- Email: [email protected]
Transport of basic amino acids through the ion-exchange membranes and their recovery by electrodialysis
Desalination 241 (2009) 86 90
Transport of basic amino acids through the ion-exchange membranes and their recovery by electrodialysis T.V. Eliseeva*, V.A. Shaposhnik, E.V. Krisilova, A.E. Bukhovets Voronezh State University, Universitetskaya pl., 1, Voronezh 394006, Russia Tel. +7 4732 789932; Fax +7 4732 789755; email: [email protected] Received 2 August 2007; revised 28 January 2008; accepted 4 February 2008
Abstract Transport of basic amino acids during the electrodialysis is studied and the procedures of their recovery from various mixtures are suggested. Peculiarities of basic amino acids transfer through the ion-exchange membranes are closely connected with their amphoteric nature and high values of isoelectric points in comparison with neutral amino acids. Dimensionless concentrations for the components of systems basic amino acid tartaric acid are calculated, the values of amino acid recovery are measured. The possibility of basic amino acids solutions demineralization using the method of electrodeionization is shown. Keywords: Basic amino acid; Ion-exchange membrane; Electrodialysis; Separation; Transport; Demineralization
1. Introduction Basic a-amino acids include lysine, ornithine, histidine and arginine. In the course of their synthesis by various methods such as microbiological, chemical synthesis and protein hydrolysis, one can obtain complex mixture of components, containing for example of microbiological synthesis mineral ions, sugars and possibly other non-target amino acids if the synthesis goes on another way. So one can find *Corresponding author.
the purposes: to provide demineralization of the solution, to separate sugars and byproduct amino acid as well. Some aspects of amino acids solutions demineralization in an electromembrane system have been considered earlier [1]. The necessary conditions of amino acids and sugars separation by electrodialysis have been suggested as well [1,2]. During the hydrolysis of proteins several amino acids are produced simultaneously that requires the recovery of individual components or modification of qualitative and quantitative composition of a mixture, pH adjustment, removal of impurities.
Presented at the Third Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Siofok, Hungary, 2–6 September 2007. 0011-9164/09/$– See front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2008.02.030
87
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
2. Experimental The amino acids used in our study are listed in Table 1. Distribution diagram for basic amino acid ionic forms (e.g., lysine) is shown in Fig. 1. This diagram permits to determine what forms of amino acid exist at a given pH value and to predict their transport through the membranes. The solutions of amino acids were analyzed by the method of spectrophotometry. The experiments were carried out in an ordinary laboratory seven-compartment cell with alternating cationand anion-exchange membranes MC-40 and MA-41 (UCC Ltd., Shchekinoazot, Russia). The base of the membrane MC-40 is strong
1.0 0.8
α
J.W. Traxler was the first who has separated groups of neutral, basic and acidic amino acids during the electrodialysis [3]. A single amino acid can be produced by the chemical synthesis, but in this case racemate is formed and the extraction of L-isomer is the important task of the process. It can be solved using the different solubility of some diastereoisomeric salts, for example with D-tartaric or L-tartaric acid. At the last stage of the process L-amino acid tartrate or bitartrate of is obtained and it is necessary to separate pure target product, i.e., L-amino acid. The main purpose of this work is to study basic amino acids transfer through the ion-exchange membranes in an electromembrane system with the subsequent application of the observed regularities in separation procedures development.
0.6
2+
±
–
0.4 0.2 0.0
0
2
4
6 pH
8
10
12
14
Fig. 1. Distribution diagram of lysine ionic forms in a solution at various pH values.
acidic cation-exchange resin, the base of the membrane MA-41 is strong basic anionexchange resin. Every compartment had separate input and output for a solution. The height of the compartments was 20 cm. The membrane effective area was 20 cm2. The electrodeionization of amino acids solutions was studied with utilization of the diluate compartments with the mixed bed consisting of the resins Diaion SK1A and SA10A (Mitsubishi) (Fig. 2). Electrodeionization uses benefits of ion-exchange resin, while eliminating the disadvantages of chemical regeneration. The conversion of amino acid tartrate or KNO3 AA MA
MC
MA
K NO3– 1
Table 1 Basic amino acids (Ajinomoto) characteristics
+
MC
+
K
NO3– 2
3
MA
MC
+
+
K
NO3– 4
5
6
7 H2O AA + KNO3
Amino acid
M
pI
pK1
pK2
pK3
Histidine Lysine Ornithine
155.16 146.19 132.16
7.60 9.74 9.74
1.77 2.18 1.94
6.00 8.95 8.65
9.17 10.50 10.76
Fig. 2. The scheme of the electrodeionization cell with alternating cation-exchange membranes MC-40 and anion-exchange membranes MA-41. 1 7, numbers of compartments; MC, cation-exchange membrane; MA, anion-exchange membrane; AA, amino acid.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
88
AA
10.0
H2Tart
1:2 MB
MC
MB
MC
+
OH
+
H
9.8
MC
+
AA –
MB AA
–
OH
+
H
2:3
9.6 –
OH
+
H
9.4 2
3
4
5
6
7
pH
1
H2O
9.2
3:2
Tart(Bitart)
9.0
Fig. 3. The scheme of the electrodialysis cell with alternating cation-exchange membranes MC-40 and bipolar membranes MB-3. 1 7, numbers of compartments; MC, cation-exchange membrane; MB, bipolar membrane, Tart(Bitart), basic amino acid tartrate or bitartrate.
bitartrate into free amino acid was carried out in the electrodialysis cell with alternating bipolar membranes MB-3 (UCC Ltd.) and monopolar membranes MC-40 (Fig. 3). Bipolar membrane MB-3 is produced using cation-exchange resin with phosphonic groups and strong basic anionexchange resin. 3. Results and discussion The possibilities and conditions of basic amino acids solutions demineralization have been studied during the electrodeionization in the cell shown in Fig. 2. Similar research was done by us for the neutral amino acids [4], electrodeionization of basic amino acids solutions was not described in literature. The solution (0.01 M KNO30.025 M lysine) was fed into dilute compartments with linear velocity 1103 m/s. The main task of the experiments is the choice of the mixed bed composition that would permit to reach the maximum degree of desalinaton at minimum losses of basic amino acid. The pH value of solution is the main factor that has influence on the losses of lysine during the electrodeionization, because pH determines the proportion of particles with different charge that are able to electromigration. Changes of mixed bed composition allow the /
/
2:1
8.8 8.6
0
5
10
15 20 i (A/m2)
25
30
Fig. 4. The dependence of pH value in the dilute compartment on the current density (i ) at various volume ratio of cation-exchange resin (c) to anionexchange resin (a) in the mixed bed.
control of pH value without adding of other electrolytes ions. Fig. 4 shows the dependence of pH in dilute compartment on the current density at various ratio of cation-exchange resin to anionexchange resin in the mixed bed. The increase of the anion-exchange resin fraction in the mixed bed leads to pH value rise; also one can observe the slight rise of pH with an increase of current density. Obviously, it is reasonable to choose pH value close to amino acid isoelectric point (pI in Table1). Optimal ratio of cation-exchange resin to anion-exchange resin in the mixed bed is 1:2, it provides minimal losses of the product. The dependence of desalination degree on the current density at the ratio of cation-exchange resin to anion-exchange resin 1:2 is shown in Fig. 5, for the individual solution of KNO3 and for the lysine-KNO3 mixture. The comparison of desalination effectiveness for KNO3 solution and KNO3 lysine solution shows that amino acid presence in the solution decreases the effectiveness from 9598% to 85 92% at optimal composition of the mixed bed.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690 1.00 1
1-Ci/C0
0.95
2
0.90 0.85 0.80 0.75 5
0
10
15 20 i (A/m2)
25
30
Fig. 5. The dependence of desalination degree on the current density (the measured value *concentration of NO3 ions). (1) KNO3 solution; (2) KNO3-lysine solution.
The reason of mineral ions fluxes decrease is participation of amino acid in the current transfer. (For pHpI9.74 along with bipolar ions one can find cations and anions of lysine in the solution which can migrate in the electric field). The dependence of lysine flux through the cation-exchange membrane MC-40 on the current density is shown in the Fig. 6 for the ratio of cation-exchange resin to anion-exchange resin /
/
J (10–5 mol/m2s)
4
3
2
1
0
0
5
10
15 20 i (A/m2)
25
30
Fig. 6. The dependence of lysine flux through the cation-exchange membrane on the current density.
89
1:2. Its form remains the same as in the cell with “empty” compartments [1]. In order to increase the effectiveness of desalination for industrial application it is necessary to use the experience of optimization which is known for ultra pure water production. Particularly, one can increase the height of the compartments, to optimize velocity of the solution in concentrating compartments or to increase intermembrane distance [5,6]. Another task of this work is to study basic amino acid recovery from solution of its tartaric salt. That procedure is necessary at the final stage of chemical synthesis during the process of racemate separation. The optimal conditions of amino acid recovery by electrodialysis correspond to intensive current regime when the facilitated electromigration of ampholytes takes place [1]. Besides, generation of hydrogen ions by bipolar membranes leads to the additional quantity of amino acid cations, which transfer through the cation-exchange membranes. The experiments with basic amino acids tartrates and bitartrates were carried out in the cell shown in Fig. 3. We fed the salt solution into the even compartments 2 and 4 and water into non-even compartments. The solutions at the outlet of the compartments 3 and 5 were analyzed. The pH values of the feed solutions are ornithine tartrate, pH 4.72; lysine tartrate, pH 6.50; ornithine bitartrate, pH 3.20; lysine bitartrate, pH 3.55 and histidine bitartrate, pH 3.50. Fig. 7 shows the dependences of basic amino acids dimensionless concentration for the diluate compartment on the current density during the electrodialysis of bitartrates and tartrates. The pH values of tartrates solutions are higher (4.5 6.0) than for the corresponding bitartrates (3.0 3.6). Fluxes of basic amino acids through the cation-exchange membranes are more from tartrates solutions because in the case of bitartrates high competitive transfer of hydrogen ions takes place.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
90
1.00
6
C i/C0
0.75
0.50 5 0.25
0.00 0
40
80 i (A/m2)
120
4 3 2 1 160
which can be returned to the stage of racemate separation. Peculiarities of basic amino acids transport through the ion-exchange membranes deal with their amphoteric nature and high values of isoelectric points in comparison with neutral amino acids. The obtained regularities during the electrodialysis can be effectively used for basic amino acids recovery from various mixtures. References
Fig. 7. The dependence of dimensionless concentration (Ci/C0) for (1,3) ornithine, (2,4) lysine, (5) histidine and (6) tartrate ions on the current density during the electrodialysis of salt solutions in the cell shown in Fig. 3. (1,2) Tartrates, (3 5) bitartrates (the initial concentration of all amino acids is 0.01 M).
[1]
We have calculated the values of recovery as the ratio of amino acid concentration in permeate to the initial concentration. The results for the current density 150 A/m2 are ornithine tartrate, 0.98; lysine tartrate, 0.90; ornithine bitartrate, 0.82; lysine bitartrate, 0.79 and histidine bitartrate, 0.63. The experiments allow to obtain pure amino acid in permeate and tartaric acid in retentate,
[4]
[2]
[3]
[5]
[6]
T.V. Eliseeva, V.A. Shaposhnik and I.G. Luschik, Desalination, 149 (2002) 405 409. T.V. Eliseeva, A.Yu. Tekuchev, V.A. Shaposhnik and I.G. Luschik. Russ. J. Electrochem., 37 (2001) 423 426. J.W. Traxler, U.S. Patent. 3051640, Filed 02.09.1959, Patented 28.08.1962. I.G. Luschik, T.V. Eliseeva and V.A. Shaposhnik, Sorb. and Chromatograph. Prots., 3 (2003) 722 730. V.A. Shaposhnik, A.K. Reshetnikova, R.I. Zolotareva, I.V. Drobisheva and N.I. Isaev, Russ. J. Appl. Chem., 46 (1973) 2569 2663. A. Dey and G. Thomas, Electronics Grade Water Preparation, Tall Oaks Publishing Inc., Littleton, 427pp.
Transport of basic amino acids through the ion-exchange membranes and their recovery by electrodialysis T.V. Eliseeva*, V.A. Shaposhnik, E.V. Krisilova, A.E. Bukhovets Voronezh State University, Universitetskaya pl., 1, Voronezh 394006, Russia Tel. +7 4732 789932; Fax +7 4732 789755; email: [email protected] Received 2 August 2007; revised 28 January 2008; accepted 4 February 2008
Abstract Transport of basic amino acids during the electrodialysis is studied and the procedures of their recovery from various mixtures are suggested. Peculiarities of basic amino acids transfer through the ion-exchange membranes are closely connected with their amphoteric nature and high values of isoelectric points in comparison with neutral amino acids. Dimensionless concentrations for the components of systems basic amino acid tartaric acid are calculated, the values of amino acid recovery are measured. The possibility of basic amino acids solutions demineralization using the method of electrodeionization is shown. Keywords: Basic amino acid; Ion-exchange membrane; Electrodialysis; Separation; Transport; Demineralization
1. Introduction Basic a-amino acids include lysine, ornithine, histidine and arginine. In the course of their synthesis by various methods such as microbiological, chemical synthesis and protein hydrolysis, one can obtain complex mixture of components, containing for example of microbiological synthesis mineral ions, sugars and possibly other non-target amino acids if the synthesis goes on another way. So one can find *Corresponding author.
the purposes: to provide demineralization of the solution, to separate sugars and byproduct amino acid as well. Some aspects of amino acids solutions demineralization in an electromembrane system have been considered earlier [1]. The necessary conditions of amino acids and sugars separation by electrodialysis have been suggested as well [1,2]. During the hydrolysis of proteins several amino acids are produced simultaneously that requires the recovery of individual components or modification of qualitative and quantitative composition of a mixture, pH adjustment, removal of impurities.
Presented at the Third Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Siofok, Hungary, 2–6 September 2007. 0011-9164/09/$– See front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2008.02.030
87
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
2. Experimental The amino acids used in our study are listed in Table 1. Distribution diagram for basic amino acid ionic forms (e.g., lysine) is shown in Fig. 1. This diagram permits to determine what forms of amino acid exist at a given pH value and to predict their transport through the membranes. The solutions of amino acids were analyzed by the method of spectrophotometry. The experiments were carried out in an ordinary laboratory seven-compartment cell with alternating cationand anion-exchange membranes MC-40 and MA-41 (UCC Ltd., Shchekinoazot, Russia). The base of the membrane MC-40 is strong
1.0 0.8
α
J.W. Traxler was the first who has separated groups of neutral, basic and acidic amino acids during the electrodialysis [3]. A single amino acid can be produced by the chemical synthesis, but in this case racemate is formed and the extraction of L-isomer is the important task of the process. It can be solved using the different solubility of some diastereoisomeric salts, for example with D-tartaric or L-tartaric acid. At the last stage of the process L-amino acid tartrate or bitartrate of is obtained and it is necessary to separate pure target product, i.e., L-amino acid. The main purpose of this work is to study basic amino acids transfer through the ion-exchange membranes in an electromembrane system with the subsequent application of the observed regularities in separation procedures development.
0.6
2+
±
–
0.4 0.2 0.0
0
2
4
6 pH
8
10
12
14
Fig. 1. Distribution diagram of lysine ionic forms in a solution at various pH values.
acidic cation-exchange resin, the base of the membrane MA-41 is strong basic anionexchange resin. Every compartment had separate input and output for a solution. The height of the compartments was 20 cm. The membrane effective area was 20 cm2. The electrodeionization of amino acids solutions was studied with utilization of the diluate compartments with the mixed bed consisting of the resins Diaion SK1A and SA10A (Mitsubishi) (Fig. 2). Electrodeionization uses benefits of ion-exchange resin, while eliminating the disadvantages of chemical regeneration. The conversion of amino acid tartrate or KNO3 AA MA
MC
MA
K NO3– 1
Table 1 Basic amino acids (Ajinomoto) characteristics
+
MC
+
K
NO3– 2
3
MA
MC
+
+
K
NO3– 4
5
6
7 H2O AA + KNO3
Amino acid
M
pI
pK1
pK2
pK3
Histidine Lysine Ornithine
155.16 146.19 132.16
7.60 9.74 9.74
1.77 2.18 1.94
6.00 8.95 8.65
9.17 10.50 10.76
Fig. 2. The scheme of the electrodeionization cell with alternating cation-exchange membranes MC-40 and anion-exchange membranes MA-41. 1 7, numbers of compartments; MC, cation-exchange membrane; MA, anion-exchange membrane; AA, amino acid.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
88
AA
10.0
H2Tart
1:2 MB
MC
MB
MC
+
OH
+
H
9.8
MC
+
AA –
MB AA
–
OH
+
H
2:3
9.6 –
OH
+
H
9.4 2
3
4
5
6
7
pH
1
H2O
9.2
3:2
Tart(Bitart)
9.0
Fig. 3. The scheme of the electrodialysis cell with alternating cation-exchange membranes MC-40 and bipolar membranes MB-3. 1 7, numbers of compartments; MC, cation-exchange membrane; MB, bipolar membrane, Tart(Bitart), basic amino acid tartrate or bitartrate.
bitartrate into free amino acid was carried out in the electrodialysis cell with alternating bipolar membranes MB-3 (UCC Ltd.) and monopolar membranes MC-40 (Fig. 3). Bipolar membrane MB-3 is produced using cation-exchange resin with phosphonic groups and strong basic anionexchange resin. 3. Results and discussion The possibilities and conditions of basic amino acids solutions demineralization have been studied during the electrodeionization in the cell shown in Fig. 2. Similar research was done by us for the neutral amino acids [4], electrodeionization of basic amino acids solutions was not described in literature. The solution (0.01 M KNO30.025 M lysine) was fed into dilute compartments with linear velocity 1103 m/s. The main task of the experiments is the choice of the mixed bed composition that would permit to reach the maximum degree of desalinaton at minimum losses of basic amino acid. The pH value of solution is the main factor that has influence on the losses of lysine during the electrodeionization, because pH determines the proportion of particles with different charge that are able to electromigration. Changes of mixed bed composition allow the /
/
2:1
8.8 8.6
0
5
10
15 20 i (A/m2)
25
30
Fig. 4. The dependence of pH value in the dilute compartment on the current density (i ) at various volume ratio of cation-exchange resin (c) to anionexchange resin (a) in the mixed bed.
control of pH value without adding of other electrolytes ions. Fig. 4 shows the dependence of pH in dilute compartment on the current density at various ratio of cation-exchange resin to anionexchange resin in the mixed bed. The increase of the anion-exchange resin fraction in the mixed bed leads to pH value rise; also one can observe the slight rise of pH with an increase of current density. Obviously, it is reasonable to choose pH value close to amino acid isoelectric point (pI in Table1). Optimal ratio of cation-exchange resin to anion-exchange resin in the mixed bed is 1:2, it provides minimal losses of the product. The dependence of desalination degree on the current density at the ratio of cation-exchange resin to anion-exchange resin 1:2 is shown in Fig. 5, for the individual solution of KNO3 and for the lysine-KNO3 mixture. The comparison of desalination effectiveness for KNO3 solution and KNO3 lysine solution shows that amino acid presence in the solution decreases the effectiveness from 9598% to 85 92% at optimal composition of the mixed bed.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690 1.00 1
1-Ci/C0
0.95
2
0.90 0.85 0.80 0.75 5
0
10
15 20 i (A/m2)
25
30
Fig. 5. The dependence of desalination degree on the current density (the measured value *concentration of NO3 ions). (1) KNO3 solution; (2) KNO3-lysine solution.
The reason of mineral ions fluxes decrease is participation of amino acid in the current transfer. (For pHpI9.74 along with bipolar ions one can find cations and anions of lysine in the solution which can migrate in the electric field). The dependence of lysine flux through the cation-exchange membrane MC-40 on the current density is shown in the Fig. 6 for the ratio of cation-exchange resin to anion-exchange resin /
/
J (10–5 mol/m2s)
4
3
2
1
0
0
5
10
15 20 i (A/m2)
25
30
Fig. 6. The dependence of lysine flux through the cation-exchange membrane on the current density.
89
1:2. Its form remains the same as in the cell with “empty” compartments [1]. In order to increase the effectiveness of desalination for industrial application it is necessary to use the experience of optimization which is known for ultra pure water production. Particularly, one can increase the height of the compartments, to optimize velocity of the solution in concentrating compartments or to increase intermembrane distance [5,6]. Another task of this work is to study basic amino acid recovery from solution of its tartaric salt. That procedure is necessary at the final stage of chemical synthesis during the process of racemate separation. The optimal conditions of amino acid recovery by electrodialysis correspond to intensive current regime when the facilitated electromigration of ampholytes takes place [1]. Besides, generation of hydrogen ions by bipolar membranes leads to the additional quantity of amino acid cations, which transfer through the cation-exchange membranes. The experiments with basic amino acids tartrates and bitartrates were carried out in the cell shown in Fig. 3. We fed the salt solution into the even compartments 2 and 4 and water into non-even compartments. The solutions at the outlet of the compartments 3 and 5 were analyzed. The pH values of the feed solutions are ornithine tartrate, pH 4.72; lysine tartrate, pH 6.50; ornithine bitartrate, pH 3.20; lysine bitartrate, pH 3.55 and histidine bitartrate, pH 3.50. Fig. 7 shows the dependences of basic amino acids dimensionless concentration for the diluate compartment on the current density during the electrodialysis of bitartrates and tartrates. The pH values of tartrates solutions are higher (4.5 6.0) than for the corresponding bitartrates (3.0 3.6). Fluxes of basic amino acids through the cation-exchange membranes are more from tartrates solutions because in the case of bitartrates high competitive transfer of hydrogen ions takes place.
T.V. Eliseeva et al. / Desalination 241 (2009) 8690
90
1.00
6
C i/C0
0.75
0.50 5 0.25
0.00 0
40
80 i (A/m2)
120
4 3 2 1 160
which can be returned to the stage of racemate separation. Peculiarities of basic amino acids transport through the ion-exchange membranes deal with their amphoteric nature and high values of isoelectric points in comparison with neutral amino acids. The obtained regularities during the electrodialysis can be effectively used for basic amino acids recovery from various mixtures. References
Fig. 7. The dependence of dimensionless concentration (Ci/C0) for (1,3) ornithine, (2,4) lysine, (5) histidine and (6) tartrate ions on the current density during the electrodialysis of salt solutions in the cell shown in Fig. 3. (1,2) Tartrates, (3 5) bitartrates (the initial concentration of all amino acids is 0.01 M).
[1]
We have calculated the values of recovery as the ratio of amino acid concentration in permeate to the initial concentration. The results for the current density 150 A/m2 are ornithine tartrate, 0.98; lysine tartrate, 0.90; ornithine bitartrate, 0.82; lysine bitartrate, 0.79 and histidine bitartrate, 0.63. The experiments allow to obtain pure amino acid in permeate and tartaric acid in retentate,
[4]
[2]
[3]
[5]
[6]
T.V. Eliseeva, V.A. Shaposhnik and I.G. Luschik, Desalination, 149 (2002) 405 409. T.V. Eliseeva, A.Yu. Tekuchev, V.A. Shaposhnik and I.G. Luschik. Russ. J. Electrochem., 37 (2001) 423 426. J.W. Traxler, U.S. Patent. 3051640, Filed 02.09.1959, Patented 28.08.1962. I.G. Luschik, T.V. Eliseeva and V.A. Shaposhnik, Sorb. and Chromatograph. Prots., 3 (2003) 722 730. V.A. Shaposhnik, A.K. Reshetnikova, R.I. Zolotareva, I.V. Drobisheva and N.I. Isaev, Russ. J. Appl. Chem., 46 (1973) 2569 2663. A. Dey and G. Thomas, Electronics Grade Water Preparation, Tall Oaks Publishing Inc., Littleton, 427pp.