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Cationic polyacrylamides increase the rate of liquefaction and hydrolysis of cornstarch

Authors

  • Kendra E. Maxwell,

    1. Institute of Paper Science and Technology, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, NW Atlanta, GA
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  • Alison L. Krantz,

    1. Institute of Paper Science and Technology, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, NW Atlanta, GA
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  • Sujit Banerjee

    Corresponding author
    • Institute of Paper Science and Technology, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, NW Atlanta, GA
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Correspondence concerning this article should be addressed to and S. Banerjee at sb@gatech.edu.

Abstract

Cationic polyacrylamides (c-PAMs) bind to starch granules and decrease the temperature for the onset of gelatinization by 8°C. c-PAM increases the binding of α-amylase to cornstarch; the rate of cornstarch hydrolysis also increases. By analogy to previous work on the c-PAM promoted hydrolysis of cellulose, it is proposed that the polymer reduces the charge on the surface of starch through a charge-patch mechanism. Because both enzyme and substrate are negatively charged, the bound c-PAM reduces the charge repulsion experienced by the approaching enzyme, which leads to stronger enzyme-substrate binding and faster hydrolysis. Overall, the c-PAM reduces enzyme dose by up to 62% under the conditions used. There is a mirror image relationship between the viscosity of the medium and the hydrolysis rate, which allows optimization of these parameters with enzyme and c-PAM dosage. Low c-PAM levels increase viscosity by agglomerating the substrate, but the viscosity drops at higher c-PAM concentration. © 2012 American Institute of Chemical Engineers AIChE J, 59: 79–83, 2013

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