Characterization of an Estrogen-degrading Culture, Novosphingobium tardaugens ARI-1

In this study, experiments were conducted to characterize the bacterium Novosphingobium spp ARI-1, which is the only known estradiol-degrading strain. The kinetic parameters, the effects of acetone on cell growth, and the effects of starvation on estrogen degradation have been measured. A quantitative fingerprinting molecular technique, called real-time-t-RFLP, was used to characterize microbial communities of activated sludge samples collected from six wastewater treatment plants in east Tennessee. The experimental data showed that ARI-1 was capable of growing on estrogens in the presence and absence of acetone. In the absence of acetone, ARI-1 grew on 17α-estradiol, 17β-estradiol, and estrone with cell yields Y=0.05-0.13 (mg VSS/mg estrogen). The half-velocity constant (K_m) was 7.8±2.3mg/L for 17β-estradiol and 5.1±1.5mg/L for estrone. The maximum specific substrate utilization rate ( qˆ , mg estrogen/mg VSS-day) was 14.0±4.5d^-1 for 17β-estradiol and 14.0±4.4d^-1 for estrone. Degradation rates decreased when ARI-1 was deprived of estrogen for 1, 3, and 7 days. After growing in LB (nutrient-rich) medium without exposure to 17β-estradiol for 7 days, ARI-1 degraded 17β-estradiol at a much slower rate and failed to degrade estrone for more than 10 days. The results of microbial community analysis of activated samples suggested but not confirmed the presence of ARI-1. The results of this study, including the kinetic parameters of estrogen degradation by ARI-1, starvation effects, and prevalence of ARI-1 in various activated sludge system, are valuable for engineers to design a biological treatment system for enhanced estrogen removal.