Process for preparing L-aspartic acid

Details Process for preparing L-aspartic acid Process for preparing L-aspartic acid

1999-05-20

2001-07-10

Lilling, Herbert J. (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...

C435S232000

Reexamination Certificate

active

06258572

ABSTRACT:

L-Aspartic acid is an essential starting material for a wide variety of additives for the pharmaceutical industry and the food sector. For example, L-aspartic acid is used for preparing artificial sweetener, such as aspartame. Therefore, a multiplicity of chemical and enzymatic processes have already been described for preparing L-aspartic acid. In the enzymatic variants, L-aspartic acid is usually obtained by enzymatic addition of ammonia to fumaric acid with subsequent precipitation from the resultant ammonium L-aspartate solution.
According to the prior art, L-aspartic acid can be precipitated, for example, by adding sulfuric acid or hydrochloric acid or other acids, such as p-toluenesulfonic acid.
However, the disadvantages of this are that the loss of ammonia is high and a large amount of wastewater having a high concentration of ammonium salts of the acids used is discharged.
For this reason, attempts have been made to find possible methods of decreasing or completely avoiding the wastewater problem.
According to U.S. Pat. No. 4,560,653, the L-aspartic acid is precipitated, for example, by adding maleic acid. After separating off L-aspartic acid, the remaining mother liquor is subjected to an isomerization step in which maleic acid is isomerized into fumaric acid, for instance using a catalyst comprising bromine ions, then purified and fed back to the enzymatic reaction. In order to bypass the isomerization step, other suitable additives for precipitating L-aspartic acid have been sought.
In the Japanese Laid-Open Application JP 08-33493 (Chem. Abstracts 1224:315 167), the use of fumaric acid or salt of fumaric acid as precipitant is described. The disadvantage of this process variant is the poor water solubility of fumaric acid, as a result of which, during the workup of the mother liquor, either large amounts of water have to be distilled off or a very dilute procedure having high reaction volumes is necessary.
The object of the invention is therefore to find a process which avoids the previous problems in the precipitation of L-aspartic acid and leads to L-aspartic acid in high yields and high purity.
Unexpectedly, this object was achieved by using nitric acid as precipitant and subsequent nanofiltration of the mother liquor.
The invention therefore relates to an improved process for preparing L-aspartic acid by enzyme-catalyzed reaction of fumaric acid with ammonia, which comprises
a) reacting fumaric acid with ammonia to form ammonium L-aspartate in the presence of aspartase or aspartase-producing microorganisms in an inert diluent,
b) removing any excess ammonia from the reaction mixture and
c) precipitating L-aspartic acid by adding nitric acid, separating it off from the reaction mixture, washing and drying it, then
d) separating off residual L-aspartic acid and residual fumaric acid from the precipitation filtrate by nanofiltration, recycling the retentate to step c) and
e) concentrating the filtrate from step d), adding the resultant distillate in step a) to any ammonia excess separated off in step b) and feeding the concentrated filtrate to a nitrogen fertilizer process.


REFERENCES:
patent: 5952206 (1999-09-01), Giselbrecht et al.
patent: 6150142 (2000-11-01), Mukouyama et al.
patent: 298438 (1972-05-01), None
patent: 0 798 377 (1997-10-01), None
Chemical Abstracts, 238:74403s (1998).

Affiliated with

Also associated with

Rating

Process for preparing L-aspartic acid does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing L-aspartic acid, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing L-aspartic acid will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2484332