Applied Biochemistry and Biotechnology

, Volume 66, Issue 1, pp 39–56

Isotherms for adsorption of cellobiohydrolase I and II fromtrichoderma reesei on microcrystalline cellulose

  • József Medve
  • Jerry Ståhlberg
  • Folke Tjerneld
Article

Abstract

Adsorption to microcrystalline cellulose (Avicel) of pure cellobiohydrolase I and II (CBH I and CBH II) fromTrichoderma reesei has been studied. Adsorption isotherms of the enzymes were measured at 4‡C using CBH I and CBH II alone and in reconstituted equimolar mixtures. Several models (Langmuir, Freundlich, Temkin, Jovanovic) were tested to describe the experimental adsorption isotherms. The isotherms did not follow the basic (one site) Langmuir equation that has often been used to describe adsorption isotherms of cellulases; correlation coefficients (R2) were only 0.926 and 0.947, for CBH I and II, respectively. The experimental isotherms were best described by a model of Langmuir type with two adsorption sites and by a combined Langmuir-Freundlich model (analogous to the Hill equation); using these models the correlation coefficients were in most cases higher than 0.995. Apparent binding parameters derived from the two sites Langmuir model indicated stronger binding of CBH II compared to CBH I; the distribution coefficients were 20.7 and 3.7 L/g for the two enzymes, respectively. The binding capacity, on the other hand, was higher for CBH I, 1.0 Μmol (67 mg) per gram Avicel, compared to 0.57 Μmol/g (30 mg/g) for CBH II. The isotherms when analyzed with the combined Langmuir-Freundlich model indicated presence of unequal binding sites on cellulose and/or negative cooperativity in the binding of the enzyme molecules.

Index entries

Trichoderma reesei cellulase cellobiohydrolase adsorp-tion isotherm cellulose hydrolysis 

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Copyright information

© Humana Press Inc. 1997

Authors and Affiliations

  • József Medve
    • 1
  • Jerry Ståhlberg
    • 2
  • Folke Tjerneld
    • 1
  1. 1.Department of BiochemistryUniversity of LundLundSweden
  2. 2.Department of Molecular Biology, Biomedical CentreUniversity of UppsalaUppsalaSweden

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