Abstract

Adsorption of hexavalent uranium (U(VI)) by extracellular polymeric substances (EPS) has been studied, but the possibility of simultaneous U(VI) reduction mediated by EPS has not had experimental confirmation, as the reduction products have not yet been directly proven. Here, we reported the first direct evidence of lower-valent products of U(VI) immobilization by loosely associated EPS (laEPS) isolated from a fermenter strain of Klebsiella sp. J1 when the laEPS was exposed to H2. During the 120-min tests for similarly 86% adsorption under O2, N2, and H2, 8% more U was immobilized through a non-adsorptive pathway by the EPS for H2 than for N2 and O2. A set of solid-state characterization tools (FT-IR, XPS, EELS, and TEM-EDX) confirmed partial reduction of U(VI) to lower-valence U, with the main reduced form being uraninite (UIVO2) nanoparticles, and the results reinforced the role of the reduction in accelerating U immobilization and shaping the characteristics of immobilized U in terms of valency, size, and crystallization. The laEPS, mostly comprised of carbohydrate and protein, contained non-cytochrome enzymes and electron carriers that could be responsible for electron transfer to U(VI). Taken together, our results directly confirm that EPS was able to mediate partial U(VI) reduction in the presence of H2 through non-cytochrome catalysis and that reduction enhanced overall U immobilization. Our study fills in some gaps of the microbe-mediated U cycle and will be useful to understand and control U removal in engineered reactors and in-situ bioremediation.

Original languageEnglish (US)
JournalBiotechnology and Bioengineering
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

Immobilization
Adsorption
Electrons
Environmental Biodegradation
Uranium
Klebsiella
Crystallization
Catalysis
Nanoparticles
Carbohydrates
Fermenters
Bioremediation
Electron energy loss spectroscopy
Enzymes
Energy dispersive spectroscopy
Proteins
X ray photoelectron spectroscopy
Transmission electron microscopy

Keywords

  • Extracellular polymeric substances (EPS)
  • H
  • Nanoparticles
  • Uranium reduction

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

Cite this

Direct solid-state evidence of H2-induced partial U(VI) reduction concomitant with adsorption by extracellular polymeric substances (EPS). / Li, Ang; Zhou, Chen; Liu, Zhuolin; Xu, Xiaoyin; Zhou, Yun; Zhou, Dandan; Tang, Youneng; Ma, Fang; Rittmann, Bruce.

In: Biotechnology and Bioengineering, 01.01.2018.

Research output: Contribution to journalArticle

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T1 - Direct solid-state evidence of H2-induced partial U(VI) reduction concomitant with adsorption by extracellular polymeric substances (EPS)

AU - Li, Ang

AU - Zhou, Chen

AU - Liu, Zhuolin

AU - Xu, Xiaoyin

AU - Zhou, Yun

AU - Zhou, Dandan

AU - Tang, Youneng

AU - Ma, Fang

AU - Rittmann, Bruce

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Adsorption of hexavalent uranium (U(VI)) by extracellular polymeric substances (EPS) has been studied, but the possibility of simultaneous U(VI) reduction mediated by EPS has not had experimental confirmation, as the reduction products have not yet been directly proven. Here, we reported the first direct evidence of lower-valent products of U(VI) immobilization by loosely associated EPS (laEPS) isolated from a fermenter strain of Klebsiella sp. J1 when the laEPS was exposed to H2. During the 120-min tests for similarly 86% adsorption under O2, N2, and H2, 8% more U was immobilized through a non-adsorptive pathway by the EPS for H2 than for N2 and O2. A set of solid-state characterization tools (FT-IR, XPS, EELS, and TEM-EDX) confirmed partial reduction of U(VI) to lower-valence U, with the main reduced form being uraninite (UIVO2) nanoparticles, and the results reinforced the role of the reduction in accelerating U immobilization and shaping the characteristics of immobilized U in terms of valency, size, and crystallization. The laEPS, mostly comprised of carbohydrate and protein, contained non-cytochrome enzymes and electron carriers that could be responsible for electron transfer to U(VI). Taken together, our results directly confirm that EPS was able to mediate partial U(VI) reduction in the presence of H2 through non-cytochrome catalysis and that reduction enhanced overall U immobilization. Our study fills in some gaps of the microbe-mediated U cycle and will be useful to understand and control U removal in engineered reactors and in-situ bioremediation.

AB - Adsorption of hexavalent uranium (U(VI)) by extracellular polymeric substances (EPS) has been studied, but the possibility of simultaneous U(VI) reduction mediated by EPS has not had experimental confirmation, as the reduction products have not yet been directly proven. Here, we reported the first direct evidence of lower-valent products of U(VI) immobilization by loosely associated EPS (laEPS) isolated from a fermenter strain of Klebsiella sp. J1 when the laEPS was exposed to H2. During the 120-min tests for similarly 86% adsorption under O2, N2, and H2, 8% more U was immobilized through a non-adsorptive pathway by the EPS for H2 than for N2 and O2. A set of solid-state characterization tools (FT-IR, XPS, EELS, and TEM-EDX) confirmed partial reduction of U(VI) to lower-valence U, with the main reduced form being uraninite (UIVO2) nanoparticles, and the results reinforced the role of the reduction in accelerating U immobilization and shaping the characteristics of immobilized U in terms of valency, size, and crystallization. The laEPS, mostly comprised of carbohydrate and protein, contained non-cytochrome enzymes and electron carriers that could be responsible for electron transfer to U(VI). Taken together, our results directly confirm that EPS was able to mediate partial U(VI) reduction in the presence of H2 through non-cytochrome catalysis and that reduction enhanced overall U immobilization. Our study fills in some gaps of the microbe-mediated U cycle and will be useful to understand and control U removal in engineered reactors and in-situ bioremediation.

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