Browsing by Subject "Phytoestrogens"

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    The environmental fate of the phytoestrogens genistein and daidzein
    (2013-08) Kelly, Megan
    Genistein and daidzein are two phytoestrogens, compounds that come from plants (especially legumes) and interact with the estrogen receptors present in humans, fish, and other animals. Although they are naturally produced in the environment, they can become concentrated in the effluent of facilities treating the waste of plant-processing industries. They are also detected in run-off from fields where plants such as red clover are found. At environmentally-relevant concentrations, genistein and daidzein have been shown to produce reproductive, behavioral, and immunosuppressive effects in fish. This work develops the chemical and microbiological parameters necessary to predict the concentrations of genistein and daidzein in a body of water receiving a discharge containing the phytoestrogens. The attenuation processes studied include direct and indirect photolysis, sorption to settling particles, and biodegradation. Biodegradation is shown to be an extremely efficient removal process. Work by the Aquatic Toxicology Lab at Saint Cloud State shows that estrogenicity is removed by biodegradation, but some component of the biodegradation product mixture produces an androgenic or anti-estrogenic effect. Therefore, more research is needed to fully understand the exposure of aquatic wildlife to phytoestrogens and their degradates.
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    Phytoestrogen distribution and degradation in natural and engineered systems
    (2012-12) Fleischhacker, Nathan T.
    Phytoestrogens are plant-derived hormonally active compounds known to cause varied reproductive, immunosuppressive and behavioral effects in fish. Environmentally relevant concentrations of phytoestrogens have been identified in numerous industrial and wastewater effluents, but their presence in surface water has received little attention. Additionally, no work has been performed to assess the degradability of phytoestrogens in surface waters or to determine which microbial communities may be responsible for their degradation. Given the fundamental questions that exist regarding phytoestrogens in the environment, the objectives of this research were three-fold: 1) Determine the degradation capacity of genistein, a potent and common phytoestrogen species, in surface waters under a variety of environmental conditions, 2) Monitor the temporal and spatial fluctuations of 6 phytoestrogen species in wastewater-impacted and unimpacted surface waters, 3) Examine if genistein, like similarly structured steroidal estrogens, is capable of being degraded cometabolically by nitrifying organisms. Triplicate batch reactors with triplicate negative controls were used to investigate genistein degradation in both surface water and enriched nitrifying cultures. Grab samples were collected from impacted and unimpacted surface waters to identify temporal and spatial phytoestrogen patterns. Genistein degradation rates in surface water samples were found to vary significantly and depended on initial concentration, incubation temperature, season of water collection, and surface water source. Overall genistein degraded rapidly and variably, with the time to 50% degradation ranging from 15 to 70 hours. In reactors amended with 100 μg/L genistein, an enrichment period during which there was no or little degradation was followed by a period of rapid genistein degradation (zero-order), suggesting that genistein may be degraded intentionally as an energy source rather than incidentally via some cometabolic pathway. Experiments with nitrifying organisms indicated that genistein was not cometabolically degraded by nitrifying organisms, but it was degraded by organisms that were enriched under nitrifying conditions. Temporal and spatial studies detected several phytoestrogen species in surface waters at low nanogram per liter concentrations with no discernible temporal or spatial pattern. This research suggests that like genistein, phytoestrogens in general may be readily degraded in surface waters. It also suggests that phytoestrogens are not likely to cause widespread ecological harm, but caution should be taken as numerous compounds in this class exist and only a limited number of surface waters were sampled for phytoestrogen presence.