Interactions between H_(2)O_(2)and dissolved organic matter during granular activated carbon-based residual H_(2)O_(2)quenching from the upstream UV/H_(2)O_(2)process

Granular activated carbon(GAC)filtration can be employed to synchronously quench residual H_(2)O_(2)from the upstream UV/H_(2)O_(2)process and further degrade dissolved organicmatter(DOM).In this study,rapid small-scale column tests(RSSCTs)were performed to clarify the mechanisms underlying the interactions between H_(2)O_(2)and DOM during the GAC-based H_(2)O_(2)quenching process.It was observed that GAC can catalytically decompose H_(2)O_(2),with a long-lasting high efficiency(>80%for approximately 50,000 empty-bed volumes).DOM inhibited GAC-based H_(2)O_(2)quenching via a pore-blocking effect,especially at high concentrations(10 mg/L),with the adsorbed DOM molecules being oxidized by the continuously generated·OH;this further deteriorated the H_(2)O_(2)quenching efficiency.In batch experiments,H_(2)O_(2)could enhance DOM adsorption by GAC;however,in RSSCTs,it deteriorated DOM removal.This observation could be attributed to the different·OH exposure in these two systems.It was also observed that aging with H_(2)O_(2)and DOM altered the morphology,specific surface area,pore volume,and the surface functional groups of GAC,owing to the oxidation effect of H_(2)O_(2)and·OH on the GAC surface as well as the effect of DOM.Addi-tionally,the changes in the content of persistent free radicals in the GAC samples were insignificant following different aging processes.This work contributes to enhancing understanding regarding the UV/H_(2)O_(2)-GAC filtration scheme,and promoting the application in drinking water treatment.

Genome-wide analysis of UGT gene family identified key gene for the biosynthesis of bioactive flavonol glycosides in Epimedium pubescens Maxim

Epimedium pubescens Maxim.is a well-known traditional Chinese medicinal herb with flavonol glycosides as the major pharmaceutically active compounds.UDP-glycosyltransferases(UGTs)are a group of enzymes responsible for the glycosylation of flavonoid glycosides.In this study,a genome-wide analysis was performed to identify UGT family genes in E.pubescens.As a result,a total of 339 putative UGT genes were identified,which represents the largest UGT gene family known thus far,implying a significant expansion of the UGT gene family in E.pubescens.All EpUGTs were unevenly distributed across six chromosomes,and they were classified into 17 major groups.The expression profiles showed that UGT genes were differentially expressed in roots,leaves,flowers,shoots and fruits.In particular,several EpUGTs were highly induced by high light intensity,which was consistent with the accumulation level of bioactive flavonoids in E.pubescens.Six UGT79 genes that were preferentially expressed in roots or leaves were successfully expressed in E.coli,and only the recombinant EpGT60 protein was found to be active toward 8-prenylkaempferol and icaritin to produce the key bioactive compounds baohuoside II and baohuoside I.The optimal temperature,pH,k_(m) and V_(max) were determined for the recombinant EpGT60 protein.In addition,expression of recombinant EpGT60 in E.coli cell culture led to successful production of baohuoside II when fed 8-prenylkaempferol.Our study provides a foundation for further functional characterization of UGT genes in E.pubescens and provides key candidate genes for bioengineering bioactive flavonoids in E.pubescens.