| Summary: | 碩士 === 東吳大學 === 微生物學系 === 94 === In this study, we investigated the biodegradation of di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in three soils (Pingtung, Taoyung and Kaohsiung soils). The orders of PAEs degradation rates were Pingtung soil > Taoyung soil > Kaohsiung soil. The results showed that Pingtung soil was the higher degradation rate than other two soils. The adsorption constant of soil were Kaohsiung soil > Taoyung soil > Pingtung soil. The higher adsorption capacity for PAEs, the lower degradation rates in soil.Degradation rate of DBP was higher than DEHP in three soil samples. The optimal condition was pH 7 and 30℃. At concentration of 5, 10, 50 μg/g had no significant difference on PAEs degradation. At concentration of 50 ppm for DEHP could not inhibit activity of microbes in soil. We also noted that the degradation of DEHP was enhanced when the two compounds were present simultaneously or individually. However, there is no significant diffference by addition of DBP individually.
We compared degradation of PAEs by amended compost such as Taisu, Chunghsing and Wannung compost, respectively. The results showed that the degradation rates were Chunghsing compost > Wannung compost > Taisu compost. We also found that there are the same orders for degradation rates when composts were amended to soil. We separated the compost particles with different sizes and studied the biodegradation rate of PAEs by addition these particles to soil. We found that the particles size of 0.1-0.45 μm was the higher degradation rate. When addition of these particles to soil, compost particles size of 50-105 μm showed the higher degradation rate for DBP, compost particles size of 0.1-0.45 μm for DEHP. The bioreactor experiment also showed that DEHP degradation rates with compost higher than without compost. However, the ability of degradation rates were decreased when addition of DEHP two or three times. We used respiratory meter to detect the accumulation of oxygen uptake when microbes utilized DBP as the carbon source by various treatments. The results showed that the orders of accumulation of oxygen uptake were compost > soil & compost > soil. Various concentration of DBP was 50 ppm > 10 ppm > 5 ppm. The two compounds were present simultaneously or individually were DBP & DEHP > DBP > DEHP.
We also isolated several pure microbial strains from soil and compost samples. Four bacterial strains were capacity of aerobically degrading DBP and DEHP using them as a carbon source. The strain L2 showed the greatest degradation potential. The degradation rate and half-life were 4.42 1/day and 0.1 days for DBP, 0.26 1/day and 2.6 days for DEHP, respectively. Identification of strain L2 was closely related to Rhodococcus rubber with a similarity of 98%. There was no significance difference on PAEs degradation by addition of strain L2 to soil. Addition of EDTA inhibited the biodegradation rate. However, addition yeast extract, brij 30, tween-80 enhanced the degradation rate.
In conclusion, the optimal condition of biodegradation rates of DBP and DEHP could be applied on removing PAEs in soil, and the isolated strains could be used for more related research.
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