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http//www.icpf.cas.cz/
Fermentation Coupled with Pervaporation
P. Izák1, K. Schwarz2, M. Kohoutová1, W.Ruth2,
H. Bahl2, U. Kragl2
1Department of Separation Processes, Institute of
Chemical Process Fundamentals, Rozvojová 135,
16502 Prague 6, CZ 2Institute of Chemistry,
University of Rostock, Albert Einstein Str.3a,
18059 Rostock, Germany
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Supported ionic liquid membranes offer a range of
possible advantages

• Molecular diffusion is much higher in liquids
  than in solids, allowing high fluxes
• The selectivity of the separation can be
  influenced by variation of the liquid -
  especially ionic liquids offer the advantage of a
  wide variety of properties
• Ionic liquids as liquid membranes easily allow
  three-phase systems due to their special mixing
  behavior

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• Due to their good thermal stability, reactive
  processes may take place at high temperatures (up
  to around 250 ºC), which leads to faster kinetics
  in the case of endothermic reactions
• The use of nano-, ultra- and micro-filtration
  ceramic modules helps to diminish concentration
  polarization due to rough liquid-membrane
  surface
• Contrary to the extraction,
• only small amounts of liquids
• are necessary to form the liquid
• membrane, thus allowing the
• use of more expensive materials.

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The only problem is longtime stability of the
liquid in the pores.
Stability of the hydrophobic ILs inside the pores
(in hours)
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Experimental

• As a support matrix for the polymer-IL membrane
  the ceramic ultrafiltration module made from TiO2
  with pore size 60 nm was used.
• The PDMS was prepared by mixing a solution of RTV
  615A and RTV 615B (General Electric) in 101
  ratio at 60C for 0.5 hour.
• 15 wt of tetrapropylammonium tetracyano-borate
  ionic liquid and 85 wt polydimethylsiloxane.

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• The ternary system - practical application in
  biotransformation processes, where the
  fermentation broth from Clostridium
  acetobutylicum is normally used
• The compound of interest is biofuel, namely
  BIObutanol
• It is the main product of butan-1-ol fermentation
  and it is also the primary inhibitory product
  affecting the bioconversion

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• Fermentation was carried out at 37C and pH 4.5.
• The enrichment factor of butan-1-ol increased
  from 2.2 (PDMS) up to 10.9 (IL-PDMS) (Izák P,
  Ruth W, Dyson P, Kragl U (2007) Selective Removal
  of Acetone and Butan-1-ol from Water with
  Supported Ionic Liquid - Polydimethylsiloxane
  Membrane by Pervaporation, Chem. Eng. J., 139/2
  (2008) 318-321)
• Firstly, a continuous fermentation with removal
  of ABE by pervaporation was measured without any
  butan-1-ol addition to test, if the SILM was
  selective and stable.

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• After successful tests, the concentration of
  butan-1-ol was several times increased to test
  the SILM under more stringent conditions and to
  study the effect of pervaporation on the cells.
• After 3 months of the experiment we did not
  observe any change of mass or selectivity of IL
  in the pores of the ultrafiltration membrane.

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Experiment

• C. Acetobutylicum ATCC 824 was grown under
  anaerobic phosphate-limited conditions.
• In the chosen fermentation system, especially the
  phosphate concentrations as well as the dilution
  rates were responsible for the amount of produced
  solvents.

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• Schema of continuous culture fermentation
  connected with pervaporation
• 1.Waste tank 2. Tank with substrate 3. Culture
  vessel 4. Pervaporation cell 5. Cold trap 6.
  Vacuum pump

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Dependence of permeate concentration on
fermentation time at 37C, at dilution rate 0.075
h-1, 0.5 mM phosphate concentration in supplying
vessel and pH 4.5.
? Butan-1-ol (summary of the produced and added
butan-1-ol) ? Acetone ? Ethanol ? Acetate x
Butyrate
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Dependence of butan-1-ol and acetone permeation
flux on its culture vessel concentration.
? Butan-1-ol ? Acetone
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Dependence of butan-1-ol and acetone enrichment
factor on its culture vessel concentration.
? Butan-1-ol ? Acetone
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Conclusions

• To get more effective ABE removal from fermentor
  we used pervaporation with IL-PDMS nonporous
  membrane.
• Using this membrane we were able to remove ABE
  from the culture supernatant more effectively
  than it was described by others (Qureshi et al.
  (1992), Soni et al. (1987), Liu et al. (2004)).

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Conclusions

• The supported ionic liquid membranes were
  weighted after all experiments and no weight
  changes were observed stable SILM.
• Higher diffusion coefficient is most probably
  responsible for higher permeation flux and
  enrichment factors of butan-1-ol in IL-PDMS
  membrane.
• If we would run pervaporation with continuous and
  complete removal of butan-1-ol from the culture
  supernatant, it would lead to more stable
  fermentation process with higher production of
  BIObutanol.

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Acknowledgement

• This research was supported by Marie Curie
  Reintegration Fellowships within the 6th European
  Community Framework Programme and and to the
  Czech Science Foundation for grant No.
  104/08/0600.
• Thank you for your attention!