17β-Estradiol-Degrading Bacteria Isolated from Activated Sludge

Fourteen phylogenetically diverse 17β-estradiol-degrading bacteria (strains KC1−14) were isolated from activated sludge of a wastewater treatment plant. These isolates widely distributed among eight different generaAminobacter (strains KC6 and KC7), Brevundimonas (strain KC12), Escherichia (strain KC13), Flavobacterium (strain KC1), Microbacterium (strain KC5), Nocardioides (strain KC3), Rhodococcus (strain KC4), and Sphingomonas (strains KC8−KC11 and KC14)of three Phyla: Proteobacteria, Actinobacteria, and Bacteroidetes. All 14 isolates were capable of converting 17β-estradiol to estrone, but only three strains (strains KC6, KC7, and KC8) showed the ability to degrade estrone. Only strain KC8 could use 17β-estradiol as a sole carbon source. Based on the degree of estrogens being transformed and the estrogenicity of metabolites and/or end products of estrogen degradation, three different degradation patterns (patterns A−C) were observed from degradation tests using resting cells. Eleven out of 14 isolates showed degradation pattern A, where 17β-estradiol was stoichiometrically converted to estrone. Estrone was confirmed to be a degradation product of 17β-estradiol; however, estrone was not further degraded during the course of experiments. Strains KC6 and KC7 exhibited degradation pattern B, where both17β-estradiol and estrone were degraded, with slower 17β-estradiol degradation rates than those observed in pattern A. Strain KC8 was the only strain exhibited degradation pattern C, where 17β-estradiol and estrone were rapidly degraded within 3 days. No residual 17β-estradiol and estrone or estrogenic activity was detected after 5 days, suggesting that strain KC8 could degrade 17β-estradiol into nonestrogenic metabolites/end products. Strains KC6−8 exhibited nonspecific monooxygenase activity but not nonspecific dioxygenase activity. However, the relationship between nonspecific monooxygenase activity and its estrogen degradation ability was unclear.