| Environmental hormones, also called environmental endocrine disruption chemicals, were discharged into the environment because of humanbeing's daily life and production . Environmental hormones mainly disrupt endocrine systems and effect on the functions of hormones of human and animals, resulting in disorder of reproductive, developmental and nerve systems.Phthalic acid esters (PAEs) were one of most important environmental hormones. Phthalic acid esters were most widely used as plastifier in plastic industry. di-(2-ethylhexyl) phthalate (DEHP) constituted about 60% of the total phthalate ester production. DEHP were often detected at relatively high levels in soil, sediments, and waters.Biodegradation is a critical process affecting the environmental fate of DEHP. This paper focused on the isolation of high efficiency DEHP-degrading microorganisms and study on their DEHP-degrading characteristics to provide the theoretic and technical basis for biotreating DEHP-containing wastewater and soil.The research results were showed following:1,Two efficient DEHP-degrading bacteria EA,GG were isolated from crude oil-contaminated soils. They were respectively identified as Rhodococcus sp.,Gordonia sp., according to their morphological, physiological biochemical characteristics and n sequences analysis of 16S rDNA.2,Both isolates were all gram-positive, had spherical and bacilliform growth cycle. EA could form orange colony on LB agar medium after 2～3 days of incubation, whereas GG could form gray-colored colony. The optimum temperature and pH value for EA growth were 35℃and 7.0 respectively. The optimum temperature and pH value for GG growth were 30℃and 7.0 respectively. GG and EA could sustain up to 1% and 3% NaCl respectively. Both strains grew well when using glucose or fructose as sole carbon sources, and peptone, beef cream or yeast extract as sole nitrogen sources.3,Studies indicate that both isolates could use DEHP as the sole carbon. 100mg/LDEHP could be completely degraded by two strains within 2～3 days incubation. Both isolates degraded DEHP better at neutral or a little alkaline condition. The optimum temperature for DEHP biodegradability were 35℃和30℃respectively. Adding yeast extract and glucose in media could accelerate the biodegradation of DEHP at beginning of incubation, but not influence the final biodegradability of the isolates. The 5% inoculums reached best degradation of DEHP. Both isolates degraded DEHP better when DEHP concentration below 500 mg/L. Besides DEHP, both isolates could degrade DMP, DEP, DBP and DOP.4,Accordance to the homology of PhtA among different species, 2495bp DNA sequence was cloned by rapid chromosome walking. The result show that the2495bp DNA contained complete sequence of PhtB, partial PhtAa and other unknown sequence. This will lay the foundation for further study. |
