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HUNGARIAN JOURNAL
OF INDUSTRIAL CHEMISTRY
VESZPRÉM
Vol. 32. pp. 23-31 (2004)

INVESTIGATION OF REVERSE PHASE SMB-CHROMATOGRAPHIC
BIOSEPARATIONS OF AMINO ACID AQUEOUS SOLUTIONS

Z. MOLNÁR1, M. NAGY1, A. ARANYI2, L. HANÁK1, T. SZÁNYA1 and J. ARGYELÁN1

1University of Veszprém, Department of Chemical Engineering,
H-8201 Veszprém, P.O.Box 158, HUNGARY;

Fax number: +36 88 421 905 e-mail: hmolnar78@freemail.hu
2Gedeon Richter Pharmaceutical Works, H-1475 Budapest,

P.O.Box. 27, HUNGARY

The authors investigated amino acid aqueous solutions as model system for the purpose of studying reverse
phase chromatographic bioseparation. Desalting of DL-β-phenylalanine was studied on a small-laboratory
scale simulated moving bed (SMB) preparative liquid chromatograph (number of columns=6, column
length=125mm, column I.D.=13mm). DIAION HP20 polymeric adsorbent resin was used for the reverse
phase chromatography. The feed (sample) of the SMB equipment is 3.5g DL-β-phenylalanine/dm3 and 58.5g
sodium-chloride/dm3 aqueous solution. With the three zones opened loop SMB with 2-2-2 column
configuration can amino acid product be achieved with less than 50ppm NaCl in crystal form after
evaporation. Later a large laboratory scale (number of columns=4, column length=500mm, column
ID=50mm) automatized SMB equipment was constructed. The applied model system for bioseparation
contains glycine (1.5g/dm3), L-phenylalanine (3.3g/dm3) in water and SEPABEADS SP825 adsorbent. Both
L-phenylalanine and glycine were produced in more than 99.9% m/m purity and 99% yield at productivity
3.7-9.5mg/(g adsorbent h) in case of three zones open loop 2-1-1 column configuration. The SMB
experiments were simulated with the help of equilibrium cascade model. The measured and calculated data
agreed well.

Keywords: simulated moving bed (SMB), column liquid chromatography, polymeric adsorbent resin, amino acid
aqueous solution

Introduction

It is typical in biotechnology and pharmaceutical
industry that water phase mixture for processing
contains end-product or active ingredient in small
concentration beside the contaminant or polluting
components. Simulated moving bed (SMB)
preparative chromatography can be advantageous
among the end-product recovery methods for
continuous processing of high purity products, or
products being difficult to isolate.

Basically the SMB chromatograph works
similarly to the true moving bed (hereafter
abbreviated as TMB). The TMB works in the
following way by Figure 1a: in a column the
mobile phase moves upwards through the
adsorbent that moves downwards simultaneously.

The column is fitted with a feed inlet in the middle
of the side-wall, a raffinate outlet on the upper part
and an extract outlet on the lower part. Choosing
the appropriate adsorbent moving velocity value
and suitable eluent, feed, extract and raffinate flow
rates, a stationary state can be obtained in the
column with constant concentration profiles. The
more binding component occurs in the lower (I-II)
part of the column and the less binding one is
located on the upper part (III-IV) of the column.
This way two pure components can be obtained
simultaneously in the extract and in the raffinate.
The chromatographic quality of TMB is difficult to
realize technically, therefore an SMB was
employed in the preparative chromatography.

SMB liquid chromatograph (hereafter-
abbreviated SMB-LC) (Fig. 1b) is a multi-column
system with two inputs and outputs (products), in

which liquid phase moves in counter-current of
adsorbent phase. The counter-current stream is not
real, but simulated, since the packed
chromatographic stationary phase moves
periodically after each switching time. The shorter
the switching time and the more the number of
columns are in the SMB-LC, the better it
converges to the TMB-LC.

The SMB technique is basically a two product
preparative chromatographic operation. It is
suitable for mixtures to be separated having two
components or can be produced two product
fractions.

In case of continuous system the two input
streams are the fresh eluent and feed, the two
outputs are the extract and raffinate. Above all in
basic case regenerated eluent of re-circulating
stream is added to the fresh eluent.

Similarly to the TMB the lower part (I-II) of
the column is rich in the more binding component
and at the upper part (III-IV) of the column
contains the less binding component. The inlet and
the outlet fluid flow streams divide the column
system into four zones (Fig.1.)

III

Eluens

A Rec D+D Rec

D Rec

III

D+D Rec

D Rec

A; B;
Figure 1. The scheme of a) true moving bed (TMB) and b)

simulated moving bed (SMB). True moving bed (TMB)
adsorber: I, II, III, IV – zones; D – desorbent (solvent, eluent);
D Rec – recirculated eluent; A Rec – adsorbent recirculation;
E – extract stream with the better adsorbed component A; F –

feed stream with the components A and B; R – raffinate
stream with the less adsorbed component B. Simulated

moving bed (SMB) liquid chromatograph – I, II, III, IV –
zones, respectively HPLC columns; CM – direction of

simulated moving of HPLC columns.

The inlet liquid stream of the first zone is the
mixture of the fresh and recirculated eluent. The
first column of the first zone has to be regenerated
till the end of each switching time period to protect
carrying strongly adsorbed components by
adsorbent phase. The inlet liquid stream of the
second zone is the mobile phase from the first zone
minus the flow stream of the extract. This flow

stream must be determined so that the less binding
component could leave the first column of the
second zone till the end of the switching period
avoiding to get into the extract. The inlet liquid
stream of the third zone is the mobile phase from
the second zone plus the feed stream to be
separated. The function of this zone is holding the
more binding component in the adsorbent phase,
since the less binding component is taken away as
a raffinate at the end of the zone. Four-zone SMB
is favourable when retarding the less binding
component – regenerating the solvent. The
regenerated solvent can be recycled and added to
the fresh eluent. In case of recycled solvent the
system is called closed loop SMB. This version is
more favourable compared to the open loop system
from economic and environmental point of view.
Three-zone SMB is preferred in systems with high
selectivity factor, when the less binding component
has low capacity factor flowing nearly together
with the mobile phase [1,2].

According to the above facts the operational
parameters of the process are the switching time,
the flow rates of the mobile phase in each zones
determined by the external flow rates (fresh and
recycled eluent, extract, feed, raffinate).

Summing up the possibilities for amino acid
preparative separation the following
chromatographic methods were applied in practice:
ion-exchange column liquid chromatography, ion-
exchange parametric pumping, size-exclusion
chromatography, reverse phase adsorption
chromatography.

In case of reverse phase adsorption
chromatography for separation of amino acids
solved in water: the styrene-divynilbenzene
copolymers with non-polar surface and the
polymethacrylate resins with weakly polar surface
can be used in the presence of electrolytes or polar
solvent. In such systems the adsorption equilibrium
depends on the temperature, the solvent strength,
the pH [3,4] and on the electrolyte concentration of
aqueous solution [2].

The design of industrial scale SMB-LC process
requires numerous preliminary experiments. At the
selection of the packing we can reduce the number
of the possible alternatives if we consider the
chemical character of the adsorbents. The most
frequently used technique is the determination of
adsorption selectivity with an analytical HPLC
instrument with a given adsorbent by injection
method. The adsorbent is giving the best selectivity
to be examined further on within small-scale or
large-scale laboratory circumstances. We examined
the model samples by frontal adsorption-desorption

method on the small scale lab size column packed
with polymer adsorbent. The advantage of this
method is that frontal adsorption and desorption
processes of the SMB-LC can be investigated.

After determining the equilibrium data of the
selected systems and the column packing
characteristics the initial operating parameters of
the SMB can be calculated. The initial operating
parameters for a three zone open loop SMB was
calculated by the method of Morbidelli et al. [5].
The first zone regeneration is appropriate when:

)L(1

LT
A
D

mK IA ε

−

−
=< (1)

The less binding component must be removed
from the second zone till the end of the switching
time. The function of the third zone is the retarding
of the better-adsorbed component, namely this
component must not break through the third zone:

AIIB K)L(1

LT
A

m<K <
−

−
−

=
ε

ε
(2)

AIIIB K)L(1

LT
A

F+ED

m<K <
−

−
−

=
ε

ε
(3)

In a two component-system a mII-mIII area can
be determined from the geometric data of the SMB
equipment, the equilibrium parameters of
Langmuir-type isotherms and the concentrations of
the mixture to be separated.

The given operating conditions determined a
point in the mII-mIII diagram. This point must be
placed in the Morbidelli-area (or Morbidelli-
triangle), then both products stream purity are
theoretically 100%. When the optimal
chromatographic packing is selected, the following
operating variable can have influence on the SMB-
LC operation: fresh eluent, recirculated eluent,
feed, extract and raffinate flow rates, column
switching time. During calculation the influence of
a given parameter can be investigated while the
others must be considered as constants.

Better productivity, product purity, yield,
eluent consumption can be achieved by optimizing
operating conditions by computer.

The Morbidelli-area changes with the change
of the following parameters during the planning:
geometrics of SMB equipment, temperature and
exchange of adsorbent, composition of fresh eluent
and feed.

During the planning of a preparative
chromatography it must be considered, that the
models of linear chromatography described is not
appropriate the system. Many research schools are

dealing with the mathematical modeling of the
nonlinear chromatography [6,7].

Experiments

The examined model systems during research are
the aqueous solution of DL-β-phenylalanine and
sodium-chloride, and the aqueous solution of
glycine and DL-β-phenylalanine.

Select reversed phase packing

In case of L-phenylalanine and glycine amino
acids separation in water the next reversed phase
non-polar polymer adsorbents were studied by
frontal adsorption-desorption methods: DIAION
HP20, SEPABEADS SP825. For desalting DL-β-
phenylalanine DIAION HP2MG, Amberlite XAD7
polymethacrylate, Amberlite XAD1180, DIAION
HP20 styrene-divynilbenzene copolymer resins
were investigated.

Parameters of research: measurement went on
glass column in which resin bed length was 122 mm,
I.D. 13 mm. L-phenylalanine concentration 0.005
mol L-phenylalanine/dm3 aqueous solution, glycine
concentration 0.0025 mol glycine/dm3 aqueous
solution, volumetric stream 2.9 ml/min. L-
phenylalanine was detected on-line by GILSON116
UV-spectrophotometer at 271 nm wavelength.
Glycine and phenylalanine analyses went on
afterwards, samples fractionally taken in each 4 ml
by OE914 amino acid analyzer. While desalting 0.02
mol/dm3 DL-β-phenylalanine aqueous solution and
1mol sodium-chloride/dm3 aqueous solution, the next
detection was used during adsorbent selection. The
phenylalanine was detected on-line UV at 271nm,
NaCl by conductivity meter with flowing through
cuvette. Ion exchanged water was used for all
experiments as desorbents.

Measurement of packing properties

Frontal adsorption–desorption method for
adsorbent selection gave the best packing filled by
slurry technique into SMB-LC column. After
packing, the number of theoretical plate (NTP) was
measured in function of volume stream for
L=500mm I.D.=50mm preparative SMB-column
in 30-180 cm3/min range using Na2SO4 detecting
compound. In case of L=125mm ID=13mm small-

laboratory SMB column NTP and column porosity
(ε) were determined in 3.0-22 cm3/min range by
injection method with 0.25 mol Na2SO4/dm3 water
solution at 20°C. The answer function of the
injection was detected by a RADELKIS OK102/1
conductivity meter with flow-through cuvette. This
date is necessary for modeling, too. Measurement
of bulk density: resin being packed in a column
was quantitatively removed and placed in max 5
mm thin layer on a plate in known mass and dried
at 85-90°C till constant mass, then re-measured.

Measurement of equilibrium isotherms

Multi-step frontal adsorption method was used in a
glass column (L=122 mm, ID=13 mm) packed
with DIAION HP20 respectively SEPABEADS
SP825 at 20°C in 0.002 mol/dm3…0.02 mol/dm3
aqueous solution concentration range with 0.002,
0.005, 0.01, 0.015, and 0.02 mol amino acid /dm3
water solutions, cc. 2 cm3/min volumetric stream.
The 60°C isotherm measurement went on jacketed
glass column equipped with plunger with 147 mm
packing length and ID 12 mm similarly to the
measurement at 20°C. L-phenylalanine was
detected at 271 nm, glycine at 230 nm by UV-
spectrophotometer. The equilibrium isotherms of
DL-β-phenylalanine were measured in ion-
exchanged water, further in 0.25 and 1 mol NaCl /
dm3 aqueous solutions. Equilibrium data were used
for planning processing parameters and
mathematical models.

Description of production-scale SMB-LC and
small-laboratory SMB-LC equipments

There are geometric and other parameters of the 4-
column production scale SMB-LC equipment
being constructed by the Central Workshop of
University of Veszprém: column number is four
and made of stainless steel. Useful column length:
500 mm, ID 50 mm. Special hole-channel system
and 50 µm stainless steel fritts assure liquid
distribution and collection on the full cross-section.
Columns are supplied with stainless steel
thermostable jacket. Joining pipes are 1/8’’ made
of stainless steel. For switching time controlling of
input and output sites 4 pieces of 4-way 5 set and 4
pieces of 2 way 3 set cocks were built in. Above
all, there are 2 pieces of 2 ways 3 set deairation
cocks built in for removing air from pump outputs.

The two input streams are assured by membrane
pumps in 0-250 ml/min region; output streams are
forwarded by two plunger type pumps. Pumps are
placed on separate scaffolds. The third output
point, where regenerated solvent is taken away in
the four-zone running, is open to the atmosphere
without recirculation. There are the working
parameters of the 4-column SMB-LC: a four-zone
1-1-1-1-column configuration and a 3-zone 1-1-2-
0, 2-1-1-0 and 1-2-1-0 column configuration. The
listed working methods have been built in the
program of the PLC controlled automation.

The six-column, three-zone small-laboratory
SMB-LC was built of six glass columns of equal
geometry, with packing length of 127 mm and with
inner diameter of 13 mm, a six-position low
pressure multifunction valve, a time actuator and
Teflon pipes. The upper part of the valve is fixed
through which the inlet of the sample and the eluent
is carried out. The lower part is the rotating one
which revolves along with the columns by a column
position in every given time interval (Fig. 2.)

Figure 2. Photography of a) production scale SMB and b)
small-lab SMB equipment.

Parameters of SMB-LC measurements

The L-phenylalanine – glycine – water separation
was carried out on the production scale SMB
equipment (AA03, AA06). The initial experiment at
20°C, later on at 60°C was improved with the help
of the equilibrium cascade model. The
desalinization process of DL-β-phenylalanine was
carried out on the small-lab scale SMB (SMB 3, 4,
5) unit. We varied the flow streams of eluent, feed,
raffinate, extract and the switching time (Table I.)

a) b)

27
Table I. Operating conditions of desalting of phenylalanine with the small-laboratory scale six-column SMB (SMB3, SMB4,

SMB5), and of phenylalanine-glycine separation with the preparative four-column SMB (AA03, AA06).

Column configuration Temperature T D E F R
Phe NaCl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min)

Column configuration Temperature T D E F LROUT
Phe NaCl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min)

AA06 3.3 1.5 2:1:1:0 43.5 78.8

cF (g/dm
3)

20.3 60.6

60°C 30 237.4 202.1

AA03 3.3 1.5 2:1:1:0 20°C 45 241.9 201.6

1.21 5.11

Prep.
SMB

0.83 3.93

SMB5 3.5 58.5 2:2:2 20°C 12.5 6.95 3.06

20°C 15 5.55 2.45SMB4 3.5 58.5 2:2:2

1.23 0.33 1.962:2:2 20°C 26 2.86

cF (g/dm
3)

SMB3 3.5 58.5

Small lab
SMB

SMB product stream analysis

Production scale SMB unit – phenylalanine –
glycine separation: Both extract and raffinate were
collected in separate reservoir by switching times.
After shaking it, sample was taken out of the
reservoirs and analyzed by AminoChromII OE914
amino acid analyzer. Over the average sample, part
sample was taken in the last switching time by a
given periodicity to examine concentration
transient within cycle [quasi-stationary state]. Half
a minute sample was taken in every 7 minutes at
the 20°C measurement, at 60°C first in the second
minute, then by 5 minutes.

Summarizing the amino acid analysis: glycine
and L-phenylalanine were separated on high
efficiency Durrum DC-4A cation exchange column
at constant pH and ion strength. Components
leaving the column were mixed with ninhydrine
reagent and reacted in capillary pipe reactor at 80
°C for ca. 10 min, the forming colorful products
were detected by spectrophotometer at 570 nm.
After proper dilution the samples were injected by
automatic injector from the 30 µl loop (extract was
not diluted, raffinate and feed in 5 times dilution).
Used eluent pH is 4.25, ion strength is 0.2, volume
stream is 20 ml/hour. Ninhydrine volume stream is
10 ml/hour. Amino acid content of the sample is
proportional to the area beneath the
chromatographic peak. Amino acid mixture was
used as calibrating standard with 0.0005 mol/l
amino acid concentration. The analysis time was
ca. 25 min/sample.

Small-lab SMB unit – phenylalanine desalting:
both in extract and raffinate stream on-line UV
detection of amino acid at 271 nm wavelength. Salt
detection: on-line by conductivity meter with
flowing-through cuvette.

Results

Packing selection

Frontal measurements were evaluated by the next
capacity relation:

NaCl

NaClaminoacid'

V
VV

k
−

= (4)

Dead volume (VNaCl) was defined by 1 mol
NaCl/dm3 water injection (VNaCl). The following
capacity factors were given at 20°C for the selected
resins:

HP20 for desalinization: DL-phenylalanine
k’=4.20

SP825 for glycine-phenylalanine separation: L-
phenylalanine k’=12.99; glycine k’=0.73
(Table II.)

Table II. Capacity factors of the investigated resins.

NaCl Phe NaCl Phe

XAD7 123.00 3.00 13.80 29.30 1.12

58.40 3.00 13.80 23.40 0.70

58.40 3.00 13.80 23.80 0.72

HP2MG 58.50 2.70 12.10 33.20 1.74

58.50 3.22 12.10 21.00 0.74

XAD1180 58.50 2.70 14.00 62.90 3.49

58.50 3.22 14.00 56.00 3.00

HP20 58.50 2.70 12.50 75.30 5.02

58.50 3.22 12.50 65.00 4.20

Gly Phe Gly Phe

HP20 1.50 3.30 14.85 62.70 0.19 4.03

SP825 1.50 3.30 16.50 133.65 0.73 12.99

Adsorbent for Gly-
Phe separation

Sample composition
[g dm-3]

Volume/breaktrough
curve inflection point

[cm3]

Capacity
factor k'
Gly Phe

Capacity
factor

Adsorbent for Phe
desalinization

Sample composition
[g dm-3]

Volume/breaktrough
curve inflection point

[cm3]

Equilibrium measurement

L-phenylalanine and glycine adsorption on SP825
resin can be written by Langmuir equilibrium
isotherms. The amino acid isotherms at 20°C (Fig.
3.a):

Gly

Gly
Gly 0.9291c1

0.5344c
q

+
= and

Phe

Phe
Phe 0.1621c1

34.01c
q

+
= (5)

At 60°C:

Gly

Gly
Gly 0.9535c1

0.353c
q

+
= and

Phe

Phe
Phe 0.671c1

23.47c
q

+
= (6)

The unit of liquid phase concentrations (cPhe,
cGly) is mg amino acid/cm3 solution, the solid phase
concentrations (qPhe, qGly) are in mg amino acid/ g
dry resin. Rising temperature solid phase amino
acid quantity decreases.

0 0,5 1 1,5 2 2,5 3 3,5 4
c [mg amino acid/ml solution]

q
[m

g
am

in
o

ac
id

/g
d

ry
a

ds
or

be
nt

]

0,5

1,5

2,5

3,5

4,5

Phe t=20°C
Phe t=60°C
Gly t=20°C
Gly t=60°C

SEPABEADS

(a)

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0 0,005 0,01 0,015 0,02 0,025
c phenylalanine [mol/dm3]

q
ph

en
yl

al
an

in
e

[m
ol

/d
m

3 ]

DIAION HP20

(b)

Figure 3. a) Adsorption isotherms of glycine and of L-
Phenylalanine in aqueous solution at temperature 20°C and

60°C on SP825 resin. c: liquid phase amino acid concentration
in mg amino acid/ cm3 liquid, q: solid phase amino acid

concentration in mg amino acid/ g dry adsorbent. b) Isotherms
of DL-β-phenylalanine on HP20 resin. Langmuir parameters

depends on the NaCl concentration of the liquid phase: in
water (marker *): a=20.86, b=33.5; in 0.25 M NaCl solution
(marker +): a=22.37, b=32.1; in 1 M NaCl solution (marker

x): a=26.94, b= 32.8. The dimension of Langmuir-b
parameter: cm3 mmol-1. Langmuir-a is dimensionless.

The investigated adsorption of the DL-β-

phenylalanine in aqueous phase and in salt solution
on HP20 adsorbent can be characterized also by
Langmuir isotherms (Fig. 3.b). Increase of the
concentration of the salt solution means the DL-β-
phenylalanine concentration increase in the resin
phase. Taking into consideration the dependence of
the “a” parameter of the Langmuir equation on the
salt concentration it can be written as:

Phe

PhePheNaCl
Phe 32.8c1

20.86cc6.08c
q

+
+

= (7)

The concentration units are in mmol amino
acid/ ml solution (cNaCl, cPhe), respectively in mmol
amino acid/ ml packing total volume (qPhe).

Packing characteristics

SMB-LC columns were characterized by Na2SO4 –
water solution injection at different volumetric
streams. The production-scale SMB-columns
I.D.=50mm L=500mm were packed with 0.3 mm
particle diameter SP825 resin by water slurry
technique. Each column was filled with 265.0 g
SP825 adsorbent air dried till constant mass value.
For example the NTP of the column No.2. can be
determined with the following equation:

1.20350.0043u
50

NTP
+

= (8)

Unit of “u” : cm3/min mobile phase flow rate.
The NTP is defined with this equation for 500 mm
packing length. Overall porosity of columns were
determined by salt-solution injection and ε=0.59
value was received for all the four columns. The
bulk density value is 0.27 g dry resin/cm3 column
volume.
The NTP of the small-lab scale SMB packed with
16.0 g HP20 resin per column can be determined:

0.02910.00225v
125

NTP
0 +

= (9)

Unit of „v0” : mm/min mobile phase velocity.
Overall porosity: ε=0.71 .

Results of SMB-LC measurements

Results of measurement at 20°C on 2-1-1-0
column configuration of the production-scale four-
columns SMB unit: more than 99.9% m/m amino
acid purity in extract for L-phenylalanine and in
raffinate for glycine. The yields are over 99% for
both amino acids. Productivity depending on the
feed, volumetric velocity and concentration is
relatively low. L-phenylalanine productivity is
3.76 mg/g SP825/h, glycine productivity is 1.72
mg/g SP825/h (AA03 measurement).

In case of measurement at 60°C (AA06
measurement) on 2-1-1-0 column configuration the
feed volumetric velocity was increased from 25 to
45 ml/min, so productivity was increased 1.8 times
and less diluted product output was given. Values
of purity are over 99.9% m/m and the yields over
99% m/m. Desalting DL-β-phenylalanine (SMB 3,
4, 5 measurements): productivity for phenylalanine
was 0.67-2.3 mg/g HP20/h, yield 89-96% and
amino acid purity 98.5% m/m (Table III.)

Discussion

Planning of SMB-LC processing parameters

The task of the first zone in the 4 zone
recirculation SMB-LC is the regeneration of
adsorbent, namely the washing down and
desorption of the better binding component, till the
end of switching time. The second and third zones
are the separation zones. The less binding
component must be removed from the second zone
till the end of the switching time. The function of
the third zone is the retarding of the better binding
component on the stationary phase. In the fourth
zone a portion of the eluent is recovered purely, so
here the less adsorbing component is to be
adsorbed, retained. Because of the very weak
glycine respectively NaCl adsorption in this water
phase system, very low recirculation is possible –
not much more than empty volume liquid quantity
calculated from column total porosity. Thus, the
fourth zone was neglected and the work was
continued in the open three-zone SMB-LC system.

0 5 10 15 20 25

mII

m
II

Morbidelli triangle t=20°C
AA03 measurement t=20°C
Morbidelli triangle t=60°C
AA06 measurement t=60°C

(a)

0 5 10 15 20

mII

m
II

KPhe
mII=mIII
SMB3
SMB4
SMB5

(b)

Figure 4.The measurements points placed in the Morbidelli
triangle: a) phenylalanine-glycine separation at temperature

20°C (AA03) and 60°C (AA06) b) desalting of phenylalanine
(SMB 3, 4, 5).

30
Table III. Operation parameters of the SMB separations.

SMB3

SMB4

SMB5

Phenylalanine Glycine Phenylalanine Glycine Phenylalanine Glycine

AA03, t=20°C 3.760 1.724 >99.9 >99.9 >99.9 >99.9

AA06, t=60°C 8.130 3.697 >99.9 >99.9 >99.9 >99.9

Small lab SMB

Preparative SMB

Phenylalanine
95.58

89.072.302

Phenylalanine
98.34

98.5

98.21
Productivity [mg/gh] Purity [%] Yield [%]

Productivity [mg/gh] Purity [%] Yield [%]
Phenylalanine

0.667

1.645

Beside the prescribed purity and yield in
industrial production the productivity must be the
highest, the solvent use the less and adsorbent
utility is the best. The initial operating conditions
were planned with the help of Morbidelli’s
equilibrium method (Fig. 4.). The first parameters
can be improved, while increasing the feed value
or concentration. An obvious possibility is the
increase of all flow rates (eluent, feed, extract,
raffinate) proportionally and decrease the
switching time. We used this method for desalting
of DL-β-phenylalanine on the small-lab SMB.
There are kinetic limits of the flow rate increase
(Fig. 5.). Other possibility is to improve the
regeneration of the first zone for example by
increasing temperature. With this method less fresh
eluent is necessary, thus we can increase the feed
flow rate and so the productivity improves. By the
phenylalanine–glycine separation lower selectivity
was measured at higher temperature. The initial
steep of adsorption equilibrium isotherm
decreased, therefore L-phenylalanine desorption
went on easier. Thus the switching time could be
reduced from 45 min to 30 min, so feed stream was
increased from 20.3 ml/min to max. 43.5 ml/min.

Conclusions

We planned initial parameters with the help of
Morbidelli’s equilibrium method for SMB
separation in water of phenylalanine-glycine,
respectively phenylalanine–sodium-chloride model
systems on polymer adsorbents. We investigated
two ways to improve the productivity. The increase
of all flow streams and the decrease of period time
in the desalting of DL-β-phenylalanine is limited
by adsorption and desorption kinetics of the amino
acid: the productivity was increased 3 times, but

the yield decreased from 95.6% to 89% (SMB 3, 4,
5 measurements).

0 12.5 25 37.5 50 62.5 75 87.5

measurement time [min]

U
V

, c
on

du
ct

iv
ity

s
ig

na
l [

m
V

]

(a)

0 12.5 25 37.5 50 62.5 75 87.5

measurement time [min]

U
V

, c
on

du
ct

iv
ity

s
ig

na
l [

m
V

]

(b)

Figure 5. Measured concentration commensurable signals by

SMB5 experiment in a) raffinate and b) extract. Markers:
signal of phenylalanine (+) and signal of NaCl (*).

The phenylalanine–glycine SMB-LC system

temperature was risen from 20°C to 60°C (AA03,
AA06 measurements), thus productivity was
increased 1.8 times. Rising temperature gives
solution only for an optimal value because
application of ventiles, cocks, fittings, etc. is
limited by temperature.

SYMBOLS

D – flow rate of eluent (cm3/min)
E – flow rate of extract (cm3/min)
F – flow rate of feed to be separated (cm3/min)
T – period time or column switching time (min)
A – cross-section of the SMB-column (cm2)
L – column length (cm)
ε – overall porosity
mI, mII, mIII, mIV – Morbidelli’s parameters
KA, KB – equilibrium distribution coefficient
k’ – capacity factor
Vaminoacid, VNaCl – inflection point of the

breakthrough curve (cm3)
qPhe – phenylalanine concentration in stationary

phase (mg/g)
cPhe – phenylalanine concentration in mobile phase

(mg/cm3)
cNaCl – NaCl concentration in mobile phase

(mg/cm3)

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