Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-09-02
2001-01-30
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S332000, C528S342000, C528S363000, C525S420000, C525S451000, C252S175000, C252S363500
Reexamination Certificate
active
06180752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the production of polyaspartic acid homo- and copolymers by biotechnological processes and to the use of the resulting products (for influencing the crystallization or agglomeration behavior of sparingly soluble salts or solids in aqueous systems).
2. Description of the Related Art
Crystallization and agglomeration processes are, as biological mineralization, among the fundamental processes of animate nature. Thus, they are involved, for example, in the structure of skeletons or shells in living organisms. In nature, these mineralization processes are controlled by naturally occurring proteins and polysaccharides. (S. Weiner, Biochem. 22, (1983), 4139-45; C. S. Sikes, A. P. Wheeler, in Chemical Aspects of Regulation of Mineralisation., Eds. C. S. Sikes , A. P. Wheeler University of South Alabama Publ. Services (1988), 15-20).
Unfortunately, both in nature and in the industrial sector, unwanted mineralization processes also occur and result in tenacious, troublesome deposits and encrustations such as, for example, dental plaque, organ concretions or, in the industrial sector, encrustations on heat exchanger surfaces or cooling towers particle agglomerations in pigment dispersions, encrustations on hard (for example glass metal) and soft (textile) surfaces. In the past, various proposals have been made for exploiting this natural action principle for industrial problems. Thus, the U.S. Pat. Nos. 4,534,881, 4,585,560, 4,587,021 describe the inhibition of calcium carbonate deposits by protein fractions, polysaccharide fractions or polyamino acid fractions from calcium carbonate-forming organisms such as crustaceans etc.
In addition, the inhibition of mineral deposits by polyanionic hydrophobic polypeptides with a block copolymer structure and related phosphorylated polypeptides is claimed in the literature (U.S. Pat. No. 4,868,287). The polypeptides used are prepared by methods of peptide chemistry. WO 92/17194 states that an improved synthesis of these polypeptides is provided.
Since the proteins described above acquire their polyanionic characteristics through a high aspartic acid content, aspartic acid homo- and copolymers are also claimed for this purpose. These polyaspartic acids are, however, all obtained by chemical synthesis. Thus, for example, a polyaspartic acid sodium salt can be prepared by thermal polycondensation of aspartic acid to polysuccinimide and subsequent basic hydrolysis. (Kovacs et al. J. Org. Chem, 26 (1961)1084-1091). Further applications claim the preparation and use of polyaspartic acids by thermal polycondensation of aspartic acid in the presence of acidic catalysts such as phosphoric acid. In addition, polyaspartic acids are also prepared by thermal polymerization starting from aspartic acid precursors such as maleic acid ammonium salt (EP 0 256 366), maleic amide (EP 0604 813) and maleic anhydride, and ammonia-releasing compounds.
BRIEF SUMMARY OF THE INVENTION
The present invention now describes biological methods for producing aspartic acid homo- and copolymers and the use of the resulting polymers for inhibiting mineral deposits and dispersing solid particles.
To date, three different polyamino acids have been found in nature, poly-&ggr;-glutamate, poly-&Sgr;-lysine and poly-&agr;-arginylaspartate (cyanophycin).
Poly-&ggr;-glutamate is produced by various Gram-positive bacteria such as, for example,
Bacillus licheniformis, Bacillus subtilis
natto or
Bacillus anthracis.
poly-&Sgr;-Lysine is produced by
Streptomyces albulus.
Poly-&agr;-arginylaspartate is produced by many cyanobacteria such as, for example,
Spirulina platensis,
Aphanocapsa PCC 6308 or
Anabena cylindrica.
Synthesis takes place by the non-ribosomal pathway, resulting in a polypeptide which has a polydisperse molecular weight distribution and is stored in the form of cyanophycin granules inside cells.
To date, only the biotechnological production of poly-&ggr;-glutamate using
Bacillus subtilis
or
Bacillus licheniformis
is disclosed in the patent literature. (JP 1-174397 (1989), JP 43-24472 (1969) and U.S. Pat. No. 2,895,882).
DETAILED DESCRIPTION OF THE INVENTION
We have now found that aspartic acid homo- and copolymers can be produced using various cyanobacteria via the intermediate cyanophycin. The resulting polymers have the following structures.
R
1
: ≡OH or arginyl
n: 5-400
If the total of all the R
1
radicals corresponds to 100%, then the proportion of R
1
═OH is between 5% and 100%, preferably 30%-100% and particularly preferably 70% to 100%. The molecular weight of the polymers is generally between 1000 and 100,000, preferably between 2000 and 50,000, particularly preferably between 2000 and 30,000.
The total n of all repeating units depends on the cleavage conditions to which the intermediate cyanophycin is subjected. Arginine elimination can take place both with acid and with base. If an acidic hydrolysis is carried out, stoichiometric amounts of acid in relation to the incorporated arginine are necessary because the acid is trapped as arginine salt. It is possible to employ as acid all mineral acids such as, for example, hydrochloric acid, sulfuric acids, phosphoric acids and lower fatty acids of C
1
-C
5
. The hydrolytic cleavage can moreover take place under pressure using carbonic acid or CO
2
. Depending on the concentration of the acid employed and on the reaction conditions, depolymerization by hydrolytic cleavage of the polyaspartate chain may also take place, in addition to the arginine elimination. However, the unwanted depolymerization can be minimized by suitable choice of the reaction conditions, such as dilute acid, moderate reaction times, temperatures not exceeding 100° C.
However, the hydrolysis can also advantageously be carried out under basic conditions, because the polyaspartate chain is more stable under these conditions. The reaction is carried out at a pH≧8.5, preferably 9-12, and at temperatures between 20° C. and 150° C., preferably 50° C.-120° C. After the hydrolysis, the reaction product is removed by filtration from the unreacted cyanophycin and the alkali-insoluble arginine. Suitable as base for the alkaline hydrolysis are all metal hydroxides or carbonates which make pH values>8.5 possible in aqueous medium. Alkali metal and alkaline earth metal hydroxides are preferred.
The cyanophycin employed for the hydrolytic formation of the aspartic acid homo- and copolymers is obtained by fermentation of cyanobacteria such as, for example, Aphanocapsa PCC 6308,
Anabena cylindrica
or
Spirulina platensis.
A possible biosynthetic pathway is described in the experimental part.
The aspartic acid homo- and copolymers obtained as products were characterized by elemental analysis, amino acid analysis and NMR spectroscopy. The molecular weight was determined with the aid of aqueous GPC. In addition, for industrial applications, the products were tested for their ability to inhibit mineral deposits such as calcium carbonate, calcium sulfate, calcium phosphate, calcium oxalate and barium sulfate, and for their dispersing capacity for solid particles. The calcium carbonate inhibiting capacity was carried out inter alia by a method of C. S. Sikes, A. P. Wheeler in Chemical Aspects of Regulation of Mineralisation, pp. 53-57, University of South Alabama Publication Series (1988). The products are completely biodegradable owing to their natural polypeptide structure based on &agr;-linked L-aspartic acid.
They can be employed, for example, as cobuilders in detergents and cleaners, for inhibiting and dispersing deposits in cooling and heating circulations for diminishing and dispersing deposits, and for reducing corrosion and inhibiting gas hydrates in petroleum and natural gas production.
REFERENCES:
patent: 2895882 (1959-07-01), Thorne et al.
patent: 4534881 (1985-08-01), Sikes et al.
patent: 4585560 (1986-04-01), Sikes et al.
patent: 4587021 (1986-05-01), Wheeler et al.
patent: 4839461 (1989-06-01), Boehmke
patent: 4868287 (1989-09-01), Sikes et al.
pa
Groth Torsten
Hai Tran
Joentgen Winfried
Oppermann Fred Bernd
Steinb{umlaut over (u)}chel Alexander
Bayer AG
Connolly Bove & Lodge & Hutz LLP
Hampton-Hightower P.
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