3
[m3/h] vv 30000. 20000. 10000- Formelzeichen Abb. 3. nete und experimentelle Werte). Abhangigkeit des Volumenstromes vom Druck p1 (berech- (p in kp/m2, in m3/h). p2 bzw. p; wurden durch Ausgleichsrech- nung zu 223,4 und 190,l ermittelt. Mit den an einem groBtechnischen Rohrleitungssystem zum Trans- port von Rohgas durchgefuhrten Untersuchungen wurde nachgewie- sen, daB durch Laufzeitmessungen mit Hilfe von Radionukliden der Volumenstrom in Abhangigkeit von der alternierenden Belastung be- stimmt werden kann. Es besteht zudem eine Korrelation zwischen dem Volumenstrom und dem Druck am Eingang des Rohrleitungssy- stems (Berechnung der Korrelationskoeffizienten, Ermittlung iiber den klassischen Weg des Druckverlustes in Rohrleitungen). Durch Kalibrierung der Druckmessung p1 (an M1) in Volumenstromeinhei- ten ergibt sich damit fur die Kohledruckvergasung in Abhangigkeit von der Generator-Betriebsweise die Moglichkeit der Bilanzie- rung. Eingegangen am 25. Mai 1987 [K 9071 - C %ax K, K* L M(l-3) n P r Re 'a tpax V [m/sI mittlere Stromungsgeschwindigkeit [m/sI Stromungsgeschwindigkeit in Rohrmitte [ml MeBstreckenlange Konstanten MeBstellen Exponent [kp/m21 Druck an MeBstelle M [mml Rohrradius [SI [SI [m3/h] Volumenstrom Reynolds-Zahl Laufzeit am Beginn des Zahlratenanstieges Laufzeit im Maximum der Zahlraten Literatur [l] Merz, A , ; Vogg, H.: Chem.-1ng.-Tech. 50 (1978) S. 108. [2] Charlton, J. S.: IAEA-CN-40/110, Grenoble 1981. [3] Braun, H.: VDI-Z. 123 (1981) S. 601. [4] Konnecke, H.-G.; Otto, R.; Hecht, P.: Wiss. Fortschr. 32 (1982) S. 109. [5] Konnecke, H.-G.; Luther, D., et al.: Erdol Kohle, Erdgas, Petro- chem. 39 (1986) S. 329. [6] Hengstenberg, J., et al.: Messen, Steuern und Regeln in der Che- mischen Technik, Springer-Verlag, Berlin 1980, 3. Aufl., Bd. 1. [7] DD-PS 236 988, 6. 5. 1985, Akademie der Wissenschaften der DDR (Konnecke, H.-G.; Luther, D.; Abendroth, H.-Chr.; Gleis- berg, F.; Schlegel, H.; Seifert, G.; Gaflner, W.; Allstadt, H.; Fraschke, D.; Schlanzke, G.). [8] Bohl, W.: Technische Stromungslehre, Vogel-Buchverlag, 6. Aufl., Wiirzburg 1984. Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis Michael Czytko, Kiyoshi lshii and Kimitoshi Kawai* 1 Introduction Today's world production of lactic acid is 30 000 t a-'. About half of it is L-lactic acid from glucose fermentation. The fermentation is carried out as a batch process, with low lactic acid productivities of 2-3 g 1-' h-l. CaC03 or Ca(OH), must be added to maintain the pH at 5 or 6. After completion of fermentation, Ca(OH), is added to raise the pH to 10. The broth is then heated and filtered. The filtrate is treated with activated carbon and concentrated by evaporation. Sulfuric acid is added, the calcium sulfate precipitate is filtered off, and the lactic acid filtrate goes on to a charcoal decolorization, and is then concentrated by acid evaporators [l]. The disadvantages of the fermentation pro- cess are the low reaction rate and the elaborate product recovery. The aim of our investigations was to overcome these disadvantages. We found that the process can be remarkably improved by fermenting glucose continuously and recovering lactic acid by electrodialysis. * Dr. M. Czytko, Hiils AG, Postfach, D-4370 Marl, and K. Ishii, K. Kawai, Daicel Chemical Industries, Ltd., AboshVJapan. 2 Apparatus and Materials The experimental set-up is shown in Fig. 1. The fermenter was a stirred tank of 1-2 1 volume. The cross section of the E D stack was 2 dm2. A strain of Lactobacillus casei was used as lactic acid producer. A con- centrated solution of 380 g I-' glucose, 10-110 g I-' yeast extract, and mineral salts were fed into the fermenter. The broth was recycled through an electrodialysis stack. Electrodialysis was used for acid re- covery and pH control. In the ED stack, lactate ions were removed and replaced by OH- ions just as fast as lactic acid was produced in the fermenter. The OH- ions were formed by water electrolysis in the cathode com- partment. At the anode, H+ ions were formed which migrated into compartment No. 2 to combine with lactate ions to form lactic acid. 3 Results and Discussion At the beginning of each fermentation the cells were grown batchwise, as shown in Fig. 2 fort = 0-9 h. The pH was maintained by adding NaOH. From t = 23 h the concentrated feed solution was pumped into the reactor, and the lactic acid formed was removed by electrodialysis. Productivity of lactic acid rose to 25 g I-' h-', due to increased cell density. The erratic shape of the glucose concentration curve was caused by trouble with the feed pump. The anion exchange mem- brane between compartment Nos. 3 and 4 was decomposed by the NaOH solution in compartment No. 4, and at t = 52 h the run had to be terminated. 952 Chem.-1ng.-Tech. 59 (1987) Nr. 12, S. 952-954 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1987 0009-286X/87/1212-0952 $ 02.50/0

Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis

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Page 1: Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis

[m3/h] vv 30000.

20000.

10000-

Formelzeichen

Abb. 3. nete und experimentelle Werte).

Abhangigkeit des Volumenstromes vom Druck p 1 (berech-

(p in kp/m2, in m3/h). p2 bzw. p; wurden durch Ausgleichsrech- nung zu 223,4 und 190,l ermittelt. Mit den an einem groBtechnischen Rohrleitungssystem zum Trans- port von Rohgas durchgefuhrten Untersuchungen wurde nachgewie- sen, daB durch Laufzeitmessungen mit Hilfe von Radionukliden der Volumenstrom in Abhangigkeit von der alternierenden Belastung be- stimmt werden kann. Es besteht zudem eine Korrelation zwischen dem Volumenstrom und dem Druck am Eingang des Rohrleitungssy- stems (Berechnung der Korrelationskoeffizienten, Ermittlung iiber den klassischen Weg des Druckverlustes in Rohrleitungen). Durch Kalibrierung der Druckmessung p1 (an M1) in Volumenstromeinhei- ten ergibt sich damit fur die Kohledruckvergasung in Abhangigkeit von der Generator-Betriebsweise die Moglichkeit der Bilanzie- rung.

Eingegangen am 25. Mai 1987 [K 9071

- C

%ax K , K* L M(l-3) n P r Re 'a tpax V

[m/sI mittlere Stromungsgeschwindigkeit [m/sI Stromungsgeschwindigkeit in Rohrmitte

[ml MeBstreckenlange Konstanten

MeBstellen Exponent

[kp/m21 Druck an MeBstelle M [mml Rohrradius

[SI

[SI [m3/h] Volumenstrom

Reynolds-Zahl Laufzeit am Beginn des Zahlratenanstieges Laufzeit im Maximum der Zahlraten

Literatur

[l] Merz, A , ; Vogg, H.: Chem.-1ng.-Tech. 50 (1978) S. 108. [2] Charlton, J. S.: IAEA-CN-40/110, Grenoble 1981. [3] Braun, H.: VDI-Z. 123 (1981) S. 601. [4] Konnecke, H.-G.; Otto, R.; Hecht, P.: Wiss. Fortschr. 32 (1982)

S. 109. [5] Konnecke, H.-G.; Luther, D., et al.: Erdol Kohle, Erdgas, Petro-

chem. 39 (1986) S. 329. [6] Hengstenberg, J., et al.: Messen, Steuern und Regeln in der Che-

mischen Technik, Springer-Verlag, Berlin 1980, 3. Aufl., Bd. 1. [7] DD-PS 236 988, 6. 5. 1985, Akademie der Wissenschaften der

DDR (Konnecke, H.-G.; Luther, D.; Abendroth, H.-Chr.; Gleis- berg, F.; Schlegel, H.; Seifert, G.; Gaflner, W.; Allstadt, H.; Fraschke, D.; Schlanzke, G . ) .

[8] Bohl, W.: Technische Stromungslehre, Vogel-Buchverlag, 6. Aufl., Wiirzburg 1984.

Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis

Michael Czytko, Kiyoshi lshii and Kimitoshi Kawai*

1 Introduction

Today's world production of lactic acid is 30 000 t a-'. About half of it is L-lactic acid from glucose fermentation. The fermentation is carried out as a batch process, with low lactic acid productivities of 2-3 g 1-' h-l. CaC03 or Ca(OH), must be added to maintain the pH at 5 or 6. After completion of fermentation, Ca(OH), is added to raise the pH to 10. The broth is then heated and filtered. The filtrate is treated with activated carbon and concentrated by evaporation. Sulfuric acid is added, the calcium sulfate precipitate is filtered off, and the lactic acid filtrate goes on to a charcoal decolorization, and is then concentrated by acid evaporators [l]. The disadvantages of the fermentation pro- cess are the low reaction rate and the elaborate product recovery. The aim of our investigations was to overcome these disadvantages. We found that the process can be remarkably improved by fermenting glucose continuously and recovering lactic acid by electrodialysis.

* Dr. M . Czytko, Hiils AG, Postfach, D-4370 Marl, and K . Ishii, K . Kawai, Daicel Chemical Industries, Ltd., AboshVJapan.

2 Apparatus and Materials

The experimental set-up is shown in Fig. 1. The fermenter was a stirred tank of 1-2 1 volume. The cross section of the E D stack was 2 dm2. A strain of Lactobacillus casei was used as lactic acid producer. A con- centrated solution of 380 g I-' glucose, 10-110 g I-' yeast extract, and mineral salts were fed into the fermenter. The broth was recycled through an electrodialysis stack. Electrodialysis was used for acid re- covery and pH control. In the E D stack, lactate ions were removed and replaced by OH- ions just as fast as lactic acid was produced in the fermenter. The OH- ions were formed by water electrolysis in the cathode com- partment. At the anode, H+ ions were formed which migrated into compartment No. 2 to combine with lactate ions to form lactic acid.

3 Results and Discussion

At the beginning of each fermentation the cells were grown batchwise, as shown in Fig. 2 for t = 0-9 h. The pH was maintained by adding NaOH. From t = 23 h the concentrated feed solution was pumped into the reactor, and the lactic acid formed was removed by electrodialysis. Productivity of lactic acid rose to 25 g I-' h-', due to increased cell density. The erratic shape of the glucose concentration curve was caused by trouble with the feed pump. The anion exchange mem- brane between compartment Nos. 3 and 4 was decomposed by the NaOH solution in compartment No. 4, and at t = 52 h the run had to be terminated.

952 Chem.-1ng.-Tech. 59 (1987) Nr. 12, S. 952-954 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1987 0009-286X/87/1212-0952 $ 02.50/0

Page 2: Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis

Productivity --1

I I I I I I

I I

- - - - - - - -

glucose yeast extract mineral salts __-- - drain I

I

f ermenter

I I I I ED-stack

1j f broth ermentation

C: cation exchange membrane lactic A=anlon ,,

'hsLp-LI

Fig. 1. Continuous fermentation with lactic acid recovery.

In successive runs, productivities of up to 35 g I-' h-' were observed. The current efficiency was 90-96 %. Lactic acid was withdrawn from the solution recycled through compartment No. 2. Its concentration was 300 g 1-1 or more. The high reaction rate corresponds to observations made by Vick Roy [2], who found up to 70 g I-' h-' in continuous fermentation with cell recycle. When an alkali-resistant anion exchange membrane was used for the cathode compartment, experiments running over several weeks could be performed. We were surprised by the observation that no special effort was necessary to keep the system free of contaminating microorganisms. During the initial growth period of each run ( t = 0-9 h in Fig. 2) the system was operated under sterile conditions, but afterwards continu- ous fermentation and acid recovery by electrodialysis were carried out in non-sterile manner. However, no contaminating microorganisms could be detected in the broth. In one experiment a single charge of bacteria was used over five weeks. No alien bacteria were found on microscopic examination, and the lactic acid withdrawn was free of acetic and butyric acid. When the ED was switched off before termination of the run and the lactic acid produced was neutralized by addition of NaOH, some alien organ- isms could be detected. The bactericidal effect of electric fields has been described in the lit- erature [3]. The E D system seems to selectively inactivate contami- nating organisms. A simple explanation for this phenomenon might be that only lactic acid bacteria grow fast enough to overcome the kill- ing rate of the ED, since conditions favour their growth. The growth rates of contaminating organisms are too low. In continuous operation a steady increase in electrical resistance was observed. After 30-100 h the resistance was too high for further op- eration, due to deposition of bacteria on the membrane between com- partment No. 2 and 3. The membrane had to be replaced. Non-ionic surfactants like Baker's Triton XlOO are known to prevent attachment of bacteria to polystyrene [4]. Triton XlOO was introduced into the fermentation broth, up to a concentration of 100 ppm, but an increase in electrical resistance was still observed. Deposits were no longer found on the membrane, but the bacteria formed clusters in the spacer between the membranes.

I I A g Lactic acid I I I

I I I d I I

I f I / "

I 1 I

I I I I I

I I I

I

20 - I I I I I

10 - I I I

I I

I I

0' I

I 40 I 50 t /h I I I

0 7' I

0 110 30 I

Concentration I

I overnightstop1 continuous I fermentation

0 10 20 30 40 50 t/h @cam

Fig. 2 . Continuous glucose fermentation, T = 42 OC, pH 6.

The electrodialysis unit could only be operated with cell-free solu- tions. The cells had to be filtered by microfiltration and recycled, as shown in Fig. 3. The fermenter concentrations of a typical run are shown in Fig. 4. Cell density was ca. 17 g I-', glucose was ca. 6 g I-], sodium lactate 41 g I-' (as lactic acid), and sodium pyruvate 0,05 g I-' (as pyruvic acid). Except for the changes in cell density all other concentrations were nearly at steady state.

I I I I

yeast extract I mineral salts

I I

f '.t, er men ter MF -module drain, H Ac-\---

ED -stack

C =cation exchange membrane A=anion

lactic acid

Fig. 3. Continuous operation with cell recycle.

Chem.-1ng.-Tech. 59 (1987) Nr. 12, S. 952-954 953

Page 3: Continuous Glucose Fermentation for Lactic Acid Production: Recovery of Acid by Electrodialysis

- ~

A+*- 100 x pytuvic acid

0 16.9 1 4 9 20.9 22,9 t / h

rn

Fig. 4. Continuous fermentation with cell recycle, steady state con- centrations in the fermenter.

The driving force for lactate transport across the microfiltration mem- branes was a concentration difference of 10-15 g I-'. The sodium ion concentration was uniform on both sides of the membrane, hence in the sodium lactate solution recycled through the ED stack the pH was

11.8. The current efficiency sank to 50%, due to competitive OH- and lactate ion charge transferance through the central membrane. When the system was run with NH4+ instead of Na+ as counterion to lactate, the pH was 8.7 and the current efficiency rose to 84 Yo. However, there were still two major shortcomings in the system. About 7 YO of the lactic acid formed was lost by diffusion through the cation exchange membrane into the sulfuric acid solution of the anode recycle. Part of this lactic acid was oxidised to pyruvic acid at the anode and migrated back into the lactic acid in compartment No. 2. Its concentration in the final product was 5200 ppm based on lactic acid. Despite these drawbacks, which should be overcome, the process is advantageous with respect to reaction rate and product recovery.

Received: June 9, 1987 [K 9101

References

[l] Inskeep, G. C.; Taylor, G. G.; Breitzke, W. C.: Ind. Eng. Chem. 44

[2] Vick Roy, T. B.: Dissertation, Univ. of California, Berkeley 1983. [3] Sato, T.; Tanaka, T.;Suzuki, T.: Denki Kagaku 52 (1984) pp. 239. [4] Paul, J . H.;Jefiey, W. H.:Can. J. MicrobioLSZ(1985)pp. 224.

(1952) pp. 1955.

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Turbulence and Random Processes in Fluid Mechanics. Von M . T. Landahl und E. Mollo-Christensen. Cambridge University Press, Cambridge - New York 1987. VI, 154 S.; zahlr. Abb., geb., $17,95. - ISBN 0-521-34687-8.

Nonlinear Diffusive Waves. Von P. L. Sachdeu. Cambridge University Press, Cambridge - New York 1987. VII, 246 S., geb., $ 49,50. - ISBN 0-521-26593-2.

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Solar Energy Utilization. Herausgeg. von H . Yiincii, E . Paykoc und Y. Yener. Martinus Nijhoff Publishers, Dordrecht - Boston - Lancaster 1987. IX, 753 S., zahlr. Abb. u. Tab., geb., US-$ 172,-. - ISBN 90-247-3537-8.

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parat-Jahrbuch MeBtechnik 1987. Herausgeg. von H.-D. Junge. VCH Verlagsgesellschaft, Weinheim - Basel - Cambridge - New York 1987. IX, 194 S., 122 Abb., 15 Tab., geb., DM 50,-. - ISBN 3-527-26594-5.

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