Bioprocess Engineering

, Volume 10, Issue 5–6, pp 217–223 | Cite as

Evaluation of sensors for the control of a continuous ethanol fermentation

  • M. Polakovic
  • C. F. Mandenius


A method is presented for the evaluation of sensors used in the control of continuous fermentations. Simulations of open-loop response to input disturbance provided a starting point for the choice of sensor type. This was evaluated quantitatively through a sensitivity ratio. It was shown that in the case of ethanol fermentation, there existed three regions where different sensors could be used for the process control depending on the inlet sugar concentration. Sugar sensors were preferable above an inlet sugar concentration of 50 kg/m3, while ethanol sensors were preferable below 25 kg/m3. In the intermediate region, sugar and ethanol sensors demonstrated equally good performance. A controllability study of a continuous ethanol fermentation was also made. A single-stage continuous stirred-tank fermentor was simulated operating at a dilution rate of 0.1 1/h and inlet glucose concentration of 160 kg/m3. The outlet glucose concentration was controlled with a PI controller. Mean square error of the controller input signal during the first five hours after introducing input disturbance was taken as a measure of the controllability. This was studied in the relation to the two key sensor characteristics, sampling time and accuracy.


Fermentation Glucose Concentration Dilution Rate Sensor Characteristic Ethanol Fermentation 
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List of Symbols

cp kg/m3

ethanol concentration

cp kg/m3

fermentor ethanol concentration corresponding to c si and D

cs kg/m3

substrate (glucose) concentration

cs kg/m3

fermentor glucose concentration corresponding to c si and D

csi kg/m3

inlet substrate (glucose) concentration

csi kg/m3

inlet glucose concentration value used for sensitivity evaluation

csm kg/m3

glucose concentration — measured value

css kg/m3

glucose concentration setpoint value

cx kg/m3

biomass concentration

D 1/h

dilution rate

D 1/h

dilution rate value used for sensitivity evaluation

Di 1/h

dilution rate at ith sampling interval

D0 1/h

dilution rate at steady state

Kc m3/kgh

controller gain

Kp kg/m3

product inhibition constant

Ks kg/m3

Monod constant

n1, n2

random numbers

rp kg/m3 h

ethanol production rate

rs kg/m3 h

substrate (glucose) consumption rate

rx kg/m3 h

biomass growth rate

\(\vec \alpha \)

vector of independent variables


ith dependent variable


ethanol yield


biomass yield

\(\vec x\)

parameter vector


jth parameter


sensitivity of yi with respect to αj


sensitivity of fermentor ethanol concentration


sensitivity of fermentor glucose concentration


sensitivity ratio

Δcp kg/m3

ethanol concentration difference corresponding to a change of c si by 5%

Δcs kg/m3

glucose concentration difference corresponding to a change of c si by 5%

Δcsi kg/m3

concentration difference added to c si

εi kg/m3

error at ith sampling interval

μ 1/h

specific growth rate

μm 1/h

maximum specific growth rate

σs kg/m3

standard deviation of monitored glucose concentration

τI h min kg/m3

integral time

τs min

sampling period


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  1. 1.
    Gódia, F.; Casas, C.; Sola C.: A survey of continuous ethanol fermentation systems using immobilized cells. Process Biochem. (April 1987) 43–48Google Scholar
  2. 2.
    Mandenius, C. F.; Mattiasson, B.; Axelsson, J. P.; Hagander, P.: Control of an ethanol fermentation carried out with alginate entrapped Saccharomyces cerevisiae. Biotechnol. Bioeng. 29 (1987) 941–949Google Scholar
  3. 3.
    Tzeng, J.-W.; Fan, L.-S.; Gan, Y.-R.; Hu, T.-T.: Ethanol fermentation using immobilized cells in a multistage fluidized bed bioreactor. Biotechnol. Bioeng. 38 (1991) 1253–1258Google Scholar
  4. 4.
    Cysewski, G. R.; Wilke, C. R.: Rapid ethanol fermentation using vacuum and cell recycle. Biotechnol. Bioeng. 19 (1977) 1125–1143Google Scholar
  5. 5.
    Mandenius, C. F.: Controlling fermentation of lignocellulose hydrolysates in a continuous hollow-fiber reactor using biosensors. Biotechnol. Bioeng. 32 (1988) 123–129Google Scholar
  6. 6.
    Groot, W. J.; Kraayebrink, M. R.; Waldram, R. H.; van der Lans, R. G. J. M.; Luyben, K. Ch. A. M.: Ethanol production in an integrated process of fermentation and ethanol recovery by pervaporation. Bioproc. Eng. 8 (1992) 99–111Google Scholar
  7. 7.
    Christen, P.; Minier, M.; Renon, H.: Ethanol extraction by supported liquid membrane during fermentation. Biotechnol. Bioeng. 36 (1990) 116–123Google Scholar
  8. 8.
    Tyagi, R. D.; Ghose, T. K.: Batch and multistage continuous ethanol fermentation of cellulose hydrolysate and optimum design of fermentor by graphical analysis. Biotechnol. Bioeng. 22 (1980) 1907–1928Google Scholar
  9. 9.
    Chattaway, T.; Goma, G.; Renaud, P.-Y.: Modelling ethanol and secondary inhibitions of ethanol fermentation in a multistage reactor. Biotechnol. Bioeng. 32 (1988) 271–276Google Scholar
  10. 10.
    Chen, H. C.; Mou, D. G.: Pilot-scale multi-stage multi-feeding continuous ethanol fermentation using non-sterile cane molasses. Biotechnol. Lett. 12 (1990) 367–372Google Scholar
  11. 11.
    Kida, K.; Asano, M.; Yamadaki, M.; Iwasaki, K.; Yamaguchi, T.; Sonoda, Y.: Continuous high-ethanol fermentation from cane molasses by a flocculating yeast. J. Ferm. Bioeng. 69 (1990) 39–45Google Scholar
  12. 12.
    Warren, R. K.; Hill, G. A.; Macdonald, D. G.: Improved bioreaction kinetics for the simulation of continuous ethanol fermentation by Saccharomyces cerevisiae. Biotechnol. Prog. 6 (1990) 319–325Google Scholar
  13. 13.
    Wall, J. B.; Hill, G. A.: Optimum CFST bioreactor design: Experimental study using batch growth parameters for Saccharomyces cerevisiae producing ethanol. Canad. J. Chem. Eng. 70 (1992) 148–152Google Scholar
  14. 14.
    Vigié, P.; Goma, G.; Renaud, P. Y.; Chamilothoris, G.; Dahhou, B.; Pourciel, J. B.: Adaptive predictive control of a multistage fermentation process. Biotechnol. Bioeng. 35 (1990) 217–223Google Scholar
  15. 15.
    Vigié, P.; Dahhou, B.; Queinnec, M.; Lakrori, M.; Chéruy, A.; Pourciel, J. B.: Control of substrate concentration in a continuous bioprocess. Bioproc. Eng. 6 (1991) 259–263Google Scholar
  16. 16.
    Queinnec, I.; Dahhou, B.; Roux, G.; Goma, G.; Pourciel, J. B.: Estimation and control of a continuous alcoholic fermentation process. J. Ferm. Bioeng. 72 (1991) 285–290Google Scholar
  17. 17.
    Dahhou, B.; Najim, K.; Roux, G.; Queinnec, I.: Robust pole placement control of a fermentor. Bioproc. Eng. 8 (1992) 73–78Google Scholar
  18. 18.
    Chtorou, M.; Najim, K.; Roux, G.; Dahhou, B.: Control of a bioreactor using a neural network. Bioproc. Eng. 8 (1992) 251–254Google Scholar
  19. 19.
    Ghose, T. K.; Tyagi, R. D.: Rapid ethanol fermentation of cellulose hydrolyzate. II. Product and substrate inhibition and optimization of fermentor design. Biotechnol. Bioeng. 21 (1979) 1401–1420Google Scholar
  20. 20.
    Hill, G. A.; Robinson, C. W.: A modified Ghose model for batch cultures of Saccharomyces cerevisiae at high ethanol concentrations. Chem. Eng. J. 44 (1990) B69-B80Google Scholar
  21. 21.
    Aiba, S.; Shoda, M.; Nagatani, M.: Kinetics of product inhibition in alcohol fermentation. Biotechnol. Bioeng. 10 (1968) 845–864Google Scholar
  22. 22.
    Axelsson, J. P.; Mandenius, C. F.; Holst, O.; Hagander, P.; Mattiasson, B.: Experience in using an ethanol sensor to control molasses feed-rates in baker's yeast production. Bioproc. Eng. 3 (1988) 1–9Google Scholar
  23. 23.
    Fraleigh, S. P.; Bungay, H. R.; Clesceri, L. S.: Continuous culture, feedback control and auxostats. Trends Biotechnol. 7 (1989) 159–164Google Scholar
  24. 24.
    Fraleigh, S. P.; Bungay, H. R.; Clesceri, L. S.: Aerobic formation of ethanol by Saccharomyces cerevisiae in a computerized pHauxostat. J. Biotechnol. 13 (1990) 61–72Google Scholar

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • M. Polakovic
    • 1
  • C. F. Mandenius
    • 1
  1. 1.Department of Physics and Measurement Technology, Bioprocess Measurement Technology GroupLinköping Institute of TechnologyLinköpingSweden

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