Jung Ho Ahn

Contents Introduction Objective Experimental procedure Result Conclusion

Introduction ABE fermentation Acetone-butanol-ethanol fermentation Produce feed stock chemicals & liquid fuels from renewable biomass Product inhibition is a severe problem for bioconversion – Low concentration of fermentative product (< 5 wt%) – Cost intensive (product sep, downstream processing, waste water treatment)

Introduction Butanol Main product of ABE fermentation Primary inhibitory product affecting the bioconversion Less volatile than water – Distillation unfavorable Butanol concentration <5 % – Energy consumption for butanol purification exceed energy content of butanol recovered More efficient butanol recovery process required

Based on selective permeation of ABE components through a membrane in preference to water Advantage – Coupling with fermentation Inhibitory products from fermentation broth removed continuously as soon as they are formed (productivity ) – Only membrane permeated components undergo liquid-vapor phase change Economical than distillation – No external mass separating agent involved No harmful effect on the microorganisms in the fermentation broth – Non-porous membrane Fermentation medium can be retained by the membrane without clogging the pores of asymmetric membranes Disadvantage – Very few organophilic membranes available for this application Introduction Why pervaporation?

Introduction Membrane material Polydimethylsiloxane (PDMS) most widely used Poly ether block amide (PEBA) 2533 used in this study – 80 wt% organophilic poly(tetramethylene glycol) soft segments + 20 wt% nylon 12 hard segments – High affinity to butanol Butanol dissolves PEBA at elevated temperatures

Objective Explore the applicability utilizing PEBA 2533 membranes for the separation of ABE from dilute aqueous solution pertinent to ABE removal from fermentation broths

Experimental Procedure 1.Evaluation of permselectivity from separation of binary mixtures by membrane 2.Study effect of feed composition, operating temperature, membrane thickness on membrane performance 3.Study of quaternary ethanol-butanol- acetone-water mixture separation

Result Effect of feed concentration Pervaporative enrichment of ABE solvents from respective aqueous solutions through PEBA 2533 membrane investigated

Result Effect of feed concentration Result showed preferential sorption PEBA 2533 dissolves only in butanol at elevated temperature – Indication of strong affinity Unlike ethanol and acetone butanol is partially miscible to water – Forces that retain butanol molecules in water weak Membrane permeability – Butanol > Acetone > Ethanol

Result Effect of feed concentration High solubility plasticize membrane Swelling effect Selectivity high at low feed organic concentrations Selectivity higher after phase separation

Result Effect of temperature Water permeation rate large at high temperature Magnitude of temperature dependence of water flux affected by organic compound present in feed – Butanol > Ethanol > Acetone Partial flux of organic compounds follow different trend Molecular size of ethanol and acetone relatively small – Diffusion through membrane easy – Increase in vapor pressure

Result Effect of temperature Increase in temperature will help retain more butanol molecule in water – Decrease in repulsive force between butanol and water molecule

Result Effect of membrane thickness Thinner membrane desired – Higher permeation flux – Concentration polarization in boundary layer Boundary layer effect most significant for butanol-water separation Permeation flux and membrane selectivity

Result Effect of membrane thickness Concentration polarization influenced by permeation flux and membrane selectivity

Result Pervaporation of quaternary aqueous ABE mixtures Data consistent with those obtained from binary mixtures separation, and the membrane selectivity still follow Butanol > Acetone > Ethanol Coupling effects among permeating species in the system – Permeant-permeant interaction – Permeant-membrane interaction

Conclusion PEBA membrane can be used to extract butanol

Electrodialysis as a useful technique for lactic acid separation from a model solution and a fermentation broth 라승환

Introduction  Lactic acid - food industry, beverage production, pharmaceutical industry chemical industry, medicine - fermentation method : calcium lactate lactic acid  Electrodialysis BPM : bipolar membrane AEM : anion exchange membrane CEM : cation exchange membrane

Previous study  Lactic acid fermentation (Boyaval) - total cell recycling, ultrafiltration, electrodialysis : 85 g/L  Lactic acid fermentation (Yao) - similar system, H2SO4 (donor of proton) : 90 g/L  Two-stage electrodialysis (Lee) - (first) lactate:115g/L, current efficiency: 90%, - (second) converted lactic acid : %, current efficiency: 80% - total energy consumption : kWh/kg  Electrodialysis with double exchange (Heriban) - lactic acid (model solution) : 236.8g/L, energy consumption : kWh/kg  Two- & three- compartment electrodialysis with bipolar membrane (Kim) - high volumetric productivity : 71.7 g/L.h

Methods  Lactic acid fermentation  Pretreatment - Ultrafiltration (remove the cells) - Decolourisation (decrease electrodialysis efficiency : dye fixing on the membrane) - Removal of multivalent metal ions (irreversible damage to the electrodialysis membrane: bipolar)  Desalting electrodialysis  Electrodialysis with bipolar membranes

Results  Desalting electrodialysis - determination of the limiting current Maximum : 8.8 mA/cm 2 Current density : 7.8 mA/cm 2 Constant voltage : 18 V

Results  Desalting electrodialysis (Model sodium lactate solution)

Results  Desalting electrodialysis (fermentation broth)

Results  Desalting electrodialysis (Model sodium lactate solution) (Fermentation broth)

Results - current density lactate transport - concentrate & diluate volume (water passage) - other component (glucose: no effect, salt: current efficiency) - lower initial lactate con. transport rate  Desalting electrodialysis  Two-level electrodialysis - initial lactate con. : 36.6 g/L - final con. : 146 g/L (4-times higher) - current efficiency : 64%, Energy consumption : 0.34 kWh/kg

Results  Electrodialysis with bipolar membranes (Sodium lactate lactic acid) Current density : 67.6 mA/cm 2

Results  Electrodialysis with bipolar membranes (Sodium lactate lactic acid) (Model sodium lactate solution) Final lactic acid conc. : g/L Conversion : % Energy consumption : 1.1 kWh/kg Final base conc. : mol/L Current efficiency : % (Fermentation broth) Final lactic acid conc. : g/L Conversion : % Energy consumption : 1 kWh/kg Final base conc. : mol/L Current efficiency : %

Conclusions  Two-stage electrodialysis is a suitable and efficient technique  First ED step final lactate conc. : 175 g/L  Second ED step final lactic acid conc. : 151 g/L  Total required energy : 1.5 kWh/1kg

Minsoo Kim

§ Introduction £ Fermentation of concentrated sugar solution 1. Benefits ① High ethanol concentration broth → Decrease of purification costs ② Less water carried through the system → Reduce equipment size → Low capital cost ③ Reduced waste → Low waste treatment costs ④ High cell concentrations → Increase volumetric productivity 2. Limitation ∙ Product inhibition → To relieve this problem membrane distillation system was studied

§ Introduction £ Membrane distillation 1. Components ① Warm feed ② Porous hydrophobic membrane → poly(tetrafluoroethylene) (PTFE) ③ Cold fluid on permeate side 2. Driving force Partial vapor pressure gradient Warm Feed Cool Permeate Hydrophobic Microporous Membrane Vapor Space Evaporation Condensation

§ Materials and methods

→ Effect on the specific ethanol production rate at three feed medium

§ Results and discussion £ Continuous fermentation of concentrated glucose solution A 1. Experimental condition ∙ Fixed PTFE module size ∴ High cell concentrations → Ethanol accumulation ∴ Control feed rate of glucose solution A → Constant cell concentrations 2. Conclusion ① Specific ethanol production rate ∙ With ethanol stripping : 0.21 gEtOH/gcell∙h ∙ Without ethanol stripping : 0.06 g/g ∙h

§ Results and discussion ② Usage of PTFE module → Low ethanol concentration of fermentation broth = High ethanol concentrated solution removed from the broth → Higher cell activity

§ Results and discussion £ Continuous fermentation of concentrated glucose solution B 1. Experimental condition ∙ Cell growth not controlled ( Feed rate controlled → Maintain glucose concentration constant ) ∙ Control yeast concentration ( Production rate by yeast cells = removal rate by PTFE module ) → Due to the size of the module ( limiting factor )

§ Results and discussion £ Continuous fermentation of concentrated glucose solution B 2. Conclusion ① Specific ethanol production rate : 0.22 g/g∙h → Relatively low → Increased feed rate → Specific ethanol production rate : 0.38 g/g∙h → Decrease cell concentration to 18 g/l → Specific ethanol production rate : 0.4 g/g∙h ② Average ethanol concentration in the cold trap after 180 hour : 350 g/l

§ Results and discussion £ Continuous fermentation of concentrated molasses 1. Conclusion ∙ Flocculation of the yeast cells was adversely affected ; cell washout occurred

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