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α-Amylase adsorption on starch crystallites

Authors

  • V. M. Leloup,

    Corresponding author
    1. Institut National de la Recherche Agronomique, BP 527-44026 Nantes Cedex 03, France
    • AFRC Institute of Food Research, Norwich Laboratory, Colney Lane, Norwich NR47UA, United Kingdom
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  • P. Colonna,

    1. Institut National de la Recherche Agronomique, BP 527-44026 Nantes Cedex 03, France
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  • S. G. Ring

    Corresponding author
    1. Institut National de la Recherche Agronomique, BP 527-44026 Nantes Cedex 03, France
    • AFRC Institute of Food Research, Norwich Laboratory, Colney Lane, Norwich NR47UA, United Kingdom
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Abstract

The goal of this work was to characterize the adsorption of Bacillus subtills α-amylase onto crystalline starchy materials of the B-type polymorph. Monodisperse spherulitic particles (R ż6; 5.0 μm), essentially resistant to α-amylolysis at 25°C were prepared from short amylose chains (DPn ≈ 15). The α-amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 μg/cm2 at 25°C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was ΔG ≈ −20.7 kJ/mol. This is smaller than published values for the binding of α-amylase to soluble amylosic chains (ΔG < −30 kJ/mol).

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