SELECTIVE ACCUMULATION OF LIGHT OR HEAVY RARE EARTH ELEMENTS USING VARIOUS MICROORGANISMS

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SELECTIVE ACCUMULATION OF LIGHT OR HEAVY RARE
EARTH ELEMENTS USING VARIOUS MICROORGANISMS

• Takehiko Tsuruta

Department of Applied Chemistry, Tohwa
University, Fukuoka, JAPAN
Bio Micro World 2005, International Conference on
Environmental, Industrial and Applied
Microbiology Marth 15-18th 2005, Badajoz,
Spain.
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Abstract The accumulation of Sm from the
solution containing Sm only by Arthrobacter
nicotianae was examined. The amount of Sm
accumulated wae strongly affected by the
concentration of Sm and pH of the solution.
Accumulation of Sm by the strain was very rapid
and reached equiliblium within 3 h. The selective
accumulation of Sm-Eu or Eu-Gd from the solution
containing each two metal was also examined. The
selective accumulations of 5 kinds of rare earth
elements (REEs), such as Y, La, Sm, Er, and Lu,
from the solution containing these elements by
some actinomycetes and gram-positive bacteria
were also studied. Among the strains tested, the
amount of Sm accumulated by Bacillus megaterium,
that of Lu accumulated by Streptomyces albus and
S. levoris, and that of both Sm Lu by A.
nicotianae were higher than that of other metals
from a solution containing 5 kinds of REEs.
Additionally, the selective accumulation of light
or heavy REEs by A. nicotianae and S. albus was
examined. S. albus can accumulate Lu selectively
from the solution containing Y and 8 kind of
heavy REEs. On the other hand, A. nicotianae can
accumulate Tb and Yb from the same solution.
Other selective accumulation were also
examined.
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Introduction The separation of REE from a
solution is very difficult, because of their very
similar chemical properties. The solvent
extraction methods are performed for the
separation of REE, however a large amount of
organic solvent is used and the environmental
issue then becomes serious. The adsorption of
several actinides and lanthanides by
Mycobacterium smegmatis was investigated,
however, the amount of adsorbed lanthanide was
law and there almost no difference in the amount
of extracted lanthanides. Recently, it was
reported that Variovorax paradoxus reduced the
amount of light REE, such as yttrium, lanthanum,
cerium, and neodymium more than that of the other
REE. It was also reported that Streptomyces sp.
decreased the amount of Yb.
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We have investigated the accumulation of REE
from the solution containing one kind of REE by
microbes. The amount of REE accumulated by
gram-positive bacteria were much higher than
those by gram-negative bacteria, fungi, and
yeasts. Most species of the gram-positive
bacteria had higher REE accumulating abilities
than actinomycetes, however, actinomycetes and
other gram-positive bacteria had different
accumulating features as in the case of the
accumulation of U. The amounts of U
accumulated at pH 5.8 by gram-positive bacteria
were higher than all the actinomycetes strains
tested. The amounts of U accumulated at pH 3.5 by
half strains of actinomycetes were higher than
those by all gram-positive bacteria except A.
nicotianae. Therefore, actinomycetes and
other gram-positive bacteria are expected to have
the different accumulating features of REE from
the solution containing many kinds of REE.
Accordingly, the separation of REE by
actinomycetes and other kinds of gram-positive
bacteria were examined in this study.
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Fig.1. Effect of external Sm concentration on Sm
accumulation from the solution containing Sm only
by Arthrobacter nicotianae or Bacillus
licheniformis. Resting cells (15.0 mg dry wt.
basis) were suspended in 100 ml of the solution
(pH5.0) containing a desired concentration of
each metal for 3h at room temperature.
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Fig. 2. Effect of pH on Sm accumulation from the
solution containing Sm only by Arthrobacter
nicotianae IAM12342. Resting cells (15.0 mg dry
wt. basis) were suspended in 100 ml of the
solution containing 66.5 mM of Sm for 3h at room
temperature.
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Fig. 3. Time course of Sm accumulation by A.
nicotianae IAM12342 cells. Resting cells (15 mg
dry wt. basis) were suspended in 100 ml solution
containing 66.5 mM Sm at room temperature.
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Fig.4. Relationship on separation factor of Eu/Sm
and Eu/Gd using various microbes. Resting
cells (15 mg dry wt. basis were suspended in 100
ml of the solution (pH 5.0) containing 20 mM of
Eu and 150 mM of Sm or 120 mM of Gd for 3 h at
room temperature. The ratio of the metals
concentration of the solution is almost same as
that of natural field.
S.F.(Eucells/Mcells)/(Eusolution/M
solution) Eucells the amounts of Eu
accumulated in the cells Mcells the amounts of
Sm or Gd accumulated in the cells Eusolution
the amounts of Eu remained in the solution M
solution the amounts of Sm or Gd remained in
the solution
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(No Transcript)
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Fig. 5-(A). Accumulation of light rare earth
elements using Arthrobacter nicotianae IAM12342
from the mixed solution containing Y, Ce, Pr, Nd,
Sm, and Eu. Resting cells (15.0 mg dry wt.
basis) were suspended in 100 ml of the solution
(pH5.0) containing 66.5 mM each of metals for 3h
at room temperature.
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Fig. 5-(B). Accumulation of light rare earth
elements using Streptomyces albus HUT6047 from
the mixed solution containing Y, Ce, Pr, Nd, Sm,
and Eu.
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Fig. 6-(A). Accumulation of Y and heavy rare
earth elements using Arthrobacter nicotianae
IAM12342 from the mixed solution containing Y,
Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
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Fig. 6-(B). Accumulation of Y and heavy rare
earth elements using Streptomyces albus HUT6047
from the mixed solution containing Y, Gd, Tb, Dy,
Ho, Er, Tm, Yb, and Lu.
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Fig. 7. Selective accumulation of Sm and some
metals using Arthrobacter nicotianae IAM12342
cells. Resting cells (15.0 mg dry wt. basis)
were suspended in 100 ml of the solution (pH5.0)
containing 150 mM of Sm, each metals or 150 mM of
Sm and 225 mM of each metal for 3h at room
temperature.
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Conclusions (1) The accumulation of Sm by A.
nicotianae from the solution containing Sm only
was examined. The amounts of Sm accumulated Were
increased with the increasing the Sm
concentration and pH of the solution. The
accumulation rate was very rapid and reached
Equilibrium within 3 hours. (2) The selective
accumulations of Eu/Gd and Eu/Sm from the
solution containing each two metals using some
actinomycetes and other gram- positive bacteria
were examined. S. F.Eu/Gd using all
gram-positive bacteria were higher than those
using actinomycetes. The amounts of S. F.Eu/Sm
were the values between 0.90 and 1.1, however S.
F.Eu/Sm of B. megaterium was 0.83. Therefore,
the selectivity of Sm from the solution
containing Sm and Eu by B. megaterium was highest
of the strains tested.
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(3) The selective accumulation of REE using
various microorganisms from a solution
containing 5 kinds of REEs was examined. Among
the strains tested, the amount of Sm accumulated
using B. megaterium cells and that of Lu
accumulated using S. albus and S. levoris cells,
is higher than that of the other metals. On the
other hand, the amounts of both the accumulated
Sm and Lu using A. nicotianae are higher than
those of the other metals. (4) The selective
accumulations of light REEs using A. nicotianae
and S. albus were examined. The amount of Sm
accumulated was the highest from the solution
containing 6 kinds of light REEs using A.
nicotianae. On the other hand, the amounts of Sm
and Eu accumulated from the same solution using
S. albus was almost same and higher than other 4
kinds of light REEs.
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(4) The selective accumulations of Y and heavy
REEs using A. icotianae and S. albus were
examined. Two peaks was appeared in the case of
the accumulation from the solution containing Y
and 8 kinds of heavy REEs using A. nicotianae.
The amount of Tb accumulated was the highest and
the other peak was that of Yb. On the other
hand, the amount of Lu accumulated from the same
solution using S. albus was the highest, whereas
the small peak of Tb was also appeared. (5) The
selective accumulation of Sm and 6kinds of metals
using A. nicotianae was examined. The amount of
Sm accumulated was much higer than each amount of
metals acuumulated. Therefore, this strain can be
accumulated REEs selectively from the solution
containing other type of metals. Acknowledgement
This work was supported by the Metal Mining
Agency of Japan (MMAJ). We would like to thank to
MMAJ.