Degradation Characteristics And Metabolite Identification Of Phenazine-1-Carboxylic Acid (PCA) Degraded By The Strain Sphingomonas Sp.DP58

Shenqinmycin, whose key component is pheazine-1-carboxylic acid (PCA), has a good effect on prevention pimiento epidemic and watermelon wilt diseases, which is broad-spectrum, high efficiency, low toxicity, good environmental compatibility and low cost. During the previous experimentation, it was found that PCA would be degraded easily in field and its protection efficiency was reduced. Therefore, it is important to investigate the biodegrading pathway to improve the prevention efficiency of Shenqinmycin. In our laboratory, a bacterial strain effectively capable of degrading PCA had been isolated and the strain had been named Sphingomonas sp.DP58 after bacterial identification.In this paper, the degradation characteristics of PCA by the strain Sphingomonas sp.DP58 were studied. Firstly, PCA was added into the mineral salt medium as the sole source of carbon, nitrogen and energy. By changing PCA concentration and inoculation quantity, it was found that there was linear relationship between the decreasing concentration of PCA and the increasing number of the cells, and the lagging period was prolonged when increasing the initial concentration of PCA or reducing the inoculation quantum. Besides, the upper limit of the concentration of PCA was between 2000mg/L and 3000mg/L. Then, it was indicated that the degradation of PCA by Sphingomonas sp.DP58 could be inhibited by glucose in the study of the characteristic of different substrate. Furthermore, by using orthogonal experiment, it was found that pH was the first key factor affecting the degradation among the three factors including temperature, pH and shaker's rotation speed. Finally, the degradation of phenazine which was similar to PCA was studied for researching the relationship between the molecular structure of PCA and PCA degradation. The results showed that it was much more difficult for Sphingomonas sp.DP58 to degrade phenazine than PCA.The metabolites of PCA degraded by Sphingomonas sp.DP58 were also studied in this paper. Two main metabolites were isolated by using preparative high-performance liquid chromatography (HPLC). In addition, they were subsequently characterized by liquid chromatography-mass spectrometry(LC-MS), gas chromatography (GC)-mass spectrum (MS) after N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) derivatization , 1H-nuclear magnetic resonance (NMR). They were identified as 4-hydroxy-1-(2-carboxyphenyl) azacyclobut-2-ene-2-carbonitrile (HPAEC) and 4-hydroxy-1-(2-carboxyphenyl)-2-azetidinecarbonitrile (HPAC). The two metabolites had transformational relationship between each other. According to the metaboltes, one pathway for PCA degradation was proposed.