Removal properties of dissolved boron by glucomannan gel.

Boron ions have long been known to form complexes with the cis-diol group of a polysaccharide. Konjac glucomannan (KGM) which is one of polysaccharides was used to remove dissolved boron in this study. KGM forms a complex with boron, but does not remove boron from contaminated waters as well as other polysaccharides because of its high water solubility. Therefore, the removal efficiencies of dissolved boron were examined using both an insoluble KGM gel and KGM semi-gel. The former did not remove dissolved boron, but the latter did. The difference in the ability of boron removal was due to the presence of diol group inside. KGM loses free diol group during the process of gelation. On the other hand, the semi-gel gelated only surface layer in water has diol group inside. The boron removal capacity of the semi-gel was highest at pHs⩾11, when the boron species is present as B(OH)4(-). The capacity was slightly increased by the addition of Al, Ca and Mg under high pH conditions. This was due to co-precipitation of boron with Ca dissolved from the semi-gel. The boron adsorbed to the semi-gel easily was desorbed under low pH conditions and the hysteresis was not found.

Removal of dissolved estrogen in sewage effluents by ß-cyclodextrin polymer.

Substances with estrogenic activity are found in effluents of municipal sewage plants and dairy farms. These effluents have the potential to induce feminization in male fish. In this study, cyclodextrin polymers (CDPs) that are insoluble in both polar and non-polar solvents were selected for the removal of dissolved estrogens in the effluent of a municipal sewage plant. The removal capacity of CDPs was high in the order of ß-CDP≥γ-CDP≫α-CDP. The mechanism for adsorption of estrogens to ß-CDP was not only due to a host-guest interaction as molecular recognition by ß-cyclodextrin (ß-CD), but also due to adsorption by the polymer matrix. ß-CDP of 0.2% (w/v) removed 17ß-estradiol (E2) of about 70% from 10(-11)mol/L, and more than 90% from ≥10(-10)mol/L. The removal ratios of E2 in the presence of cholesterols, which are contained at higher concentrations than estrogens in sewage effluents and are adsorptive competitor for ß-CDP, were about 85% at a cholesterol/E2 molar ratio of 100 and >90% at molar ratios of 0.1, 1, and 10. The effluent from a municipal sewage plant had estrogenic activity corresponding to 5.5×10(-11)molE2/L by yeast two-hybrid assay. The estrogens in the effluent were also removed >90% by the ß-CDP treatment. Therefore, ß-CDP is able to remove dissolved estrogens over a wide range of concentrations in the presence of various contaminants such as wastewaters.

Suppression of estrogenic activity of 17-beta-estradiol by beta-cyclodextrin.

The suppressive effects of cyclodextrins (CDs) on the strong estrogenic activity of 17beta-estradiol (E2) in water environments were investigated in this study. Cyclodextrins are doughnut-shaped molecules that possess a hydrophobic cavity and a hydrophilic exterior. The cavity can incorporate nonpolar molecules as guests to form inclusion complexes. beta-CD and 2-hydroxypropyl-beta-CD (HP-beta-CD) were the most successful in forming a complex with E2 and improving its low aqueous solubility. The E2/CDs complexes bound to the estrogen receptor in a cell-free system as determined by ELISA and suppressed the hormone activities as measured by a yeast two-hybrid assay. These results indicate that hydrophobic E2 is easily transported through the lipid zone of the plasma membrane into the target cell and can bind to the nuclear receptor. However, the hydrophilic E2/beta-CD and E2/HP-beta-CD complexes do not penetrate the membrane. Therefore, these CDs are able to suppress the hormone activity of E2 through complex formation.