Lm. He et al., Bacillus lichenformis gamma-glutamyl exopolymer: Physicochemical characterization and U(VI) interaction, ENV SCI TEC, 34(9), 2000, pp. 1694-1701
Citations number
59
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
Complexation by microbially produced exopolymers may significantly impact t
he environmental mobility and toxicity of metals. This study focused on the
conformational structure of the bacterial exopolymer, gamma-D-poly(glutami
c acid):and its interactions with U(VI) examined using ATR-FTIR spectroscop
y. Solution pH, polymer concentration, and ionic strength affected the conf
ormation of the exopolymer, and U(VI) binding was monitored. At low pH, low
concentration, or low ionic strength, this exopolymer exists -in an alpha-
helical conformation, while at high pH, concentration, or ionic strength th
e exopolymer exhibits a beta-sheet structure. The change in exopolymer conf
ormation is likely to influence the number and nature of exposed surface fu
nctional groups, sites most responsible for metal complexation. We found th
e polyglutamate capsule binds U(VI) in a binuclear, bidentate fashion; in c
ontrast the glutamate monomer forms a mononuclear, bidentate complex with U
(VI). The apparent polynuclear binding of U(VI) may induce beta-sheet struc
ture formation provided the U(VI) concentration is sufficiently high.