Applied Biochemistry and Biotechnology

, Volume 166, Issue 1, pp 87–111 | Cite as

Design and Evaluation of an Optimal Controller for Simultaneous Saccharification and Fermentation Process

  • Ganti S. Murthy
  • David B. Johnston
  • Kent D. Rausch
  • M. E. Tumbleson
  • Vijay Singh


Ethanol from corn is produced using dry grind corn process in which simultaneous saccharification and fermentation (SSF) is one of the most critical unit operations. In this work an optimal controller based on a previously validated SSF model was developed by formulating the SSF process as a Bolza problem and using gradient descent methods. Validation experiments were performed to evaluate the performance of optimal controller under different process disturbances that are likely to occur in practice. Use of optimal control algorithm for the SSF process resulted in lower peak glucose concentration, similar ethanol yields (13.38±0.36% v/v and 13.50±0.15% v/v for optimally controlled and baseline experiments, respectively). Optimal controller improved final ethanol concentrations as compared to process without optimal controller under conditions of temperature (13.35±1.28 and 12.52±1.19% v/v for optimal and no optimal control, respectively) and pH disturbances (12.65±0.74 and 11.86±0.49% v/v for optimal and no optimal control, respectively). Cost savings due to lower enzyme usage and reduced cooling requirement were estimated to be up to $1 million for a 151 million L/yr (40 million gal/yr) dry grind plant.


Dry grind corn ethanol Saccharomyces cerevisiae Cybernetic model SSF process Optimal controller Gradient descent Process disturbances 


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Copyright information

© Springer Science+Business Media, LLC (outside the USA)  2011

Authors and Affiliations

  • Ganti S. Murthy
    • 3
  • David B. Johnston
    • 1
  • Kent D. Rausch
    • 2
  • M. E. Tumbleson
    • 2
  • Vijay Singh
    • 2
  1. 1.Eastern Regional Research CenterARS, USDAWyndmoorUSA
  2. 2.Department of Agricultural and Biological EngineeringUniversity of IllinoisUrbanaUSA
  3. 3.Biological and Ecological EngineeringOregon State UniversityCorvallisUSA

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