Biodegradation of phthalic acid esters by a newly isolated Mycobacterium sp. YC-RL4 and the bioprocess with environmental samples
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Bacterial strain YC-RL4, capable of utilizing phthalic acid esters (PAEs) as the sole carbon source for growth, was isolated from petroleum-contaminated soil. Strain YC-RL4 was identified as Mycobacterium sp. by 16S rRNA gene analysis and Biolog tests. Mycobacterium sp. YC-RL4 could rapidly degrade dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), dicyclohexyl phthalate (DCHP), and di-(2-ethylhexyl) phthalate (DEHP) under both individual and mixed conditions, and all the degradation rates were above 85.0 % within 5 days. The effects of environmental factors which might affect the degrading process were optimized as 30 °C and pH 8.0. The DEHP metabolites were detected by HPLC-MS and the degradation pathway was deduced tentatively. DEHP was transformed into phthalic acid (PA) via mono (2-ethylhexyl) phthalate (MEHP) and PA was further utilized for growth via benzoic acid (BA) degradation pathway. Cell surface hydrophobicity (CSH) assays illuminated that the strain YC-RL4 was of higher hydrophobicity while grown on DEHP and CSH increased with the higher DEHP concentration. The degradation rates of DEHP by strain YC-RL4 in different environmental samples was around 62.0 to 83.3 % and strain YC-RL4 survived well in the soil sample. These results suggested that the strain YC-RL4 could be used as a potential and efficient PAE degrader for the bioremediation of contaminated sites.
KeywordsPhthalic acid esters Mycobacterium sp. Metabolic mechanism Cell surface hydrophobicity Bioremediation
We thank Nahurira Ruth (Graduate School of Chinese Academy of Agricultural Sciences) for the revision of the manuscript, Jing Zhou (Agricultural Resources and Regional Planning Institute of CAAS, China) for providing the soil, Lida Han (Biotechnology Research Institute of CAAS, China) for great help and good suggestions for HPLC and MS analyses, and we also thank Gérald Thouand for his kind suggestions on the manuscript (Université de Nantes, France). We also acknowledge the intellectual and material contributions of Organization of Women in Science in the Developing World (OWSD) andSwedish International Development Cooperation Agency (SIDA). This work was supported by the National Natural Science Foundation of China (NSFC, 31170119 and 31540067) and the Basic Research Fund of CAAS (0042014006, 0042012003, and 0042011006).
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