1. Technical Field of the Invention
The present invention relates to a method of producing [S,S]-ethylenediamine-N,N'-disuccinate (hereinafter abbreviated as [S,S]-EDDS). More specifically, the present invention relates to a method of producing [S,S]-EDDS from maleic acid, maleic anhydride or maleic acid salt and ethylenediamine by action of microorganisms or enzymes.
2. Disclosure of the Related Art
[S,S]-EDDS has the high ability to capture heavy metals and is bio-degradable when released into the nature. Hence [S,S]-EDDS is expected to be used as a bleaching agent for photography, an electroless plating agent, or a builder for detergent.
The present inventors have already proposed methods of producing [S,S]-EDDS by microorganisms: (1) a method of producing [S,S]-EDDS from fumaric acid and ethylenediamine (JP-A-9-140390, U.S. Pat. No. 5,707,836, and European Patent No. 0731171), (2) a method of producing the same from maleic acid and ethylenediamine (JP-A-9-289895) and the method of (1) under the presence of metal ion (European Patent No. 0805211, JP-A-10-52292).
In terms of raw materials, the method of (2) has the advantage of providing a more economical method of manufacturing [S,S]-EDDS, since fumaric acid is industrially produced from maleic acid through an isomerization process by chemical methods (U.S. Pat. Nos. 2,816,923, 2,955,136, and 2,332,992).
The method disclosed in JP-A-9-289895, wherein maleic acid and ethylenediamine are used as substrates, is not a sufficient method because of its low yields.
Accordingly, an object of the present invention is to obtain [S,S]-EDDS in high yield using maleic acid as a raw material.
The present inventors have intensively investigated an application of malate isomerase (JP2664648, JP-A-8-51989, and European Patent No. 693557) to the production of [S,S]-EDDS. There are many biochemical studies about malate isomerase (W. Scher et al., J. Biol. chem., 244, 1878-1882 (1969), Y. Takamura et al., Agr. Biol. Chem., 33, 718-728 (1969), T. Kimura et al., Agr. Biol. Chem., 50, 89-94 (1986), and T. Nakajima-Kambe et al., J. Ferment. Bioeng., 84, 165-168 (1997)). Moreover, the malate isomerase has been proposed for the production of aspartic acid.
The present inventors have now found that the addition of both a microorganism having malate isomerase activity and a microorganism having ethylenediamine-N,N'-disuccinate ethylenediamine lyase (hereinafter referred to as EDDSase) activity to a solution containing maleic acid and ethylenediamine in the presence of a metal ion e.g., alkaline earth metal can largely increase the conversion rate of maleic acid to [S,S]-EDDS, although the addition of only these microorganisms to the solution results in a low conversion rate to [S,S]-EDDS.