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Degradation and Biosorption of Environmental Endocrine Disruptor Di-(2-ethylhexyl) Phthalate (DEHP) by Gordonia Sp. YK1

Byung Chun Kim, Cheol-Hee Kang, Byoung-In Sang, and Youngsoon Um. Center for Environmental Technology Research, Korea Institute of Science and Technology (KIST), Seoul, South Korea

In this study, isolation of DEHP-degrading microorganism was successfully achieved by establishing highly enriched aerobic cultures capable of degrading DEHP. DEHP in the culture with the isolated microorganism was rapidly degraded with the growth of cells and disappeared in 48 hr (more than 90% degradation). Based on 16S rDNA analysis, the isolated DEHP-degrading microorganism belongs to the Gordonia. Of interest was that the DEHP-degrading microorganism, Gordonia sp. YK1, was attached to DEHP droplets and formed aggregation in the liquid medium during the degradation of DEHP as a sole carbon source. Simultaneous biosorption and degradation of DEHP by Gordonia sp. YK1 was investigated with 50 ppm DEHP by detecting DEHP concentration in supernatant and biomass phases. With 11 mg biomass and 50 ppm DEHP, more than 60% of DEHP was removed by biosorption in 15 min, and adsorbed DEHP was degraded rapidly (73% degradation of DEHP in 30 min). Interestingly, cell attachment to DEHP oil drops was observed even with the autoclaved biomass of Gordonia sp. YK1. The biosorption capacity of the autoclaved Gordonia sp. YK1 cells was 40 mg DEHP/g biomass with the initial concentration of 50 ppm DEHP, and increased to 400 mg DEHP /g biomass with 500 ppm DEHP. Since it is known that there are long aliphatic chains of the mycolic acids in cell wall for the Gordonia genera, strong hydrophobicity of the cell surface of Gordonia sp. YK1 resulting from the presence of mycolic acids is likely to be involved in DEHP biosorption and, consequently, effective DEHP biodegradation by facilitating DEHP uptake. Hydrophobicity of cell surface was also measured with and without DEHP to investigate how biodegradation of DEHP is associated with biosorption ability of DEHP by Gordonia sp. YK1.