Continuous process for the recovery of betaine

Abstract: This invention relates to the manufacture of etha­ nol, glycerol, betaine, L-pyroglutamic acid, succinic an lactic acid, potassium sulfate and a free flowing distill­ er's dry grain and solubles useful as an animal feed or a compound of food for humans or as a premix for agricultural fertilizer and/or a feed additive. The process disclosed is an improvement in the area of enhancement of glycerol production during fermentation of a biomass mash, and involves production of glycerol in amount in excess of 10 grams per 100 grams of reducing sugar in the starting biomass mash. The process also produces the recovery of both glycerol and betaine from sugar beet stillage.

Description: This invention relates to the manufacture of glycerol, betaine and optionally also succinic acid, lactic acid, potassium sulfate and/or L-pyroglutamic acid, from beet stillage. More particularly the invention relates to the recovery of the above products as a result of the fermentation and distillation of raw materials into ethanol and stillage, from which a solid fertilizer is produced. The manufacture of each of the products named above by other processes has been known heretofore, and all have commercial uses. Ethanol is used as a beverage, a chemical, and a fuel derived from renewable resources, and is typically manufactured by fermentation and distillation processes starting from biological materials such as corn, wheat or other grain, sugar cane or beets, grapes or other fruit, potatoes, cassava, sweet sorghum, cheese whey or the like. Glycerol, while known to be produced in small quantities as a by-product of ethanol fermentation and distillation processes or yeast and yeast extract production, has been manufactured commercially only by processes which have soap as the primary product or which synthesize glycerol from petrochemical feedstocks. Betaine is conventionally produced synthetically or by crystallization of the aqueous liquors of beet molasses. Succinic acid is conventionally synthesized from maleic or acetic acid or produced by means of a highly specific fermentation. Lactic acid is conventionally produced by fermentation with Lactobacillus delbrueckii, B. dextrolacticus, or similar microorganisms. Potassium sulfate is conventionally obtained by reacting sulfuric acid with potassium chloride. Potassium chloride usually occurs in nature as the mineral sylvine or sylvite. If the substrate from which distillates are produced is a sugar beet material, then the residue is typically used only as a liquid fertilizer, feed additive or treated as a waste. The manufacture of ethanol is sufficiently well known and the interested reader is referred to the available literature for descriptions of the basic processes. The manufacture of glycerol is, by way of example, discussed in Hildebrandt United States Patent No. 2,160,245;; Wallerstein United States Patent No. 2,772,207, to which the interested reader is referred. Some suggestion that glycerol might be more economically recovered from stillage appears in a paper by Burris entitled "Recovery of Chemicals Such as Glycerol, Dextrose, and Amino Acids from Dilute Broths" which was presented to the "International Conference on Fuel Alcohols and Chemical from Biomass" on November 10-12, 1986 in Miami Beach, Florida. The process there disclosed includes a very precise sequence of operations including ultrafiltration (organic membranes with pore size of <0.1 µm), pH adjustment, filtration, ion exclusion, ion exchange and carbon treatment. This sequence of operations has not proven to provide a commercially feasible glycerol recovery process. Betaine production is, by way of example, discussed in WO-A-81/02420, US-A-4,359,430, Japanese Patent No. 51/039625; and Japanese Patent No. 80/045067. WO-A-81/02420 also describes the recovery of betaine from vinasse by chromatographic separation followed by crystallization. While the production of betaine from sugar beet molasses is a known commercially feasible process as described in the above listed patents, attempts to produce betaine from stillage have tended to result in a serious fouling of the chromatographic resin by yeast cells, microorganisms and other compounds. The manufacture of glycerol, succinic acid and free flowing distiller's dry grain from fermented mash is described in WO-A-89/05861. The fermented mash is clarified by microfiltration and glycerol is separated from the other constituents by passage through an ion exclusion material. The present invention consists in a continuous process for recovering glycerol and betaine from stillage produced from the fermentation and distillation of sugar beets, whichresults in ethanol and said stillage, said continuous process comprising the steps of (a) clarifying said stillage by subjecting it to a cross-flow microfiltration process utilising inorganic membranes having pore sizes in the range of 0.1-10 µm; (b) subjecting the clarified stillage to a first chromatographic separation by passing the clarified stillage through an ion-exclusion apparatus for separating glycerol and betaine as a mixture from other constituents of the clarified stillage; (c) subjecting the glycerol/betaine mixture to a second chromatographic separation by passing the mixture through a second ion exclusion apparatus in which the glycerol is separated from the betaine; and (d) purifying the separated glycerol and betaine. By means of the invention, betaine and glycerin, and optionally other components, can be isolated from stillage of ethanol fermentations with sugar beet derivatives. The preparation of the feed with microfiltration and the two chromatographic separation steps for the production of pure glycerin and betaine are critical. Cross-flow microfiltration with inorganic membranes, which may be followed by enzymatic hydrolysis of proteinaceous matter and/or removal of potassium sulfate crystals in the permeate (if required) will yield a truly clarified stillage. The clarified stillage may now be concentrated to a very high solids concentration for further processing in two chromatographic separation steps, each with its own specific resin, yielding high purity glycerin and betaine streams. This novel process has several advantages over existing and different methods in use as described in the patents listed above, such as energy and water savings, reduced capital investment, very high solids concentrations, high quality glycerin and betaine. The process of the present invention allows the production of glycerol and betaine or betaine-HCl, and optionally one or more of the other products mentioned, in a commercially feasible manner in a fermentation and distillation or similar process. In realising the process of the present invention, the efficiency of the known ethanol producing fermentation and distillation processes is essentially maintained, while an additional valuable product is derived. More particularly, ethanol production follows known and widely published pathways of biochemical reactions. In its most general sense, fermented mash is distilled in a stripping column with the vaporized ethanol being removed from overhead. The remaining stillage is then clarified by centrifuging (if required) followed by microfiltration. The microfiltration step, in which particles in the range of 0.1 to 10 microns are separated from the stillage, is the key to the recovery of glycerol, betaine and by-products in such quantities as to be economically feasible. Earlier attempts (Burris) to recover glycerol had suggested ultrafiltration (separation of particle sizes of less than 0.1 microns) combined with other operative steps, however, due to fouling of ultrafiltration membranes, insufficient quantities of glycerol resulted to make the process economically feasible. The unexpected result of microfiltration with inorganic membranes is that, while the stillage is truly clarified, the subsequent recovery of by-products such as glycerol results in greatly enhanced quantities thereof, making its recovery for the first time commercially feasible. Further, the resulting solids are freer of sticky by-products and thus more free flowing and easier to handle. The accompanying drawing is a schematic representation of the flow of the materials in the processes and apparatus of the present invention is shown. Referring now more particularly to the drawing accompanying this disclosure, there are depicted certain steps which in the sequence disclosed hereinafter, illustrate preferred embodiments of this invention. Certain steps, being well known to those having skill in the relevant arts, have not been shown in detail but will be described for the reader. It is known that the formation of ethanol in a fermentation process with yeast cells or other microorganisms is growth associated and that the formation of glycerol and succinic acid is interrelated. More specifically, in the Embden-Meyerhof pathway, NADH from triose phosphate oxidation exceeds the rate of acetaldehyde reduction, thus accounting for normal glycerol formation when the cell starved for ATP from glycolysis shifts excess NADH to the reduction of dihydroxyacetone phosphate to glycerol. Additional NADH is supplied through the Kreb's citric acid cycle. As used herein, NADH refers to nicotinamide adenine dinucleotide and ATP to adenosine triphosphate. In a conventional well run fermentation process without the recycle of stillage, some 48 grams of ethanol, 4.0 grams of glycerol, 0.6 gram of succinic acid, and small quantities of lactic acid are formed per 100 grams of reducing sugar consumed. Ethanol producers using a corn wet milling process generally have substantial quantities of lactic acid present in their fermented mash, as do certain wine and other fermentation. Turning now to the drawing, after fermentation the next step is normally distillation, preferably in a stripping column, accompanied by overhead removal and collection of the ethanol vapors. The remaining still bottoms or stillage then contains glycerol and betaine as well as all or any of the by-product components described hereinabove. The further processing will determine which of the by-products are recovered. The first step after distillation is the clarification process, which may begin with a centrifuging pretreatment with or without chemical treatment. In some cases, a protease(s), a protein digesting enzyme, is added in the pretreatment to break down peptides and proteins, which would tend to clog subsequent filtering membranes. Following pretreatment, if any, the stillage goes through the step of cross-flow microfiltration with inorganic membranes. Microfiltration, which is defined elsewhere in the disclosure as the subjection of the stillage to cross-flow microfiltration with a ceramic or inorganic membrane having pore sizes in the range of 0.1 to 10 µm separates the stillage into retentate and permeate, and is the critical step to producing a truly clarified stillage and the recovery of the by-products in economically feasible quantities. The retentate, containing the larger solid particles, goes to fertilizer or animal feed processing. The permeate, depending upon the raw material used, may have to be softened to prevent fouling of the chromatographic separation resins used downstream. The permeate is then concentrated to as high a solids concentration as practicable (50-75%). The concentrated permeate is then either directly passed on to chromatographic separation (for recovery of glycerol, betaine and optionally succinic acid, L-pyroglutamic acid or lactic acid) or is first subjected to a crystallization operation (for recovery of potassium sulfate). The first chromatographic separation yields glycerol and betaine. These are separated in the second chromatographic step and each product is purified, concentrated, and refined. The first process parameter to be addressed for enhanced glycerol and/or succinic acid formation during fermentation relates to the form of yeast used in the fermentation process. It has been determined that a properly immobilized organism will enhance and increase production of glycerol and succinic acid. These results are achieved where the yeast is in a stable ionic and high density matrix. Other process parameters which are contemplated as being subject to adjustment in accordance with this invention include yeast cell concentration and DE or carbohydrate concentration. As yeast cell concentration and carbohydrate concentration rise, production of glycerol and succinic acid are enhanced. Still other process variables which are contemplated by this invention as being optimized for the production of the desired products while maintaining ethanol production include osmotic pressure during fermentation; concentration of dissolved carbon dioxide; pH; temperature; selection of the microorganism used; the mode of fermentation; and the formulation and preparation of fermentation media. More precisely, increased osmotic pressure from recycling stillage, increased solute concentration, and/or increased temperature increases production of glycerol and succinic acid, as does increased dissolved carbon dioxide. Yeast cells, as most microorganisms, are able to regulate its internal pH quite effectively within a range of mash pH of from 3 to 7, and thus the effect of process variations in pH may appear minimal. It has been determined, however, that production of glycerol and succinic acid is enhanced where an essentially constant pH is maintained during the first half of the fermentation step (when the bulk of glycerol and succinic acid are produced) by the addition of a suitable alkali such as sodium carbonate. The fermentation media, or mash, characteristics will affect the production of glycerol and succinic acid due to the interacting effects of the raw material itself, the concentration of any liquefying enzyme, the ratio of fermentable sugars to nonsugars, the type of nonsugars present, and the nutritional requirements of the particular fermentation microorganism chosen. Generally, the first further processing step after fermentation is distillation of the fermented mah to produce ethanol. Such distillation may be by use of a stripping column capable of handling a solids containing stream. The still bottoms or stillage is then centrifuged (if required) and the centrate processed further in a clarification step, removing the dispersed solids to obtain a (sparkling) clear liquid. Clarification is accomplished with (cross-flow) microfiltration systems containing ceramic or mineral membranes. In this process particles in the range of 0.1 - 10 µm, depending on the membrane selected are separated from the thin stillage. High and stable fluxes may be obtained through computer controlled backflushing and proper membrane selection. These new microfiltration membranes are known as such and are commercially available from known suppliers. Such known apparatus may be incorporated into the overall apparatus which practices the processes of this invention. A chemical clarification process may proceed by taking up to 20 percent of the stillage and liming it to a pH of 9.0 to 12.0 while at or near boiling. The remainder of the stillage is adjusted to a pH range of 4.5 to 7.5 with sodium hydroxide, calcium hydroxide and/or sodium carbonate at temperatures as high as practicable. The two portions are then mixed and a precipitate of salt forms, the separation of which is improved by the addition of polyelectrolytes, followed by centrifugation. Depending upon the raw material following microfiltration or chemical clarification is a (partial) softening step; mainly for the reduction of the divalent cation levels of calcium and magnesium. This will prevent the plugging and fouling of the downstream ion exclusion resin by salt deposits of divalent cations due to potential process upsets which would considerably reduce the operating efficiency. As the stillage is clarified, it may be passed to and through an evaporator to remove as much water as possible and effect as high a solids concentration as is practicable. Due to proper clarification, the overall heat transfer coefficient involved will be considerably improved over thin stillage which has not been clarified, while the fouling of heat transfer surfaces will also be minimized. The clarified and concentrated stillage is passed to an ion exclusion apparatus. The apparatus may be a simple or multiple column system used as a pulsed bed or a simulated moving bed. Recycling may be used to maintain or increase product purity and/or recovery efficiency. Condensate as is from any evaporators used in the apparatus may serve as desorbent, with desorbent to feed ratios in the range of from 1.6 to 3.0. Such a column is in ionic equilibrium and requires no regeneration. The resulting by-product stream of the ion exclusion step is ideal for use as a backset in the fermentation. It is a "clean" stream, which will increase osmotic pressure levels as well as reduce process water requirements. The glycerol stream recovered from the ion exclusion apparatus and process may be further purified in a mixed bed ion exchanger and then concentrated and purified to any desired grade. Such concentration and purification may, for example, be accomplished by the use of an energy efficient vacuum/steam multiple effect evaporator, and distillation and refining unit such as those available from G. Mazzoni SpA of Italy, with the more concentrated glycerol being deodorized, bleached, filtered and/or polished as desired. In a process according to one embodiment of the invention, the fermented mash is distilled to strip off ethanol. The bottoms or whole stillage is clarified to obtain a clear liquid. In the preferred process, as previously described, cross flow microfiltration systems with inorganic and/or organic membranes having pore sizes in the range of from 0.1 µm to 10 µm are used to remove particulate matter. Such inorganic membranes for the first time allow proper stillage clarification. Hot stillage, either as received or after centrifugation and/or filtration to remove coarse particles, may now be processed. Preferably, computer controlled backflushing (at high pressure if necessary) will allow for high on-line stream factors for the microfiltration modules and will in most cases eliminate the need for (harsher) chemical cleaning. The feed may be pretreated chemically to produce a floc, which under controlled conditions, will form a "dynamic membrane" layer and improve the clarification. Known filtration apparatus having the characteristics recited may be incorporated in the overall apparatus which is used in practicing this invention. Microfiltration yields a concentrate or retentate which is further processed into a fertilizer base to which may be added the by-product stream from chromatographic separation processes described hereinafter. The microfiltration permeate may, if necessary, be softened to remove divalent cations which could otherwise foul the downstream chromatographic separation resins. The clarified stillage is next concentrated to as high a solids concentration as practicable. Due to the clarification, the overall heat transfer coefficients involved have been improved while scaling of heat exchange surfaces has been minimized. Cooling and/or addition of sulfuric acid will bring about the formation of potassium sulfate, which may be recovered through crystallization to yield yet another valuable by-product. Chromatographic separation of the clarified, concentrated stillage then follows. The material passes through an ion exclusion apparatus containing a suitable resin. Ion exclusion and exchange resins may be kept in the potassium monovalent form, which will maximize the separation between ionic and nonionic components as well as improve formation of potassium sulfate. The chromatographic separation apparatus may be a single or multiple column system used as a pulsed bed or a simulated moving bed in a continuous process. The condensate from any evaporators used in the process may be used as the desorbent, thus minimizing make up water requirements. Desorbent to recovered glycerol ratios are in the range of from 10 to 25. Such a system is in ionic equilibrium and does not normally require regeneration. Betaine and glycerol may exit the chromatographic separation together. It is then necessary to use the following (smaller) chromatographic separation to produce a pure betaine stream from which betaine may be recovered with standard processes. Using a resin such as IWT-AM-63, excellent separations were obtained. Over 98 percent of the glycerol and over 92 percent of the betaine were recovered making it simple to produce pure products. The desorbent may be condensate produced in the overall process. In a large scale test at 60°C, the desorbent used was 5.7 weight parts of water to 1 weight part of betaine and 13.6 weight parts of water to 1 weight part of glycerol, while 3.95 kg of betaine per minute and per square metre (0.81 lb/min/ft 2 ) and 1.66 kg of glycerol per minute and per square metre (0.34 lb/min/ft 2 ) were obtained. The glycerol product stream is concentrated in double effect LTV evaporators to approximately 85% dry solids. Feed forward systems employing a thermo-compressor with high pressure steam and feed backward systems using greater quantities of lower pressure steam may be used. The concentrated crude glycerin may be neutralized before it is fed into the rectifying section of a high efficiency distillation column. Through evacuation and direct steam injection the column partial pressure is kept low to minimize glycerol decomposition. Glycerol leaves the evaporators for condensors, and then is deodorized with steam and bleached with granular activated charcoal. Consumption of charcoal is minimized due to the already relatively purified state of the glycerol feedstock. The product then passes through polishing filters and a cooler to produce ultra pure glycerin. The evaporation, distillation and refining equipment are known, as such, and is available with the inclusion of design improvements over conventional glycerin apparatus from G. Mazzoni SpA of Italy. The following example illustrates how glycerol, betaine, succinic acid, L-pyroglutamic acid, potassium sulfate and a solid fertilizer may be produced from beet molasses stillage without the specific preparation of a stillage having enhanced levels of glycerol and succinic acid. Example As shown in the drawing, stillage from a plant producing ethanol from sugar beet molasses, was processed into ultra-pure glycerin and betaine-HCl in a continuous process. Enhanced formation of glycerol was not pursued during the fermentation. The hot stillage was clarified in a cross-flow microfiltration unit with 0.2 µm alpha aluminium oxide membranes. The permeate obtained was treated enzymatically at 50°C to hydrolyze proteinaceous matter and consequently evaporated to a solids concentration of over 66 wt. %. Through cooling and crystallization in a malaxeur, potassium sulfate crystals were formed which through centrifugation, washing and drying were recovered as a technical-grade K 2 SO 4 , which is more valuable then leaving it in the remaining stillage (fertilizer). The centrate was then fed to the first chromatographic separation system in which a mixture of betaine plus glycerol is separated from the rest. This ion exclusion system used a strong acid cation exchange resin in the potassium form with a mean particle size of approximately 375 µm and a moisture retention capacity of approximately 52.5% (H+ form; IWT SM-51). The product stream contained 36.3% total solids with approximately 92% purity in terms of glycerine plus betaine. Water was used as the desorbent. This product stream was next concentrated to 75% total solids and fed to a second, considerably smaller chromatographic system, which contained a polystyrene strong base anion exchange gel resin in the sulfate-form. Its mean particle size is approximately 350 µm and its water holding capacity between 41-46%. Both resins used meet all requirements for use in food applications (FDA Regulation Title 21, Subpart A, Section 173.25). Water was again the desorbent. This second chromatographic separation step did yield a glycerine stream with a purity of 97.6% (after mixed-bed ion exchange) and a betaine stream with a purity of 88.2%. The glycerine stream was easily further processes into ultra-pure glycerine with G. Mazzoni SpA equipment. The betaine stream was further processed into pure betaine and betaine HCl. Overall recovery was 88.5% for glycerine and 93.2% for betaine. The remaining stillage was combined with the by-product stream from the first chromatographic separation step, the retentate from the microfiltration step as well as the by-product streams from glycerine purification and then concentrated and dried into a solid fertilizer premix or feed additive. In the second chromatographic separation step, another resin used also resulted in the production of pure glycerine and betaine streams. This resin is a strong acid cation exchange resin in the calcium-form with a mean particle size of 350 µm and a moisture retention capacity (H+ form) of 57.5-61.0%. Succinic acid and L-pyroglutamic acid were not recovered. The concentration of key components in weight percent at intermediate stages was as follows: Total Solids Suspended Solids Glycerol Betaine Stillage 7.5 1.0 0.7 1.5 Microfiltration Permeate 6.5 0.7 1.5 Evaporator Concentrate 60.0 6.3 13.5 After First Chromatographic Separation 36.3 10.6 22.7 Evaporator Concentrate 75.0 22.0 47.0 Glycerol Stream After Second Chromatographic Separation 38.2 37.3 Betaine Stream After Second Chromatographic Separation 23.7 0.5 20.9

Claims: A continuous process for recovering glycerol and betaine from stillage produced from the fermentation and distallation of sugar beets, which results in ethanol and said stillage, said continuous process comprising the steps of: (a) clarifying said stillage by subjecting it to a cross-flow microfiltration process utilising inorganic membranes having pore sizes in the range of 0.1-10 µm; (b) subjecting the clarified stillage to a first chromatographic separation by passing the clarified stillage through an ion-exclusion apparatus for separating glycerol and betaine as a mixture from other constituents of the clarified stillage; (c) subjecting the glycerol/betaine mixture to a second chromatographic separation by passing the mixture through a second ion exclusion apparatus in which the glycerol is separated from the betaine; and (d) purifying the separated glycerol and betaine. A process according to claim 1, wherein said fermentation, distillation clarification, chromatographic separation, and purification are all a part of a continuous process. A process according to claim 1 or claim 2, wherein the step of clarifying further comprises initially centrifugally separating solids from liquid constituents prior to subjecting the stillage to microfiltration. A process according to any preceding claim, wherein the cross-flow microfiltration process is accomplished in a unit having 0.2 µm alpha aluminium oxide membranes. A process according to any preceding claim, wherein the clarified stillage from step (a) is enzymatically treated to hydrolyze proteinaceous material. A process according to any preceding claim, wherein the permeate from the microfiltration step is concentrated to as high a solids concentration as practicable before passing through said ion exclusion material. A process according to claim 6, wherein the permeate is concentrated to 50-75% solids and the resulting potassium sulfate crystals are removed therefrom. A process according to any preceding claim wherein the first chromatographic separation step is carried out using a strong acid cation exchange resin in the potassium form with a mean particle size of approximately 375 micron and a moisture retention capacity of approximately 52,5%. A process according to any preceding claim, wherein the glycerol/betaine stream from the first chromatographic separation step is concentrated to approximately 75 wt. percent before passing onto the second chromatographic separation step. A process according to any preceeding claim wherein the second chromatographic separation step is carried out using a polystyrene strong base anion exchange gel resin in sulfate form with a mean particle size of approximately 350 microns and a moisture retention capacity in the range of 41-46%. A process according to any one of claims 1 to 10, wherein said second chromatographic separation step comprises feeding said clarified stillage to a chromatographic separation system containing a strong acid cation exchange resin in the calcium form with a mean particle size of approximately 350 microns and a moisture retention capacity in the range of 57.5-61.0%. A process according to any preceding claim, wherein the glycerol stream is purified by ion exchange, evaporation to a concentration of 80-85% glycerol, further distillation into almost pure glycerol, and refining into ultra-pure glycerol. A process according to to any preceding claim, wherein the glycerol stream and the betaine stream which issue from the second chromatographic separation step are each subjected to ion exchange, further concentration, and purification by distillation and refining into glycerol and crystallisation into betaine-HCl or betaine.

Inventors: KAMPEN WILLEM HEMMO, KAMPEN, WILLEM HEMMO
Applicants: KAMPEN WILLEM HEMMO, KAMPEN, WILLEM HEMMO
Application year: 1990
Main classification: C12F3
IPC codes: C12P17, C12F3, C07D207, C07C29, C07C229, C07C31, C07C55, C12P7, C07C59