| 5-aminolevulinic acid (ALA) is the precursor of tetrapyrroles and porphyrins. It exists in all organisms and has wide utilities both in agriculture and in medicine. The main metabolic pathway used in the production of ALA is C4 pathway with glycine and succinate as precursors. However, ALA could not be produced conveniently and applied widely because of its low stability. So this dissertation will pay attention to the stability of ALA.ALA belongs to the class of a-amino ketones. It dimerizes spontaneously to 2,5-dicarboxyethyl-3,6-dihydropyrazine at alkaline condition in vitro. The formed dihydropyrazine can be further oxidized irreversibly to 2,5-dicarboxyethyl pyrazine in the presence of oxygen. In this course, ALA solution has its pH, max absorption bands changed, corresponding to the alteration of ALA structure.Based on the mechanism, the thesis investigated the reaction balance of ALA in aqueous solution first. High concentration, temperature and pH all accelerated ALA degradation. Illumination didn't affect ALA stability distinctly. Dissolved oxygen made ALA degrade following the irrevesible second-order reaction. But it's found 1.5g/L ALA standard solution stored at 4℃ was very stable.A reversed phase high performance liquid chromatography with precolumn derivatization was developed for the determination of ALA in E. coli fermentation broth. Compared with water solution, ALA in fermentation broth degraded more quickly because dissolved oxygen and complicated components presenting in culture medium. Besides physiological factors, components in culture medium also influenced ALA stability.
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