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Steroid estrogen is one class of endocrine disrupting compounds of particular concerns due to the compelling evidence that correlates the feminization of male fish to the exposure to treated wastewater containing estrogenic compounds. The major estrogenic compounds identified in the treated wastewater include natural estrogen (17β-estradiol, estrone, an estriol) and synthetic estrogen (17α-ethynylestradiol, which is a synthetic oral/patch conceptive and 17α-estradiol, which is a hormone replacement drug). Those hormones are not readily biodegradable and reported removal in wastewater treatment plants is varied for each compound ranged from 40% to 95%. Recently, only estrogen-degradation culture, a NOVOSPHINGOBIUM TARDAUGENS ARI-1 (ARI-1), has been recently isolated from activated sludge in Japan. ARI-1 is known to degrade 17β-estradiol, estrone and estriol, but not 17α-ethynylestradiol. ARI-1 is currently listed a new strain; however, many other characteristics has not been fully studied.

In this study, we examine the growth of ARI-1 in the presence and absence of acetone and degradation kinetics of three selected hormones, 17α-estradiol, 17β-estradiol and estrone. Our preliminary data showed that ARI-1 was capable of growing on estrogens in the presence and absence of acetone. Although ARI-1 does not degrade 17α-ethynylestradiol, the strain can degrade 17α-estradiol, a commonly used synthetic estrogen. The yields (Y) for 17α-estradiol, 17β-estradiol and estrone were 0.03, 0.08, and 0.03, respectively. The doubling times ranged from 0.3 to 0.5 d. The half-velocity constants (Km) were 5.1 mg/L for 17β-estradiol and 4.8 mg/L for estrone. The maximum substrate utilization rates (k) were 7.4 d−1 for 17β-estradiol and 10.1 d−1 for estrone. Results of this study are very valuable for enhanced estrogen removal during wastewater treatment processes by selecting this culture through optimized operating conditions, or designing a stand-alone bioreactor specific for estrogen degradation.

Document Type: Research Article


Publication date: January 1, 2003

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