Adsorption of α-amylase onto poly(acrylamide/maleic acid) hydrogels

Poly(acrylamide/maleic acid) [P(AAm/MA)] hydrogels were prepared by irradiating the ternary mixtures of AAm/MA and water by γ rays at ambient temperature. The influence of the MA on the adsorption of α-amylase, optimum working conditions and storage stability of enzyme were investigated. The adsorption capacity of hydrogels were found to increase from 0.40 to 0.71 mg α-amylase/g dry gel with increasing amount of MA in the gel system. Maximum enzyme activities were observed at lower pH values and higher temperatures for adsorbed enzyme compared with free enzyme. Kinetic parameters were calculated as 2.51 g/dm³ for K(m) and 1.67 x 10^-3 g/dm³ min for V(max) for free enzyme and in the range of 12.3-12.9 g/dm³ for K(m) and 1.63 x 10^{- 3}-1.96 x 10^-1-3 g/dm³ min for V(max) depending on the amount of MA in the hydrogel. While, the enzymatic activity of free enzyme was completely lost after 20 days, adsorbed enzyme retained 47-59% of its original activity after 20 days, depending on the amount of MA in the hydrogels.