異菌体間共役反応法による5'-グアニル酸生産プロセスの開発

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An enzymatic process for the production of 5'-guanylic acid(GMP), a flavoring nucleotide, was developed. Since it is difficult to produce GMP by direct fermentation, we examined a method of fermentatively producing 5'-xyanthilic acid(XMP), a precursor of GMP, first, and then enzymatically aminating XMP to produce GMP. The amination reaction is catalyzed by GMP synthetase(or XMP aminase)and requires ATP. As ATP is very expensive, we developed a means of producing GMP from XMP without the need to add ATP by regenerating and repeatedly using a catalytic amount of ATP. In the reaction to regenerate ATP, a "resting cell" -that is a bacterial cell in which the permeation barrier against nucleotides is removed by treating the cell with a surfactant -was used as an enzyme source. First, we developed a self-coupling reaction in which the ATP-regenerating and GMP synthetase activities possessed by resting cells of Corynebacterium ammoniagenes were utilized. This enabled the XMP fermentation liquor and the culture liquor of the converting strain to be utilized as sources of XMP and GMP synthetase, respectively. Next, we developed a process to make use of the ATP-regenerating activity possessed by the cells after XMP fermentation. In this process, we employed E.coli whose GMP synthetase activity was enhanced 370-fold compared with that of the host by self-cloning as a source of GMP synthetase. Establishment of this coupling reaction between different cells, in which ATP(and AMP)is exchanged between resting cells of an XMP-producing strain and a small amount of Escherichia coli resting cells, made it possible to increase the ratio of the XMP fermentation liquor and to greatly improve the GMP productivity. Also, since GMP could be produced from glucose using a single fermentor, a process seemingly very close to direct fermentation was established. Application of the process to the production of 5'-inosinic acid(IMP)and CDP-choline is also briefly discussed.
社団法人日本生物工学会の論文
1999-03-25

異菌体間共役反応法による5'-グアニル酸生産プロセスの開発

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