In this study, α-amylase was immobilized on silica gel via adsorption with glutaraldehyde in the presence and absence of magnetic field and was compared with free enzyme. The α-amylase (free enzyme) and the enzymatic reaction (immobilized and free enzyme) were treated by 13mT magnetic field for 100 min and 1.5 min, respectively, at 25°C compared with the control sample which was not exposed to the magnetic field and characteristics including activity, kinetic parameters {maximum velocity(vmax), michaelis-menten constant(km), catalytically constant(kcat)} in different pH (6, 6.5, 6.9, 7.6)were investigated. The highest activity of free enzyme was obtained at pH 6.9 while this value was shifted to pH 6.5 for immobilized enzyme. The amount ofreduced sugar (maltose) was determined spectrophotometrically at 620 nm. Using kinetic data for Lineweaver– Burk plots, Km and Vmax values were calculated from the slopes of the curve. Results showed that the activity of the free enzyme decreased in the presence of magnetic field and in the case of enzymatic reactions the reduction rate in the presence of magnetic field was more than other modes, and immobilization activity in the presence of magnetic field also showed enhancement. Km for immobilized α- amylase was found to be higher than that of the free enzyme, which may be due to interparticle diffusional mass transfer restrictions.

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