Immobilization of α-amylase via adsorption on magnetic particles coated with polyaniline

The immobilization of alpha-amylase via adsorption on magnetic particles coated with polyaniline was studied. The support was characterized by field emission scanning electron microscopy (FESEM). The obtained magnetic particles were agglomerates of nanoparticles with sizes below 100 nm. The effects of various factors on immobilization, including time, the initial enzyme concentration, pH, and temperature, were examined. The optimum pH, temperature, and time for immobilization were established to be 7, 45 degrees C and 75 min, respectively. The maximum amount of adsorbed alpha-amylase of 10/100mg support was determined at the 5 mg/mL enzyme concentration. It appeared that alpha-amylase was stabilized in terms of pH and temperature by adsorption on magnetic particles coated with polyaniline. The good agreement of the equilibrium data with the Langmuir isotherm model confirmed the monolayer coverage of enzyme molecules on the surface of magnetic particles, and the maximum adsorption capacity was found to be 55.6/100mg support at 25 degrees C. The biocatalyst retained 55.5 +/- 1.63% of its initial activity after nine cycles of reuse in starch hydrolysis at 60 degrees C in a batch reactor. The immobilized enzyme also showed very good storage stability.