Clinoptilolite particles as a carrier for biocatalysts immobilization: invertase immobilization and characterization

Clinoptilolite, a natural zeolite, was proposed as a carrier for immobilized biocatalyst systems by polyethyleneimine and glutaraldehyde activation. Invertase (EC 3.2.1.26, beta-fructofuranosidase) as a model biocatalyst was covalently attached onto the particles by direct chemical reaction between aldehyde groups on the particles and amine groups of the enzyme. The effects of polyethyleneimine concentration, activation agent (glutaraldehyde) concentration, pH and invertase concentration on immobilization process were determined. Approximately 7 mg invertase was immobilized on a gram of clinoptilolite particles with 78% retained activity under optimum immobilization conditions. Immobilization did not affect optimum pH of the enzyme, but it brought out a wider pH-activity curve that was accepted as the indication of better pH stability. Immobilization resulted in an increase at the optimum temperature from 55 to 60 degrees C. The K-M value of immobilized invertase biosystem was found as approximately 1.5 times higher than that of the free enzyme. Immobilization provided improvement on the thermal stability of invertase, and activity half-life of the immobilized invertase was found as approximately four times longer than that of the free invertase. (c) 2013 Curtin University of Technology and John Wiley & Sons, Ltd.