A Kinetic Model for Simultaneous Saccharification and Fermentation of Avicel With Saccharomyces cerevisiae

Authors

  • Josebus M. van Zyl,

    Corresponding author
    1. Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa; +27-21-808-5846
    • Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa; +27-21-808-5846.
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  • Eugéne van Rensburg,

    1. Department of Process Engineering, University of Stellenbosch, Stellenbosch, South Africa
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  • Willem H. van Zyl,

    1. Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa
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  • Thomas M. Harms,

    1. Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa; +27-21-808-5846
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  • Lee R. Lynd

    1. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
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Abstract

This work describes a numerical model for predicting simultaneous saccharification and fermentation of Avicel, an insoluble crystalline cellulose polymer. Separate anoxic cultivations of 40 g/L glucose and 100 g/L Avicel were conducted to verify model predictions and obtain parameters to describe the reaction kinetics. Saccharification of Avicel was achieved with Trichoderma reesei cellulases from the enzyme preparation Spezyme CP with an enzyme loading of 10 FPU/g cellulose. Cultivations were supplemented with 50 IU/g cellulose of β-glucosidase from Novozym 188 to prevent product inhibition by cellobiose. Saccharomyces cerevisiae MH-1000 is a robust industrial strain and was used to ferment glucose to ethanol, glycerol, and carbon dioxide. The numerical model presented in this paper differs from previous models by separating the endoglucanase and exoglucanase enzyme kinetics and allowing for inhibitive site competition. Assuming all enzymes remain active and that each enzyme complex has a corresponding constant specific activity, the model is capable of predicting adsorbed enzyme concentrations with reasonable accuracy. Comparison of predicted values to experimental measurements indicated that the numerical model was capable of capturing the significant elements involved with cellulose conversion to ethanol. Biotechnol. Bioeng. 2011; 108:924–933. © 2010 Wiley Periodicals, Inc.

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