Evaluation of two different Concanavalin A affinity adsorbents for the adsorption of glucose oxidase

Concanavalin A (Con A) was selected as ligand and thus immobilized onto two different supports, namely the polymeric Toyopearl and the inorganic silica, with the protection of its binding sites provided during the coupling procedure. The prepared Con A affinity adsorbents were then employed to evaluate their adsorption behaviour for the enzyme glucose oxidase (GOD). The immobilization kinetics showed that the immobilization of Con A on silica supports was much faster than that on Toyopearl supports, which could highly reduce the possibility of the denaturation of Con A. The optimal adsorption conditions for binding of GOD onto the ligand were determined in terms of the pH value and the ionic strength of the adsorption medium. The adsorption isotherms for binding GOD onto two Con A affinity adsorbents fitted well with the Langmuir equation. The maximum adsorption capacity qm of Toyopearl Con A and silica Con A were 7.9 mg/ml and 4.9 mg/ml, with a dissociation constant Kd of 4.8 × 10−7 M and 2.6 × 10−6 M, respectively. Due to the less diffusive resistance, silica Con A showed both higher adsorption and desorption rates for GOD when compared with Toyopearl Con A. The nonspecific adsorption of GOD was less than 8% for both end-capped Toyopearl and silica supports. The dynamic adsorption of GOD for five times repeated processes showed a high stability for both prepared adsorbents. All the results indicate a good suitability of both Con A adsorbents for affinity adsorption of GOD.