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| Isolation, identification, and degradation characteristics of a DMP-degrading strain |
| Received:January 16, 2018 |
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| KeyWord:dimethyl phthalate;16S rDNA;degradation kinetics;degradation gene;intermediate metabolites |
| Author Name | Affiliation | E-mail | | XU Wei-hui | College of Life Science and Agroforestry, Qiqihar University, Qiqihar 161006, China | | | LIU Shuai | College of Life Science and Agroforestry, Qiqihar University, Qiqihar 161006, China | | | WANG Zhi-gang | College of Life Science and Agroforestry, Qiqihar University, Qiqihar 161006, China
Key Laboratory of Urban Agriculture in South China, Ministry of Agriculture, Guangzhou 510640, China | wzg1980830@sina.com |
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| Abstract: |
| To isolate a dimethyl phthalate(DMP) -degrading strain, the soil that had been exposed to long-term plastic pollution was collected and used. The DMP-degrading strain was screened out using selective media method, and identified by morphological, physiological, and biochemical analyses, as well as 16S rDNA sequence analysis. Moreover, the degradation characteristics were studied. The results showed that the DMP-degraded strain was classified as Paracoccus sp., named as QD15-1 and belongs to Gram-negative bacterium. The substrate utilization tests showed that the QD15-1 strain could utilize phthalic acid esters(PAEs)pollutants, such as DMP, dibutyl phthalate(DBP), diethyl phthalate(DEP)and diethylhexyl phthalate(DEHP). When DMP was the only carbon source, the optimized conditions of the QD15-1 strain were as follows:pH, 8; temperature, 30℃. The degradation kinetics of QD15-1 were studied in varied initial DMP concentrations under optimal conditions; the results indicated that degradation of DMP conforms to the pseudo-first order kinetic equation, and the half life of DMP was shortened as the initial concentration was increasing up. Importantly, PCR analysis showed the QD15-1 strain to contain PAE-degrading genes, such as the phthalate dioxygenase gene(PAphtAb), and 3, 4-dihydroxy-3, 4-dihydrophthalate dehydrogenase (PAphtB). Liquid mass spectrometry showed that the intermediate metabolites in the minimal medium included o-benzene dicarboxylic acid monoester and phthalic acid. The DMP degradation pathway in the gram-negative strain Paracoccus sp. QD15-1 was speculated to operate as follows:DMP was degraded into o-benzene dicarboxylic acid monoester, decomposed into phthalic acid, and was then further degraded by the above-mentioned genes. These results indicate that QD15-1 is a high-efficiency DMP-degrading strain, and it is expected that the strain QD15-1 could be used to clear DMP pollution in future. |
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