TY - JOUR
T1 - Direct solid-state evidence of H 2 -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
N1 - Funding Information:
National Natural Science Foundation of China, Grant number: 51578179
Publisher Copyright:
© 2018 Wiley Periodicals, Inc.
PY - 2018/7
Y1 - 2018/7
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 H 2 . During the 120-min tests for similarly 86% adsorption under O 2 , N 2 , and H 2 , 8% more U was immobilized through a non-adsorptive pathway by the EPS for H 2 than for N 2 and O 2 . 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 (U IV O 2 ) 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 H 2 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 H 2 . During the 120-min tests for similarly 86% adsorption under O 2 , N 2 , and H 2 , 8% more U was immobilized through a non-adsorptive pathway by the EPS for H 2 than for N 2 and O 2 . 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 (U IV O 2 ) 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 H 2 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.
KW - H
KW - extracellular polymeric substances (EPS)
KW - nanoparticles
KW - uranium reduction
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U2 - 10.1002/bit.26592
DO - 10.1002/bit.26592
M3 - Article
C2 - 29574765
AN - SCOPUS:85045221511
SN - 0006-3592
VL - 115
SP - 1685
EP - 1693
JO - Biotechnology and bioengineering
JF - Biotechnology and bioengineering
IS - 7
ER -