Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing alpha or beta amino acid or substituted amino acid...
Reexamination Certificate
1999-11-22
2002-02-05
Lankford, Jr., Leon B. (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing alpha or beta amino acid or substituted amino acid...
C562S552000, C562S571000, C435S142000
Reexamination Certificate
active
06344348
ABSTRACT:
The present invention relates to a process for the production of aspartic acid poly-condensates (herein also referred to as aspartic acid condensates). More particularly, the present invention relates to a process for the production of aspartic acid condensate from a carbohydrate via a fermentation route.
Aspartic acid is an acidic amino acid with a molecular formula of HOOCCH
2
CH(NH
3
)COO. It is used in products such as the aspartame sweetener and for formation of the biodegradable polymer polyaspartic acid (PAA). The latter could be utilized as a cobuilder or as a sequestrant in detergents, as a superabsorbent polymer and in other applications. The biodegradability of PAA is very attractive, and the potential market is large. It strongly depends, however, on the availability of a low cost aspartic acid and a non-contaminating process for the preparation of aspartic acid.
Heating of aspartic acid or compositions containing fumaric acid and/or maleic acid (or anhydride), and ammonia to temperatures of about 200° C. and higher, results in its polycondensation to polysuccinimide. The latter can be hydrolyzed to form polyaspartic acid or salts thereof. These products could be used in low phosphate environmentally-friendly detergent compositions. Presently these detergents contain polycarboxylic acids such as polyacrylic acid. These polycarboxylic acids have an important drawback, they are not biodegradable. Polyaspartic acid manufactured from aspartic acid is fully biodegradable (while that formed from fumaric acid, maleic acid or maleic anhydride is not). Yet, in order to replace the well established polycarboxylic acids, the polyaspartic acid should be compatible on price basis. This seems nearly impossible in the cost structure based on present technology.
In WO 93/23452 there is described and claimed a process for the preparation of a salt of polyaspartic acid comprising reacting maleic acid and ammonia, wherein the ammonia is present in molar excess at 200° C.-300° C., and converting the resultant polymer into a salt by adding a hydroxide.
In the publication, the following state of the prior art is noted:
U.S. Pat. No. 4,839,461 discloses a method for making polyaspartic acid from maleic acid and ammonia by reacting these constituents in a 1:1-1.5 molar ratio by raising the temperature to 120° C.-150° C. over a period of 4-6 hours and maintaining it for 0-2 hours.
U.S. Pat. No. 5,057,597 discloses a method for the polycondensation of aspartic acid to product polyaspartic acid by heating the aspartic acid in a fluidized bed reactor to 221° C. for a period of 3-6 hours in a nitrogen atmosphere followed by conventional alkaline hydrolysis.
Kovacs et al. (J. Org. Chem., 26 1084 [1961]) prepared polyaspartic acid by heating aspartic acid to 200° C. in a vacuo for a period of 120 hours, or in boiling tetralin over a period of 100 hours. Kovacs et al., showed that the intermediate formed in the thermal polymerization of aspartic acid was polysuccinimide.
In WO 95/00479 polyaspartic acid having a weight average molecular weight of 1000 to 5000 is produced by hydrolysis of anhydropolyaspartic acid that has been produced by condensation polymerization of L-aspartic acid, wherein conversion in excess of 80 percent is achievable utilizing “temperature vs. time” profiles.
In said publication, the following state of the prior art is noted:
Thermal condensation of aspartic acid to produce polyaspartic acid is taught by Etsuo Kokufuta, et al., “Temperature Effect on the Molecular Weight and the Optical Purity of Anhydropolyaspartic Acid Prepared by Thermal Polycondensation”, Bulletin of the Chemical Society of Japan 51(5):1555-1556 (1978). Kokufuta et al. teach that the molecular weight of the polyaspartic acid produced by this method increases with increased reaction temperature. Moreover, the suggested maximum percent conversion of the aspartic acid to anhydropolyaspartic acid is no more than 68% using oil bath temperatures of between 163° C. (325° F.) and 218° C. (425° F).
A more recent work by Brenda J. Little et al., “Corrosion Inhibition By Thermal Polyaspartate”
Surface Reactive Peptides and Polymers
. pp 263-279, American Chemistry Society Symposium Series 444 (1990), cites Kokufuta et al. Oil bath temperatures of 190° C. (374° F.) were reportedly used to produce anhydropolyaspartic acid from powdered aspartic acid over a period of 24 to 96 hours. The reported results were no better than those reported by Kokufuta et al., however.
Presently, maleic anhydride is produced in a petrochemical process and isomerized to fumaric acid. Each mole of the latter is reacted with two moles of ammonia to form a solution of diammonium fumarate, which is converted in an enzymatic process (bioconverted) to monoammonium aspartate. The solution of monoammonium aspartate is reacted with a strong mineral acid, typically sulfuric acid. Protons are transferred from the strong acid to the aspartate ion to form aspartic acid. The solubility of aspartic acid in aqueous solutions is low and the acid is separated by crystallization. The ammonium salt of the strong mineral acid is formed as a low or negative value by-product.
Important contributors to the overall production costs are the consumption of the mineral acid and the losses of ammonia to the by-product. German patent 4,429,108 assigned to BASF suggests saving on the cost of mineral acid by heating ammonium aspartate or other derivatives of aspartic acid to form polysuccinimide. Thus, said patent teaches and claims a method for the polycondensation of ammonia derivatives of aspartic acid by heating asparagin, iso-asparagin, ammonium aspartate or aspartic acid diamide, characterized in that the polycondensation is performed at temperatures of at least 150° C. Thus, in the process of said application, the acidulation step is thereby avoided. Yet, the main cost element in the above described process is that of petrochemical fumaric acid. Fumaric acid was produced in the past by fermentation. A calcium base, probably calcium carbonate, was used as a neutralizing agent in the fermentation, which resulted in calcium fumarate. The fumaric acid was recovered from said salt by acidulation with sulfuric acid to form gypsum and fumaric acid. This method suffered from many difficulties. Some of them resulted from the fact that the neutralizing agent, calcium carbonate, the fermentation product, calcium fumarate, the final product, fumaric acid and the by-product, gypsum are all of low water solubility, which interferes in separation between reagents, products and by-product and between those and the biomass. Another problem results from the consumption of lime and sulfuric acid and the formation of gypsum to be disposed of. These and other important drawbacks, such as relatively low yield and low productivity in the fermentation, made the fermentation-produced fumaric acid more expensive than the petrochemical fumaric acid. The fermentation route was dropped in the forties. Based on this comparison one would not expect polyaspartic acid manufacture based on a fermentation-produced fumaric acid, using a carbohydrate as a raw material, to be competitive with polyaspartic acid based on petrochemical fumaric acid.
Furthermore, the fermentation route is fraught with problems relating to major impurities. In the petrochemical route fumaric acid is obtained in a quite pure form which, in turn, results in a relatively pure ammonium aspartate. In the fermentation route fumaric acid represents, according to prior art, only about 80% of the acids formed in the fermentation. Typically, glycerol, malic acid, succinic acid and ketoglutaric acid are also formed in the fermentation. In addition, the liquor formed in the fermentation contains nonutilized carbohydrates, mineral anions and cations resulting from the added nutrients, amino acids, proteins, biomass, etc. Considering the difficulties related to the low solubility of the reagents and the products in this fermentation as described above, one would expect most of these impurities to follow the fumarate into
Cami Pierre
Chattaway Thomas
Eyal Aharon
Jansen Robert J.
Jarry Bruno
Amylum Belgium N.V.
Coe Susan D.
Lankford , Jr. Leon B.
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