicted in Figure 2. The maltose-enriched product stream corresponding to 16 is either used as is or sent to an evaporation zone 17 to afford more concentrated solutions of maltose9 or even dry maltose.
In the initial step of our process, a feedstock of thinned starch is selectively enzymatically hydrolyzed by a glucose-prbducing enzyme, chiefly AG, to an effluent containing from about 50% to about 92% glucose. This selective hydrolysis step often is referred to as a saccharification step. The AG used nay be soluble, in which case it is recycled with the glucose-depleted stream, or it may be an immobilized AG.
In either case pullulanase or alpha-amylase, or both, may be present in the thinned starch feedstock to aid hydrolysis. The temperature at which the enzymatic hydrolysis is conducted depends upon the thermal stability of the enzyme used, but generally the temperature is between about 40 and 80C, with the temperature of about 60C being the most usual one.
however, the AG from at least one microorganism is known to be sufficiently thermostable to allow the process to be run at temperatures even up to about 100C. The pressure at which enzymatic hydrolysis is conducted is from 1 to 1000 pounds per square inch. the residence time during which the 23~7~-3~
starch is in contact with lmmobilized enzyme is relatively short, that is, in a range of from 4 minutes to 1.6 hours and is in correlation with liguid hourly space velocities which may range from about 2 to about S0.
The space velocity and residence time are correlated in such a manner, i.e., short resiclence time and high space velocity within the ranges hereinbefore set forth so as to provide a conversion rate within the desired range. Conversely, it is also contemplated that long residence times and low space velocities with the aforesaid range may also be employed to effect the desired result.
The residence time during which the starch is in contact with soluble enzyme is relatively short in comparison to conYentional processes, that is, in a range of from 2 hours to 48 hours.
A desirable consequence of hydrolyzing thinned starch to an effluent containing from 50% to 92% glucose is a substan-tial reduction in reaction $ime. Thus, hydrolysis to a product con-taining 50% glucose may take less than one-fourth of the time needed to attain 94% glucose, hydrolysis to 90~ glucose may take only one-half the time, and even hydrolysis to 92% glucose may take only three-fifths the time. Another desirable consequence is a decided improve-ment in organoleptic characteristics through substantial reduction of the bitter principal, isomaltose9 hydrolysis to 50~ glucose may be accompanied by only about one-fourth as much isomaltose as accompanies the 94% glucose product.
A feedstock of thinned starch containing from about 30% to about 45% dry solids is conventional in the industry, although our pro-cess is not limited thereto. However, a dry solids level from about35% to about 45% is preferred in the practice of this invention to obtain the full advantage of the salutary effect of higher dry solids on enzyme stability and the rate of glucose formation.
Prior art methods continue the hydrolysis to maxlmum flu-cose formation, which corresponds to glucose leYels of about 94%. How-ever, an essential feature of our process is continuation of hydrolysis to an effluent containing from 50% to 92%, but usually not more than 90% glucose. An effluent containing from about 60% to about 85%
glucose is deisrable, and one containing from aout 70% to about 80 glucose is particularly preferred.
The hydrolysis effluent recovered from this saccharification step is then separated into a glucose-enriched product stream and a glucose-depleted stream in a separation step. Where the glucose-enriched product stream is used as the feedstock for isomerization to fructose, the stream will c.ontain at least about 94% glucose since present processes for forming fructose from glucose require a feedstock containing a least about that level of glucose purity.
Where a feedstock of less Han 94% glucose is acceptable, a less stringent separation to afford 10wer purity glucose may be effected. As a practical matter9 the glucose-enriched product stream generally will contain at least about 90X glucose. It also must be understood that separation may be performed to obtain higher purity glucose, i.e., 94~ glucose. In fact, our invention may be used to continually produce glucose of greater than 99% purity where such high purity material is desired.
Generally, this separation step will comprise a single stage.
Hohever, multi-stage separation may be advantageous in some circumstances, and these are considered to be within the scope of our invention. In any event, the glucose-enriched product stream from the separation step is recovered for subsequent use or processing.
Any method of separation which is selectiYe for glucose rel-ative to disaccharides and higher polysaccharides is suitable. where maltose, a disaccharide. is formed the separation needs to be selec-tive relatiYe only to higher polysaccharides. For example, a membrane-based separation may be effectively utili2ed. As another example, a separation based on solid adsorbents may be utilized. Examples of _g_ the latter include aluminas, silicas, various clays, zeolites, and so forth. Still another method of separation is selective crystalliza-tion of glucose prom the saccharide mixture. Still other methods r of separation which may be used in the process herein include solvent extraction and supercritical extraction, to cite but two further exemplary methods.
An integral part of this invention is the recycling of the glucose-depleted stream to the hydrolysis step. When a plurality of hydrolysis zones connected in series flow are used in the hydrolysis or saccharification step, the particular hydrolysis zone which is the entry point for the recycled stream will depend on process parameters such as reactor configuration, the activity of the particular enzyme, the concentration of reactants and/or products in the recycle stream, whether the enzyme is soluble or immobilized, the enzyme concentration if soluble, desired purity of the product, the particular means of separation, and so forth. Under many process conditions the location of the recycle point may be varied broadly without substantial impact.
or instance, where the enzyme i5 immobilized, a portion of the glucose-depleted stream may be recycled to join the feed prior to entering the hydrolysis zone. But in any eYent it should be clear that the determina-tion of a suitable entry point will depend upon the specific parameters utilized in any particular process with its determinat;on well within the capability of the skilled worker.
As heretofore set forth, the enzymes which are utilized in the process of this invention most often comprise amyloglucosidase or betaamylase which may be composited on a solid support. By utilizing enzymes which are immobilized on a support, it is possible to stabilize the enzyme in a relative manner and therefore to permit effective use of enzyme which otherwise might be lost in the reaction medium. Such immobilized or insolubilized enzymes may be employed in various reactor 3t~ Ç~
systems such as in packed columns, stirrinq tank reactors, etc., depend--ing upon the nature of the substrhte which is utilized therein. By per mitting the reuse of the enzymes which are in a relatively stable condi-tion and thus may be utilized for a relatively lengthy period of time, it is possible to operate the process in a commercially attractive and economical manner.
The particular enzyme may be immobilized on a solid support in any manner known in the art. One such method of immobilizing the enzyme which may be used as an illustration of a method for immobilizing the enzyme is taught in U.S. Patent 4,141,~57.
As hereinbefore set forth, it is also contemplated withir, the scope of this invention that ultra-filtration membranes may be used to recover glucose or maltose from a partially hydrolyzed reaction mixture resulting from the treatment of a liquid starch feedstock with an enzyme. Any membrane which possesses an appropriate molecular weight as well as pore sizes capable of yielding the desired high glucose or maltose content as the permeate while retaining the rejected material which contains unhydrolyzed oligosaccharides is suitable. The ultra-filtration membrane will possess a molecular weight cut-off in the range of from about 100 to about 5000 and will also possess pore sizes in the range of from about 5 to about 125 Angstroms. Some speci-fic examples of these membranes which may be utilized will include cellulose acetates such as cellulose diacetate, cellulose triacetate or mixtures thereof, a membrane resulting from polyethyleneimine cross-linked with a dialdehyde, a diacidchloride, or a diisocyanate9 polyacrolein, chitosan cross-linked with a dialdehyde such as glutaraldehyde9 polystyrene-sulfonates, etc. It is to be understood that these ultra-filtration membranes are only representative of the class of membranes which may be employed and that the present invention is not necessarily limited thereto.
The two-step process o the present invention may be effected in any sultable manner and may comprise either a batch or contlnuous type operation. For example, when a batch type operation it cmployed, a qunntlty of the feedstock comprisiug a liquid starch which ha been previously treated with alpha-amylase to increase the dextrose equivalent is contacted wlth an lmmobillzed amyloglucoslda~e9 in the event that a syrup high ln glucose content ls desired, for a predetermined period of time while employing reaction conditions which include a temperature of from about 45 to about 70C and a pressure which may range from about 1 to about 1000 psl. In addition, the resldence time during which the feed6tock ~B in contact with the immobilized enzyme iB correlated wlth the liquid hourly space velocity at which the feed is introduced Jo as to produce a conversion of the liquid starch to glucose within the desired range. After passage over the immobllized enzyme, the effluent iB recovered and the partially hydrolyzed starch is then subjected to an ultrafiltration step. In thls step, the reactlon mixture is psssad through sn ultrafiltration membrane o the type hereinbefore set forth whereby the permeate which possesses a high glucose or maltose content is recovered as the permeate upon separation from the retentate.
The latter may then also be recycled, a portion of the recycle stream belng ndmixed with the ef1uent from the enzyme trea~me~t while another poFtion of the retentate iB admixed with the ieed stream to the immobllized enzyme treatment zone. It is also contemplated that a third portion, if BO desired, may be recycled back to the zone ln which the feedstock i8 pretreated wlth alpha-amylase.
It is also contemplated within the scope of thih in~entlon that the process may be effected in a continuous manner of operation.
When this type of operation is employed, the feedstock compri~lng the treated liquified starch i8 continuously charged to a reaction vessel such as a column which contains the desired immobilized enzyme, said column being maintained at the proper operating condi-,~:
rm~
tions of temperature and pressure. After passage over the enzyme at a predetermined liquid hourly space velnclty which ls sufficiently high so as to only partially hydrolyze the feedstock, with a con-comitant low or nonexistent production of reversion products such as isomaltose, the effluent is continuously withdrawn and charged to an ultrafiltration apparatus which contains a membrane of the type hereinbefore set forth. After passage through this apparatus, which is also maintained at the proper operating cond;t;ons of temperature and pressure, the pen~eate comprising syrup which has a high glu-cose or maltose content, l.e., above 90X, is recovered. The reten-tate material which contains unhdydrolyzed oligosaccharides such as those which have a DP rating of DP7, DP8, DPg+ (the designation DP
being the degree of polymer kation) is also recovered and a portion thereof recycled back to the column containing the immobilized enzyme for further use as a portion of the feedstock, another portion admixed with the effluent from the immobilized enzyme treatment and, if so desired, a portion to the alpha-amylase step for pretreatment.
Each of the heretofore mentioned membrane separations may be performed using solid adsorbents as well. One such adsorbent is dis-c10sed in U.K. Patent No. 1,585,369, and comprises X or Y zeolites containing one or more selected cations at the exchangeable cationic sites.
Potassium -X zeol;te 7S a particularly preferred adsorbent exhibiting selectivity for glucose with respect to disaccharides and higher ol;gosaccharides and the polysaccharides.
The following eleven examples are given for the purpose of thus trating the present inYention. However, it ;s to be understood that these examples are given merely for purposes of illustration and that the present process us not necessarily limited thereto.
I, , ~L~J~7~3 EXAMPLE I
To illustrate the process of the present invention, a starch feedstock was treated with alpha-amylase to adjust the dextrose equivalent to 15 DE. In this case, the enzyme was immobilized and comprised amylglucosidase composited on a solid alumina support. The treated starch feedstock was passed through a column of 40 cc of the immobilized enzyme, said starch feedstock con-taining 0.1% benzoate and 50 ppm of sodium omadine at a pH of 4.2.
The starch was treated at a temperature of 45C, and a pressure greater than atmospheric at a liquid hourly space velocity of 3.21.
The effluent from this column was analyzed by means of liquid chroma-tography. The analysis showed the following area in which DP is the degree of polymerization (or examp1e, DP7 = seven ~7) monomers of glucose in the oligosaccharide):
9+ 8 7 DP6 DP~ DP4 DP3 DP2 Glucose 19.1 0.2 0.1 - - - 0.3 3.1 77.2 l The e~luent in an amount ox 200 cc which was recovered from this column was then passed through a cellulose acetate membrane, 1~0.7 cc out ox the original 200 cc being obtained and constituting the permeate. Analysis of the permeate aFter passage through the mem-brane at a temperature of 22C and a pressure of 9~ psi showed that said penmeate contained 94.2% glucose, 3.6% maltDse and only 1.7% of the oligosaccharides having a DP of 9~.
The retentate which is recovered from the treatment with the cellulose acetate membranes may then be recycled and utilized as a portion of the feedstock which is charged ts the zone containing the immobilized enzyme comprising amyloglucosidase composited on the treated alumina support.
7~
EXAMPLE II
In a manner similar to that hereinbefore set forth in Ex-ample I, a treated liqui~ied starch ~eedstock was again passed through an lmmobilized amyloglucosidase column under conditions sim-ilar to those in Example I. The effluent from this column, which contained 77.2% glucose as well as minor amounts of maltose, DP3, DP7, DP8 and a major amount of DPg+oligosaccharides, was passed through a membrane comprising polystyrenesulfonate and sold under the trade mark Amicon UM2. The volume ox the effluent which passed through the membrane was 122.8 cc. Analysis of the permeate by means of liquid chromatography showed 97.6~ glucose, 2.3 maltose, and only 0.1% of DPg+ oligosaccharides.
When the above experiment was repeated using a membrane comprising cellulose acetate sold under the trade name Nuclepore and the effluent from the immobilized amyloglucosidase column was passed over this membrane at a temperature of 22C and a pressure of 90 psi, the penmeate was found to contain 97.5% glucose, 2.3% maltose, and 0.2% DP9~ oligosaccharides.
Likewise, the retentate which may be recovered from the treatment of the effluent with the cellulose acetate membrane may be recovered and recycled a portion of the retentate being admixed with the effluent from the immobilized enzyme treatment while the other portion is recycled to form a portion of the ~eedstock which is charged to the inmobilized enzyme treatment zone.
EXAMPLE I_ TD illustrate the ability Do the process of the present in-~L~3~7q~
vention to recover a product containing a high maltose concentration, a liquified starch feedstock which had been pretreated with alpha-amylase to adjust the dextrose equivalent to the desired level was passed through a column containing 100 cc of beta-amylase immobilized on a solid matrix similar to that set forth in Example I above. The feedstock which had a pH of 5.0 contained 0.1 mole ox acetate and 0.2 mole of benzoate which acted as a buffer. The feedstock was passed over the enzyme at a temperature of 55C, a pressure greater than atmo-spheric, at a liquid hcurly space velocity of 5. The effluent which was recovered from this column was subjected to liquid chromatography analysis with the following result:
HPLC ANALYSIS: (AREA %) 9~ B 7 DP6 DP5 DP4 DP3 DP2 Glucose 36.9 0.9 0.3 , 0.3 0.1 0.5 11.1 50.2 O5 The effluent from this column in an amount of 100 cc was passed through a cellulose acetate membrane while maintaining the mem-brane apparatus at a temperature of 22C and a pressure of gO psi.
Analysis of the permeate by means of liquid chromatography showed the presence of 79.0% maltosep 16.3% of a DP3 product and 2.4% of a DPg+
oligosaccharide.
When the aboYe experiment was repeated using an ultraf;l-tration membrane sold under the trade mark of Amicon UM2, the permeate was found to contain 90.1% maltosep 9.7~ of a DP3 oligosaccharide and only 0.2X of a DP9~ oligosaccharide.
In a similar manner the retentate which is recovered from the treatment with the ultrafiltration membrane of the above paragraph may be recycled, a port;on being admixed with the effluent withdrawn from the treatment with the immobilized beta-amylase while another portion may be admixed with the feedstock comprising the liquified starch prior to passage over the immobilized enzyme.
EXAMPLE IV
In this example, a liquified starch feedstock which may be pretreated with alpha-amylase Jo adjust the dextrose equivalent of said starch to a predetermined level may be passed through an immobilized amyloglucosidase column at a temperature of 45C and a pressure greater than atmospheric. The effluent from the column may be withdrawn after having been in contact with the immobilized enzyme for a predetermined period of time sufficient to permit a conversion to glucose of about 75% and may then be passed through an ultrafiltration membrane compris-ing polyacrolein, said passage over the membrane being effected at con-ditions which Jill include ambient temperature and a pressure of about
2~ psi. The permeate may be recovered while the retentate may ye re-cycled to be admixed with the effluent prior to passage over the afore-sa;d membrane.
In a similar manner, a liquified starch feedstock which con-tains a dextrose equivalent of about 15 may also be passed over an im-mobilized enzyme comprising beta-amylase composited on a treated alu-mina support, the reaction conditions including a temperature of about 50C and a pressure greater than atmospherk. After passage over the enzyme it a predetermined liquid hourly space velocity and for a resi-dence time sufficient to permit a conversion of about 75% of the starch to glucose, the effluent may be continuously withdrawn and pas-sed over the membrane comprising polyethyleneimine dialdehyde, said
In a similar manner, a liquified starch feedstock which con-tains a dextrose equivalent of about 15 may also be passed over an im-mobilized enzyme comprising beta-amylase composited on a treated alu-mina support, the reaction conditions including a temperature of about 50C and a pressure greater than atmospherk. After passage over the enzyme it a predetermined liquid hourly space velocity and for a resi-dence time sufficient to permit a conversion of about 75% of the starch to glucose, the effluent may be continuously withdrawn and pas-sed over the membrane comprising polyethyleneimine dialdehyde, said
3~7~ 3~
passage over the membrane being effected at a temperature of about 25C and a pressure of about 100 psi. The permeate which may contain over 90% glucose may be recovered while the retentate may be recycled, one portion of which may be admixed with the effluent, withdrawn from the enzyme treatment zone, a second portion may be recycled to be ad-mixed with the liquified starch feedstock entering the immobilized en-zyme zone, while a third portion may be recycled to the pretreatment 20ne in which the starch feedstock is contacted with alpha-amylase, the alpha-amylase acting to raisP the dextrose equivalent of the starch to a predetermined level.
The effluent which is continuously withdrawn from the treat-ment with the immobilized enzyme may also be passed over an ultrafil-tration membrane comprising chitosan dialdehyde at reaction conditions which include a temperature of bout 22C and a pressure of about 100 psi, the permeate oomprising a major portion of glucose being re-covered while the retentate may be recycled to be admixed with the ef-fluent which is dispersed from the i~obilized enzyme treatment 70ne.
l 3~ J
The seven examples whlch follow are merely illustrative of this invention and are not intended to limit or rest;rict it in any way. ,~
Thinned starch used as the feedstock was Maltrin-150, a typical analysis for which showed about 1% glucose, 3% DP2, 6% DP3, 4Y~ DP4, 4% DP5, 9% DP6, 16% DP7, and 58D/o DP~ and hiyher.
Glucoamylase was assayed as follows. Jo 4 ml of a starch solution, 300fD dry solids, was added 25 microliters of the enzymP solu-tion, and the mixture was incubated 30 minutes at 6~C. Hydrolysis was quenched bythe addition of 1 ml 0.2N NaOH, and the mixture was cooled. The amount of glucose formed was determined using a glucose analyzer. The number of grams of glucose produced per hour is the AG
activity expressed in Miles units.
EXAMPLE V
-A solution of AG (77 units/liter) at pH 4.2 in glucose so-lutions containing varying levels of dry solids was maintained at 60~C.
Aliquots were withdrawn periodically and assayed for AG activity. the enzyme half-life was found to be 4.8, 12.3, and 21.9 days at dry solids levels of 30%, 44% and 55%, respectively. Thus, enzyme stab;lity as measured by halt e at 60~G is increased over 4.5-fold in going from 30D/. to 55% dry solids.
* trade mark _19_ g~3q~
EXAMPLE Vl Feedstocks of Maltri~-150*of different dry solids (DS) level at pH 4.2 containing AG at 77 units per liter were hydrolyzed at 60C.
glucose concentration as determined by high pressure liquid chromatog-raphy was monitnred with time, the results being su~arized in the ac-5companying table.
TABLE 1. Glucose Concentration With Hydrolysis Time Time Glucose conc., grams/liter (hours) 30% DS 44% DS 55% DS
26~ ~90 3~5 320 405 42~
330 ~40 340 525 ~00 The results clearly show that glucose production rates in-creases with increasing dry solids level of fe dstock.
EXAMPLE Vll A feedstock of Maltrin-150* 30% dry solids9 at pH 4.2 and containing AG at 77 units per ljter was hydrolyzed at 60C. Product was analyzed for glucose, total disaccharides 5DP?), and isomaltose.
Results using two different lots of AG are summarized in the table below.
* trade mark l 3~;:3~3 1 TABLE 2. Glucose, Disaccharide, and Isomaltose Production _ _ _ _ Time Weight %
Run 1 (hours) ,glucosed;saccharides isornaltose 2 28 ~.5 0 58 9.0 0.6 6 7~ 4.5 0.9 88 4.0 0.9 lQ 90 4.5 1.3 12 92 4.R 1.3 5.8 ~.2 9~ 7.0 3.
Run 2 1.8 45.1 17.3 0
passage over the membrane being effected at a temperature of about 25C and a pressure of about 100 psi. The permeate which may contain over 90% glucose may be recovered while the retentate may be recycled, one portion of which may be admixed with the effluent, withdrawn from the enzyme treatment zone, a second portion may be recycled to be ad-mixed with the liquified starch feedstock entering the immobilized en-zyme zone, while a third portion may be recycled to the pretreatment 20ne in which the starch feedstock is contacted with alpha-amylase, the alpha-amylase acting to raisP the dextrose equivalent of the starch to a predetermined level.
The effluent which is continuously withdrawn from the treat-ment with the immobilized enzyme may also be passed over an ultrafil-tration membrane comprising chitosan dialdehyde at reaction conditions which include a temperature of bout 22C and a pressure of about 100 psi, the permeate oomprising a major portion of glucose being re-covered while the retentate may be recycled to be admixed with the ef-fluent which is dispersed from the i~obilized enzyme treatment 70ne.
l 3~ J
The seven examples whlch follow are merely illustrative of this invention and are not intended to limit or rest;rict it in any way. ,~
Thinned starch used as the feedstock was Maltrin-150, a typical analysis for which showed about 1% glucose, 3% DP2, 6% DP3, 4Y~ DP4, 4% DP5, 9% DP6, 16% DP7, and 58D/o DP~ and hiyher.
Glucoamylase was assayed as follows. Jo 4 ml of a starch solution, 300fD dry solids, was added 25 microliters of the enzymP solu-tion, and the mixture was incubated 30 minutes at 6~C. Hydrolysis was quenched bythe addition of 1 ml 0.2N NaOH, and the mixture was cooled. The amount of glucose formed was determined using a glucose analyzer. The number of grams of glucose produced per hour is the AG
activity expressed in Miles units.
EXAMPLE V
-A solution of AG (77 units/liter) at pH 4.2 in glucose so-lutions containing varying levels of dry solids was maintained at 60~C.
Aliquots were withdrawn periodically and assayed for AG activity. the enzyme half-life was found to be 4.8, 12.3, and 21.9 days at dry solids levels of 30%, 44% and 55%, respectively. Thus, enzyme stab;lity as measured by halt e at 60~G is increased over 4.5-fold in going from 30D/. to 55% dry solids.
* trade mark _19_ g~3q~
EXAMPLE Vl Feedstocks of Maltri~-150*of different dry solids (DS) level at pH 4.2 containing AG at 77 units per liter were hydrolyzed at 60C.
glucose concentration as determined by high pressure liquid chromatog-raphy was monitnred with time, the results being su~arized in the ac-5companying table.
TABLE 1. Glucose Concentration With Hydrolysis Time Time Glucose conc., grams/liter (hours) 30% DS 44% DS 55% DS
26~ ~90 3~5 320 405 42~
330 ~40 340 525 ~00 The results clearly show that glucose production rates in-creases with increasing dry solids level of fe dstock.
EXAMPLE Vll A feedstock of Maltrin-150* 30% dry solids9 at pH 4.2 and containing AG at 77 units per ljter was hydrolyzed at 60C. Product was analyzed for glucose, total disaccharides 5DP?), and isomaltose.
Results using two different lots of AG are summarized in the table below.
* trade mark l 3~;:3~3 1 TABLE 2. Glucose, Disaccharide, and Isomaltose Production _ _ _ _ Time Weight %
Run 1 (hours) ,glucosed;saccharides isornaltose 2 28 ~.5 0 58 9.0 0.6 6 7~ 4.5 0.9 88 4.0 0.9 lQ 90 4.5 1.3 12 92 4.R 1.3 5.8 ~.2 9~ 7.0 3.
Run 2 1.8 45.1 17.3 0
4.7 69.0 10.8 0
5.6 74.~ 7.5 0 7.5 8~.9 ~.5 13.0 91.1 3.2 ~.0 20.0 93.5 3.4 O.B
- ~8.0 94.8 4.1 1.6 Thus, relative to the time needed to attain a 94% glucose product attainment of a 90% glucose product takes bout half the time, and attainment of a 92% glucose product takes about 60% Df the time.
These results also clearly show the accumulation of is~mal-tose during the latter stages of conversion.
~.~3 7~ D
EXANPLE VIII
lhis exnmyle compares results from a once-through reactor, to a conventional operatlon in which thinned starch is hydrolyzed to about 94% or greater glucose, with a clo~ed-loop system where reactor eEfllJent iB Kent to a membrane, a gluco~e-enrlched product strenm iB drawn off, and the gluco~e-depleted stream is recycled to the beginnlng of the reactor.
All hydrolyses were performed at 60C, pH 4.5~5.5. Run A 1B the conven-tional, once-through reactor; both Runs B and C are closed-loop ~y~ems, wlth B using a cellulo6e acetate membrane hazing a 10,000 molecular weight cutoff operating at 60C, 150 prig, and C UBing a polyelec~rolyte membrane with a 500 molecular weight cutoff operatlng at 60C, 300 psig, both supplied by Amicon Co. under their trade marks YM10 and UN05, respectively Results are listed in Table 3, where DPl repre~entR total mono~accharldes, nearly all of which is gluco6e7 DP~ represents disaccharides, DP~ are poly-saccharides of four or more units, end DS i8 dry solits. For Runs B and C reactor effluent, product and recycle stream analyses are equilibrium values .
rm/Ad TABLE 3. Companion of Once-Through (Single Pays) Reactor With Clo~ed-Loop, Recycle Reactor Run A Run B Run C
enzyme (AG) dosage, unlt~/llter 77 34 58 Residence time, hours 48 14 20 Feedstock Composition (%) DS 30.0 26.1 24.7 DPl 1.0 1.2 1.6 DP2 4-5 4~3 3-9 DP4+ 87.5 87.8 88.3 Reactor Effluent DS 33.0 27.0 30.4 DP 95.7 90.5 83.4 DPl 4.1 2.9 4.4 DP4+ 0.2 6.3 11.6 Product Stream DS 26.1 24.7 DP 93.6 98.0 DPl 3.1 2.0 DP4+ 2.~ 0.0 Recycle Stream DS 27.4 34.2 DPl 89.9 82.5 DP2 3.5 3.8 DP4+ 6.3 13.1 EXAMPLE IX
A kinetic model was developed from experime~$al data which not only closely reproduced exiting experimental dnta but alto had reliably hlgh predictive abillty. Among the variable (experlmental parameters) accommodated by the model were feedstock (thinned starch) composltlon, enzyme dotage, reactor re~ldence tlme, membrane type and operating condition.
` .j.
. .
rm/~
Output included glucose and 1somaltose concentration in the p~odl1ct strenm.
The feedstock of thinned starch hod 30~6 weight percent dry solids with 1.2% DPl, 4.8X DP2, and 87~ DP~. Run A represents a once through reactor, nnd Runs B and C represent a closed-loop recyc]e reactor usi11g the polyelectrolyte membrane described in tke prior example with the glucose-depleted streRm recycled to the top of the reactor. Reactor efflue~ and product compositions are equillbrlum values.
TABLE 4. Isomaltose Accumulation Run A Run B Run C
AG concentration, units/liter 77 9 18 Residence time, hours 48 lO lO
Reactor effluent: % glucose 95.774 87.3 % isomalto6e 1.66 0.7 l.B5 Product % glucose 95.5 97.2 % isomaltose 0.34 0~73 These data clearly show that the closed-loop, recycle process produces glucose at as high concentration as that from a conventional, once-through reactor at substantially lower enzyme dotage, with one-fourth the isomaltose content. In fact, Run C 8hows that one can lncrease glucose in .he product to over 97% (using one-fourtb the enzyme concentration) and still have less than half the isomaltose content a that from the con-ventional process.
EXAMPLE X
In this example the aforementioned kinetic model was used to determlne the effect of recycle location on glucose and isomaltose concen-tration ln the Rteady state product and reactor effluent streams. Data rm~ia ~ri~t7 re summarized ln Table 5, where "reactor volume" refers to the percent reactor volume prior to the recycle loc~tlo~; 0 represellts the top, 100 represents the bottom of the reactor. Thinnad starch feed~tock had the composition of that in the foregolng example; reactor time was lO hour and the polyelectrolyte membrane of example 4 way used under the stated condition TABLE 5. Effect of Recycle Point on Product Composltion 0 30 50 70 ~0 95 AG concentratlon: 18 u/l Reactor effluent glucose 87.4 88.0 87.0 85.0 73.0 57.0 isomaltose 1.85 1.8 1.7 1.3 0.6 ~25 Product glucose 97.2 97.2 97.2 96.9 96.9 90.7 isomaltoee 0.73 0~71 0.66 0.55 0.27 0.13 AG concentratlon: 77 u/l Reactor effluent glucose 91.5 91.5 91.5 91.5 92.3 91.0 isomaltose 4.75 4.8 4.7 4.4 3.35 2.5 Product glucose 96.9 96.9 9o.9 97.0 97.3 97.4 isomaltose 1.73 1.74 1.70 1.59 1.22 0.93 The results it the table reflece the iact thae at high AG con-centration the product eomposition i8 rather insensitive to recycle point throughout, and at lower enzyme concentration no substantial change in product composition is seen when the recycle point is between 0-90% of reactor volume. The overall conclusion iR that recycle location will be a process choice depending upon other process parameter such as enzyme concentration, residence time, separation means used, product composition desired, etc.
f 3 16 EXAMPLE XI
These data generated by the kinetic model show the advan-tages,absent in a once-through reactor,accruing from a feedstock with high dry solids used in a closed loop, recycle process. F~eds~ock had the composition of Example 5 with only the dry solids (weight percent) varying. the recycle reactor utilixed the polyelectr~lyte membrane nf Example 4 under the conditions stated therein.
TABLE 6. Effect of Dry Solids Variation Closed lop Once-~hrough reactor recycle reactor % Dry solids 30 40 40 Residence time, hours 48 71 10 AG concentratinn, units/liter 77 77 18 Product, wt. I: glucose 95.7 93.6 95.6 isomaltose 1.7 .2.2 0.7 In a ~nce-through reactor residence time is unacceptably long end isamaltose toncentration is unacceptably high using 40~ dry solids fe~dstock~` whereas in the closed loop recycle reactor configuration residence time is reduced told, isomaltose concentration 3-~old. and enzyme concentration 4-~old.
-~6-
- ~8.0 94.8 4.1 1.6 Thus, relative to the time needed to attain a 94% glucose product attainment of a 90% glucose product takes bout half the time, and attainment of a 92% glucose product takes about 60% Df the time.
These results also clearly show the accumulation of is~mal-tose during the latter stages of conversion.
~.~3 7~ D
EXANPLE VIII
lhis exnmyle compares results from a once-through reactor, to a conventional operatlon in which thinned starch is hydrolyzed to about 94% or greater glucose, with a clo~ed-loop system where reactor eEfllJent iB Kent to a membrane, a gluco~e-enrlched product strenm iB drawn off, and the gluco~e-depleted stream is recycled to the beginnlng of the reactor.
All hydrolyses were performed at 60C, pH 4.5~5.5. Run A 1B the conven-tional, once-through reactor; both Runs B and C are closed-loop ~y~ems, wlth B using a cellulo6e acetate membrane hazing a 10,000 molecular weight cutoff operating at 60C, 150 prig, and C UBing a polyelec~rolyte membrane with a 500 molecular weight cutoff operatlng at 60C, 300 psig, both supplied by Amicon Co. under their trade marks YM10 and UN05, respectively Results are listed in Table 3, where DPl repre~entR total mono~accharldes, nearly all of which is gluco6e7 DP~ represents disaccharides, DP~ are poly-saccharides of four or more units, end DS i8 dry solits. For Runs B and C reactor effluent, product and recycle stream analyses are equilibrium values .
rm/Ad TABLE 3. Companion of Once-Through (Single Pays) Reactor With Clo~ed-Loop, Recycle Reactor Run A Run B Run C
enzyme (AG) dosage, unlt~/llter 77 34 58 Residence time, hours 48 14 20 Feedstock Composition (%) DS 30.0 26.1 24.7 DPl 1.0 1.2 1.6 DP2 4-5 4~3 3-9 DP4+ 87.5 87.8 88.3 Reactor Effluent DS 33.0 27.0 30.4 DP 95.7 90.5 83.4 DPl 4.1 2.9 4.4 DP4+ 0.2 6.3 11.6 Product Stream DS 26.1 24.7 DP 93.6 98.0 DPl 3.1 2.0 DP4+ 2.~ 0.0 Recycle Stream DS 27.4 34.2 DPl 89.9 82.5 DP2 3.5 3.8 DP4+ 6.3 13.1 EXAMPLE IX
A kinetic model was developed from experime~$al data which not only closely reproduced exiting experimental dnta but alto had reliably hlgh predictive abillty. Among the variable (experlmental parameters) accommodated by the model were feedstock (thinned starch) composltlon, enzyme dotage, reactor re~ldence tlme, membrane type and operating condition.
` .j.
. .
rm/~
Output included glucose and 1somaltose concentration in the p~odl1ct strenm.
The feedstock of thinned starch hod 30~6 weight percent dry solids with 1.2% DPl, 4.8X DP2, and 87~ DP~. Run A represents a once through reactor, nnd Runs B and C represent a closed-loop recyc]e reactor usi11g the polyelectrolyte membrane described in tke prior example with the glucose-depleted streRm recycled to the top of the reactor. Reactor efflue~ and product compositions are equillbrlum values.
TABLE 4. Isomaltose Accumulation Run A Run B Run C
AG concentration, units/liter 77 9 18 Residence time, hours 48 lO lO
Reactor effluent: % glucose 95.774 87.3 % isomalto6e 1.66 0.7 l.B5 Product % glucose 95.5 97.2 % isomaltose 0.34 0~73 These data clearly show that the closed-loop, recycle process produces glucose at as high concentration as that from a conventional, once-through reactor at substantially lower enzyme dotage, with one-fourth the isomaltose content. In fact, Run C 8hows that one can lncrease glucose in .he product to over 97% (using one-fourtb the enzyme concentration) and still have less than half the isomaltose content a that from the con-ventional process.
EXAMPLE X
In this example the aforementioned kinetic model was used to determlne the effect of recycle location on glucose and isomaltose concen-tration ln the Rteady state product and reactor effluent streams. Data rm~ia ~ri~t7 re summarized ln Table 5, where "reactor volume" refers to the percent reactor volume prior to the recycle loc~tlo~; 0 represellts the top, 100 represents the bottom of the reactor. Thinnad starch feed~tock had the composition of that in the foregolng example; reactor time was lO hour and the polyelectrolyte membrane of example 4 way used under the stated condition TABLE 5. Effect of Recycle Point on Product Composltion 0 30 50 70 ~0 95 AG concentratlon: 18 u/l Reactor effluent glucose 87.4 88.0 87.0 85.0 73.0 57.0 isomaltose 1.85 1.8 1.7 1.3 0.6 ~25 Product glucose 97.2 97.2 97.2 96.9 96.9 90.7 isomaltoee 0.73 0~71 0.66 0.55 0.27 0.13 AG concentratlon: 77 u/l Reactor effluent glucose 91.5 91.5 91.5 91.5 92.3 91.0 isomaltose 4.75 4.8 4.7 4.4 3.35 2.5 Product glucose 96.9 96.9 9o.9 97.0 97.3 97.4 isomaltose 1.73 1.74 1.70 1.59 1.22 0.93 The results it the table reflece the iact thae at high AG con-centration the product eomposition i8 rather insensitive to recycle point throughout, and at lower enzyme concentration no substantial change in product composition is seen when the recycle point is between 0-90% of reactor volume. The overall conclusion iR that recycle location will be a process choice depending upon other process parameter such as enzyme concentration, residence time, separation means used, product composition desired, etc.
f 3 16 EXAMPLE XI
These data generated by the kinetic model show the advan-tages,absent in a once-through reactor,accruing from a feedstock with high dry solids used in a closed loop, recycle process. F~eds~ock had the composition of Example 5 with only the dry solids (weight percent) varying. the recycle reactor utilixed the polyelectr~lyte membrane nf Example 4 under the conditions stated therein.
TABLE 6. Effect of Dry Solids Variation Closed lop Once-~hrough reactor recycle reactor % Dry solids 30 40 40 Residence time, hours 48 71 10 AG concentratinn, units/liter 77 77 18 Product, wt. I: glucose 95.7 93.6 95.6 isomaltose 1.7 .2.2 0.7 In a ~nce-through reactor residence time is unacceptably long end isamaltose toncentration is unacceptably high using 40~ dry solids fe~dstock~` whereas in the closed loop recycle reactor configuration residence time is reduced told, isomaltose concentration 3-~old. and enzyme concentration 4-~old.
-~6-
Claims (11)
1. A process for selectively obtaining a sugar which is either glucose or maltose from thinned starch comprising hydrolyzing a feedstock of thinned starch under the action of a glucose- or maltose-producing enzyme to an effluent stream containing from about 50% to 92% of said sugar, separating the effluent stream into a sugar-enriched product stream and a sugar-depleted stream, recovering the sugar-enriched product stream, and recycling the sugar-depleted stream to the hydrolysis step.
2. The process of claim 1 where the feedstock contains from about 30% to about 45% dry solids.
3. The process of claim 1 where the product stream contains from about 60% to about 85% sugar.
4. The process of claim 3 where the product stream contains from about 70% to about 80% sugar.
5. The process of claim 1 where the hydrolysis step is catalyzed by a soluble enzyme.
6. The process of claim 1 where the hydrolysis step is catalyzed by an immobilized enzyme.
7. The process of claim 1 where the enzyme is amyloglucosidase and the sugar is glucose.
8. The process of claim 1 where the enzyme is beta-amylase and the sugar is maltose.
9. The process of claim 1 where the sugar-enriched stream contains at least about 90% sugar.
10. The process of claim 1 where a membrane-based separation step is utilized.
11. The process of claim 1 where a solid adsorbent-based separation step is utilized.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000466548A CA1237086A (en) | 1984-10-29 | 1984-10-29 | Glucose or maltose from starch |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000466548A CA1237086A (en) | 1984-10-29 | 1984-10-29 | Glucose or maltose from starch |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1237086A true CA1237086A (en) | 1988-05-24 |
Family
ID=4129026
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000466548A Expired CA1237086A (en) | 1984-10-29 | 1984-10-29 | Glucose or maltose from starch |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1237086A (en) |
-
1984
- 1984-10-29 CA CA000466548A patent/CA1237086A/en not_active Expired
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