Laccase-Driven 17β-Estradiol Humification in the Presence of Humic Acids at Varying pH Levels

2022 ◽  
Vol 148 (2) ◽  
Author(s):  
Shunyao Li ◽  
Rui Zhu ◽  
Huijie Wei ◽  
Michael Gatheru Waigi ◽  
Kai Sun ◽  
...  
Keyword(s):  
2021 ◽  
Author(s):  
Kai Sun ◽  
Rui Zhu ◽  
Huijie Wei ◽  
Shunyao Li ◽  
Michael Gatheru Waigi ◽  
...  

Abstract Estrogens with tremendous ecological risks are proverbially found in water. Laccase can drive humification of estrogens to reduce their ecotoxicity and removability, but little investigation existed in exploring the effect of humic acids (HAs) on E2 conversion kinetics and polymerization products at different pH conditions. Here, Trametes versicolor laccase (Tvlac) was capable of efficiently converting a representative estrogen, 17β-estradiol (E2) with two different HAs, and the process followed a pseudo-first-order kinetics. The velocity constants were respectively 0.048, 0.022, and 0.020 min− 1 for HA-free, peat-derived HA, and commercial HA at pH 5.0. The changing pH not only impacted E2 coupling kinetics in Tvlac-evoked humification, but altered the aromaticity and humification degrees of HAs. A total of five intermediate species including estrone (E1), E2 dimer, trimer, and tetramer, as well as E1-E2 cross-linked products were tentatively detected, in which the dominating species were E2 self-oligomers resulting from radical-centered carbon-carbon/oxygen stepwise polymerization routes. Yields of dimeric, trimeric, and tetrameric species with increased molecular sizes were the highest at pH 5.0 in the given pH values, and they were readily handled by precipitation and filtration. Especially E2 was able to be covalently incorporated into humic constituents to generate new humified co-polymers, thereby accelerating E2 humification and detoxification. These findings demonstrate that pH exhibits a far-reaching influence on the conversion kinetics, humification degrees, and products distribution of E2 and HAs in Tvlac-reinforced polyreaction. Thus, there is need to reappraise the fate and transport of estrogens with HAs present in natural water at varying pH levels.


2020 ◽  
pp. 15-27

In order to study the effect of phosphogypsum and humic acids in the kinetic release of salt from salt-affected soil, a laboratory experiment was conducted in which columns made from solid polyethylene were 60.0 cm high and 7.1 cm in diameter. The columns were filled with soil so that the depth of the soil was 30 cm inside the column, the experiment included two factors, the first factor was phosphogypsum and was added at levels 0, 5, 10 and 15 tons ha-1 and the second-factor humic acids were added at levels 0, 50, 100 and 150 kg ha-1 by mixing them with the first 5 cm of column soil and one repeater per treatment. The continuous leaching method was used by using an electrolytic well water 2.72 dS m-1. Collect the leachate daily and continue the leaching process until the arrival of the electrical conductivity of the filtration of leaching up to 3-5 dS m-1. The electrical conductivity and the concentration of positive dissolved ions (Ca, Mg, Na) were estimated in leachate and the sodium adsorption ratio (SAR) was calculated. The results showed that the best equation for describing release kinetics of the salts and sodium adsorption ratio in soil over time is the diffusion equation. Increasing the level of addition of phosphogypsum and humic acids increased the constant release velocity (K) of salts and the sodium adsorption ratio. The interaction between phosphogypsum and humic acids was also affected by the constant release velocity of salts and the sodium adsorption ratio. The constant release velocity (K) of the salts and the sodium adsorption ratio at any level of addition of phosphogypsum increased with the addition of humic acids. The highest salts release rate was 216.57 in PG3HA3, while the lowest rate was 149.48 in PG0HA0. The highest release rate of sodium adsorption ratio was 206.09 in PG3HA3, while the lowest rate was 117.23 in PG0HA0.


2011 ◽  
Vol 47 (1) ◽  
pp. 97-104
Author(s):  
V. A. Medved' ◽  
P. D. Klochenko ◽  
O. V. Vasilenko ◽  
T. A. Vasilchuk
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